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01 сентября 2001 00:00

Myocardial revascularization with the left internal thoracic artery Y graft configuration

Background . The proved long-term patency of the left internal thoracic artery (LITA) has made it the conduit of choice for myocardial revascularization. Maximal utilizable LITA length can be achieved by using a semi-skeletonizing harvest technique. Expanded LITA use with sequential and Y graft techniques allows for a wider territory of myocardial revascularization.
Methods . A retrospective analysis of 30 patients undergoing coronary artery bypass surgery with a LITA-Y graft between December 1994 and November 1996 was performed. In selected patients the LITA was cut to length and anastomosed to the left anterior descending artery (LAD), with the redundant length of LITA used as a free graft to the lateral circumflex and diagonal systems. The proximal end of the free LITA was anastomosed to the in situ LITA to form the Y graft. Selection criteria included: a) minimal distal disease in the LAD and circumflex systems; and b) graftable circumflex branches proximal to the mid free wall of the left ventricle, allowing total revascularization of the left coronary system with the Y graft.
Results . Thirty patients (22 male, 8 female) underwent the LITA-Y graft procedure. There were no deaths or episodes of myocardial infarction. One patient required inotropic and intraaortic balloon pump support. Two patients with isolated coronary ostial stenosis developed recurrence of angina due to occlusion of the free limb of the LITA.
Conclusions . In patients with suitable coronary artery anatomy, the LITA-Y graft can be successfully performed with good short-term outcome, but may be contraindicated in the management of isolated coronary ostial stenosis.
 
 
 
The superior short- and long-term patency of the left internal thoracic artery (LITA) has made it the conduit of choice in myocardial revascularization. Abandonment of traditional pedicle harvesting technique in favor of a semi-skeletonizing one [1] allows for maximal utilizable LITA length. The use of the LITA has provided enhanced patient survival and improved freedom from angina, myocardial infarction, and reoperation [2] . In selected patients with favorable coronary artery anatomy, we have extended the use of the LITA to completely revascularize the left coronary system.
Material and methods
Patients
A retrospective analysis of all patients (n = 30) who underwent myocardial revascularization with the LITA-Y graft configuration between December 1994 and November 1996 was performed. Patients were deemed suitable for the procedure if there was: a) minimal distal disease in the left anterior descending artery (LAD) and circumflex arterial systems; and b) graftable circumflex branches proximal to the mid free wall of the left ventricle (normally marked by the lateral cardiac vein), allowing total left coronary system revascularization with the LITA-Y graft configuration . [Figure 1] Patients with flow-limiting lesions of circumflex branches beyond the lateral cardiac vein were not considered for the procedure because of insufficient conduit length.
            Operative technique
The procedure was performed via median sternotomy, and the LITA harvested using a semi-skeletonizing technique from the upper border of the first rib to its terminal division into musculophrenic and superior epigastric arteries [3] . Medial thymic attachments of the LITA were divided. A lateral pericardiotomy was made at the level of the left atrial appendage down to the left phrenic nerve. Routine cardiopulmonary bypass with intermittent antegrade cold blood cardioplegia was used in all cases. The LITA was measured for length to the LAD anastomotic site and divided. The distal free segment of LITA was anastomosed to the target free wall artery. The in situ LITA was then anastomosed to the LAD. Thereafter, the proximal end of the free LITA was anastomosed end to side to the in situ LITA to form the composite Y graft [4] . All anastomoses were constructed with a running 7/0 polypropylene suture.
Follow-up
Electrocardiogram and chest roentgenogram were performed postoperatively on days 0, 1, 2, and 5. All patients underwent surgical review at 5 weeks, and thereafter by their referring cardiologists. Follow-up was performed by a questionnaire to the referring cardiologists. Exercise stress testing was performed according to the routine practice of the cardiologist.
Results
There were 22 males and 8 females with a mean age of 62 years (range 50−77) who underwent the Y graft procedure using the LITA. Left ventricular ejection fraction was greater than 0.5 in 25 patients (range 0.3−0.7). Nine patients underwent semi-urgent revascularization, 7 for left main coronary artery stenosis or equivalent, and 3 with unstable angina (one with both). Twenty-three patients had double-vessel disease and underwent revascularization with the LITA-Y configuration. Seven patients had triple vessel disease and had an additional aorto-coronary bypass graft to the right coronary system. A total of 78 distal anastomoses were performed, with an average of 2.6 anastomoses per patient. The free limb ended at an high diagonal artery in 1 case, the intermediate artery in 7 cases, and to the lateral circumflex artery in 22 cases. Sequential anastomoses with the free limb were performed in 3 patients and with the in situ LITA in 4 patients . [Figure 2] There were no deaths or episodes of myocardial infarction. One patient developed electrocardiographic changes with S-T elevation and inadequate hemodynamic parameters after initial separation from cardiopulmonary bypass. An aorto-coronary saphenous vein graft was performed to the lateral circumflex artery. Inotrope and intraaortic balloon pump support were used for subsequent separation from cardiopulmonary bypass. All patients were alive at follow-up (mean 8.4 months; range 1−23 months). Two patients developed recurrence of angina at 2 and 7 months. These were 2 of the only 3 patients in the series with isolated left coronary ostial stenosis preoperatively. Seventeen other patients underwent postoperative exercise stress tests, which were negative. Four patients had repeat angiography. Of the 2 patients with recurrent angina, 1 had an occluded free limb of the Y graft and the other had a «string sign» of the free limb. A third patient had atypical chest pain in the first few days postoperatively, and despite the absence of objective evidence of ischemia, underwent repeat angiography before discharge . [Figure 3] He remained free of angina thereafter. The fourth patient, who was asymptomatic and active, consented to elective angiography at 6 months, and this showed occlusion of the limb to the LAD. He had undergone surgery for triple-vessel disease but the LAD had a low-grade stenosis.
Discussion
The LITA has the highest patency rate of all bypass conduits, both short and long term. An increase in diameter of the ITA graft in response to flow demand has been observed [5] . The expanded use of the LITA as a sequential [6] and a Y configuration [4] [7] has been previously described. Use of the LITA to bypass the LAD and circumflex systems in double-vessel disease avoids the donor site morbidity associated with harvesting a second conduit. The skeletonizing technique of harvest provides sufficient length for most lateral circumflex anastomoses proximal to the mid free wall of the left ventricle. The absence of distal coronary artery disease allows for the anastomosis in the proximal half of the LAD, leaving sufficient length of free LITA to reach the circumflex system. Two of the 3 patients who had isolated coronary ostial stenosis developed recurrence of symptoms. It is considered that in these patients the coronary artery perfusion pressure at rest may be close to normal such that there is competitive flow. The gradient across the ostial stenosis becomes significant with exercise. It is likely that competitive flow will cause graft closure if the diameter of the conduit is significantly less than the diameter of the coronary artery at the level of the anastomosis. Thus, the smaller free limb tends to close. It is recommended that either coronary ostial vein patching or coronary bypass grafting with conduit of sufficient diameter to match the recipient coronary arteries be performed in this situation.
The patient who received a supplemental vein graft may have had internal thoracic artery (ITA) flow insufficiency or myocardial stunning. The causes of ITA insufficiency include subclavian or ITA atherosclerosis, unrecognized damage during harvesting, and technical error in the performance of the anastomosis. The cause was not identified, and vein graft augmentation is considered the safest option.
 
 
 
 
References
1.Horii T., Suma H.. Semiskeletonization of the internal thoracic artery. Ann Thorac Surg 1997;63:867−868.
2.Loop F.D., Lytle B.W., Cosgrove D.M.. Influence of the internal mammary artery graft on 10−year survival and other cardiac events. N Engl J Med 1986;314:1−6.
3.Cunningham J.M., Gharavi M.A., Fardin R., Meek R.A.. Considerations in the skeletonization technique of internal thoracic artery dissection. Ann Thorac Surg 1992;54:947−951.
4.Bonchek L.I., Burlingame M.W., Vazales B.E., Lundy E.F.. Maximal utilization of the left internal mammary artery for coronary bypass grafting. Ann Thorac Surg 1996;61:1848−1849.
5.McBride L.R., Barner H.B.. The left internal mammary artery as a sequential graft to the left anterior descending system. J Thorac Cardiovasc Surg 1983;86:703−705.
6.Tector A.J., Schmahal T.M., Canino V.R., Kallies J.R., Sanfillipo D.. The role of the sequential internal mammary artery graft in coronary surgery. Circulation 1984;70:222−225.
7.Slater A.D., Gott J.P., Gray L.A.. Extended use of bilateral internal mammary arteries for coronary artery disease. Ann Thorac Surg 1990;49:1014−1015.
 

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