Background: Different haemodynamics are present in left ventricular hypertrophy (LVH) due to arterial hypertension and aortic stenosis (AS) and these can have different effects on the microvasculature. We explored this by applying wave intensity analysis to (1) identify the proximal- and distal-originating intracoronary waves determining the flow velocity waveform and (2) investigate the extravascular influences on these waves.

Methods: Thirty-one patients (mean age 63±12years, 18 female) with unobstructed coronary arteries, ten of whom had severe aortic stenosis, underwent simultaneous pressure and Doppler velocity measurements with sensor-tipped intra-arterial wires in each of the left coronary arteries to derive wave intensity.

Results: In subjects with normal valves, the microcirculatory waves already accounted for the majority of the intra-coronary wave energy (54.7±6.0%), but in the AS patients this rose to 74.1±10.7%, p<0.001. This resulted from larger absolute microcirculatory originating waves, both during systolic microvascular compression (no valve disease: 1.4 [0.6–3.2] x10³Wm⁻²s⁻¹ versus AS: 11.7 [5.4–25.5] x10³Wm⁻²s⁻¹, p<0.001) and during diastolic microvascular relaxation (no valve disease: 14.0 [6.6–18.0] x10³Wm⁻²s⁻¹ versus AS: 31.1 [20.4–47.4] x10³Wm⁻²s⁻¹, p<0.001). Haemodynamic loading of the left ventricle accounted for the extent of the compression wave (r=0.79, p<0.001) and the diastolic microvascular relaxation wave was accounted for by reduced diastolic time (r=−0.62, p<0.001).

Conclusion: Coronary circulation in aortic stenosis is even more dependent on distal-originating waves than it is in normals and this is in contrast to what is seen in LVH due to arterial hypertension. This is because the enhanced extravascular force overwhelms any local impairment within the microvasculature.