A client arrives in the emergency department with chest pain, but all test results come back negative. The healthcare provider diagnoses the client with angina pectoris and orders additional testing. Which test requires the client to exercise on a treadmill while being monitored for myocardial ischemia?

A. Cardiac catheterization: This is an invasive procedure where a catheter is threaded through the femoral or radial artery to inject dye and visualize the coronary anatomy. It is performed while the patient is stationary on a procedure table, not while exercising on a treadmill. It is the gold standard for diagnosing blockages but is not a "stress test." B. Electrocardiogram: A standard 12-lead ECG records the electrical activity of the heart while the patient is at rest. While it can show signs of previous infarction or current ischemia, it does not involve physical exertion. It is a baseline diagnostic tool rather than a functional assessment of the heart under stress. C. Stress test: An exercise stress test involves monitoring the patient's heart rate, blood pressure, and ECG while they walk on a treadmill at increasing levels of difficulty. This test is designed to uncover myocardial ischemia that may only be present when the heart's oxygen demand is elevated. It is a key functional evaluation for patients with suspected angina. D. Echocardiogram: An echocardiogram uses ultrasound waves to visualize the structures and motion of the heart valves and chambers. While it can be performed after exercise in a "stress echo," the primary test focused on exercising on a treadmill for ischemia detection is the stress test. A standard echo is typically a resting imaging study.