Coronary Microvascular Dysfunction

Chest pain in patients without obstructive coronary artery disease has been realized as a frequent problem encountered in clinical practice. Invasive flow investigations have suggested that up to two-thirds of patients with nonobstructive coronary atherosclerosis may have microvascular dysfunction (MVD). Positron emission tomography myocardial perfusion imaging in conjunction with tracer-kinetic modeling enables the concurrent quantification of myocardial blood flow (MBF) in milliliters per minute per gram of tissue. This allows the assessment of hyperemic MBFs and myocardial flow reserve for the noninvasive identification and characterization of MVD as an important functional substrate for angina symptoms amenable to intensified and individualized medical intervention with nitrates, calcium-channel blockers, statins, angiotensin-converting enzyme inhibitors, and/or angiotensin II type 1 receptor blockers. Recent investigations suggest that cardiac magnetic resonance and computed tomography may also be suitable for the noninvasive detection of MVD. Whether intensified and individualized treatment related improvement or even normalization of hyperemic MBF and/or myocardial flow reserve may lead to a persistent reduction in angina symptoms and/or improved cardiovascular outcome as compared to standard care, deserves further testing in large-scale randomized clinical trials.