tests associated with cardiac disorders
DESCRIPTION
Tests associated with cardiac disordersTRANSCRIPT
TESTS ASSOCIATED
WITH CARDIAC DISORDERS
Cardiac disorders :
primary diagnosis :Auscultation.
Detecting abnormal heart sounds.
Blood pressure – sphygmomanometer.
SIGNS AND SYMPTOMS:
Chest pain.
Dyspnea with or without orthopnea.
Paroxysmal nocturnal dyspnea.
Cyanosis.
Fatigue.
Palpitations.
Cough.
Edema.
Syncope.
Abnormal heart sounds.
DIAGNOSIS OF CARDIAC DISORDERS:
Heart sounds
Laboratory tests
Chest X-ray
Electrocardiogram
Ambulatory ECG Monitoring
Echocardiogram
Doppler echocardiography
Transoesophageal echocardiography
Cardiac catheterisation
Angiography
Computed tomography
Magnetic resonance imaging
Radiology
Radionuclide imaging
HEART SOUNDS: Stethoscope is the commonest instrument used. FIRST SOUND: (L-U-B-B) Occurs at the onset of ventricular systole.o DURATION: 0.1 – 0.17 seco CAUSES: Occurs due to sudden closure of the AV valves. Ejection of blood from the ventricles & the vibration transmitted to the walls of the pulmonary artery & aorta.
o SIGNIFICANCE: Indicate the condition of myocardium. Indicates proper closing of AV valves.o CLINICAL IMPLICATIONS: INCREASED FIRST SOUND: Hypertrophy. SHORT & LOW PITCHED FIRST SOUND: Myocardial weakness.
SECOND SOUND: (DUP)
Occurs at the onset of the diastole.
o DURATION: 0.1 -0.14 sec
o CAUSES:
Caused by the sudden closure of the semi lunar valves in the aorta & pulmonary artery.
o SIGNIFICANCE:
Indicates the end of systole & beginning of diastole.
Its pitch is directly proportional to the BP.
Indicates proper closing of semilunar valves.
o CLINICAL IMPLICATIONS:
DECREASED DIASTOLIC PERIOD: ( PAUSE)
Increased heart rate.
THIRD SOUND:
o DURATION: 0.04 sec
o CAUSES:
Sudden rush of atrial blood.
o SIGNIFICANCE:
Indicates ventricular filling.
FOURTH SOUND:
o DURATION: 0.01 sec
o CAUSE:
Contraction of atria
o SIGNIFICANCE:
Indicates the ending of ventricular filling.
LABORATORY TESTING :
1. BLOOD TESTS :
SERUM CHOLESTROL :
o Total cholesterol : 150 – 200 mgs
o TGL : Up to 170 mgs
o HDL : 35 – 55 mgs
o LDL : Up to 170 mgs
o VLDL : 20 – 40 mgs
CLINICAL IMPLICATION :
• Elevated cholesterol level (HYPERCHOLESTEROLEMIA )
Coronary heart disease
Hypothyroidism
Diabetes mellitus
Cholestasis
Hepatocellular disease
Biliary cirrhosis
Glomerulonephritis
Werner’s syndrome
Obesity
Chronic renal failure
• Decreased cholesterol level: ( HYPOCHOLESTEROLEMIA )
Myleoproleferative diseases
Hyperthyroidism
Malnutrition
Megaloblastic anemia
Severe burns
Inflammation
Infection
Chronic obstructive lung disease
Mental retardation
HIGH DENSITY LIPOPROTEIN CHOLESTEROL :
Normal value : 35 -55 mgs
CLINICAL IMPLICATIONS :
o ↓ HDL-C Values:
Uremia
Hepatocellular disease
Chronic renal failure
Cholestasis
Diabetes mellitus
o ↑ HDL-C Values:
Atherosclerosis
Myocardial occlusion
LOW DENSITY LIPOPROTEIN (LDL)
Normal value : Up to 170 mgs
CLINICAL IMPLICATIONS :
o Increased LDL levels:
Premature CHD
Hyperlipidemia
Nephrotic syndrome
Chronic renal failure
Porphyria
Myocardial infarction
Coronary artery occlusion
Anorexia nervosa
oDecreased LDL levels :
Hypoproteinemia
Tangier disease
Hyperthyroidism
Chronic anemias
Severe hepatocellular disease
Reye’s syndrome
Acute stress
Inflammatory joint disease
Chronic pulmonary disease
2. ENZYME TESTS :
ENZYME NORMAL LEVEL
DISEASE CONDITION
SGOT Up to 40 U/LT Myocardial Infarction
LDH M→82-285 U/LTW→103-227 U/LT
Congestive cardiac failure
CPK M→<190 U/LTW→>165 U/LT
Various heart disease
AST / SGOT : NORMAL VALUES:
MEN : 14 – 20 U/L
WOMEN : 10-36 U/L
CLINICAL IMPLICATIONS:
Increased AST levels occur in MI:
Increased to 4-10 times the normal value.
AST level reaches a peak in 24 hrs & returns to normal by post MI day 3-7.
Secondary rise in AST levels suggest extension or recurrence of MI.
Increased AST levels occur in liver diseases:(10-100 times normal)
Acute hepatitis & chronic hepatitis ( ALT > AST)
Active cirrhosis( drug induced ; alcohol induced :( AST >ALT)
Hepatic necrosis & metastasis
Primary or metastatic carcinoma
Alcoholic hepatitis
Reye’s syndrome
Other diseases with elevated AST levels:
Hypothyroidism
Trauma & irradiation of skeletal muscle
Shock
Hemolytic anemia
Decreased AST levels:
Azotemia
Chronic renal dialysis
Vitamin B6 deficiency
LDH ( LACTATE DEHYDROGENASE) NORMAL VALUES:
MEN : 82-285 U/L
WOMEN : 103-227 U/L
CLINICAL IMPLICATIONS:
Increased LDH levels:
High levels occur within 36-55 hrs after MI & continue longer than elevations of SGOT or CPK ( 3-10 days)
In pulmonary infarction increased LDH occurs within 24 hrs of pain onset . The pattern of normal SGOT & elevated LDH levels of 1-2 days after an episode of chest pain – pulmonary infarction.
Congestive heart failure
Liver diseases ( cirrhosis, alcoholism, acute viral hepatitis )
Cancer , leukemia
Hypothyroidism
Lung diseases
Skeletal muscle diseases
Megaloblastic & pernicious anemias , hemolytic anemia, sickle cell disease
Seizures
Shock, hypotension
Renal infarction
LACTATE DEHYDROGENASE ISOENZYMES :
NORMAL VALUES :
LD1 : 17-27% of total or 0.17-0.27
LD2 : 29-39% of total or 0.29-0.39
LD3 : 19-27% of total or 0.19-0.27
LD4 : 8-16% of total or 0.08-0.16
LD5 : 6-16% of total or 0.06-0.16
CLINICAL IMPLICATIONS:
DISEASE LD1 LD2 LD3 LD4 LD5
Myocardial infarction
√ √
Pulmonary infarction
√ √
Congestive heart failure
√ √
Viral hepatitis
√ √
Toxic hepatitis
√ √
DISEASE LD1 LD2 LD3 LD4 LD5
Leukemia √ √
Pancreatitis
√ √
Carcinomatosis (extensive)
√ √
Megaloblastic anemia
√ √
Hemolytic anemia
√ √
Muscular dystrophy
√ √
CHEST X-RAY:
First diagnostic test in cardiac work shop.
Provides global information about position & size of the heart & chambers & surrounding anatomy.
The std CXRs for evaluation of lungs & heart are standing posteroanterior & lateral views taken at maximal inspiration.
Portable CXRs – less satisfactory.
The PA CXR outlines superior vena cava , right atrium on the right & left sides , aortic knob ,main pulmonary artery, left atrial appendage & left ventricle.
In the lateral view CXR visualizes right ventricle , inferior vena cava & left ventricle.
Cardiac enlargement is determined by cardio thoracic ratio.
ELECTROCARDIOGRAM ( ECG ) :
Painless process.Records the electrical
activity of the heart.Detected from the body
surface by electrodes ( leads ) and a galvanometer( ECG machine ).
The recordings can be displayed on a moving graph paper or on a screen to give visual impression.
Cardiac cycle begins with impulses from the SA node.
The electrical impulses spreads through both atria causing atrial contraction(depolarisation ).
Atrial depolarisation -P wave
The electrical impulse is delayed for approximately 0.04sec at the AV node so that the atria have time to eject their contents into the ventricles-PR interval represents this delay.
The impulse then travels through the AV node & AV bundle down the bundle branch & through the purkinje fibres & the ventricles contract – ventricular depolarisation
Ventricular depolarisation - QRS complex
Ventricular repolarisation - T wave.
Total duration of depolarisation and repolarisation - QT interval.
U wave – non specific recovery after potential
NORMAL DURATIONS:
P wave - ≤ 0.11sec
P-R interval - 0.12-0.20 sec
QRS complex- ≤ 0.12 sec
QT interval - ≤ 0.42 sec
ECG CONVENTIONS & INTERVALS :
Depolarisation towards electrode – positive deflection.
Depolarisation away from electrode – negative deflection.
Sensitivity – 10 mm = 1 mV
Paper speed – 25 mm/sec
Each large ( 5mm ) square = 0.2 sec
Each small ( 1 mm ) square = 0.04 sec
Heart rate = 1500/ R-R interval (mm)
( 300/number of large squares btwn beats)
NORMAL VOLTAGE MEASURMENTS :
Voltage from the top of the R wave to the bottom of the S wave – 1 mV
Voltage of P wave – 0.1 -0.3 mV
Voltage of T wave – 0.2 – 0.3 mV
The standard external 12 lead ECG uses two sets of leads :
6 limb leads & 6 precordial (chest ) leads
6 limb leads divided into 2 :
1. Standard bipolar lead
2. Standard unipolar lead
Standard bipolar lead
Lead I - right arm & left arm
Lead II - right arm & left leg
Lead III - left arm & left leg
Standard unipolar lead :
VR –centre of heart and right arm
VL-centre of heart and left arm.
VF-centre of heart and left leg.
6 chest leads :
V1
V2
V3
V4
V5
V6
RECORDING OF ELECTRICAL IMPULSES :
Limb leads ( I,II,III,AVL,AVF,AVR ) record events in the frontal plane of the heart.
Chest leads ( V1,V2,V3,V4,V5,V6 ) record a horizontal view of the heart electrical activity.
CLINICAL VALUE OF ECG:
Interpretation of cardiac arrhythmias
Diagnosis of ischaemic heart disease
Assessment of ventricular hypertrophy
STANDARD BIPOLAR LEADS:
STANDARD UNIPOLAR LEADS:
CHEST LEADS:
CLINICAL IMPLICATIONS :
ECG abnormalities are categorized in to 5 areas
1) Heart rate
2) Heart rhythm
3) Axis or position of heart
4) Hypertrophy or increase in the size of the heart
5) Infarction / ischemia
TYPICAL ABNORMALITIES :
Pathologic rhythms
Heart conduction system disturbances
Myocardial ischemia
Myocardial infarction
CLINICAL IMPLICATION ASSOCIATED WITH WAVES,COMPLEX & INTERVALS OF ELECTROCARDIOGRAPHY :
I. P WAVE
Mean vector of normal atrial depolarisation is directed leftward & downward producing a positive ECG deflection.
NORMAL VALUE : 0.08-0.11 sec
CLINICAL IMPLICATIONS:
RA hypertrophy & LA hypertrophy
Primary intra atrial conduction abnormality
II. PR INTERVAL : Represents the time beginning of
atrial activation to the beginning of ventricular activation.
NORMAL VALUE : 0.12 – 0.20 sec CLINICAL IMPLICATIONS : Cardiac arrhythmiasIII. QRS COMPLEX : Ventricular excitation begins
predominantly in the middle third of the left side of inter ventricular septum .
Initial wave of depolarisation spreads through right side.
Resultant vector produces QRS deflection.
NORMAL VALUE : CLINICAL IMPLICATIONS : Right & left ventricular hypertrophy. Right bundle branch block
( prolonged QRS – >0.12 sec ,wide S wave).
IV. ST WAVE: Steady membrane
polarization from the end of depolarization to the beginning of repolarisation.
CLINICAL IMPLICATIONS:
Myocardial ischemia
ST segment depression
T wave inversion
Myocardial infarction
Tall T waves
ST segment elevation
v. Hypertrophy of heart
vi. Pulmonary infarction
vii. Altered K , Ca, Mg levels
viii.Pericarditis
ix. Ventricular hypertrophy
DRUGS THAT CHANGES ECG:o Quinidine
o Procainamide
o Amiodaroneo Quinineo Mefloquineo Halofantrineo Terfenadineo Astemizoleo Amitryptylineo Risperidoneo Propanololo Sotalol
o Penicillino Pentamidineo Erythromyci
no Amantadineo Doxorubicino Lithiumo Carbamazepi
neo Probucolo Cotrimazoleo Digoxino Verapamilo Diltiazem
AMBULATORY ECG MONITORING :
Also known as Holter monitoring.
During AEM patient wears a portable ECG recorder.
3 types of monitors are available.
Continuous monitor - record an ECG strip over the duration of the test.
Intermittent recorder - continuously monitor the ECG but only record preprogrammed abnormal ECG events.
Real time analytical recorder -record through out the monitoring period and analysis each beat as it occurs.
Monitors digitize , encode and store the information in a solid state memory or on a magnetic tape
Clinical values of ambulatory ECG includes
Aid to detect ,document ,characterize and evaluate arrhythmias and other ECG abnormalities.
ECG abnormalities include ST segment deviation , QRS complex ,PR intervals.
ECHOCARDIOGRAM :
Ultrasound imaging of the heart and allows the structures of the heart to be visualized as a two dimensional slice.
Transducer is held over the patient chest wall to produce an ultrasound.
Its an instrument that transmits high frequency sound waves.
ECHO is mainly based on the principle of reflection and refraction.
The ability of the ultrasonic beam to penetrate chest wall structures is inversely proportional to the frequency of the signal.
Helpful in detecting
-mitral stenosis
-heart diseases
-chamber enlargement
DOPPLER ECHOCARDIOGRAPHY
Depends on the principle that sound waves reflected from moving objects such as intra cardiac red blood cells undergo frequency shift.
The greater the frequency faster the blood is moving.
Used for studying the pressure changes on either side of the valve & abnormal directions of blood flow.
TRANSOESOPHAGEAL ECHOCARDIOGRAPHY :
An ultrasound probe in the shape of an endoscope is passed into the oesophagus and positioned immediately behind the left atrium.
Helps in detecting *patient with valve dysfunction. *congenital abnormalities . *patient with systemic embolism.
CARDIAC CATHETERISATION :
It involves passing a catheter into the right or left side of the heart.
Right sided heart catheterisation helps to detect oxygen saturation in different chambers.
Left heart catheterisation helps to assess coronary artery diseases.
Mild sedative is given prior to test.
Procedure takes 90 mins to 3 hrs.
Radio opaque contrast material & indicator solutions can be injected via the catheter.
ANGIOGRAPHY :
Medical imaging technique in which an X ray image is taken to visualize the inside of blood vessels and organs of the body.
A catheter is inserted into the artery ,a radio opaque dye is injected with the aid of fluoroscopy allowing the imaging of blood vessels.
Used to detect lesion that occlude the vessels.
COMPUTED TOMOGRAPHY :
Rarely used.
More expensive.
Non invasive method.
Used to detect congenital heart diseases.
Useful in imaging the chambers of the heart , great vessels ,pericardium.
Chamber size and volume can also be measured.
MAGNETIC RESONANCE IMAGING :
Very expensive. Technician places a small sticky
electrode patches on your chest and back.
These electrodes are attached to ECG monitor.
Used for detecting -CHF -MI
RADIOLOGY :
Chest radiograph is useful for determining the size and shape of the heart.
Cardiothoracic ratio should be less than 0.5.
Transverse cardiac diameter should be less than 15.5cm.
RADIONUCLIDE IMAGINGGamma emitting radionuclide with a short half life.
Gamma rays are detected by means of a planar or tomographic camera.
Blood pool imaging.
Myocardial perfusion imaging.
BLOOD POOL IMAGING :
The isotope is injected intravenously and mixes with the circulating blood.
The gamma camera detects the amount of isotope emitting blood in the heart at different phases of the cardiac chambers.
By linking the gamma camera to the ECG it is possible to collect information over multiple cardiac cycle.
MYOCARDIAL PERFUSION IMAGING :
This technique involves obtaining scintiscans of the myocardium at rest & during stress after the administration of an intravenous radioactive isotope such as thallium.
REFERENCES:PHARMACOTHERAPY –A PATHOPHYSIOLOGIC APPROACH-JOSEPH T DIPIRO.
DAVIDSONS PRINCIPLES AND PRACTICE OF MEDICINE-CHRISTOPHER HASLET-19th ed
MEDICAL SURGICAL NURSING –SHAFER 5th ed
ESSENTIALS OF PHARMACOTHERAPEUTICS-F.S.K BARAR-4th ed.
A MANUAL OF LABORATORY & DIAGNOSTIC TESTS –FRANCES FISCHBACH , 8th ed.
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