SUDAN UNIVERSITY OF SCIENCE & TECHNOLOGY

COLLEGE OF GRADUATE STUDIES

LIPID PROFILE IN SUDANESE PATIENTS WITH MYOCARDIAL INFARCTION

Presented by:Sulieman Mohi-eldin Omar

BSC Medical Laboratory science

Supervisor: Dr. Badr-eldien Hassan AlabidMBBS, MD Clinical Pathology

Associate professor of clinical pathology

A Thesis Submitted In Partial Fulfillment For HD. Degree in Clinical Chemistry

2006

1

DEDICATION

To the best

creature who is my

life, my sole is no

thing without thee,

I offer this.

2

Acknowledgement

My first thankful is to Allah all of His affluences, appearing

and disappearing, and my great appreciations and gratuities were

extend to my supervisor Dr. Badr-eldien Hassan Alabid for his

precious advice and guidance upon this study.

Thanks and regards were extend to ICCU of Elshaab

Teaching Hospital staff for helping in sample collection, and

extended the members of the Laboratory of Research Unit for

helping in sample analysis.

I affirm my thanks to my teachers, colleagues and friends for

helping and encouragement.

3

ABSTRACT

Serum total cholesterol, HDL-cholesterol, LDL-cholesterol

and triglyceride were estimated in 20 patients (12 males, 8

females) with acute myocardial infarction during acute phase (the

first two days). Serum total cholesterol, HDL-cholesterol and LDL-

cholesterol levels showed no significant differences, while

triglycerides level showed significant increased levels when

compared with results of healthy subjects (5 males, 5 females) as

control. The ratios of total cholesterol/HDLc and LDLc/HDLc also

showed no significant differences compared with control ratios. It

is concluded that in exception of triglycerides levels, there is no

change in serum lipid profile in patients with MI during the acute

phase.

4

CONTENTSTopic Page

Dedication IIAcknowledgement IIIAbstract IVContent VList of figures VIIList of tables VIIIChapter One Introduction and Literature Review 1 1.1. Normal function & structure of the heart 21.2. Heart failure 31.3. Ischaemic heart disease 41.4. Acute myocardial infarction 51.4.1. Clinical feature 51.4.2. Morphological feature 51.4.3. Complications of myocardial infarction 61.4.4. Diagnosis of myocardial infarction 81.4.4.1. Electrocardiography 91.4.4.2. Cardiac markers 101.4.5. Treatment of myocardial infarction 121.5. Lipids 121.6. Fatty acids 131.7. Triglycerides 131.8. Cholesterol 131.9. Phospholipids 131.10. Apolipoproteins 131.11. Lipoproteins 141.12. Classification of lipoproteins 161.13. Metabolism of lipoproteins 181.13.1. Chylomicrons 181.13.2. Very low density lipoproteins 181.13.3. Low density lipoproteins 181.13.4. High density lipoproteins 191.13.5. Lipoprotein receptors 191.14. Disorders of lipids metabolism 211.14.1. Predominant hypercholesterolaemia 221.14.2. Secondary hypercholesterolaemia 231.14.3. Primary hypercholesterolaemia 231.14.4. Predominant hypertriglyceridaemia 241.14.5. Mixed hyperlipidaemia 24

5

1.15. Treatment of hyperlipidaemia 251.15.1. Treatment of hypercholesterolaemia 25II.3.4.1 Treatment of hypertriglyceridaemia 25Chapter TwoThe Objectives of The Study

27

Chapter Three Materials and Methods

28

3.1. Patients and Controls 28

3.2. Samples Collection 283.3. Estimation of lipid profile 283.3.1. Equipments 293.3.2. Reagents 293.4.1. Estimation of total cholesterol 303.4.2. Estimation of HDL-cholesterol 313.4.3. Estimation of LDL-cholesterol 323.4.4. Estimation of triglyceride 333.5. Statistical analysis 33Chapter Four Results

34

4.1. Study group 344.2. Estimation of total cholesterol 344.3. Estimation of HDL-cholesterol 344.4. Estimation of LDL-cholesterol 344.5. Estimation of triglycerides 35Chapter FiveDiscussion

43

Chapter SixConclusion and Recommendation

45

Chapter SevenReferences

46

6

LIST OF FIGURESFig. Title Page

1.1 General structure of plasma lipoprotein 15

4.1 Age distribution in study groups of patients 334.2 Age distribution in control subjects 334.3 Comparison of diabetes in study groups of AMI with

control subjects.34

4.4 Comparison of hypertension in study groups of AMI with control subjects.

36

4.5 Comparison of family history in study groups of AMI with control subjects.

39

LIST OF TABLES Table Title Page

1.1. The Composition of the Major Lipoprotein Complexes

17

4.1 Multiple Comparisons of lipid profile level

(mg/dL) in study subgroups of patients with AMI

and control subjects

41

4.2 Relationship of lipid profile levels in study groups of AMI with control subjects

42

7

INTRODUCTION

Opinion is divided on the changes that occur in serum lipoproteins

following myocardial infarction (MI). Most workers have reported a

reduction in total cholesterol,1-10 HDL-cholesterol9 and LDL-cholesterol7-9

after acute myocardial infarction. Others have, however, reported no

change in serum total cholesterol11 and HDL-cholesterol.7-11 Similar

variations have also been noted in serum triglyceride levels.4,11,12 From

these reports it is clear that phasic changes do occur in patients following

MI and therefore there is a recommendation for detection of

hyperlipidaemia in patients with AMI that the serum lipid should be

assessed either within 24 hours after infarction or after 2-3 months of

AMI.10,13,14 While the recommendation may hold true for absolute levels

there is no consensus on when ratios of various fractions of lipids should

be assessed. Further, the magnitude, pattern and mechanism of these

changes in lipoproteins are also not clearly outlined for our Sudanese

subjects.

The present study was, therefore, undertaken to examine the change

in serum triglyceride, total cholesterol and lipoproteins including ratios of

total cholesterol/HDL and LDL/HDL in our Sudanese subjects with

myocardial infarction.

8

CHAPTER ONE

LITERTURE REVIEW

1.1. Normal Function and Structure of the Heart:

The heart is a muscular pump divided on each side into two chambers

(an atrium and a ventricle) each separated by a valve, tricuspid on the right,

mitral on the left. The inner wall of the cardiac chamber and the surface of the

valve cups are lined by a layer of endothelial cells (the endocardium). The

bulk of the chamber (the myocardium) comprises a network of striated muscle

cells, each separated by an intercalated disc. The heart is invested by patches

of adipose tissue and a layer of mesothelium (the epicardium). This layer of

epicardium forms the visceral aspect of the pericardial sac, which normally

contains a small volume of clear fluid to lubricate the surface during cardiac

contraction.

Venous blood from the systemic circulation, drain into the right atrium,

which contract during diastole to force the blood through the tricuspid valve

into the right ventricle. During systole the right ventricle contract, expelling the

blood through the pulmonary valve and into the pulmonary circulation. A

synchronous sequence event takes place on the left side: the pulmonary veins

drain oxygenated blood into the left atrium; in diastole the blood is forced

through the mitral valve; in systole the left ventricle contract to expel blood

through the aortic valve into the aorta. The atria on each side are of similar

dimensions, but the myocardium of the left ventricle is much thicker than that

of the right ventricle; this is commensurate with the relative systolic blood

pressure in the aorta and pulmonary artery trunk.15

The regular and coordinated contraction of the myocardium is

determined by the pacemaker cells in the sino-atrial (AS) and atrio-ventricular

(AV) nodes; the action propagates through the bundle of His and Purkinje

9

network. The electrical activity of the heart can be monitored on the skin

surface by electrocardiography (ECG).15

Myocardial cell contraction and relaxation is brought about by

changes in the concentration of cytosolic calcium. The cyclical contraction of

the heart is initiated by the spontaneous depolarization of the pacemaker cells

in the SA node during diastole.

The myocardium is supplied by the coronary arteries originating from

the root of the aorta just above the aortic valve cusps. The right coronary

artery supplies the right ventricle, the posterior part of the interventricular

septum, and part of the posterior wall of the left ventricle. The left coronary

artery, via its principal branches supplies the interior part of the interventricular

septum and most of the left ventricular myocardium. Blood flow through the

coronary arteries is maximal during diastole when the ventricular myocardium

is relaxed.15

The cardiac myocytes are permanent cells; if some die, as in

myocardial infarction, the others cannot regenerate to replace those that are

lost and the defect is repaired by fibrosis. Similarly, in either hypertension or

narrowing of the ventricular outflow tract, the myocardium of the appropriate

chamber becomes correspondingly thicker due the hypertrophy rather than

hyperplasia.15

1.2. Cardiac Failure:

Cardiac failure complicates all forms of severe cardiac diseases.

It exists when the heart is unable to pump blood at the rate required for normal

metabolism. In the early stages the pumping action of the heart may be

maintained by compensatory mechanism such as increased ventricular filling.

The clinical diagnosis of early, compensated heart failure is very difficult and

there is no laboratory test, which is helpful in this regard.15

10

Ischaemic heart disease, systemic hypertension and valvular heart

disease, either singly or in combination, is responsible for the vast majority of

clinical cases of cardiac failure.

1.3. Ischaemic Heart Disease:

Ischaemic heart disease result when the blood supply becomes

insufficient, because; either the blood supply is impaired or, the myocardium

becomes hypertrophic and makes a greater demand on the blood supply.

When the vessel lumen is more than 75% occluded, ischaemia develops.

Aerobic metabolism is essential, as there are very poor reserves of high-

energy phosphates. Cardiac muscle death occurs when tissue adenosine

triphosphate (ATP) levels are very low and when anaerobic glycolysis has

virtually ceased. As with other tissues, the precise cause of death is uncertain,

but lethal cardiac muscle injuries are associated with membrane damage and

the sudden entry of calcium into the cell cytoplasm. After brief periods of

ischaemia cardiac blood flow can be re-established. However, after a critical

interval reperfusion is impossible, as a result of swelling of capillary

endothelial cells.15

The sub-endocardial layers of the myocardium are at risk from

ischaemia. Even through there is a well developed sub-endocardial plexus of

blood vessels, flow in this part of the myocardium is restricted to diastole.

Blood vessels are collapsible tubes and are susceptible to compression when

tension within the myocardial wall increases. Ischaemia is produced by:

progressive atherosclerotic stenosis

atherosclerosis with superimposed thrombosis

haemorrhage into the intima beneath and around atherosclerotic

plaques.

Ischaemic heart disease can also result from low coronary arterial

perfusion. Shock, is a frequent cause of this. Some patient with anaemia can

develop symptoms of Ischaemic diseases.15

11

1.4. Acute Myocardial Infarction:

Acute myocardial infarction (AMI), commonly known as heart attack. The

term myocardial infarction comes from “myo” referring to muscles, “cardium”

referring to the heart and “infarction” meaning tissue death. As a disease

entity, Dr James Herrick described myocardial infarction in full in 1912.15

A myocardial infarction is an area of necrosis of heart muscles resulting

from a sudden reduction in the coronary blood supply. The commonest

precipitating cause is thrombosis superimposed on, or hemorrhage within, an

atheromatus plaque in an epicardial coronary artery.

1.4.1. Clinical Feature:

The most frequent symptom of myocardial infarction is central

chest pain, which is present in 2/3 of all cases. The chest discomfort may

radiate to the shoulders or arms, neck or the back and can be slight, moderate

or severe. Pain is usually accompanied by nausea, vomiting, shortness of

breath, diaphoresis, palpitation and dizziness. In at least 10% of patients,

myocardial infarction is painless or silent.

Some patients present with acute arrhythmia, mainly ventricular

fibrillation or ventricular taychcardia, but occasionally pulse less electrical

activity, which can rapidly lead to death if untreated.15

1.4.2. Morphology:

The location and size of the infract depends on:

the site of the coronary artery occlusion

the anatomical pattern of blood supply

the presence or absence of an anastomotic circulation within the

coronary arterial tree.

When coronary angiograms are performed in patients with signs of acute

myocardial infarction, a complete obstruction of a major coronary artery can

be demonstrated in up to 90% of cases within 3-4 hours of the initial episode

12

of pain. At later intervals fewer patients have complete obstructions,

suggesting that coronary artery spasm may also be involved. Coronary artery

thrombi may dissolve, and this may account for much lower incidence of

coronary thrombi observed when careful autopsies are performed on patients

dying of myocardial infarcts.

The chief features are necrosis, inflammatory cell infiltration and, as cardiac

muscle cannot regenerate, repair by fibrous tissue. The extensive necrosis of

cardiac muscle is associated with the release of cardiac enzymes into the

circulation. Most patients show a transient leukocytosis in the first 1-3 days.15

1.4.3. Complication:

Early detection and prompt treatment of complications is important in the

management of patients with myocardial infarction. Cardiac arrhythmias,

leading to ventricular fibrillation and sudden death, are frequent in the first 24-

48 hours after the initial infract. Pericarditis, mitral incompetence and cardiac

failure are the important complications in the first week after infraction.

I. Arrhythmias:

Ventricular fibrillation is by far the commonest cause of death in MI.

Primary ventricular fibrillation occurs in first 24 hours after infarction (usually

with the first hour) and is thought to be responsible for most sudden deaths.

Secondary ventricular fibrillation occurs some days later and is associated

with extensive infarction and a significantly reduced short-and long-term

prognosis. The occurrence of frequent premature ventricular beats after the

first month or so indicates a particular liability to ventricular fibrillation. By

involving the conducting system, MI may also cause various grades of heart

block and other arrhythmias.16

II. Cardiac failure:

Extensive infarction of left ventricular muscle can cause acute heart

failure. If this progresses to cardiogenic shock the mortality rate is 80%.

13

Infarction also predisposes to heart failure which may develop at any time

after infarction and indicates a poor prognosis.

III. Mural thrombosis:

Following acute myocardial infarction, release of tissue thomboplastin

from the damaged muscle, damage to the endocardium and localized adding

of blood predispose to mural thrombosis in the ventricles. This is seen at

autopsy in about 30% of cases who have had and MI, in patients who survive,

the thrombus is eventually organized systemic emboli can result from mural

thrombosis, but are less frequent than might be expected.

IV. Venous thrombosis:

Systemic venous thrombosis usually affecting the leg veins occurs in

up to 30% of cases but fatal pulmonary embolism is an uncommon cause of

death in myocardial infarction.

V. Rupture of infracted myocardium:

This occurs in about 5% of cases, at any time within the first ten days.

Most often the rupture occurs in the wall of the left ventricle and causes

hemopericardium and death from cardiac tamponate. Rupture of either the

interventricular septum or of a mitral papillary muscle may also occur,

precipitating or aggravating acute heart of failure. These compilations can be

confirmed and assessed using two-dimensional and Doppler

echocardiography. Surgery is lifesaving in selected cases but the mortality

rate is high.

VI. Cardiac aneurysm:

The healing infarct of the left ventricle may stretch to form a cardiac

aneurysm. This occurs in 12-15% of long-term survivors. Laminated thrombus

tends to form in the cavity and may cause embolism. The aneurysm impairs

ventricular function, causing cardiac failure which in some cases can be

corrected by surgical excision of the aneurysm.

14

VII. Angina pectoris:

In some patients angina pectoris dates from a myocardial infarction

because occlusion of a major coronary artery may render the surrounding

areas of myocardium chronically ischemic.

VIII. Recurrence of infarction:

Individuals who have had a myocardial infarct are prone to re-infarction

because of the underlying coronary artery disease. Cigarette smoking greatly

increases and beta blockers significantly reduce this risk.

IX. Post-infarction (Dressler’s) syndrome:

Occasionally patients may develop pericardial and pleural effusions a

raised ESR, fever and leucocytosis up to 10 weeks following infarction, raised

titers of myocardial antibodies and resolution of the symptoms following

corticosteroid therapy suggest and autoimmune response.16

1.4.4. Diagnosis:

The diagnosis of AMI was established by the World Health Organization

(WHO) in 1979, requiring the presence of two of the following three criteria:

History of severe and prolonged chest pain,

Unequivocal electrocardiographic (ECG) changes such as persistent

Q or QS waves and evolving injury lasting longer than one day, and

Unequivocal initial increase and subsequent decrease in the activity

of enzymes collected on serial basis. The change must be properly related to

the particular enzyme with the delay between onset of symptoms and blood

sampling.17

Because of the emergence of new biochemical markers, the

European Society of Cardiology and the American College of Cardiology

redefined the criteria for diagnosis of AMI in 2000 :

15

Typical increase and gradual decrease of troponin or more rapid

increase and decrease of creatine kinase (CK-MB) with at least one of the

following:

(a) ischemic symptoms,

(b) development of pathologic Q waves on the ECG,

(C)ECG change indicative of ischemia (ST-segment elevation or depression),

(d) coronary artery intervention;

Pathologic finding of an AMI.

It was recognized that many AMIs were missed by using the WHO

guidelines because of the reliance on clinical history and ECG, both of which

are present in only about half of all cases. The new guidelines place more

emphasis on biochemical markers.17

1.4.4.1. Electrocardiography (ECG):

The classical evaluation of ECG changes in Myocardial infarction is:

peaked (hyperacute) T waves,

ST segment elevation,

formation of Q waves and T waves inversion.

These changes may occur over a few hours to several days18. On the bases

of their associated ECG finding acute Myocardial infarction can be divided into

two groups:

I. Q wave infarction (transmural infarction):

In this type of Myocardial infarction pathological Q wave develop on ECG.

These infarction result from complete thrombotic occlusion of coronary artery

and manifest on ECG by symmetrically peaked T waves replaced after several

minutes by ST segment elevation.

II. Non- Q wave infarction (subendocardial infarction):

This type of infarction develops from high- grade but non-occlusive

thrombi (obstruction of coronary artery is not complete).

16

This infarction is associated with ST- segment depression and for T wave

inversion without evaluation of pathologic Q- wave. There is also some lost of

Q- waves in leads facing the infarct.18

1.4.4.2. Cardiac Markers:

I. Aspartate Aminotransferase (AST):

The first marker of myocardial damage was aspartate aminotransferase

(AST). Although serum assays for (AST) have high sensitivity for cardiac

disease, they are not specific, as increased activities can be observed in

patient with skeletal muscle disease, hemolysis, and chronic hepatocellular

diseases. Although (AST) has cytosolic and mitochondrial isoenzymes, their

measurement dose not improve the specificity of this assay, as they are not

tissue specific to the myocardium.17

II. Lactate Dehydrogenase (LDH):

Lactate dehydrogenase (LDH) is found in cytoplasm of all human cells,

tissues and organs. In addition to myocardial disease, increases in serum

(LDH) activities can be observed in patient with hemolysis, malignancy, and

diseases of liver, lung, skeletal muscle, and kidney. The five LDH isoenzymes

consist of tetrameric combinations of M and H subunits. Interest in LDH stems

from the fact that the heart contains high concentration of the LDH1 (H4)

isoenzyme. LDH has a molecular mass of 134 kDa, which is high relative to

other cardiac markers and this made it useful as a late marker of AMI. The

LDH activity in serum remains abnormal after MI for 5 days after onset.17

III. Creatine Kinase (CK):

Creatine kinase (CK) has two subunits of 84 kDa. After myocardial injury,

CK and other cytoplasmic proteins pass through the damaged cell membrane

and enter the cardiac lymphatics to the nodes positioned between the superior

vena cava and ascending aorta, and gradually drain into the systemic

17

circulation. The release of mitochondrial CK is further delayed because these

proteins must also pass through the mitochondrial membrane.

CK isoenzymes measurement is useful because skeletal muscle and

myocardial tissue have different distributions of the isoenzymes. cytoplasmic

CK consist of dimeric combinations of either M or B subunits in the three

major forms: MM, MB and BB. In addition, posttranslational modifications of

isoenzymes will produce at least three MM and two MB isoforms.

The CK-MM isoenzyme is the predominant form found in skeletal muscle,

with trace amount (1%) of CK-MB present. In the myocardium, CK-MM also is

found in the highest concentration; however, the percentage of CK-MB is 10 to

20 fold higher than that found in the skeletal muscle. Thus in patient with

acute myocardial damage, both the total CK and the ratio of CK-MB/total CK

are abnormal.

CK-BB is found in brain and sooth muscle and is the predominant form

found in fetal muscle. Increases in the BB isoenzyme are observed in patient

with cerebral disease, trauma and certain neoplasm.17

IV. Myoglobin:

Myoglobin is a low molecular mass heme protein (17.8 kDa) found in

skeletal muscle and heart. It constitutes 2% of the total muscle protein and is

found entirely within the cytoplasm. There are no tissue-specific isoenzymes,

thus the myoglobin released from the heart is indistinguishable from that

released from skeletal muscle tissue. After AMI, myoglobin appears in the

serum earlier than dose CK-MB because of its smaller size.17

V. Troponin:

Troponin is a regulatory protein complex located on the thin filament

(actin) of striated muscles. It consists of three subunits: troponin-T, 37kDa,

troponin-I,24kDa, and troponin-C,18kDa. The majority of intracellular troponin

of muscle cells exists as a ternary T-I-C complex that is bound to actin.

18

Because the tissue content of troponin is higher than that of CK-MB, troponin

is a more sensitive marker for cardiac damage.17

Troponin-I regulates striated muscle contraction by preventing the

binding of the myosin head to actin and thus inhibiting myosin ATPase activity.

TnI also serves to bind the actin filament TnC.

The function of TnT is to bind to tropomyosin and position the

Troponin complex along the actin filament. The isoforms have different amino

acid structures and are biochemically distinct and there fore can be

differentiated from one another of particular interest are the cardiac isoforms

of troponin-T (cTnT) and Troponin-I (cTnI). Cardiac troponin-T levels in serum

begin to rise within 3- 4 hours following the onset of myocardial damage, peak

in the 10 days to 14 days following an AMI.17 .

1.4.5. Treatment:

Multidrug treatment is routine to control the many problems associated

with cardiac disease. It usually consist of compensation of vasodilators,

diuretics, beta-blockers, calcium channel antagonists, cardiac glycosides and

anticoagulants.19

Coronary artery bypass graft surgery (CABG) was introduced in the late

1960s and has become a standard treatment for ischemic heart disease since.

Percutaneous transluminal coronary angioplasty (PTCA) is a surgical

procedure in which an angioplasty balloon is inserted into a coronary artery

and expanded. this should open the lumen of the obstructed vessel and

restore blood flow to the affected area.19

1.5. Lipids:

The major lipids present in the are fatty acids, triglycerides, cholesterol

and phospholipids . Other lipid soluble substances, present in much smaller

amounts but of considerable physiological importance, include steroid

hormones and fat-soluble vitamins.19

19

1.6. Fatty Acids:

They are straight-chain carbon compounds of varying lengths with

the carboxyl end to one end and the methyl to the other end. They may be

saturated containing no double bonds, monounsaturated with one, or

polyunsaturated with more than one, double bond. Fatty acids may be

esterified with glycerol to form triglycerides, or be nonesterified or free.19

1.7. Triglycerides:

They consist of glycerol esterified with three long-chain fatty acid. They are

present in dietary fat and can be synthesized in the liver and adipose tissue to

provide a source of stored energy. Triglycerides containing both saturated and

unsaturated fatty acids are important components of cell membranes.19

1.8. Cholesterol:

They are composed of a sterol nucleus with 27 carbon atoms. It can be

synthesized de novo from the accumulation of two carbon units. And it is the

precursor to many important steroids, such as bile acids and steroid

hormones. Cholesterol esters are produced by esterification of the third

carbon in the cholesterol molecule with a fatty acid.19

1.9. Phospholipids:

They are complex lipids, resembling triglycerides, but contain phosphate

and a nitrogenous base in place of one of the fatty acids. They are important

component of cell membranes.

A common feature of lipid is their limited solubility in water. So lipids

transport in the plasma in association with proteins. Albumin is the principle

carrier of free fatty acids; the other lipids circulate in complexes known as

lipoproteins.19

1.10. Apolipoproteins:

Apolipoproteins (apo) are structural protein elements in the amphipathic

shell of lipoprotein particles and help to keep the lipids in solution during

20

circulation through the blood stream. They interact with specific cell-surface

receptors and direct the lipids to the target organs and tissues in the body.

Apo-A is the major apo of HDL. Apo-B, which is responsible for the

binding of LDL to LDL-receptors is the functional protein for transporting

cholesterol to cells. Apo B is synthesized in two forms: Apo B-100 in the liver

and Apo B-48 in the intestine. Apo B-100 is found in VLDL, IDL and LDL,

whereas Apo B-48 is found in chylomicrons. Apo-E, which promotes binding of

lipoproteins to the LDL-receptor, is also associated both with transport of

cholesterol ester in plasma and with the redistribution of cholesterol in

tissues.19

1.11. Lipoproteins:

These consist of a non-polar core of triglyceride and cholesterol esters

surrounded by a surface layer of phospholipids, cholesterol and proteins

known as apolipoproteins. There are multiple subtypes of the apolipoproteins,

and each of the lipoprotein classes exists in a continuum of size of sizes and

densities because of differences in the contents of the core lipids. In addition

there is a long list of apolipoproteins.19 Figure 1.1 shows the structure of a

lipoprotein.

21

FIGURE 1.1:

1.12. Classification of Lipoproteins:

22

Lipoproteins are classified on the bases of their densities as

demonstrated by their ultracentrifugal separation. Density increases from

chylomicrons (CM, of lowest density) through lipoprotein of very low density

(VLDL), intermediate density (IDL) and low density (LDL) to high density

lipoproteins (HDL). HDL can be separated into two metabolically subtypes,

HDL2 and HDL3. Distinct sub-types of LDL(LDL-I,II and III in increasing order

of density) are also recognized. IDL are normally present in plasma in small

amounts but can accumulate in pathological disturbances of lipoprotein

metabolism. However, it is important to appreciate that the composition of the

circulating lipoproteins is not static. They in dynamic state with continuous

exchange of component between the various types.20

Lipoprotein(a), is an atypical lipoprotein of unknown function. It is larger

and more dense than LDL but has a similar composition, except that it contain

in addition one molecule of apo(a) for every molecule of apo (B-100). The

apolipoprotein(a) structure is analogous to plasminogen which dissolve clots.

It has been demonstrated in multiple studies that an elevated Lp(a) level

presents an increased risk for myocardial infarction.20 The composition of the

major lipoprotein is shown in table (1.1).

Table 1.1 The Composition of the Major Lipoprotein Complexes

23

Complex SourceDensity

(g/ml)

Protein

%

TGa

%

PLb

%

CEc

%

Cd

%

FFAe

%

Chylomicron Intestine <0.95 1.5 86 8 3 1 0

VLDL Liver 1.006 8.5 53 19 13 9 1

IDL VLDL 1.019 11 2 26 33 9 1

LDL VLDL 1.063 21 12 24 42 9 1

*HDL2

Intestine, liver

(chylomicrons ,

VLDLs)

1.125 34 10 38 25 7 0

*HDL3

Intestine, Liver

(chylomicrons,

VLDLs)

1.21 56 8 36 28 4 6

Albumin-FFAAdipose

tissue>1.281 99 0 0 0 0 100

aTriacylglycerols, bPhospholipids, cCholesteryl esters, dFree cholesterol, eFree fatty acids*HDL2 and HDL3 derived from nascent HDL as a result of the acquisition of cholesteryl esters

1.13. lipoprotein metabolism:

24

1.13.1. Chylomicrons(CM):

Chylomicrons are the major transport form of exogenous (dietary) fat.

Triglycerides (90% of CM) are removed from chylomicrons by the action of the

enzyme lipoprotein lipase (LPL) with the result that free fatty acids are

delivered to be used as energy or stored in various tissues. LPL is activated

by apoC-II which transferred to chylomicrons from HDL with esterified

cholesterol in exchange for triglyceride. The chylomicron remnants are cleared

from the circulation by hepatic uptake depending on recognition of apo E by

hepatic receptors (LDL-related receptor protein). Under normal circumstances,

chylomicrons cannot be detected in plasma in the fasting state.20

1.13.2. Very low density lipoproteins(VLDL):

VLDL are formed from triglycerides synthesized in the liver either do novo

or by re-esterification of free fatty acids. VLDL are the principal transport form

of endogenous triglycerides and removed by the action of LPL. As the VLDL

particles become smaller, phospholipids, tree cholesterol and apolipoproteins

are released from their surfaces and taken up by HDL, thus converting the

VLDL to denser particles, IDL. Cholesterol ester is transferred back to IDL in

exchange for triglyceride and more triglycerides removed by hepatic lipase

and IDL are thereby converted to LDL. Under normal circumstances, there are

very few IDL in the circulation because of their rapid removal or conversion to

LDL.20

1.13.3. Low density lipoproteins(LDL):

LDL are the principal carrier of cholesterol esters and they are formed

from VLDL via IDL. Free cholesterol also stimulates its own esterification by

stimulating the enzyme acyl CoA:cholesterol acyl transferase(ACAT).

LDL receptors are saturable and subject to down regulation by an

increase in intracellular cholesterol. Macrophages can take up LDL via

scavenger receptors. This process occurs at normal LDL concentrations but is

25

enhanced when LDL concentration are increased and by modification of LDL.

Uptake of LDL by macrophages in arterial wall is an important event in the

pathogenesis of atherosclerosis. When macrophages becomes overloaded

with cholesterol esters, they are converted to "foam cells" the basic

component of atheromatous plaques. LDL concentrations increase during

childhood and reach adult level after puberty.20

1.13.4. High density lipoproteins(HDL):

HDL are synthesized primarily in the liver and, to lesser extent, in small

intestines, as a precursor (nascent HDL). The free cholesterol is esterified by

the enzyme lecithin-cholesterol acyltransferase (LCAT), this increases the

density of the HDL particles, which are thus converted from HDL3 to HDL2.

cholesteryl esters are transferred from HDL2 to remnant particles in exchange

for triglyceride, and also are taken up by the liver in chylomicron and IDL

remnant and excreted in bile. The HDL2 is converted back to HDL3 by the

removal of triglycerides by the enzyme hepatic lipase. Some HDL2 is removed

from the circulation by the liver, through receptors that recognize apo A-I.

Thus HDL has two important functions: it is a source of apoproteins for

chylomicrons and VLDL, and it mediates reverse cholesterol transport from

senescent cells and other lipoproteins and transferring it to remnant particles,

which are up by the liver.20

1.13.5. Lipoprotein Receptors:

The most important mechanism involving lipoprotein metabolism is the

interaction between apolipoproteins on the lipoprotein surfaces and the

receptors on various cell surfaces. Lipoprotein receptors are plasma

membrane proteins that are capable of binding with high affinity to circulating

lipoprotein particles through their interaction with apolipoproteins. The

following paragraphs discuss the major receptors.

I. LDL Receptors (LDLs):

26

LDLs are the principal plasma carriers of cholesterol delivering cholesterol

from the liver (via hepatic synthesis of VLDL) to peripheral tissues, primarily

the adrenals and adipose tissue. LDLs also return cholesterol to the liver. The

cellular uptake of cholesterol from LDLs occurs following the interaction of

LDLs with the LDL receptor (also called the apoB-100/apoE receptor). The

sole apoprotein present in LDLs is apoB-100, which is required for interaction

with the LDL receptor.20

The LDL receptor is a polypeptide of 839 amino acids that spans the

plasma membrane. An extracellular domain is responsible for apoB-100/apoE

binding. The intracellular domain is responsible for the clustering of LDL

receptors into regions of the plasma membrane termed coated pits. Once LDL

binds the receptor, the complexes are rapidly internalized. ATP-dependent

proton pumps lower the pH in the endosomes, which results in dissociation of

the LDL from the receptor. The portion of the endosomal membranes

harboring the receptor are then recycled to the plasma membrane and the

LDL-containing endosomes fuse with lysosomes. Acid hydrolases of the

lysosomes degrade the apoproteins and release free fatty acids and

cholesterol. As indicated above, the free cholesterol is either incorporated into

plasma membranes or esterified and stored within the cell.20

The level of intracellular cholesterol is regulated through cholesterol-

induced suppression of LDL receptor synthesis and cholesterol-induced

inhibition of cholesterol synthesis. The increased level of intracellular

cholesterol that results from LDL uptake has the additional effect of activating

ACAT, thereby allowing the storage of excess cholesterol within cells.

However, the effect of cholesterol-induced suppression of LDL receptor

synthesis is a decrease in the rate at which LDLs and IDLs are removed from

the serum. This can lead to excess circulating levels of cholesterol and

cholesteryl esters when the dietary intake of fat and cholesterol exceeds the

27

needs of the body. The excess cholesterol tends to be deposited in the skin,

tendons and, more gravely, within the arteries, leading to atherosclerosis.20

II. Remnant Receptors:

Remnant receptors recognize apo E and are the major receptors for the

clearance of chylomicron remnants and VLDL from blood circulation.19

III. Scavenger Receptors:

Scavenger receptors can be found on the surfaces of macrophages and

muscle cells. These receptors mediate the removal of modified LDL from

blood circulation. Macrophages can take up cholesterol from modified LDL

through scavenger receptors, resulting in cholesterol accumulation and the

formation of foam cells, which is the hallmark of early atherosclerotic lesions.19

1.14. Disorders of lipid metabolism:

Most common disorders of lipid metabolism are associated with

hyperlipidaemia. Very rare inherited disorders may be associated with

accumulation of lipid in tissues and not in plasma. The accumulation of lipid in

tissues is usually the result of severe and prolonged hyperlipidaemia and

causes cell damage.21 Lipid may accumulate in:

I. Arterial walls. This is the most important manifestation of lipid

disorders producing atherosclerosis. Atherosclerosis is due to distortion and

obstruction of the artery which may result from calcification and ulceration of

plaques. The small lipoproteins LDL and IDL are atherogenic.

II. Subcutaneous tissue, causing xanthomatosis. The nature of the lipid

fraction most affected usually determines the clinical appearance:

Eruptive xanthomata are small, itchy, yellow nodules. They are

associated with very high plasma VLDL or chylomicron (triglyceride)

concentrations, which disappear if plasma lipid concentrations fall to normal;

Tuberous xanthomata are yellow plaques found over the elbows and

knees. They are associated with high plasma concentrations of IDL;

28

Xanthelasma are lipid deposits under the periorbital skin and may be

associated with high plasma LDL concentrations.

III.Tendons. Xanthomata, usually on the Achilles tendons or the extensor

tendons of the hands, occur in familial hypercholesterolaemia;

IV. Cornea. Corneal arcus may be caused by deposition of lipid and

associated with high plasma LDL concentrations.

There is a positive correlation between the risk of developing ischaemic

heart disease and a raised plasma total cholesterol and LDL concentrations

and a negative one with plasma HDL. Hypercholesterolaemia is one of the

major risk factors of cardiovascular disease; others include smoking and

hypertension.21

1.14.1. Predominant hypercholesteraemia:

Plasma cholesterol levels at birth are usually below 100 mg/dl (2.5

mmol/l). they increase during the first year of life, but not exceed 160 mg/dl (4

mmol/l) in children. in most affluent populations plasma levels increase after

the second decade, more in men than in women during the reproductive

years. The upper limit of the reference range in many societies is about 330

mg/dl (8.5 mmol/l) in the fifth and sixth decades. It is likely that the

progressive rise in plasma cholesterol levels reflect a decreasing

concentration of LDL receptors in the liver. The risk of developing

cardiovascular disease increase as the plasma cholesterol level rise above

about 200 mg/dl (5.2 mmol/l).21

It is almost always due to a raised plasma LDL concentration, or the

development of a disorder that affects plasma LDL concentrations.

29

1.14.2. Secondary hypercholesterolaemia:

The commonest disorders that may cause a secondary increase in

plasma total and LDL-cholesterol levels are:

Primary hypothyroidism;

Diabetes mellitus;

Nephritic syndrome;

Cholestasis;

Some drugs.

1.14.3. Primary hypercholesterolaemia:

the familial incidence of hypercholesterolaemia, often associated with an

increased risk of ischaemic heart disease. The following two disorders

associated with moderate to severe hypercholesterolaemia, the pattern of

inheritance is autosomal dominant.21

I. Familial combined hyperlipidaemia, is associated with excessive

hepatic production of apoB, and therefore of LDL, and VLDL-triglyceride

synthesis due to either primary or secondary disorder. The lipid abnormalities

become apparent after the third decade. High plasma triglyceride level may

cause eruptive xanthomata.21

II. Familial (monogenic) hypercholesterolaemia, is caused by a LDL

receptor defect. The reduced cellular uptake of LDL by the liver causes an

increase in plasma total and LDL-cholesterol concentrations.

In homozygotes LDL receptors are virtually absent and plasma LDL-

cholesterol concentrations are three or four times higher than those in normal

subjects; patient rarely survive beyond the age of 20 and usually die from

ischaemic heart disease.

In heterozygotes the number of LDL receptors is reduced by about

50% and the plasma cholesterol concentrations are about twice those in

normal subjects.21

30

1.14.4. Predominant hypertriglyceridaemia:

Elevated plasma triglyceride levels may be due to an increase in

plasma VLDL or chylomicrons or both. Hypertriglyceridaemia is usually

secondary to another disorders. Primary hypertriglyceridaemia is less

common than hypercholesterolaemia.

I. Familial combined hyperlipidaemia, has been discussed above.

One-third of affected individuals have raised plasma VLDL concentration.

II. Familial endogenous hypertriglyceridaemia, is caused by

hepatic triglyceride overproduction with increased VLDL secretion. The

condition is transmitted as an autosomal dominant trait and usually apparent

after the fourth decade. It may be associated with:

Obesity;

Glucose intolerance;

Decrease in plasma HDL-cholesterol levels;

Hyperuricaemia.

Hyperchylomicronaemia is usually due either to an acquired or inherited

deficiency of lipoprotein lipase. Insulin is needed for optimal enzyme activity.

Consequently, hyperchylomicronaemia may occur in poorly controlled diabetic

patients. It may also be found with acute pancreatitis.21

1.14.5. Mixed Hyperlipidaemia:

Raised plasma concentrations of both cholesterol and triglycerides are

commonest in patients with poorly controlled diabetes mellitus, severe

hypothyroidism or the nephrotic syndrome.

The commonest primary cause is familial combined hyperlipidaemia with

elevated plasma LDL and VLDL concentrations. Less commonly, mixed

hyperlipidaemia may be caused be the accumulation of IDL and chylomicron

remnants in plasma.21

31

1.15. Treatment of Hyperlipidaemia:

Secondary causes of hyperlipidaemia and aggravating factors should be

treated. And the diet should be regulated and obese patients encouraged to

reduce body weight.

1.15.1. Treatment of Hypercholesterolaemia:

Restriction of dietary animal fats products reduces the intake of both

cholesterol and saturated fatty acids.

Drugs treatment includes:

Bile-salt sequestrants, such as cholestyramine and colestipol. These

are resins that bind bile salts in the intestinal lumen and prevent their

reabsorption and reutilization and so stimulate the hepatic synthesis of

cholesterol and the hepatic cell content is decreased. The increase of hepatic

LDL receptors lead to a fall in plasma LDL concentrations;

Hydroxyl-methyl glutaryl coenzyme A reductase inhibitors

(Simvastatin or Lovastatin), inhibit the enzyme in the cholesterol synthetic

pathway and so reduce endogenous production. As the intracellular level of

cholesterol falls the rate of synthesis of LDL receptors increases, with a

consequent fall in plasma LDL-cholesterol concentration;

Nicotinic acid may VLDL secretion and therefore the formation of

LDL. It also reduces the plasma level of lipoprotein(a).21

1.15.2. Treatment of Hypertriglyceridaemia:

Dietary restriction may be the only treatment need:

Triglyceride restriction may be effective in lowering plasma

chylomicron concentrations;

Carbohydrate restriction reduces endogenous triglyceride

synthesis and can be used to treat high VLDL concentrations.

Fibric acid derivitives are a group of drugs that activate lipoprotein lipase,

and so increase the rates of clearance of VLDL and chylomicrons from the

32

plasma. They also lower LDL-cholesterol by enhancing liver uptake and

increase HDL-cholesterol.21

33

CHAPTER TWO

THE OBJETIVES OF THE STUDY

This study aims to:

assess the levels of serum triglyceride, cholesterol, HDL and LDL

lipoproteins in Sudanese subjects with myocardial infarction;

compare the mean of serum lipoproteins levels in patients with that

of the normal subject;

evaluate the significance of using serum lipoproteins levels in

diagnosis of the acute phase of myocardial infarction;

estimate the normal range of serum lipoproteins in healthy control

subjects;

study the variations of serum lipoproteins level with reference to

some risk factors i.e. diabetes mellitus, family history, and

hypertension.

34

CHAPTER THREE

MATERIALS AND METHODS

3.1. Patients and Controls:

The study was carried in 20 patients (12male and 8 female) aged

between 40 to 70 years, admitted to intensive coronary care unit of El Shaab

Teaching Hospital during the period January -April 2006 with acute myocardial

infarction. The diagnosis of MI was established by clinical, ECG, serum

cardiac enzymes and troponin examination. None of the patients had thyroid

dysfunction, liver or kidney disease. Only those patients where finally included

who were not taking any hypolipidemic drug. A separated samples of 10

healthy subjects (5 males and 5 females) was taken a control group.

3.2. Sample Collection:

Blood samples (3mL) were taken as soon as possible after admission (the

first 48 hours after chest pain) form each patients as well as control subjects

using disposable syringes. All blood samples were allowed to clot at room

temperature and then centrifuged at 4000 R.P.M to obtain the serum.

Specimens of serum were preserved at 2-8 C ْ prior to processing. The clear

serum was taken immediately for analysis of cardiac markers or stored at 2-8

Cْ for 24 hrs.

3.3. Estimation of Lipid Profile:

Cholesterol, triglyceride, HDL and LDL were estimated by using

automated microprocessor-controlled robotic chemistry analyzer.

All patients and control subjects samples were labeled and placed in

bar-coded sample cup holders and included in test panel on the automated

chemistry analyzer. Serum total cholesterol, serum HDL-cholesterol, serum

LDL-cholesterol and triglyceride were measured by readymade kits using

enzymatic method.

35

3.3.1. EQUIPMENTS:

I. Chemistry Analyzer (HITACHI-902), ROCHE Diagnostics Co;

LTD. USA.

II. Centrifuge (C-700), APEL Co; LTD. Tokyo. Japan.

III. Disposable Syringes, JK Medical Equipment Co; LTD. China.

IV. Plane containers, JK Medical Equipment Co; LTD. China.

3.3.2. REAGENTS: DIALAB Production Co; Austria.

I. Total cholesterol Reagent (1):

Good's Buffer, PH 6.7 50 mmol/L Phenol 5 mmol/L 4-Aminoantipyrine 0.3 mmol/L Cholesterol Esterase ≥ 200 U/L Cholesterol Oxidase ≥ 50 U/L Peroxidase ≥ 3 U/L

II. HDL-cholesterol reagents: Reagent (2):

Good's Buffer, PH 7.0 30 mmol/L 4-Aminoantipyrine 0.9 mmol/L Peroxidase 2400 U/L Ascorbate Oxidase 2700 U/L Anti-human β-lipoprotein Ab.

Reagent (3)

Good's Buffer, PH 7.0 30 mmol/L Cholesterol Esterase 4000 U/L Cholesterol Oxidase 20000 U/L N-ethyl(2-hydroxy-3-sulfopropyl)-dimethoxy-

flouroaniline,sodium salt 0.8 mmol/L

III. LDL-cholesterol reagents: Reagent (4)

Good's Buffer, PH 6.8 25 mmol/L Cholesterol Esterase 5000 U/L Cholesterol Oxidase 5000 U/L

2-Hydroxy sulfopropyl dimethoxyaniline 0.64 mmol/L

36

Catalase 1000 KU/L Reagent (5):

Good's Buffer, PH 7.0 25 mmol/L 4-Aminoantipyrine 3.4 mmol/L Peroxidase 20 KU/L Sodium azide 0.1%

IV. Triglyceride Reagent (6):

Good's Buffer, PH 7.0 25 mmol/L ATP 1.0 mmol/L 3-Hydroxy tribomobenzoic acid 2.0 mmol/L Glycerophosphate oxidase ≥ 2000 U/L Lipase ≥ 200 KU/L Gkycerol Kinase 6000 U/L Peroxidase ≥ 500 U/L Sodium azide 0.1%

3.4.1. Estimation of cholesterol:

PRINCIPLE:

Cholesterol-esters were hydrolyzed by Cholesterol esterase to fatty

acids and cholesterol, which then converted to cholestenone and H2O2 by

the action of Cholesterol oxidase. The hydrogen peroxide then catalyzed by

peroxidase to yield a red colored quinonimine. The intensity of the pink/red

color is proportional to the cholesterol concentration in the sample.

PROCEDURE:

The automated chemistry analyzer was programmed to operate the

procedure automatically as follow: Specimens of serum or cholesterol

standard (10µL) were added to 1.0ml of the working reagent (1) and

incubated for 10 minutes at 37 ْC. The absorbance (A) of the sample and

the standard were measured at 500nm against the blank with a 500nm

filter. The measured absorbances converted to estimate concentrations

using stored data base.

3.4.2. Estimation of HDL-CHOLESTEROL:

37

PRINCIPLE:

Separation of the lipoprotein fractions is achieved by adding antibodies,

which absorb to the surface of chylomicrons, VLDL and LDL. In a second

step, added detergent breaks up the HDL lipoproteins, and therefore

making HDL-cholesterol available for quantitation, using an enzymatic

system.

The intensity of the blue color is proportional to the cholesterol

concentration in the sample.

PROCEDURE:

The automated chemistry analyzer was programmed to operate the

procedure automatically as follow: Specimens of serum or HDL-cholesterol

standard (10µL) were added to 900 µL of the working reagent (2) and

incubated for 5 minutes at 37 ْC. The absorbance (A1) of the sample and

the standard were measured against reagent blank at 500nm, then 300 µL

of reagent (3) was added and incubated for 5 minutes at 37 ْC and the

absorbance (A2) of the sample and the standard were measured.

The measured absorbances converted to estimate concentrations

using stored data base.

38

LDL, VLDL, Chylomicrons Ah β-L Ab HDL + Ag-Ab complex

HDL + H2O + O2 CHE& CHO cholesten + fatty acid + H2O2

H2O2 + DAOS + 4-Aminoantipyrine POD blue colored complex + H2O

3.4.3. Estimation of LDL-CHOLESTEROL:

PRINCIPLE:

Non LDL-lipoproteins were enzymatically processed, while LDL was

selectively protected (in the first incubation with reagent 3). In the second

step LDL was released and selectively determined.

The intensity of the blue color is proportional to the LDL-cholesterol

concentration in the sample.

PROCEDURE:

The automated chemistry analyzer was programmed to operate the

procedure automatically as follow: Specimens of serum or LDL-cholesterol

standard (10µL) were added to 900 µL of the working reagent (4) and

incubated for 5 minutes at 37 ْC. The absorbance (A1) of the sample and

the standard were measured against reagent blank at 500nm, then 300 µL

of reagent (5) was added and incubated for 5 minutes at 37 ْC and the

absorbance (A2) of the sample and the standard were measured. The

measured absorbances converted to estimate concentrations using stored

data base.

39

(1)

LDL + protecting reagent(4) protected LDL

HDL,VLDL,chylomicrons CHO CHE cholestenone + H2O2

H2O2 + Catalase H2O

(2)

protected LDL + releasing reagent(5) LDL-cholesterol

LDL-cholesterol CHO CHE cholestenone + H2O2

H2O2 + DAOS + 4-Aminoantipyrine POD blue colored complex + H2O

3.4.4. Estimation of triglyceride:

PRINCIPLE:

Triglycerides in the sample were hydrolyzed by lipase to fatty acids

and glycerol, which then phosphorylated by ATP to glycerol-3-phosphate

and ADP in a reaction catalyzed by glycerol kinase. Glycerol-3-phosphate

was then converted by the action glycerophosphate oxidase into

dihydroxyacetone phosphate and hydrogen peroxide, which was catalyzed

by peroxidase to yield a red colored quinonimine. The intensity of the

pink/red color is proportional to the triglyceride concentration in the sample.

PROCEDURE:

The automated chemistry analyzer was programmed to operate the

procedure automatically as follow: Specimens of serum or cholesterol

standard (10µL) were added to 1.0ml of the working reagent (6) and

incubated for 10 minutes at 37 ْC. The absorbance (A) of the sample and

the standard were measured at 500nm against the blank with a 500nm

filter. The measured absorbances converted to estimate concentrations

using stored data base.

3.5. Statistical Analysis:

Appropriate descriptive and analytical statistical procedures were

followed using statistical package for social sciences (SPSS. Version 10).

Independent samples T-test was applied to compare the levels of total

cholesterol, HDL-cholesterol, LDL-cholesterol, triglyceride and Troponin in

study groups of AMI patients and control healthy subjects. Association of

serum lipids with other variables had been studied using correlation

analysis. The level of significance was expressed as (P <0.05).

40

CHAPTER FOUR

RESULTS

4.1. Study Group:

In the present study, a total number of 20 patients (12male and 8

female) aged between 40 to 70 years, admitting to intensive coronary care

unit of El Shaab Teaching Hospital during the period January -April 2006

had been enrolled for the assessment of the serum lipids. The level of

serum lipids of patients and control groups of healthy subjects was

measured using automated microprocessor-controlled robotic chemistry

analyzer.

As illustrated in figures (4.1.) and (4.2.) the patients and also the

control subjects had an average age of 56 year with a range of 40-70year.

About 30%(n=6) of patients had diabetes mellitus, 60%(n=12) of

patients were hypertensive and 30 %(n=6) of patients had family history of

cardiac disease as showed in figures (4.3),(4.4) and(4.5) respectively.

4.2. Estimation of total cholesterol:

The male patients showed total cholesterol levels with the mean197±34

mg/dL, and the mean of male control subjects levels was163±24 mg/dL.

while female patients had the mean of202±69 mg/dL, and the mean of

female control subjects levels was179±23 mg/dL.

4.3. Estimation of HDL-cholesterol:

The male patients had HDL-cholesterol levels mean 56±16 mg/dL, and the

mean of male control subjects levels was 44±6 mg/dL. While female

patients showed the mean 52±14 mg/dL, while the mean of female control

subjects levels was 54±10 mg/dL.

4.4. Estimation of LDL-cholesterol:

The male patients had LDL-cholesterol levels with the mean 122±31

mg/dL, and the mean of male control subjects levels was105±25 mg/dL.

41

while female patients showed the mean 137±54 mg/dL, while the mean of

female control subjects levels was114±32 mg/dL.

4.5. Estimation of triglyceride:

The male patients showed triglyceride levels with the mean 186±139

mg/dL, while the mean of male control subjects levels was 80±61 mg/dL.

The female patients showed triglyceride levels with the mean 120±45

mg/dL, while the mean of female control subjects levels was56±62 mg/dL.

42

AGE(years)

70.065.060.055.050.045.040.0

6

5

4

3

2

1

0

Std. Dev = 9.19

Mean = 56.3

N = 20.00

FIGURE 4.1: Age distribution in study groups of patients

43

AGE(years)

70.065.060.055.050.045.040.0

3.5

3.0

2.5

2.0

1.5

1.0

.5

0.0

Std. Dev = 10.34

Mean = 56.3

N = 10.00

FIGURE 4.2: Age distribution in control subjects

44

CONTROLAMI

Co

un

t

30

20

10

0

diabetes

no

yes

10

14

6

FIGURE 4.3: Comparison of diabetes in study groups of AMI with control subjects.

45

CONTROLAMI

Co

un

t

30

20

10

0

hypertension

no

yes

10

8

12

FIGURE 4.4: Comparison of hypertension in study groups of AMI with control subjects.

46

CONTROLAMI

Co

un

t

30

20

10

0

family history

no

yes

10

14

6

FIGURE 4.5: Comparison of family history in study groups of AMI with control subjects.

47

Table 4.1: Multiple Comparisons of lipid profile level (mg/dL) in

study subgroups of patients with AMI and control subjects

Independent Samples Test

3.900 .058 1.672 28 .106 28.200 16.866

1.999 27.409 .056 28.200 14.105

1.981 .170 1.018 28 .317 5.350 5.253

1.180 26.132 .249 5.350 4.534

2.402 .132 1.097 28 .282 15.650 14.271

1.260 25.713 .219 15.650 12.422

.887 .354 2.380 28 .024 92.500 38.864

2.911 27.914 .007 92.500 31.774

.130 .721 .597 28 .556 .211 .354

.620 20.032 .542 .211 .341

.018 .894 .273 28 .787 7.830E-02 .286

.279 19.149 .783 7.830E-02 .280

Equal variancesassumed

Equal variancesnot assumed

Equal variancesassumed

Equal variancesnot assumed

Equal variancesassumed

Equal variancesnot assumed

Equal variancesassumed

Equal variancesnot assumed

Equal variancesassumed

Equal variancesnot assumed

Equal variancesassumed

Equal variancesnot assumed

T.cholesterol(mg/dL)

HDL(mg/dL)

LDL(mg/dL)

Triglyceride(mg/dL)

RTCHDL

RLDHDL

F Sig.

Levene's Test forEquality of Variances

t df Sig. (2-tailed)Mean

DifferenceStd. ErrorDifference

t-test for Equality of Means

48

Table 4.2: Relationship of lipid profile levels in study groups of AMI with control subjects

Correlations

1.000

.

30

-.301

.106

30

-.189

.317

30

-.203

.282

30

-.410*

.024

30

Pearson Correlation

Sig. (2-tailed)

N

Pearson Correlation

Sig. (2-tailed)

N

Pearson Correlation

Sig. (2-tailed)

N

Pearson Correlation

Sig. (2-tailed)

N

Pearson Correlation

Sig. (2-tailed)

N

Study group

T.cholesterol(mg/dL)

HDL(mg/dL)

LDL(mg/dL)

Triglyceride(mg/dL)

Study group

Correlation is significant at the 0.05 level (2-tailed).*.

49

CHAPTER FIVE

DISCUSSION

The study dealt with myocardial infarction patients admitted to

Intensive Coronary Care Unit of El Shaab Teaching Hospital. Soon after

hospital admission, blood samples were taken form patients for measuring

lipid profile. The majority of patients admitted ICCU of El Shaab Hospital

suffering from chest pain attack were at advanced ages with range of 40 -

70 years. These findings are in agreement with the result of who claimed

that cardiovascular disease is associated with old age than younger.

The study also revealed that clinical assessment showed that about

30% of patients who diagnosed, as having Myocardial infarction were

diabetic, about 30% of patients had family history and about 60% are

hypertensive.

The study found no significant difference in serum total cholesterol

levels in patients with acute MI when compared with healthy control

subjects(p>0.05) table4.1. While confirming the findings of Berlin19 and

Heldenberg et al.11, the study provides information which is in direct

contrast to that by others who found either a decrease2,4,6,9,10 or an

increase20 during the acute phase of MI. Moreover, the pattern was almost

the same in males and females.

Although there was a decrease in HDL-cholesterol levels when

compared with control subjects but it failed to reach statistical significance

(p>0.05) table4.1. Heldenberg et al.11 also reported no significant

difference. In contrast to our findings other studies have shown either a

rise10 or a decrease9 in HDL.

LDL-cholesterol, in this study, recorded no significant difference when

compared with control subjects(p>0.05) table4.1. However, a significant

decrease in LDL following MI has been reported by others8,9.

50

Serum triglycerides showed a significant increasing levels after MI

when compared with control subjects(p<0.05) table4.1. This finding was in

accordance with those mentioned by others8,11. On the contrary, Vetter et

al.23 recorded a progressive fall in triglycerides levels after MI and Ryder et

al.9 found no significant difference in triglycerides. The mechanism of

increase in triglycerides after MI may be due to elevated flux of fatty acids

and impaired removal of VLDL from the plasma12. Another possible

mechanism for elevated triglycerides levels may be the effect of β-blockers

but this contention seems to be invalid for increased triglycerides levels on

the first week as β-blockers take about two weeks to show their effect on

serum lipids27.

Several studies have advocated the value of ratios of LDL/HDL and

total-cholesterol/HDL as a correlate of the severity and extent of coronary

artery stenosis22,24,25. The present study showed no significant differences in

the ratios of LDL/HDL and total-cholesterol/HDL in the patients when

compared with control subjects(p>0.05) table4.1. while others found an

increase in these ratios27.

51

CHAPTER SIX

CONCLUSIONS & RECOMMENDATIONS

The study reveals some significant alterations in triglycerides after MI.

However, we did not find significant differences in serum total cholesterol,

LDL and HDL. To the best of my knowledge there is no such study

available in Sudanese subjects residing in Sudan. The mechanism of these

changes is still not clear. Could it be a metabolic effect of stress, hormones

etc.? One recent study has shown that acute myocardial infarction causes

a profound up regulation of cholesterol synthesis as acute phase response

and the observed plasma cholesterol levels after acute myocardial

infarction must, therefore, be explained by the parallel increase of LDL

receptor activity and thus increased cholesterol catabolism26.

The mechanistic aspect of these changes deserves further

investigations of apolipoproteins, lipoprotein(a) and lipoprotein-receptors

with larger number of patients including patients with unstable angina and

atherosclerosis.

52

CHAPTER SEVEN REFERENCES

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patients with myocardial infarction and normal control group. Acta.

Med. Scand. 156,493-497.

2. Bjorntrop, P. and Mmalmcrone, R. (1960) Serum cholesterol in

patients with myocardial infarction in younger ages. Acta. Med.

Scand. 168,151-155.

3. Dodds, C. and Mills, G.L. (1959) Influence of myocardial infarction on

plasma lipoprotein concentration. Lancet i,1160-1163.

4. Tibblin, G. and Cramer, K. (1963) Serum lipids during the course of

acute myocardial infarction and one year afterwards. Acta. Med.

Scand. 192,523-528.

5. Fyfe, T., Baxter, R.H., Cochran, K.M. and Booth, E.M. (1971) Plasma

lipid changes after myocardial infarction. Lancet ii, 997-1001.

6. Kerkeby, K. (1972) Disturbances in serum lipids and in their fatty acid

composition following acute myocardial infarction. Acta. Med. Scand.

192,523-528.

7. Avogaro, A., BittilinBon, G., Cazzalato, C., Quinci,G.B., Sanson, A.,

Sparla, H. and Zagatti, G.C.(1978) Variation in apolipoproteins B and

A during the course of myocardial infarction. Eur. J. Clin. Invest.

8,121-129.

8. Ballantyne, F.C., Melville.D.A., Mc Kenna, J.P. and Morrison, B.A.

(1979) Response of plasma lipoproteins and acute phase proteins to

myocardial infarction. Clin. Chem. Acta 99,85-92.

9. Ryder, R.E., Hayes, T.M. and Owens, D.R. (1984) How soon after

myocardial infarction should plasma lipid values be assessed? Br.

Med. J. 289,1651-1653.

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