Question

When auscultating a patient's heart sounds, what does the first sound of the cardiac cycle indicate?

A) Opening of the atrioventricular valves during ventricular systole
B) Opening of the aortic and pulmonic valves, signaling ventricular systole
C) Closure of the atrioventricular valves during ventricular systole
D) Closure of the aortic and pulmonic valves, signaling the initiation of ventricular diastole

Answer 1

The first heart sound, known as S1 or "lub," indicates the closure of the atrioventricular valves during the transition to ventricular systole.

Step-by-step explanation:

When auscultating a patient's heart sounds, the first sound of the cardiac cycle, known as S1 or the "lub" sound, indicates the closure of the atrioventricular valves during ventricular systole. This sound occurs when the ventricles begin to contract, causing ventricular pressure to rise above the pressure in the atria, which in turn leads to the closing of the tricuspid and mitral valves. This phase is known as isovolumic or isovolumetric contraction and marks the transition from diastole to ventricular systole.