Effect of Warm‐Up Exercise on Myocardial Perfusion Studied with Wave Intensity Analysis

Background The effect of warm‐up on myocardial perfusion in patients with coronary artery disease (CAD) is not well understood. We compared outcomes of repeat exercise periods using wave intensity (WI) analysis. Coronary WI reflects the effects of cardiac contraction and relaxation on coronary blood flow dynamics and distinguishes between left ventricular (forward, FW) and microcirculatory (backward, BW) originating contributions. Methods During cardiac catheterization in 10 patients with CAD, we simultaneously recorded aortic pressure, distal coronary pressure (Pd) and flow velocity (U), while the patients performed 2 serial periods of supine bicycle exercise (Ex1, Ex2). WI was calculated as (dPd/dt)(dU/dt) and the separate BW and FW contributions were derived. Results Patients reached similar exercise levels in Ex1 and Ex2, but time to ischemia was longer during Ex2. At the same cardiac workload, Pd was unchanged in Ex2 indicating absence of vasoconstriction. Concomitantly, U increased by 10% (p<0.03) and microvascular resistance (Pd/U) decreased by 20% during Ex2 (p<0.01). In contrast to FW, BW wave energy was more than 30% higher in Ex2 (p<0.05). The energy of flow accelerating waves was 20% higher in Ex2, with no difference in the flow decelerating waves. Conclusion Our results suggest a warm‐up effect as evidenced by indices of improved myocardial perfusion at repeat exercise.