Lecture 22 and 23 Flashcards
Name some things that can be determined by reading an EKG
rate
rhythm
hypertrophy
infarction
How do determine HR
- find R wave that falls on heavy black line
- count off 300, 150, 100, 75, 60, 50 for each consecutive heavy line
- Where the next R wave falls determines the rate
60-100 beats/min
normal sinus rhythm
<60 beats/min
sinus bradycardia
> 100 beats/min
sinus tachycardia
- all waves are present in each cardiac cycle and look normal
- normal distances between similar waves from one cardiac cycle to the next
- each wave in all cardiac cycle look alike
- the P-R/P-Q, Q-T, and QRS intervals are normal
normal/regular rhythm
ectopic focus discharging spontaneously producing a beat which appears earlier than expected in the rhythm
premature beats
originates suddenly in an atrial ectopic focus and produces an abnormal P wave earlier than expected
premature contraction (PAC)
originates suddenly in an ectopic focus in a ventricle producing a giant ventricular complex. occurs before a P wave can begin a new cycle. QRS complex is very wide and tall/deep
premature ventricular contraction (PVC)
Why is the QRS complex wider and normal during a PVC?
because depolarization originates in the myocardium (instead of conduction system) and therefore depolarization impulse conducted very slowly across both ventricles
Why is the QRS taller/deeper than normal during a PVC?
During normal ventricular conduction, the left and right ventricles depolarize simultaneously. As a result, depolarization going toward the left ventricle is somewhat opposed by simultaneous depolarization going toward right ventricle. Therefore, QRS is relatively small. PVC originates in one ventricle which depolarizes before the other and there is no simultaneous opposing depolarization from opposite sides. Therefore, QRS is very large.
rate between 250-350 beats/min
flutter
- originates in an atrial ectopic focus
- P waves occur in rapid succession and each is identical to the next
- P waves look identical because they arise from the same ectopic focus
- only occasionally will the atrial stimulus penetrate the AV node and produce a QRS complext
atrial flutter
- is produced by a single ventricular ectopic focus firing at an extremely rapid rate
- forms a smooth sine wave
- no P waves or T waves
ventricular flutter
rate between 350-450 beats/min
fibrillation
- caused by MANY atrial ectopic foci firing at rapid rates
- no true P wave-just spikes appear
- major concern is development of blood clots due to pooling of blood- can live with this
atrial fibrillation
- caused by rapid-rate discharges from many ventricular ectopic foci producing erratic, rapid twitching of the ventricles
- because so many foci are firing at once, each only depolarized a small area of ventricle and produces “twitching” of ventricle instead of full contraction of ventricle
- no effective pumping-will directly kill you
ventricular fibrillation
electrical blocks which retard or prevent the passage of electrical (depolarization) stimuli
heart block
- the SA node stops its pacing activity for at least once cycle.
- the P waves identical because the same SA node pacemaker is functioning before and after the pause (missed cycle)
sinus block
delay in transmission of the impulse through the AV node
AV block
results in longer pause before stimulating the ventricles; P-R interval prolonged (>0.20 seconds)
primary AV block
progressive P-R prolongation until QRS is dropped
secondary AV block
complete block- complete dissociation of atria and ventricles
tertiary AV block
- caused by block of depolarization in the right or in the left bundle branch
- normally, the impulse spreads through the right and left bundle branches simultaneously and therefore ventricles contract simultaneously
3 a block to either of the bundle branches creates a delay of the electrical impulse to that side and causes one ventricle to depolarize than the other - results in widened QRS complex often with “rabbit ears” (>0.12 seconds)
bundle branch block
- inverted symmetrical T waves
- elevated or depressed S-T segments
- Presence of significant Q waves
ischemia/infarct
- prolonged depolarization of ventricles during ischemia changes pattern of repolarization
- ventricles repolarize in opposite direction to normal repolarization
inverted symmetrical T waves
- sign of acute injury
2. can return to baseline with time
elevated or depressed S-T segments
significant is considered >1 mm deep
presence of significant Q waves make the diagnosis of infarct
