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USMLE

CV 1

QuestionAnswer
In the ventricular action potential, what causes the Phase 0 rapid upswing? opening of voltage gated Na channels
In the phase 2 plateau, Ca++ influx triggers Ca++ release from the SR causing …. myocyte contraction
What effect does Ach have on HR? decrease
What effect do catecholamines have on HR increase
Name 4 things that increase contractility: catecholamines, digitalis, an increase in intracellular Ca++, or a decrease in extracellular Na+
What effect does increased afterload have on myocardial oxygen demand? increased
how do catecholamines increase contractility? increase the activity of Ca++ pump in the SR
What effect will and MI have on contractile state of the heart? decrease
what does S1 correspond to? mitral and tricuspid valve closure
what does S2 correspond to? aortic and pulmonary valve closure
what does S3 correspond to? the end of rapid ventricular filling
what is S3 associated with? dilated CHF
what is S4 and what does it indicate? an atrial kick associated with a hyptertrophic ventricle (high atrial pressure/stiff ventricle)
what is the a wave? atrial contraction
what is the c wave? RV contraction when the tricuspid valve bulges into atrium
what is the v wave? increase in atrial pressure due to filling against a closed tricuspid valve
what is physiologic S2 splitting aortic valve closes just before the pulmonic - the difference is increased on inspiration
what is paradoxical splitting when the split is heard on expiration instead of inspiration … associated with aortic stenosis
what is meant by "HIZ" shrinkage the H, I, and Z band decrease in length on muscle contraction, the A band (myosin) stays the same length
describe the pathway of smooth muscle contraction ap - > sm muslce depolarization - > open Ca++ channels -> increase in cytosol Ca++ -> Ca++ bind Calmodulin -> activates MLCK -> relaxation ->MLCP forms a cross bridge and contraction by binding myosin to actin - > MLCK relaxes … cycle continues while Ca
in an EKG, what does the P wave represent? atrial depolarization
in an EKG, what does the PR segment represent? conduction delay through the AV (200 msec)
in an EKG, what does the QRS complex represent? ventricular depolarization(120 msec)
in an EKG, what does the QT interval represent? mechanical contraction of the ventricle
in and EKG, what does the T wave represent? ventricular repolarization
do you see atrial repolarization on an EKG? no, it is masked by the QRS complex
in an EKG, what does the ST segment represent? isoelectric, ventricles are depolarized
on an EKG, what is a U wave? caused by hypokalemia
what is Wolff-Parkinson-White syndrome when an accessory conduction pathway exists from atria to ventricle (bundle of Kent) - bypasses the AV node and ventricles partially depoliarize earlier giving rise to a delta wave. WPW syndrome may lead to recurrent entry and SVTs.
What do you see on and EKG with atrial fibrillation? chaotic erratic baseline with no disrete P waves in between iregularly spaced QRS complexes
What do you see on an EKG with atrial flutter? sawtooth, identical back to back P waves
How many kinds of AV block are there? 4: 1st degree, mobitz I, mobitz II, complete
What is 1st degree AV block? asymptomatic - PR interval longer than 200 msec
What is mobitz II AV block? driooed beats not proceeded by a progressively lengthening PR interval. Pathological … can progress to complete block
What is mobitz I AV block? progressive PR lengthening until a beat is dropped … usually asymptomatic
what is a 3rd degree AV block complete AV block, atria and ventricles beat independently … rx with pacemaker
what is v-fib completely erradic rhythm with no identifiable waves, fatal without immediate defibrillation
what is the normal right atrial pressure? 5
what is the normal left atrial pressure 12 (approx with pcwp - swan-ganz)
what is the normal right ventricular blood pressure? 25/5
what is the normal pulmonary artery pressure? 25/10
what is the normal left ventricular pressure? 130/10
what is a normal aortic blood pressure? 130/90
Created by: Asclepius