Why induce maximum hyperemic stimuli?
For a thorough evaluation of the functional significance of a coronary stenosis, it is necessary to perform pressure measurements under conditions of maximum coronary and myocardial hyperemia, corresponding to minimal (and constant) myocardial resistance and minimal distal coronary pressure. Patients are mostly asymptomatic at rest but develop ischemia when exercising. (Hyperemia simulates maximum exercise; and assessment of the functional significance of a stenosis is clearly most important under these conditions when considering the patients health). Pressure and flow are related to each other by vascular resistance. These resistances vary due to changes in myocardial oxygen demand, arterial pressure, contrast injections and coronary vasomotion. Theoretically then, flow and pressure cannot be related to each other and to stenosis severity unless these resistances are known or at least constant. This problem is avoided by measuring at maximum vasodilatation – the resistance can be ass
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