Management of complex thoracic aortic diseases with aberrant right subclavian artery.

BACKGROUND: We retrospectively evaluated early and intermediate outcomes of hybrid repair of complex thoracic aortic diseases involving an aberrant right subclavian artery. This paper aims to report features and available treatment options for this rare, hard-to-diagnose, and manage, aorta-related vascular condition. METHODS: Between January 2012 and May 2019, 13 patients (mean age, 60.1 ± 9.3 years; nine men) underwent complex thoracic aorta repair surgery. Six patients had a thoracic aortic aneurysm, two had type A aortic dissection, and five had complicated type B aortic dissection. Hybrid repair strategies included de-branching in combination with single-stage aortic arch replacement with the frozen elephant trunk technique performed in four patients, thoracic endovascular aortic repair in six patients, and 2-stage hybrid repair consisting of a total arch replacement with a conventional/frozen elephant trunk (first stage) and subsequent endovascular repair (second stage) in three patients. RESULTS: One early death occurred: a patient with acute type A aortic dissection, who underwent Bentall procedure and aortic arch replacement with the frozen elephant trunk technique, died in-hospital of multiorgan failure 41 days after the procedure. The remaining 12 patients were discharged in stable condition. The median follow-up duration was 36 months (2-71 months). Two late mortalities occurred: a patient with residual type A aortic dissection, who underwent arch replacement with the frozen elephant trunk technique, died of intracranial hemorrhage 3 months after the surgery. And 72 years old female patient died of acute exacerbation of chronic obstructive pulmonary disease 2 months after the surgery. CONCLUSION: Our study indicates that various hybrid strategies can be used to treat complex thoracic aortic diseases involving an aberrant right subclavian artery. The approach of choice depends on the features of disease pathology, the aortic segments involved, and the operating surgeon's experience.

Cost-Effectiveness and Clinical Outcome of Transcatheter Versus Sutureless Aortic Valve Replacement.

BACKGROUND: Sutureless aortic valve replacement (SU-AVR) and transcatheter aortic valve implantation (TAVI) are becoming increasingly common. The aim of this study is to compare the clinical outcome and cost-effectiveness of the two methods. METHODS: In this study, cross-sectional retrospective data were collected on 327 patients who underwent SU-AVR (n = 168) and TAVI (n = 159). Homogeneous groups were provided by the "propensity score matching" method, and 61 patients from the SU-AVR group and 53 patients from the TAVI group were included in the study sample. RESULTS: The two groups did not have statistically different death rates, complications after surgery, lengths of hospital stays, or visits to the intensive care unit. It is stated that the SU-AVR method provides an additional 1.14 Quality-Adjusted Life Year (QALY) compared to the TAVI method. The TAVI was more expensive than the SU-AVR in our study, but the difference was not statistically significant ($40,520.62 vs. $38,405.62, p > 0.05). For SU-AVR, the most expensive factor was the length of stay in the intensive care unit; for TAVI, it was arrhythmia, bleeding, and renal failure. CONCLUSIONS: These bioprostheses are safe and effective treatments for valve stenosis. Clinical outcomes were similar between the two groups. Therefore, clinicians may find it difficult to determine an effective treatment strategy. According to the evaluation made in terms of cost-effectiveness, it was found that the SU-AVR method gave a higher QALY at a lower cost compared to the TAVI method. However, this result is not statistically significant.

Comparison of percutaneous access and open femoral cutdown in elective endovascular aortic repair of abdominal aortic aneurysms.

Background: The aim of this study was to compare postoperative outcomes of percutaneous access and femoral cutdown methods for elective bifurcated endovascular abdominal aortic aneurysm repair. Methods: Between November 2013 and September 2020, a total of 152 patient (135 males, 17 females; mean age: 70.6±6, range, 57 to 87 years) who underwent endovascular repair due to infrarenal abdominal aortic aneurysm were retrospectively analyzed. According to femoral access type, the patients were grouped into two groups as the total percutaneous femoral access and open cutdown femoral access endovascular repair. Intra- and postoperative data were compared, including operative time, amount of contrast media, bleeding requiring transfusion, return to the operating room, access vessel complications, wound complications, and overall length of hospital stay. Results: Eighty-seven (57.2%) femoral cutdown access repair and 65 (42.8%) percutaneous femoral access repair cases were evaluated in the study. The two groups were comparable in terms of demographic and clinical characteristics (p>0.05), except for chronic obstructive pulmonary disease which was more frequent in the percutaneous access group (p=0.014). After adjustment, age, diabetes mellitus, chronic obstructive pulmonary disease, and obesity were not predictive of percutaneous access failure. Percutaneous femoral access was observed as the only preventing factor for wound infection (odds ratio=0.166, 95% confidence interval: 0.036-0.756; p=0.021). Conclusion: Although femoral access preference does not affect mortality and re-intervention rates, percutaneous endovascular repair reduces operation time, hospital stay, and wound site complications compared to femoral artery exposures.

Comparison between arch zones in modified frozen elephant trunk procedure for complex thoracic aortic diseases

Abstract Introduction: The aim of this study is to compare postoperative outcomes and follow-up of two different modifications facilitating surgical technique of frozen elephant trunk (FET) procedure for complex thoracic aortic diseases - zone 0 (fixation with total arch debranching) and zone 3 (fixation with islet-shape arch repair). Methods: From May 2012 to December 2018, data were collected from 139 patients who had been treated with FET procedure for complex thoracic aortic diseases. According to Ishimaru arch map, patients with proximal anastomotic site of hybrid graft at zone 0 and zone 3 were grouped as Group A (n=58, 41.7%) and Group B (n=81, 58.3%), respectively. Mean age of study population was 54.7±11.4 years, and 111 patients were male (79.9%). Results: In-hospital mortality was observed in 20 (14.4%) patients (n=12, acute type A aortic dissection, and n=4, previous aortic dissection surgery). There was no significant difference between both groups in terms of in-hospital mortality. Four patients from Group A and three patients from Group B had permanent neurological deficit (P=0.32). Three patients from both groups had transient spinal cord ischemia (P=0.334). Although mean total perfusion time was longer in Group A, duration of visceral ischemia, when compared with Group B, was shorter (P<0.001). Five-year survival rate was 82.8% in Group A and 81.5% in Group B (P=0.876). Conclusion: FET procedure is a feasible repair technique in the treatment of complex aortic diseases, providing satisfactory early results. Because of its advantageous aspects, zone 0 fixation with debranching is the preferred technique in our clinic.

Comparison between Arch Zones in Modified Frozen Elephant Trunk Procedure for Complex Thoracic Aortic Diseases.

INTRODUCTION: The aim of this study is to compare postoperative outcomes and follow-up of two different modifications facilitating surgical technique of frozen elephant trunk (FET) procedure for complex thoracic aortic diseases - zone 0 (fixation with total arch debranching) and zone 3 (fixation with islet-shape arch repair). METHODS: From May 2012 to December 2018, data were collected from 139 patients who had been treated with FET procedure for complex thoracic aortic diseases. According to Ishimaru arch map, patients with proximal anastomotic site of hybrid graft at zone 0 and zone 3 were grouped as Group A (n=58, 41.7%) and Group B (n=81, 58.3%), respectively. Mean age of study population was 54.7±11.4 years, and 111 patients were male (79.9%). RESULTS: In-hospital mortality was observed in 20 (14.4%) patients (n=12, acute type A aortic dissection, and n=4, previous aortic dissection surgery). There was no significant difference between both groups in terms of in-hospital mortality. Four patients from Group A and three patients from Group B had permanent neurological deficit (P=0.32). Three patients from both groups had transient spinal cord ischemia (P=0.334). Although mean total perfusion time was longer in Group A, duration of visceral ischemia, when compared with Group B, was shorter (P<0.001). Five-year survival rate was 82.8% in Group A and 81.5% in Group B (P=0.876). CONCLUSION: FET procedure is a feasible repair technique in the treatment of complex aortic diseases, providing satisfactory early results. Because of its advantageous aspects, zone 0 fixation with debranching is the preferred technique in our clinic.

Repair of residual aortic dissections with frozen elephant trunk technique.

BACKGROUND: In this study, we present our mid-term results of reoperation with the frozen elephant trunk procedure due to patent false lumen-related complications in patients previously undergoing supracoronary aortic repair for acute type A aortic dissection. METHODS: Between January 2013 and September 2018, a total of 23 patients (17 males, 6 females; mean age 51.5±9.7 years; range, 30 to 67 years) who underwent ascending aortic replacement due to type A aortic dissection and, later, frozen elephant trunk procedure for residual distal dissection were included. For diagnostic purposes and follow-up, computed tomography angiography was performed in all patients, and both re-entry and aortic diameters were evaluated. Echocardiography was used to evaluate cardiac function and valve pathologies. RESULTS: The Ishimaru zone 0 (n=11, 47.8%), Ishimaru zone 1 (n=1, 4.3%), Ishimaru zone 2 (n=4, 17.4%), and Ishimaru zone 3 (n=7, 30.4%) were used for frozen elephant trunk stent graft fixation. The mean duration of cardiopulmonary bypass and antegrade selective cerebral perfusion was 223.9±71.2 min and 88.9±60.3 min, respectively. In-hospital mortality was 13%, while there was one (4.3%) aortic-related death and four (17.4%) re-interventions during follow-up. CONCLUSION: Early repair should be considered in the presence of persistent dissections due to alarmingly high mortality rates of reoperations. Reoperation with the frozen elephant trunk procedure has acceptable results and the decision of the procedure to be performed should be based on preoperative risk factors of the patient.

Hybrid Treatment of Complex Aortic Arch Anomaly with Saccular Aneurysm.

Aortic arch anomalies are not clinically important unless they cause compression symptoms due to aneurysmatic dilatation. Aortic anomalies need to be treated when they cause complex thoracic aortic diseases, and the treatment approach has evolved over time from open surgical methods, which have high mortality and morbidity rates, to hybrid methods. A case of a 68-year-old male patient with complex aortic arch anomaly treated with hybrid arch repair is reported in this study. Aortic branches were common carotid trunk and aberrant right subclavian artery with a saccular aneurysm.

Hybrid treatment of complex aortic arch anomaly with saccular aneurysm

Abstract Aortic arch anomalies are not clinically important unless they cause compression symptoms due to aneurysmatic dilatation. Aortic anomalies need to be treated when they cause complex thoracic aortic diseases, and the treatment approach has evolved over time from open surgical methods, which have high mortality and morbidity rates, to hybrid methods. A case of a 68-year-old male patient with complex aortic arch anomaly treated with hybrid arch repair is reported in this study. Aortic branches were common carotid trunk and aberrant right subclavian artery with a saccular aneurysm.

Early and mid-term results of frozen elephant trunk procedure for acute type A aortic dissection.

BACKGROUND: This study aims to investigate the early and mid-term results of total thoracic aorta repair with E-vita OPEN PLUS stent graft, which we used to remove the residual false lumen and prevent late-term complications in patients with acute type A aortic dissections. METHODS: The study included 41 patients (29 males, 12 females; mean age 51.9±10.4 years; range, 30 to 77 years) who underwent total thoracic aorta repair with frozen elephant trunk stent graft for acute type A aortic dissection between November 2013 and November 2017. The reduction in false lumen size and thrombosis were evaluated by repeated computed tomographyangiography on 10th day and third, sixth, and 12th months. RESULTS: Six patients (14.6%) were lost during hospital stay and one patient (2.4%) was lost during the follow-up period. Frozen elephant trunk stent graft"s distal end at descending aorta ended at T6, T7, and T8 levels in 15 (36.6%), 21 (51.2%), and five (12.2%) patients, respectively. The supra-aortic vessels were re-implanted separately in 21 (51.2%) or as island in 20 (48.8%) patients. Transient paraparesis (spinal cord ischemia) was observed in only one patient (2.4%), while permanent neurologic deficit (stroke or coma) was observed in two patients (4.9%). Mean duration of follow-up was 26.5±20.5 months. Computed tomography-angiography at first month showed that false lumen became thrombosed at rates of 93.9% and 54.5% at pulmonary trunk and diaphragmatic level, respectively. CONCLUSION: We believe that total arcus repair in acute type A aortic dissection treatment with single-session frozen elephant trunk technique by ensuring early false lumen thrombosis is safe and successful.

Treatment of Retrograde Type B Aortic Dissection after Endovascular Repair of Abdominal Aortic Aneurysm.

Retrograde ascending aortic dissection during or after thoracic endovascular aortic repair is a nonfrequent complication (2.4%) especially in patients for type B aortic dissections with a high mortality rate (42%). This complication can occur not only during the index hospitalization but also after discharge up to 3 years. However, retrograde type B aortic dissection is much less common after standard endovascular repair for infrarenal abdominal aortic aneurysm. We present a 76-year-old female patient with a history of ascending aorta aneurysm and obesity who was referred to our clinic with retrograde type B aortic dissection 1 month after endovascular aneurysm repair due to infrarenal abdominal (contained) rupture.

Innominate vein cannulation: easy but neglected technique.

Introduction: Our experience in minimally invasive procedures and improvement of graft technology enables easy and successful operation carried out even with complex thoracic aortic diseases from limited surgical area. However, it should be more than one incision or cannulation site for such intervention. We aimed to present our experience and results of 23 patients who has ascending aorta and aortic arch pathologies of which we operated with J-shaped partial sternotomy and innominate vein cannulation. Methods: From January 2014 to January 2016, 23 patients with aorta and aortic valve pathologies who underwent aortic surgery with J-shaped partial sternotomy and innominate vein cannulation included. Operation findings, cardiopulmonary bypass (CPB) values, postoperative results, surgical mortality and morbidity rates, late conversion to full sternotomy rates, ICU and hospital length of stay were evaluated. Results: The mean age of the patients was 53.7±12 (range 19-68) and 18 (78.2%) were males. Arcus aorta debranching applied to 4 patients (17.3%) and one of these procedures was frozen elephant trunk procedure (4.3%). Neither mortality nor cerebrovascular accident occurred. Mean CPB peak flow was 4.6±0.4 L/min, mean flow index calculated as 2.01±0.38 L/min/m2 and there was no CPB problem intraoperatively. Innominate vein ligation was carried out in 5 patients but no complication was seen except one who had left arm swelling treated with elevation. Conclusion: Innominate vein cannulation with J-shaped partial sternotomy is a reliable and easily applicable method providing effective utilization of limited operative field not only in ascending aorta and aortic arch operations but also with the advancements of hybrid systems used in descending aorta pathologies.

Frozen Elephant Trunk and Antegrade Visceral Debranching in the Surgical Treatment of Type B Aortic Dissection: An Alternative Method.

Intervention is inevitable in complicated Type B aortic dissections. Classical surgical procedures and endovascular interventions are far from ideal treatments due to their high risk of periprocedural complications and mortality. There is often a need for alternative method in cases of difficult anatomy. We present the combined use of frozen elephant trunk and antegrade visceral debranching methods in the treatment of a 54-year-old male patient with complicated Type B aortic dissection.

Surgical treatment of double valve endocarditis.

BACKGROUND: We have retrospectively analyzed the results of the operations made for aortic infective endocarditis with mitral involvement in a single center in 19 years. METHODS: From May 1992 to January 2011, we have operated on 72 patients with infective endocarditis of the aortic valve with mitral valve involvement. Fifty-two patients (72.2%) were male and the mean age was 40.5 ± 15.5 (9-73) years. The blood cultures were positive in 33 patients (45.8%) and the most commonly identified microorganism was Streptococcus. Nine patients (12.5%) had prosthetic valve endocarditis. The mean duration of follow-up was 6.8 ± 4.7 (0.1-16.9) years, adding up to a total of 156.1 patient/years. RESULTS: A total of 155 procedures were performed on these 72 patients. The most commonly performed procedure was aortic valve replacement, in 63 patients (87.5%). Aortic annular involvement was present in 9 cases (12.5%). In-hospital mortality was seen in 13 patients (18.1%). Postoperatively, 13 (18.1%) patients had low cardiac output, 9 (12.5%) had heart block, and only 1 of them required permanent pacemaker implantation. The actuarial survival rates for 1, 5, and 10 years were 96.4% ± 2.5%, 84.4% ± 5.1%, and 77.4 ± 6.7%, respectively. CONCLUSIONS: Double-valve endocarditis is a serious condition and the surgeon must be aware of the high rates of mortality and morbidity in these patients. Although no association was found, heart blocks and septic embolization must be handled with caution. The patients generally do well after surgery, and recurrences and reoperations decrease by the second year after operation.

Treatment of left anterior descending coronary artery stenosis: stent or surgery.

BACKGROUND: Drug-eluting stents have emerged as a solution to the problem of restenosis after bare-metal stent implantation, as an alternative to off-pump coronary bypass, for isolated left anterior descending coronary artery lesions at short-term follow-up. However, long-term follow-up is yet to be defined. METHODS: From January to December 2004, 64 consecutive patients underwent myocardial revascularization: 31 by drug-eluting stents and 33 by off-pump coronary bypass. The primary endpoint was angiographic outcome, and the secondary endpoint was clinical outcome at 5 years. RESULTS: There was no early or late mortality in either group. Hospital stay was significantly shorter in the stent group (2.5 ± 2.1 vs. 7.1 ± 4.9 days, p = 0.003). Long-term patency was higher and major adverse cardiac events (recurrence of angina and revascularization of target vessel) were encountered less frequently in the coronary bypass group, although not significantly. CONCLUSION: The 5-year follow-up showed no significant difference between the off-pump coronary bypass and stent groups for the primary and secondary endpoints. As a significant difference between treatment options is lacking, decision-making for appropriate treatment in this group of patients requires the collaboration of cardiologists and cardiovascular surgeons and an individual approach, to achieve successful long-term outcomes.

Does aortic root enlargement impair the outcome of patients with small aortic root?

BACKGROUND: Posterior root enlargement procedures provide the implantation of suitable-sized prosthetic valves in patients with a small aortic root to prevent a high postoperative transvalvular gradient. The aim of this study was to evaluate long-term results of the posterior root enlargement. METHODS: Between 1985 and 2002, 124 patients underwent aortic valve replacement with a posterior root enlargement. The main indication was a small aortic valve orifice area to patient body surface area (indexed valve area < 0.85 cm2/m2). Fifty-four (44%) patients were male, and 70 (56%) were female with a mean age 39.1 +/- 14.3 years. Indications for operation were severe calcified aortic valve stenosis (37.1%), severe aortic insufficiency (25.8%), or combination (37.1%). Seventy-five (60%) patients received double-valve replacement. A pericardial patch was used in 100 patients (80.6%) and a Dacron patch was used in 24 patients. RESULTS: Operative mortality was 6.4% (8 patients). The causes of hospital mortality were low cardiac output syndrome (LCOS) (in 6 patients), cerebrovascular events (in 1 patient) and multiple organ failure (in 1 patient). Multivariate analysis demonstrated concomitant coronary revascularization to be a significant (p = 0.03) predictor for early mortality. There were six (5.4%) late deaths. Cox proportional hazards regression analysis demonstrated LCOS (p = 0.013) and infective endocarditis (p = 0.003) to be significant predictors for late mortality. Atrioventricular block required a permanent pacemaker was observed in 4 patients (3.2%). CONCLUSIONS: Posterior aortic root enlargement techniques can be easily applied without additional risks. Long-term survival and freedoms from valve-related complications are satisfactory.

Double supply to left anterior descending artery by additional saphenous vein graft in internal thoracic artery malperfusion syndrome.

OBJECTIVE: Internal thoracic artery (ITA) grafting to the left anterior descending artery (LAD) may have catastrophic consequences and can be fatal due to "ITA malperfusion syndrome." We have investigated the efficacy of a second graft in this syndrome. METHODS: A total of 35 patients, 29 males (82.9%) and 6 females (17.1%), with a mean age of 53.0 +/- 8.7, (range: 38 to 70) undergoing coronary artery bypass grafting required a second supply to LAD due to ITA malperfusion syndrome. This was performed using a saphenous vein graft. The mean number of distal anastomosis was 2.7 +/- 0.45 per patient (range: 1 to 5). The decision for an additional grafting procedure was made in the first operation for 18 patients (51.4%) (Group I). For the remaining 17 patients (48.6%) (Group II), the additional grafting procedures were performed during a reoperation after the development of ischemic complications in the intensive care unit (ICU). RESULTS: The early mortality rate was 8.6% (3 of 35). Two patients had perioperative myocardial infarction (MI) (5.7%). The second vein graft proved to dramatically reduce the incidence of postoperative MI. Malignant refractory arrhythmias were recorded in 17 patients (48.6%). Twelve patients (34.3%) required inotropic support and seven patients (20%), all in Group II, required intra-aortic balloon pump (IABP) support. The average duration of IABP was 5 days +/- 1.8 days (range: 3 to 7). The necessity of IABP support was found to be statistically higher in the second group compared to the first one. CONCLUSIONS: Double supply to LAD using an additional saphenous vein graft is the treatment of choice for ITA malperfusion syndrome. The time interval between the first and the second grafts appears to be crucial for postoperative patient outcome.

Does mediastinitis affect the graft patency?

As inflammation began to be recognized as a major contributor to the pathogenesis of atherosclerosis, we evaluated the patients that developed mediastinitis, a long-standing inflammatory process, after coronary artery bypass grafting. There are many studies that have focused on the graft patency. But, till now, no study has been done to detect the effects of mediastinitis to graft patency. So, we aimed to detect the effect of mediastinitis on the graft patency in patients who have undergone coronary artery bypass surgery. Sixteen of 45 patients who have been operated upon for coronary artery bypass surgery and developed mediastinitis, which was treated with open drainage and mediastinal irrigation with late wound closure, were included in the study. The mean age of the patients was 55 +/- 11 (range 35-69) and nine of the patients were male. The graft patency was evaluated with control coronary angiographies after a mean period of 30.42 +/- 43.17 months (range 1-132). The left internal thoracic artery was patent in all patients (100%). Right internal thoracic artery patency rate was 50% (1/2). One individual bypassed radial artery was patent, whereas the sequential bypassed graft was occluded. The patency ratio of radial artery anastomosis was 33% (1/3). Twelve of the 17 saphenous vein grafts were patent (70.58%). The total number of patent distal anastomosis was 30/38 (78.94%). When compared with the graft patency of patients without infection, it was found that mediastinitis does not affect the graft patency rates adversely.

Coronary artery disease and coronary artery bypass grafting in Behçet's disease.

There is a high frequency of pseudoaneurysm formation in patients with Behçet's disease and their inflammed and fragile tissues are difficult to manipulate. Five patients with Behçet's disease were referred to our cardiovascular surgery department for coronary artery bypass grafting (CABG). Three of them were operated and two were treated medically. Patients that were managed medically had left anterior descending (LAD) lesions below 80% and their stable angina pectoris responded well to medication. There was no early mortality and morbidity. One patient developed pseudoaneurysm of ascending aorta and femoral artery. This patient died in the late postoperative period. At follow-up the operated patients were in Canadian Cardiovascular Society (CCS) Class I, while the medically treated patients were in CCS Class II. Mean follow-up period was 41 +/- 36.21 months. Coronary artery disease (CAD) is extremely rare detected in patients with Behçet's disease. The affected patients are usually young males. Coronary artery bypass grafting is also rarely performed in these patients and long-term results of such operations are not available in the literature. We present five patients with Behçet's disease that had CAD, three operated and two medically treated, and report their long-term results. We suggest a conservative approach in patients with Behçet's disease because of the high risk of pseudoaneurysm formation in the postoperative period. If CABG cannot be avoided we recommend operating the patients on the beating heart with minimal aortic manipulation.

Surgery for chronic total occlusion of the left main coronary artery--myocardial preservation.

We report seven patients with chronic total occlusion of the left main coronary artery that were operated in our institution and discuss the myocardial preservation options in these patients. In addition to total occlusion of the left main coronary artery, three patients also had severe lesions of right coronary artery. Prior myocardial infarction history and significantly depressed left ventricle functions were detected in all three patients with right coronary artery lesions. Five patients were operated on cardiopulmonary bypass while two patients were operated off pump. All patients received alternating antegrade/retrograde cardioplegia for myocardial preservation. In patients with simultaneous right coronary artery disease we first established the origin of the collaterals to the left coronary system. For patients with collaterals arising from the right coronary artery segment distal to the right coronary artery lesion, the antegrade component was administered through the saphenous vein graft bypassed to a distal part of right coronary artery segment. Thus we have achieved a more effective distribution of the antegrade cardioplegia. In off-pump-operated patients the left coronary system was revascularized before the right coronary system. Postoperative low cardiac output syndrome occurred in only one patient who was operated off pump. There was no operative and early mortality. Mean follow-up was 32 +/- 21.42 (range, 4 to 60) months. Alternating antegrade/retrograde cardioplegia was used with acceptable results in patients with total occlusion of the left main coronary artery. In patients with simultaneous RCA lesion we recommend regulation of the antegrade component based on the origin of collaterals that supplies the left coronary system. In off-pump-operated patients we suggest avoiding of clamping of right coronary artery at the beginning of the operation while it still supplies all the coronary circulation.