Cross-sectional area and volume compliance of porcine left coronary arteries

We have determined the cross-sectional area (CSA) compliance of the first several generations of pig coronary arteries and the volume compliance of the coronary arterial tree (vessels >0.5 mm in diameter) using a videodensitometric technique. The coronary arteries of four KCl-arrested maximally vasodilated pig hearts were perfused with iodine and 3% Cab-O-Sil. Because Cab-O-Sil occludes small arteries, the flow can be stopped and the pressure can be maintained while the trunk of the coronary artery and its subbranches are imaged using digital angiography. The coronary arteries were preconditioned several times with cyclic changes in pressure from 0 to 160 mmHg. The pressure was then varied in a triangular pattern, and the absolute CSA of each vessel and the total arterial volume were calculated using videodensitometry in conjunction with digital subtraction angiography. Our results have shown that the pressure-diameter and pressure-volume relationships are linear in the 60-140 mmHg pressure range. Furthermore, the compliance of the coronary arteries is small; i.e., the diameter of the coronary artery changes by <15% in the 80-mmHg pressure range. The compliance data couples the mechanics of the blood vessel wall to the mechanics of blood flow to yield a pressure-flow relationship for each coronary arterial segment.