While significant advances have been made in the last five years, the most frequently used diagnostic procedure is still the exercise stress test or treadmill test. They walk on a treadmill which increases in speed and elevation until it simulates a vigorous walk up a small hill. During the test heart rate, breathing, blood pressure and EKG readings are taken to determine how well the heart responds to increased demand and whether the heart is receiving a sufficient blood supply. This increasingly available technology takes cross-sectional scans of the beating heart at high resolution and clarity. Calcium has been shown to be a significant indicator of coronary heart disease risk.
Invasive tests require the insertion of needles and other instruments into the body.
Both tests reveal how well blood flows through the heart. Coronary angiography is the insertion of a thin plastic catheter through an artery in the arm or leg and up into the coronary arteries of the heart. Angiograms reveal blockages and areas of restricted blood flow. Letterman underwent emergency surgery because his coronary angiography revealed severe blockages that were deemed life-threatening. Cardiac catheterization is the same process as angiography, only no dye is used.