38210909 electrocardiogram

8/8/2019 38210909 Electrocardiogram

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ELECTROCARDIOGRAM

An electrocardiogram (EKG or ECG) is a test that checks for

problems with the electrical activity of yourheart. An EKG translatesthe heart's electrical activity into line tracings on paper. The spikes and

dips in the line tracings are called waves. Interpretation of these details

allows diagnosis of a wide range of heart conditions. These conditions

can vary from minor to life threatening.


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BASIC ANATOMY OF THE HEART

The heart's function is so important to the body that it has its

own electrical system to keep it running independently of the rest of the

body's nervous system.

Even in cases of severe brain damage, the heart often beats

normally.

An extensive network of nerves runs throughout all 4 chambers of

the heart.

Electrical impulses course through these nerves to trigger thechambers to contract with perfectly synchronized timing

The ECG records this electrical activity and depicts it as a series of

graph-like tracings, or waves. The shapes and frequencies of these

tracings reveal abnormalities in the heart's anatomy or function.


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HEART FUNCTION AND THE ECG

Contraction of the atria and ventricles is coordinated by specialized

cardiac muscle cells in the wall of the heart that form conduction

system of the heart


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The heart normally beats between 60 and 100 times per minute,

with many normal variations.

This rate is set by a small collection of specialized heart cells

called the sinoatrial (SA) orsinus node

SA node

Located in the right atrium, the sinus node is the heart's "natural

pacemaker.

It has "automaticity,"

Two events occur with each discharge:

(1) both atria contract, and

(2) an electrical impulse travels through the atria to reach

another area of the heart called the atrioventricular(AV)

node, which lies in the wall between the 2 ventricles.


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AV node

TheAV node serves as a relay point to further propagate the

electrical impulse.

From the AV node, an electrical wave travels to both ventricles,

causing them to contract and pump blood.

The normal delay between the contraction of the atria and of the

ventricles is 0.12 to 0.20 seconds.

This delay is perfectly timed to account for the physical passage of the

blood from the atrium to the ventricle.

Intervals shorter or longer than this range indicate possible problems


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Conducting system of the heart: SA

means sinoatrial node. AV meansatrioventricular node. RB and LB

mean right and left bundle,

respectively, and are the nerves that

spread the electric impulse from the

AV node into the ventricle


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The ECG records the electrical activity that results when the heart

muscle cells in the atria and ventricles contract.


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Atrial contractions (both right and left) show up as the P wave.

Ventricularcontractions (both right and left) show as a series of 3waves, Q-R-S, known as the QRS complex.

The third and last common wave in an ECG is the T wave.

This reflects the electrical activity produced when the

ventricles are recharging for the next contraction (repolarizing).

The electrical activity results in P, QRS, and T waves that have a myriad of

sizes and shapes. When viewed from multiple anatomic-electric

perspectives (that is, leads), these waves can show a wide range of abnormalities of both the electrical conduction system and the muscle

tissue of the heart's 4 pumping chambers.


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WHY IT IS DONE

An electrocardiogram (EKG or ECG) is done to:

Check the heart's electrical activity.

Find the cause of unexplained chest pain, which could be caused

by a heart attack, inflammation of the sac surrounding the heart

(pericarditis), orangina.

Find the cause of symptoms ofheart disease, such as shortness

of breath, dizziness, fainting, or rapid, irregular heartbeats

(palpitations).

Find out if the walls of the heart chambers are too thick(hypertrophied).

Check how well medicines are working and whether they are

causing side effects that affect the heart.


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Check how well mechanical devices that are implanted in the

heart, such as pacemakers, are working to control a normal

heartbeat.

Check the health of the heart when other diseases or conditions

are present, such as high blood pressure, high cholesterol,

cigarette smoking, diabetes, or a family history of early heart

disease.

PREPARATION

Be sure to tell doctor about all the nonprescription and prescription

medicines you take. If you take heart medicines, your doctor will tell

you how to take your medicines before you have this test.

Remove all jewelry from neck, arms, and wrists. Men are usually

bare-chested during the test. Women may often wear a bra, T-shirt, or

gown. If you are wearing stockings, you should take them off. You will

be given a cloth or paper covering to use during the test.


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HOW IT IS DONE

An electrocardiogram (EKG or ECG) is usually done by a health

professional, and the resulting EKG is interpreted by a doctor, such

as an internist, family medicine doctor, electrophysiologist,

cardiologist, anesthesiologist, orsurgeon

Patient may receive an EKG as part of a physical examination at

your health professional's office or during a series of tests at a

hospital or clinic.

EKG equipment is often portable, so the test can be done almost

anywhere. If you are in the hospital, your heart may be continuouslymonitored by an EKG system; this process is called telemetry.


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During an EKG

You will lie on a bed or table.

Areas on your arms, legs, and chest where small metal discs

(electrodes) will be placed are cleaned and may be shaved to provide a

clean, smooth surface to attach the electrode discs.

A special EKG paste or small pads soaked in alcohol may be placed

between the electrodes and yourskin to improve conduction of the

electrical impulses, but in many cases disposable electrodes are used

that do not require paste or alcohol.

Technicians or sometimes a nurse, a doctor or other medicalprofessional will place a 6 small adhesive electrode pads across your

chest from your lower breast bone (sternum) to an area below your left

armpit. Other pads will be placed on each of your arms and legs.

Insulated wires will connect each of these 10 padds to the ECG

machine.


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Once these wires, called "leads," are attached, the ECG records a

few heartbeats on a single sheet of graph paper.

You will be asked to lie very still and breathe normally during thetest. Sometimes you may be asked to hold your breath. You should

not talk during the test.

Location for placement of the 6

precordial leads across the chest around

the heart (V1 to V6).


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Each heartbeat produces a set of P-QRS-T waves.

This set of waves, in turn, is recorded and analyzed from each of 12

points of view.

Six of these points of view are the locations of the 6 pads placed

across your chest. These are called V1, V2, V3, V4, V5, and V6(pronounced Vee One, Vee Two, and so on).

The other points of view represent combinations of the pads placed

on the arms and legs. These are called I, II, III , aVR, aVL, and aVF.

The interpretation of the waves produced by each of these 12 views

provides valuable information about the functioning of your heart.


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NORMAL ADULT 12-LEAD ECG

The diagnosis of the normal electrocardiogram is made by excluding

any recognized abnormality. Its description is therefore quite lengthy.

normal sinus rhythm

each P wave is followed by a QRS

P waves normal for the subject

P wave rate 60 - 100 bpm with 10% = sinus arrhythmia

normal P waves

height < 2.5 mm in lead II

width < 0.11 s in lead II

for abnormal P waves see right atrial hypertrophy, left atrial

hypertrophy, atrial premature beat, hyperkalaemia


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normal PR interval

0.12 to 0.20 s (3 - 5 small squares)for short PR segment considerWolff-Parkinson-White syndrome

orLown-Ganong-Levine syndrome (other causes - Duchenne

muscular dystrophy, type II glycogen storage disease (Pompe's),

HOCM)

for long PR interval see first degree heart block and 'trifasicular'

block

normal QRS complex

< 0.12 s duration (3 small squares)

for abnormally wide QRS considerright orleft bundle branchblock, ventricular rhythm, hyperkalaemia, etc.

no pathological Q waves


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normal QT interval

Calculate the corrected QT interval (QTc) by dividing the QT interval by

the square root of the preceeding R - R interval. Normal = 0.42 s.

Causes oflong QT interval

myocardial infarction, myocarditis, diffuse myocardial disease

hypocalcaemia, hypothyrodism

subarachnoid haemorrhage, intracerebral haemorrhage

drugs (e.g. sotalol, amiodarone)

hereditary

Romano Ward syndrome (autosomal dominant)

Jervill + Lange Nielson syndrome (autosomal recessive)

associated with sensorineural deafness


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normal ST segment

no elevation or depression

causes of elevation include acute MI (e.g. anterior, inferior), left

bundle branch block, normal variants (e.g. athletic heart, Edeiken

pattern, high-take off), acute pericarditis

causes of depression include myocardial ischaemia, digoxin effect,

ventricular hypertrophy, acute posterior MI, pulmonary embolus, leftbundle branch block

normal T wave

causes of tall T waves include hyperkalaemia, hyperacutemyocardial infarction and left bundle branch block

causes of small, flattened or inverted T waves are numerous and

include ischaemia, age, race, hyperventilation, anxiety, drinking

iced water, LVH, drugs (e.g. digoxin), pericarditis, PE, intraventricular

conduction delay (e.g. RBBB)and electrolyte disturbance.


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HOW IT FEELS

The electrodes may feel cool when they are put on your chest.

If you have a lot ofhairon your chest, a small area may need to be

shaved to put the electrodes on.

When the electrodes are taken off, they may pull your skin a little.

RISKS

There is no chance of problems while having an electrocardiogram

(EKG or ECG). An EKG is a completely safe test. In most cases, there

is no reason why you should not be able to get an EKG.

The electrodes are used to transfer an image of the electrical activity

of your heart to tracing on paper. No electricity passes through your

body from the machine, and there is no danger of getting an electrical

shock.


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The test usually takes 5 to 10 minutes to complete.

ELECTROCARDIOGRAM (EKG OR ECG) RESULTS

Normal:

The heart beats in a regular rhythm, usually between 60 and 100 beats

per minute.

The tracing looks normal.

Abnormal:

The heart beats too slow (less than 60 beats per minute).

The heart beats too fast (more than 100 beats per minute).

The heart rhythm is not regular.

The tracing does not look normal.


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STRESS TESTING

Stress testing provides your doctor with information about how yourheartworks during physical stress for some heart problems are easier todiagnose when your heart is working hard and beating fast

Doctors usually use stress testing to help diagnose coronary arterydisease (CAD) or to see how serious this disease is in those who areknown to have it.

It's sometimes used to assess other problems such as heart valveabnormalities or heart failure.

detect the following indications that your heart may not be gettingenough blood during exercise.

Abnormal changes in your heart rate or blood pressure , heart rhythm orthe electrical activity of your heart

Symptoms such as shortness of breath or chest pain


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DURING THE EXAMINATION

During a stress test, you exercise (walk or run on a treadmill orpedal a bicycle) or

given a medicine to make your heart work harder while heart testsare performed. PHARMACOLOGICAL STRESS TEST

patient walks on a

stress test treadmill to

check his heart's

functioning


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your heart is monitored using images or through dime-sized

electrodes attached to your chest, arms, or legs.

the patient may be asked to breathe into a special tube duringthe test. This will allow your doctor to see how well you'rebreathing.

If you can't exercise for as long as what's considered normal forsomeone your age, it may be a sign that not enough blood isflowing to your heart. But other factors besides CAD can preventyou from exercising long enough (for example, lung diseases,anemia, or poor general fitness


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STRESS TESTING USING IMAGING

Some stress tests take pictures of the heart when you exerciseand when you're at rest.

These imaging stress tests can show how well blood is flowing inthe different parts of your heart and/or how well your heartsqueezes out blood when it beats

imaging stress tests tend to be more accurate at detecting CAD

than standard (nonimaging) stress tests.


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An imaging stress test may be done first if you:

Can't exercise for enough time to get your heart working itshardest. (Medical problems, such as arthritis or leg arteries clogged

by plaque, may prevent you from exercising enough.)

Have abnormal heartbeats or other problems that will cause astandard exercise stress test to be inaccurate.

Are a woman. Standard stress tests are less accurate in women

than in men


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TYPE OF IMAGING STRESS TEST

echocardiography

test that uses sound waves to create a moving picture of yourheart.

It can show how well your heart's chambers and valves areworking when your heart is under stress.

The test can identify areas of poor blood flow to your heart, dead

heart muscle tissue, and areas of the heart muscle wall that aren'tcontracting normally. These areas may have been damaged duringa heart attack or may be getting too little blood.


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stress tests use a radioactive dye

use to create images of the blood flow to your heart.

The dye is injected into your bloodstream before pictures are takenof your heart.

The pictures show how much of the dye has reached various partsof your heart during exercise and at rest.

Tests that use a radioactive dye include a thallium or sestamibistress test and a positron emission tomography (PET) stress test.

The amount of radiation in the dye is safe and not a danger to youor those around you.however, if you're pregnant, you shouldn'thave this test because of risks it might pose to your unborn child.


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Some doctors may use magnetic resonance imaging (MRI)

Use to take pictures of the heart when it's working hard

This test doesn't use a radioactive dye or sound waves. Instead, ituses radio waves and magnetic fields to create images that show

blood flow in the heart and whether all parts of the heart wall arecontracting strongly.


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HOLTER MONITOR

(AMBULATORY ELECTROCARDIOGRAPH)

device that continuously records the heart's rhythms while

being worn, usually for 24 hours, during normal activity

battery operated and carried in a pocket or a small pouch

worn around the neck or waist. It is connected to electrodes

(small conducting patches) that are stuck onto the patient's

chest.

Holter monitor records the heart's electrical activity.


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Figure shows how a Holter or event

monitor attaches to a patient. In this

example, the monitor is clipped to the

patient's belt and electrodes are

attached to his chest. Figure B shows

an electrocardiogram strip, whichmaps the data from the Holter or

event monitor


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WIRELESS HOLTER MONITORS

have a longer recording time than standard Holter monitors and

record the heart's electrical activity for a preset amount of time.

They are called wireless because they use a cell phone to send the

data to the doctor's office. This happens automatically at certain

times. These monitors still have wires that connect the device to the

sensors stuck to the patient's chest.

Can be used for days or even weeks until signs or symptoms of a

heart rhythm problem occur. It is used especially to detect heart

rhythm problems that don't occur often.

Although wireless Holter monitors work for longer periods, they have

a down side. The patient must remember to write down the time of

symptoms, so that his or her doctor can match it to the heart rhythm

recording. Also, the batteries in the wireless monitor must be

changed every 1 to 2 days.


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WHY THE TEST IS PERFORMED

to determine how the heart responds to normal activity.

The monitor may also be used:

When starting a new heart medicine

After a heart attack

To diagnose heart rhythm problems

Atrial fibrillation/flutter

multifocal atrial tachycardia

Paroxysmal supraventricular tachycardia

Palpitations

Reasons forfainting


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WHAT ABNORMAL RESULTS MEAN

Abnormal results may include various arrhythmias. Changes in the

normal pattern of waves formed by the heart's electrical signals may mean

that the heart is not getting enough oxygen.

SPECIAL CONSIDERATIONS

Electrodes must be firmly attached to the chest so the machine gets

an accurate recording of the heart's activity.

While wearing the device, avoid:

Electric blankets

High-voltage areas

MagnetsMetal detectors

It is very important for you to keep a diary of symptoms. The diary

should include the date, time of day, type, and duration of symptoms.


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HOW THE TEST IS PERFORMED

Electrodes (small conducting patches) are stuck onto your chest andattached to a small recording monitor.

You carry the Holter monitor in a pocket or small pouch worn around

your neck or waist

while you wear the monitor, it records your heart's electrical activity.You should keep a diary of what activities you do while wearing the

monitor.

After 24 - 48 hours, you return the monitor to your doctor's office. The

doctor will look at the records and see if there have been any irregularheart rhythms.

It is very important that you accurately record your symptoms and

activities so that the doctor can match them with your Holter monitor

findings.


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HOW TO PREPARE FOR THE TEST

There is no special preparation for the test. Your doctor will startthe monitor. You'll be told how to replace the electrodes should

they fall off or become loose.

Tell your doctor if you are allergic to any tape or other adhesives.

Make sure you shower or bathe before you start the test. You willnot be able to do so while you are wearing a Holter monitor.

HOW THE TEST WILL FEEL

a painless test.chest shaved so the electrodes can stick.

must keep the monitor close to your body. This may make sleeping

difficult for some people.

You should continue your normal activities while wearing the monitor


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38210909 electrocardiogram

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