THE EFFECTS ON BLOOD FLOWS OF CORONARY-ARTERY BYPASS GRAFTS DURING INTRAAORTIC BALLOON PUMPING

The internal thoracic artery (ITA), as well as aortocoronary by-pass g rafts, has been used for widely coronary artery by-pass grafting. Intr a-aortic balloon pumping (lABP) is the first choice for left ventricul ar support when low output syndrome occurs during coronary artery by-p ass surgery. However, the effect of diastolic augmentation by IABP may vary to the type of grafts. Graft flow with and without IABP support were measured in six patients undergoing elective coronary artery bypa ss surgery requiring IABP at Kanazawa National Hospital. The patients ranged in age from 59 to 67 years, with a mean age of 63 years, and in cluded one woman and five men. In all cases, the left ITA was dissecte d from the thoracic wall as pedicle, and anastomosed in situ to the le ft anterior descending artery. Saphenous vein grafts (SVGs) were used for aortocoronary by-pass to the obtuse marginal branches, the first d iagonal branches, the left circumflex branches, and/or the right coron ary artery. Blood flow in 6 ITAs, 11 SVGs to the left coronary artery systems, and three SVGs to the right coronary artery was measured by u ltrasound transit-time flowmeter simultaneously with the electrocardio gram. Blood flows in ITA grafts and SVGs were measured during IABP ass ist and unassisting under hemodynamically stable conditions after disc ontinuing cardiopulmonary by-pass. The systolic and diastolic flows of each graft were measured using the peak of the R wave and the end of T wave on the electrocardiogram as the references for systole. Systoli c flow during IABP were similar to unassisted flow in both ITA and SVG s. LABP increased the diastolic flow by 76% in SVGs, but only by 28% i n ITA. The increase of the diastolic flow was lower in ITA than in SVG s (p < 0.05). In conclusion, the anatomical distance of each graft fro m the heart was an important factor in determining blood flow through a coronary by-passgraft, as well as coronary artery resistance, severi ty of stenosis in the native coronary artery and systemic blood pressu re. LABP enhances diastolic flow in the bypass graft more in SVGs than in ITA.