Which factor is a pathophysiologic mechanism of isolated systolic hypertension in the elderly?

The pathophysiologic mechanism behind isolated systolic hypertension in the elderly primarily revolves around the loss of vascular tissue elasticity. As people age, the blood vessels, especially the large arteries, tend to become stiffer and less flexible due to changes in the structure of the vascular wall, including the breakdown of elastin and increased collagen deposition. This loss of elasticity means that the arteries cannot expand as effectively to accommodate the increased volume of blood pumped during systole (the phase of the heartbeat when the heart muscle contracts). Consequently, this leads to an increase in systolic blood pressure while diastolic blood pressure may not rise to the same extent, resulting in isolated systolic hypertension.

The other options do not accurately represent the primary mechanism for this form of hypertension in the elderly. For instance, decreased cardiac output is more associated with conditions such as heart failure rather than isolated systolic hypertension. Hyperactive baroreceptors typically help regulate blood pressure rather than contribute to isolated systolic hypertension, as they would respond to changes in blood pressure by modulating heart rate and vascular resistance. Increased fluid retention is often related to other forms of hypertension and is not a central mechanism in isolated systolic hypertension in older adults.