Bifurcated (“Y”) internal thoracic–coronary artery grafts

Coronary Artery Bypass Grafting Using a Bifurcated Internal Thoracic Artery

Coronary artery bypass grafting was performed successfully on a patient by anastomosing the left internal thoracic artery and its pericardiacophrenic branch to the obtuse marginal and the posterior descending coronary artery, respectively, to form a Y graft. Preoperative angiography of the internal thoracic artery had revealed the presence of an unusually large pericardiacophrenic branch almost the size of the main trunk, which allowed us to plan for bifurcated artery grafting.

Technical aspects and outcome of in situ right internal thoracic artery grafting to the major branches of the circumflex artery via the transverse sinus

BACKGROUND

Little is known about the anatomic limitations of in situ right internal thoracic artery (RITA) grafting to the circumflex artery.

METHODS

To evaluate the technical aspects and outcome of revascularization of the proximal and distal major branches of the circumflex artery (obtuse marginal [OM] branch and posterolateral [PL] branch), a total of 145 patients who possessed a graftable branch of the circumflex artery were enrolled into the prospective project. There were 73 patients who had the PL branch as a primary target and 72 patients with OM branches, which were allocated by a blinded observer who reviewed the preoperative angiography.

RESULTS

Changes of primary target vessels were required in 9 patients (6.2%), yielding an overall success rate of RITA grafting of 93.8%. The success rates of RITA grafting to the OM branch and the PL branch were 95.8% (69/72; CI 88.3% to 99.1%) and 91.7% (67/73; CI 83.0% to 96.9%), respectively. The univariate analysis identified grafting under hypothermic ventricular fibrillation as predictors of inability to use in situ RITA grafting for revascularization of the circumflex artery. RITA grafting to the PL branch is not identified as a predictor. Postoperative angiography in 136 patients revealed only one occlusion (0.75%) of the RITA graft anastomosed to the marginal artery. There were no significant differences in patency rates between left and right ITA grafts.

CONCLUSIONS

This prospective study showed that in situ RITA was, in most cases, able to reach most branches of the major circumflex artery and demonstrated an excellent patency rate.

The impact of chronic renal failure on atherosclerosis of the internal thoracic arteries

BACKGROUND

Little is known about the impact of renal failure on atherosclerotic changes in the internal thoracic artery (ITA).

METHODS

A total of 20 consecutive patients on chronic dialysis who underwent coronary artery bypass grafting (CABG) during April 1998 through September 1999 were investigated. The 20 control patients were selected from the same interval to rigorously match risk factors. Atherosclerosis of the ITA collected from each patient was analyzed using the subjective evaluation proposed by Kay and colleagues.

RESULTS

There were no cases of greater than 25% atherosclerotic luminal narrowing among a total of 35 ITA specimens from dialysis patients. The degree of atherosclerosis was not significantly different from that of the specimens from matched patients (p = 0.18). No calcification was found in ITA grafts either microscopically or macroscopically. The number of elastic lamellae, an index of the elasticity of the ITA graft, was not significantly different from those obtained from the matched patients. Analysis of preoperative coronary angiography revealed that coronary calcification was significantly more frequent in dialysis patients (15 patients, 75%) than in matched patients (p < 0.05). By analysis of postoperative angiography in dialysis patients, no evidence of atherosclerotic changes was found in 28 opacified ITAs. In addition, despite the presence of calcification in the native coronary, no calcification was evident along the entire length of the ITAs.

CONCLUSIONS

This study revealed the minimal impact of chronic renal failure on atherosclerotic changes in the ITA. The results of this study support the continued use of ITA grafting in dialysis patients.

Is internal thoracic artery grafting suitable for a moderately stenotic coronary artery?

Grafting an internal thoracic artery to a coronary artery with moderate stenosis remains controversial. Competitive flow from the native coronary artery has been proposed as the cause of distal narrowing and ultimate failure of the internal thoracic artery graft. We investigated intraoperative phasic blood flow in internal thoracic arteries grafted to coronary arteries with various degrees of stenosis and the influence of stenosis on postoperative angiographic findings. One hundred patients who underwent coronary artery bypass grafting of an internal thoracic artery to the left anterior descending coronary artery were divided into three groups according to degree of coronary stenosis. Group 1 included 39 patients who had 75% or less stenosis, group 2 included 34 patients with stenosis from 76% to 90%, and group 3 included 27 patients with stenosis greater than 90%. Mean flow and peak systolic flow of internal thoracic artery graft in group 1 were lower than those in group 2 (p < 0.01, p < 0.05). Peak diastolic flow in group 1 showed no difference from flows in groups 2 and 3. In eight patients in group 1, internal thoracic artery flow showed a predominant diastolic peak with characteristic systolic reversal as a result of competitive flow from the native coronary artery. Angiography at 1 month showed that the internal thoracic artery graft was patent in every case. Relative contributions of native coronary artery and internal thoracic artery flow to distal perfusion differed among the three groups (p < 0.001). In group 1, 15% of patients showed native-dominant flow, 62% showed balanced flow, and 23% showed internal thoracic artery-dependent flow. In group 2, 9% of patients showed native-dominant flow, 29% showed balanced flow, and 62% showed internal thoracic artery-dependent flow. In group 3, 96% of patients showed internal thoracic artery-dependent flow. String sign of the internal thoracic artery graft developed in only three patients; in two of these patients internal thoracic arteries were grafted to coronary arteries with stenosis of 50% or less and in the other patient there was competitive flow from a diagonal vein graft. Eleven of 13 internal thoracic arteries grafted to coronary arteries with stenosis of 50% or less did not show string sign. Competitive flow from a moderately stenotic coronary artery did not predispose the patient toward string sign of the internal thoracic artery graft in the presence of substantial diastolic internal thoracic artery flow. We conclude that internal thoracic artery grafting is acceptable for a moderately stenotic coronary artery.

Greater contractility of internal mammary artery bifurcation: possible cause of low patency rates

Coronary artery bypass grafting using bifurcation of the internal mammary artery (IMA) has been reported to have a poor patency rate. To test the hypothesis that the contractility (tendency for spasm) is greater at the bifurcation than at the main IMA, segments of the bifurcation and the distal section of IMA taken from patients with coronary artery bypass grafts were studied in organ baths. The IMA rings were set up at a physiologic pressure. Concentration-response curves were established for norepinephrine, endothelin-1, U46619, potassium, and glyceryl trinitrate (precontracted with 10 nmol/L U46619). Contraction forces were standardized (gram per mm circumference) at a pressure of 100 mm Hg. The diameter was 1.50 +/- 0.08 mm (n = 38) for the bifurcation and 2.03 +/- 0.07 (n = 42) for the main IMA (p < 0.0001). The standardized contraction force was greater in the bifurcation than in the main IMA for norepinephrine (0.82 +/- 0.06 versus 0.54 +/- 0.1; p = 0.02) and endothelin-1 (1.07 +/- 0.11 versus 0.69 +/- 0.07; p = 0.02). No differences were seen for potassium, U46619, or glyceryl trinitrate, whereas the effective concentration that induced 50% of maximal effect for U46619 was 6.17-fold lower in the bifurcation than in the main IMA (9.14 +/- 0.28 versus 8.35 +/- 0.09 -log M; p = 0.003), indicating higher sensitivity in the bifurcation.(ABSTRACT TRUNCATED AT 250 WORDS)