Author Question: What is the cause of a myocardial infarction? a. Decreased perfusion to the pulmonary ar-tery b. ... (Read 27 times)

vinney12 · **on:** Jul 16, 2018

What is the cause of a myocardial infarction?

a. Decreased perfusion to the pulmonary ar-tery
b. Partial or complete obstruction of a coro-nary artery
c. Blockage in one or more of the great ves-sels
d. Narrowing of part of the aorta

Question 2

The dicrotic notch recorded in the aorta immediately follows what mechanical event of the car-diac cycle?

a. Closure of the aortic valve
b. Closure of the atrioventricular valves
c. Isovolume contraction
d. Opening of the aortic valve

katara · **Reply #1 on:** Jul 16, 2018

Answer to Question 1

ANS: B
Partial obstruction of a coronary artery may lead to tissue ischemia (decreased O2 supply), a clin-ical condition called angina pectoris. Complete obstruction may cause tissue death or infarct, a condition called myocardial infarction (MI).

Answer to Question 2

ANS: A
Rather than immediately dropping off, aortic and pulmonary pressures rise again after the semi-lunar valves close. Note the feature termed the dicrotic notch, which is caused by the elastic re-coil of the arteries. This recoil provides the extra push that helps maintain the head of pressure created by the ventricles.