Flow Study of Surgical Coronary Artery Fistula as an Alternative to Sequential Bypass

Abstract

Surgical coronary artery fistula, in which the last anastomosis is created to a low-pressure cardiac chamber, was recently introduced as an alternative method to improve graft flow and patency in a sequential graft when coronary arteries are small or diffusely diseased. To assess graft flow, effect on haemodynamics, flow distribution and to determine proper size of the distal anastomosis, a saphenous vein was sequentially anastomosed from the ascending aorta to the left anterior descending artery and then to the left atrium in eight mongrel dogs. Graft flow was measured before and after opening the fistula to the left atrium between the ascending aorta and left anterior descending artery (flow A) and between the left anterior descending artery and left atrium (flow B). Left atrium pressure and systolic left ventricular pressure (mmHg) were recorded. The diameter of the distal anastomosis was regulated with a bulldog clamp. When distal anastomosis was at 2.5–3 mm mean(s.d.) flow A increased from 64.5(19.5) to 134.7(28.5)ml/min (P<0.01) without significant left atrial pressure or left ventricular pressure change. With a distal anastomosis of 4 mm or more, flow A increased from 69.8(19.9) to 396.1 (62.2) ml/min (P< 0.001). Left atrial pressure increased from 5.6(1.0) to 6.1(0.9) mmHg (P< 0.05) without a change in left ventricular pressure. In both sizes of distal anastomosis, flow to the left anterior descending artery did not change either before or after the shunt (flow B) was opened. Neither volume loading, rapid atrial pacing, neosynephrine or epinephrine infusions caused deleterious haemodynamic effects with the shunt open. In conclusion, a surgical coronary artery fistulation of 2.5–3 mm will effectively increase total graft flow without decreasing flow to the bypassed coronary artery and does not cause deleterious cardiac haemodynamics.