Which of the following methods of cardiovascular testing evaluates heart function over 24 hr or more?

A 12-lead EKG provides a snapshot of the heart's electrical activity at a specific moment, typically lasting only a few minutes. While it is effective for diagnosing immediate heart conditions, it does not monitor heart function over an extended period, making it unsuitable for long-term evaluation.

A nuclear stress test assesses blood flow to the heart muscle during exercise and at rest using radioactive tracers. While useful for evaluating heart function under stress, the test is typically performed over a few hours and does not provide continuous monitoring over a 24-hour period.

The tilt-table test is designed to evaluate how the body responds to changes in position, particularly in diagnosing syncope (fainting) or other autonomic dysfunctions. It is conducted over a short duration and does not involve prolonged heart rhythm monitoring, thereby failing to meet the criteria for extended evaluation.