Coronary haemodynamics and wave intensity analysis in aortic stenosis

Abstract

Introduction: Coronary Wave Intensity Analysis (WIA) provides an invasive measure of energy transfer within the coronary circulation. I set out to derive a non-invasive measure of the backward expansion wave (BEW) responsible for coronary flow and assess it during exercise and in aortic stenosis (AS). Methods: 17 patients (mean age 60, 11 male) with normal cardiac function underwent invasive LAD WIA calculation using a pressure- and flow-tipped wire. Non-invasive WIA was calculated immediately after angiography from simultaneous PW Doppler of the LAD and a suprasystolic-cuff derived measure of central pressure. Non-invasive WIA was then assessed in 9 healthy volunteers whilst exercising on an exercise bike, 25 patients with varying degrees of AS (AVmax range: 2.41-5.43m/s) and 29 patients before, after and at 6 and 12 months following aortic valve intervention for severe AS. Results: Mean peak BEW was -14.7± 8.7x104 Wm-2s-2 invasively and -14.4± 8.2 Wm-2s-2 non-invasively and increased with exercise (at peak: -20.5±6.8Wm-2s-2, p=0.02) along with a rise in coronary flow (28.8cm/s to 42.1cm/s, p 0.06). A significant correlation was noted with the BEW and AS severity, strongest when valvulo-arterial impedence was assessed (r=-0.66, p<0.001). In severe AS, a reduction in coronary flow (0.41 to 0.33m/s, p<0.01) and the BEW (-22.1 vs 10.9x104Wm-2s-2, p<0.01) was seen after intervention. With LVH regression BEW increased (-21.6±12.6x104 Wm-2s-2 at 6 months) without a significant change in coronary flow. Conclusion: It is possible to construct a non-invasive measure of coronary WIA thus markedly increasing its applicability. Using this technique, the BEW is seen to increase during progressive levels of exercise accounting for the increase in coronary flow. The BEW progressively climbs with increasing AS, falls to sub-normal levels after aortic valve intervention but then increases to normal levels with LVH regression.