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

Figure 6

Clinical case of asymptomatic but severe stenosis: as detailed in the text, this 55-year-old asymptomatic man was referred for an incidental heart murmur on routine physical examination. A treadmill exercise test showed good functional capacity with no symptoms or abnormal responses, and echocardiography found normal ejection fraction. However, his bicuspid aortic valve had moderate-to-severe stenosis at baseline, rising to a mean gradient of 90 mmHg during intravenous dobutamine stress. Furthermore, his left anterior descending (LAD) coronary artery had an angiographically moderate-to-severe stenosis and fractional flow reserve (FFR) of 0.64 during intravenous adenosine infusion. When superimposing these curves (the distal coronary pressure tracing has been time-scaled to match the aortic pressure tracing), myocardial oxygen demand (systolic pressure time integral, or SPTI) greatly exceeds diastolic coronary supply (diastolic pressure time integral, or DPTI) due to increased SPTI from aortic stenosis and decreased DPTI due to coronary stenosis. Despite normal left ventricular function and a lack of symptoms, the patient underwent surgical aortic valve replacement (SAVR) and concomitant coronary artery bypass grafting (CABG) for extremely abnormal hemodynamics.