Coronary vasodilator reserve (CVR) tells us how well the heart can increase blood flow when needed. It’s the heart’s backup system during stress or exercise. If this reserve is low, it may mean blocked or damaged arteries. This makes it a helpful sign of heart trouble before symptoms start.

CVR is the heart’s ability to boost blood flow through the coronary arteries. These arteries feed oxygen to the heart muscle. When your body needs more oxygen—like during a workout—the vessels should widen. This widening is called vasodilation. If the arteries don’t open enough, the heart may not get enough blood.

This reserve is linked to coronary flow reserve (CFR) and myocardial flow reserve (MFR). Both check how well blood flow increases above normal. CFR looks at large arteries. MFR also considers tiny vessels deeper in the heart. They are used to test for coronary microcirculation function problems.

One method is Doppler echocardiography CVR. It uses ultrasound to measure flow through the heart vessels. Another test is cardiac catheterization flow reserve. This involves threading a tube into the heart to check blood flow and pressure. It helps spot blockages even when arteries look clear.

Some people with heart disease have poor CVR even without large blockages. This can happen with diabetes, rheumatoid arthritis, or hypertension. These conditions can damage the vessel lining, called the endothelium. If the lining is unhealthy, arteries can’t widen as they should.

A poor coronary reserve can mean a higher risk of heart attacks. It also points to coronary endothelial function problems and early coronary artery disease. This makes it useful for early diagnosis.

CVR is also helpful for coronary stenosis functional assessment. That means checking how much a narrow artery is limiting flow—not just how narrow it looks on a scan. In people with left ventricular hypertrophy (LVH) or CVR in diabetes, even small blockages can become dangerous if the reserve is gone.

Doctors also use CVR to watch the effects of medicine, lifestyle changes, or treatments aimed at endothelial health improvement strategies.