Coronary Microcirculation in Aortic Stenosis: Pathophysiology, Invasive Assessment, and Future Directions

Figure 2

Myocardial resistance in an animal model of aortic stenosis: at about 2 months of age, a 20–25 mmHg peak systolic gradient is created in dogs who were then studied at 10–14 months of age and compared with normal animals. During intravenous adenosine infusion, coronary flow is measured as a function of coronary pressure with progressive coronary constriction. Open circles represent normal dogs, and closed triangles represent those with supravalvular aortic stenosis. The flow versus pressure relationship (left) shifts to the right and rotates clockwise when moving from normal to aortic stenosis. Its slope relates inversely to the amount of left ventricular hypertrophy (middle), indicating a dose-response relationship. Its intercept correlates directly with left ventricular filling pressures (right). In these ways, the decrease in slope corresponds to an increase in myocardial resistance and the change in intercept to a rising zero-flow pressure due to higher LV filling pressures (reprinted from Figures 1–3 of a 1993 publication [19]).