Electrocardiogram
Terms
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- what is an ECG?
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electrocardiogram
-recording of cardiac electrical activity from electrodes placed on body surface. - how is an ECG plotted?
- voltage versus time.
- what are the electrodes in an ECG essentially?
- electrical dipoles
- what are elect. diples?
- two conductors with app. equal charge magnitude but opposite direction. located in close proximity to ea. other
- what 2 characteristics about the dipole determine voltage diffnc measured in an ECG?
-
-magnitude of charge difference
-placement of electrodes - what does ECG detect?
- changes in the polarity of the membrane -> when it depolarizes compared to a nondepolarized section of membrane.
- what is a common triangle used for connecting leads in an ECG?
- Einthoven triangle
- where are the three leads connected in an einthoven triangle?
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1. Left arm/right arm
2. Left leg/right arm
3. Left leg/left arm - what does upward deflection on an ECG tell?
- that a positive dipole has been conducted in that lead.
- What is Einthoven's triangle useful for?
- determining the mean electrical axis of a heart - indicates if problem in conduction, depolarization, or repolariz of myocardium.
- What are the components of the ECG wave?
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P wave
QRS wave
T wave -
what is the p wave?
-qrs?
-t? -
P = atrial depolarization
QRS = ventric depolarization
T = ventric repolarization - what is the PR interval?
-
time required for depolarization to travel from SA to ventricle.
-measures VA node health -
What is the ST segment?
-when is it elevated?
-when is it depressed? -
an isoelectric period.
-elevated in Myocardial infarct.
-depressed in angina. - What is represented by the duration of the QRS wave?
- the time necess to depolarize ventricles - shows health of conducting system.
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What do you know from the
-RR interval
-PP interval? -
RR = indication of ventric rate
PP = indication of atrial rate - what are 4 types of ECG abnormalities?
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1. Arrythmia
2. Long QT syndrome
3. Atrial PRemature Complex
4. Ventricular Premature complex - what is arrythmia?
- a disorder of Cardiac rate and rythm.
- what is Long QT syndrome?
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-Time btwn ventric depolariz and repolariz is longer than normal.
-due to prolonged repolarization - what symptom does long qt syndrome cause?
- -fibrillation, bag of worms moveent.
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What are APCs?
What causes them? - -Atrial premature complexes, -Early P waves arising from any part of the atria.
- What are VPCs?
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Ventricular Premature complexes.
-QRS complexes without a preceding P wave. - Who are APCs and VPCs seen in?
- present in over 60%, but usually asymptomatic.
- what are four types of AV block?
- 1st, 2nd, 3rd, and 4th degree.
- what is 1st degree AV block?
- normal conduction of P waves to ventricles, but slowed conduction through AV node.
- what is 2nd degree AV block?
- Incomplete coupling of AV and ventricles; some P waves are missed by the ventricles.
- What is a name for 2nd degree AV block type one?
- wenckebach's
- what is the symptom of wenckebach's AV block?
- PR interval is increased until there is a missed beat.
- what is 2nd degree AV block, type II?
- Mobitz syndrome. the PR interval is long, but not random -> CONSTANT. Every Nth T is missing.
- What occurs in type III av node block?
- complete dissoc. of AV node and ventricles; no impulse conduction.
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How does Myocardial Infarction affect the ST segment?
Why? - Depresses it; because ischemic injury is worse farther away from the coronary vessels.
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How does Angina pectoralis affect the ST segment?
Why? - Elevates it. Because angina ischemia involves the whole wall of the myocardium.
- What characterizes QT syndrome?
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-A congenital or drug-ind state.
-Prolonged ventricular repolarization lengthens QT int.
-Causes susceptibility to fibrillation, instant death. -
What are
-Atrial premature complexes?
-Ventric premature compexes? -
early atrial P waves
early ventricular QRS waves, not preceded by a P wave. -
What is atrial fibrillation?
What is atrial flutter? -
-Atrial activity that may not be evident.
-Regular and inappropriately rapid atrial activity - what is AV block?
- blockage to elect. conduction through the AV node.
- What is 1st degree block?
- not full blockage, just slowed conduction.
- what is 2nd degree block?
- incomplete coupling - some P waves don't conduct from AV node to ventricles.
- what is 3rd degree block?
- Full blockage; AV node excitation is decoupled from ventricular
- what are two types of 2nd degree block?
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-Wenckebach: PR interval is so long that conduction fails. Occurs in AV node.
-Mobitz: PR interval is long, but every nth T wave is missing. Occurs in Bundle branches.