Wave-intensity analysis: a new approach to coronary hemodynamics

In 10 anesthetized dogs, we measured high-fidelity left circumflex coronary (P-LCx), aortic (P-Ao), and left, ventricular (P-LV) pressures and left circumflex velocity (U-LCx; Doppler) and used wave-intensity analysis (WIA) to identify the determinants of P-LCx and U-LCx. Dogs were paced from the right atrium (control 1) or right ventricle by use of single (control 2) and then paired pacing to evaluate the effects of left ventricular contraction on P-LCx and U-LCx. During left ventricular isovolumic contraction, P-LCx exceeded P-Ao, paired pacing increasing the difference. Paired pacing increased Delta P-x (the P-LCx-P-Ao difference at the P-Ao-P-LV crossover) and average dP(LCx)/dt (P < 0.0001 for both). During this time, WIA identified a backward-going compression wave (BCW) that increased P-LCx and decreased U-LCx; the BCW increased during paired pacing (P < 0.0001). After the aortic valve opened, the increase in P-Ao caused a forward-going compression wave that, when it exceeded the BCW, caused U-LCx to increase, despite P-LV and (presumably) elastance continuing to increase. Thus WIA identifies the contributions of upstream (aortic) and downstream (microcirculatory) effects on P-LCx and U-LCx.