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what is an ECG?
-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?
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?
P wave
QRS wave
T wave
what is the p wave?
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.
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?
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?
-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.
What are APCs?
What causes them?
-Atrial premature complexes, -Early P waves arising from any part of the atria.
What are VPCs?
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?
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.
How does Myocardial Infarction affect the ST segment?

Depresses it; because ischemic injury is worse farther away from the coronary vessels.
How does Angina pectoralis affect the ST segment?

Elevates it. Because angina ischemia involves the whole wall of the myocardium.
What characterizes QT syndrome?
-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?
-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.

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