This study proposes a method to examine the in-vivo pressure-volume (P-V) relationship of an epicardial coronary artery. With the proximal left anterior descending (LAD) artery in a dog occluded, the distal LAD flow oscillates around zero. Integration of the flow with respect to time yields the intraluminal arterial segment volume changes in the region between the site of occlusion and the flow probe. The distal LAD pressure is measured via a diagonal branch. The segmental P-V relationship exhibits a hysteresis loop. The area bound by the hysteresis loop corresponds to the energy loss on the arterial wall during one cycle (12.63±8.25 [erg·cm−1], n = 7), while the dynamic arterial compliance is calculated based on the ratio of the volume to pressure excursions (1.13±0.73 [m1·mmHg−1·cm−1·10−4]). These results represent first estimates of the in-vivo mechanical properties of the coronary arterial wall based on P-V measurements.

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