Coronary microcirculatory dysfunction in aortic stenosis

Development of left ventricular hypertrophy (LVH) in aortic stenosis (AS) is accompanied by dysfunction of the coronary microcirculation, demonstrated by an impaired coronary vasodilator reserve (CVR), but the relative contribution of LVH and changes in haemodynamics remains unclear. In twenty patients with AS, an increase in resting myocardial blood flow (MBF), assessed with positron emission tomography, was demonstrated, proportional to hypertrophy measured with cardiac magnetic resonance, presumably as a result of coronary autoregulation. However, an inverse relationship between CVR and echocardiographic peak transvalvular pressure gradient and left ventricular pressure multiplied by heart rate (LVRPP) suggests that the effect of haemodynamic and intramural forces may be to counteract autoregulation, maintaining transmural MBF at rest, but impairing the coronary microcirculation stress response, particularly within the subendocardium.