Why may the heart of an 85-year-old patient struggle to meet the demands for increased blood flow?

The heart of an 85-year-old patient may struggle to meet the demands for increased blood flow primarily due to reduced reserve capacity. As individuals age, various physiological changes occur in the cardiovascular system, including the heart's ability to respond to increased demands, such as during exercise or stress.

Reduced reserve capacity refers to the diminished ability of the heart to increase its output when needed. This is due to factors such as decreased contractility, stiffening of the heart muscle, and changes in the heart's pacemaker activity. Older adults often have a lower maximum heart rate and may not be able to increase their stroke volume significantly in response to increased demands.

In contrast, increased stroke volume would imply better heart function, which is unlikely in this age group. Decreased blood pressure may occur but is not necessarily the primary issue affecting blood flow in response to stressors. Increased vascular elasticity, often seen in younger individuals, tends to decline with age as arteries become stiffer, which also contributes to the difficulty in meeting increased blood flow demands. Thus, reduced reserve capacity is a critical factor that explains why the heart may not cope well under stress in an elderly patient.