What physiological change does an S1 sound correlate with?

The S1 heart sound, often referred to as the "lub" sound, corresponds primarily with the closure of the mitral and tricuspid valves at the beginning of ventricular contraction (systole). This physiological change is significant because it marks the point at which the ventricles start to contract and pump blood out of the heart into the aorta and pulmonary artery.

As the ventricles contract, the pressure within them rises, leading to the closure of the atrioventricular valves (mitral and tricuspid), which prevents backflow of blood into the atria. This closure creates the S1 sound, making it a critical indicator of heart activity at the start of systole. Understanding this correlation can help healthcare professionals assess cardiac function and identify potential issues in the ventricular systems.