ECG Flashcards
P-wave
atrial depolarization
P-R segment
conduction from AV node to bundle of His allowing time for atria to contract
-usually < 0.20 seconds
QRS interval
ventricular depolarization
ST segment
early ventricular repolarization
T-wave
ventricular repolarization
U-wave
occassionally seen as result of abnormal electrolyte & ion concentrations
How do you determine presence of myocardial ischemia on ECG?
ST-segment depression
Sinus tachycardia
> 100 BPM
…normal during exercise
Paroxysmal atrial tachycardia
when sinus tachycardia comes on suddenly & terminates suddenly
…can occur w/ digitalis toxicity
Sinus bradycardia
< 60 BPM
…normal in athletes where SB is compensated by enhanced stroke volume due to increased L ventricular muscle mass/contractility
Premature atrial contraction
originate from irritable/ischemic myocardium
P wave looks different bc different origin
SA node “resets” itself to restore NSR
Atrial flutter
single ectopic focus fires repetitively/rapidly so slow-conducting AV node fails to conduct every impulse
- multiple P waves to every QRS
- “saw-tooth” pattern
- pts w/ ischemic heart disease or recovering from acute illness
Atrial fibrillation
No organization
multiple ectopic foci all firing at random
“quivering”
-constantly changing R to R wave, absence of P wave & jagged baseline
-pts w/ rheumatic heart disease, ischemic heart disease, hypertensive heart disease & heart failure
1st degree AV block
conduction from atria to ventricles is delayed causing prolonged PR interval
-frequently benign, occurs in endurance athletes
2nd degree AV block
type 1 - gradual prolongation of PR interval until QRS is dropped & next beat recaptures ventricles (wenckebach phenomenon)
type 2 - dropped QRS complexes but PR is fixed & remains unchanged
-rheumatic fever, acute inferior wall MI & digitalis toxicity
