What vital sign is most closely associated with cardiac function?

Heart rate is the vital sign most closely associated with cardiac function because it directly reflects the performance of the heart. The heart rate indicates the number of times the heart beats per minute, which is crucial for determining how well the heart is working to pump blood throughout the body. A proper heart rate ensures that there is adequate blood flow to organs and tissues, which is vital for maintaining normal physiological function.

While blood pressure also relates to cardiac function—indicating the force exerted by circulating blood on the walls of blood vessels—it is a measure of the pressure in the arteries rather than a direct measure of heart performance. Respiratory rate and temperature, although important vital signs, do not provide direct insight into the functioning of the heart itself. Each of these vital signs contributes to the overall assessment of health; however, heart rate is the most direct indicator of cardiac function.