Coronary-aortic interaction during ventricular isovolumic contraction

Abstract

In earlier work, we suggested that the start of the isovolumic contraction period could be detected in arterial pressure waveforms as the start of a temporary pre-systolic pressure perturbation (AIC(start), start of the Arterially detected Isovolumic Contraction), and proposed the retrograde coronary blood volume flow in combination with a backwards traveling pressure wave as its most likely origin. In this study, we tested this hypothesis by means of a coronary artery occlusion protocol. In six Yorkshire × Landrace swine, we simultaneously occluded the left anterior descending (LAD) and left circumflex (LCx) artery for 5 s followed by a 20-s reperfusion period and repeated this sequence at least two more times. A similar procedure was used to occlude only the right coronary artery (RCA) and finally all three main coronary arteries simultaneously. None of the occlusion protocols caused a decrease in the arterial pressure perturbation in the aorta during occlusion (P > 0.20) nor an increase during reactive hyperemia (P > 0.22), despite a higher deceleration of coronary blood volume flow (P = 0.03) or increased coronary conductance (P = 0.04) during hyperemia. These results show that the pre-systolic aortic pressure perturbation does not originate from the coronary arteries.

Fig. 1

Example of an aortic pressure curve with the pressure perturbation enlarged on the right. AIC_start (start of the arterially-detected isovolumic contraction) is indicated by the dash-dot vertical line and the preceding Q-top of the ECG by a triangle. The enlargement shows the touching tangent (dotted line) and the area between the pressure perturbation and this tangent (PPA)

Fig. 2

Shown are the aortic pressure and coronary blood volume flow (CBF) in the left anterior descending (LAD) and right common artery (RCA) during three vessel occlusion, with each period in a sequence expanded for one beat to show details. The start and end of occlusion are indicated with a solid vertical line. The vertical dashed lines indicate the Q-top of the ECG for the expanded beats. The ticks on the time axis represent a 1 s interval

Fig. 3

Pressure perturbation area (PPA) at baseline (BL) and during coronary artery occlusion (CAO). Shown are individual animals (open symbols) and mean ± SD (solid circles)

Fig. 4

Pressure perturbation area (PPA) at baseline (BL) and hyperemia (H). Shown are individual animals (open symbols) and mean ± SD (solid circles)