click below
click below
Normal Size Small Size show me how
USMLE
CV 1
Question | Answer |
---|---|
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 |