Which diagnostic test assesses the heart's ability to respond to stress?

The stress test is designed specifically to evaluate the heart's capacity to respond to physical stress, which is achieved through either exercise or medication-induced stimulation. During this test, the patient typically performs activities like walking on a treadmill or pedaling a stationary bike, allowing healthcare providers to monitor how the heart functions under conditions that mimic physical exertion. This testing provides critical information about the heart's rhythm, blood flow, and overall performance, which can help identify issues such as coronary artery disease or other cardiac abnormalities.

In contrast, the other options serve different diagnostic purposes. A blood test is primarily used to assess levels of various substances in the blood, which can indicate conditions such as anemia or electrolyte imbalances. An electrocardiogram records the electrical activity of the heart but does so at rest and does not assess the heart's response to physical exertion. A chest X-ray provides a visual of the heart, lungs, and surrounding structures but does not evaluate functional capacity or stress response.

Thus, the stress test is uniquely suited to evaluate how well the heart handles increased workload, making it the correct choice for assessing the heart's ability to respond to stress.