Abstract
Quantitation of stenosis severity has become an essential part of cardiac diagnosis and therapy, not only in research but also in clinical practice. Since our introduction of the concept 15 years ago, arterial coronary flow reserve for assessing effects of coronary narrowing has evolved into two independent but complementary measurements: coronary flow reserve and stenosis flow reserve. Coronary artery flow reserve and/or myocardial perfusion reserve takes into account not only stenosis geometry but also collateral function and physiologic conditions of perfusion pressure, vasomotor tone, coronary venous pressure, and myocardial vascular bed size. Coronary artery flow reserve is measured invasively by flowmeter or by Doppler catheter. Its noninvasive equivalent is myocardial perfusion reserve, assessed by myocardial perfusion imaging with positron emission tomography before and after intravenous dipyridamole with hand grip stress. Both have been experimentally and clinically validated for identifying and/or quantifying severity of coronary artery disease. By either invasive or noninvasive methods, coronary artery or myocardial perfusion reserve may be subcategorized as either absolute flow or perfusion reserve (max flow/resting flow) and/or relative flow or perfusion reserve (max flow through stenotic artery/max flow through normal artery). Absolute flow reserve depends not only on stenosis severity but also on unrelated physiologic parameters such as aortic pressure and the vasodilatory state of the distal coronary vascular bed; in contrast, relative flow reserve is independent of these physiologic variables and reflects stenosis severity alone. Stenosis flow reserve is invasively determined by automated, quantitative coronary arteriography accounting for all stenosis dimensions and is independent of ambient physiologic conditions such as pressure, vasomotor tone, or other variables affecting the distal coronary vascular bed.(ABSTRACT TRUNCATED AT 250 WORDS)
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