A cardiac stress test measures the blood flow to the heart while it is at rest and also during a period of stress, according to Mayo Clinic. A technician takes images of the heart at rest and again when it is working harder.
A routine stress test provides data about heart functions by measuring heart rate, blood pressure and breathing, notes Mayo Clinic. This test generally involves exercise on a treadmill or stationary bike. A nuclear stress test is a nuclear imaging procedure in which radioactive dye is injected into a vein, and a cardiologist evaluates blood flow and oxygen in the heart. The cardiologist may order this test if the physical stress test fails to identify the cause of symptoms or to help determine a course of treatment.