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Ann Thorac Surg 2006;81:573-576
© 2006 The Society of Thoracic Surgeons

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Original article: Cardiovascular

On-Pump Beating-Heart Coronary Artery Bypass Grafting for Acute Myocardial Infarction

Department of Thoracic and Cardiovascular Surgery, Nayoro City General Hospital, Nayoro, Hokkaido, Japan

Accepted for publication August 23, 2005.

^_* Address correspondence to Dr Izumi, Nayoro City General Hospital, West 7, South 8, Nayoro, Hokkaido 096-8511, Japan (Email: yi398ngh{at}seagreen.ocn.ne.jp).

	Abstract

Top Abstract Introduction Patients and Methods Results Comment References

 
BACKGROUND: The early results of emergent coronary artery bypass grafting by conventional operative method for acute myocardial infarction are reported to be poor. The purpose of this study is to evaluate on-pump beating-heart coronary artery bypass grafting for acute myocardial infarction.

METHODS: Thirty-one patients with acute myocardial infarction underwent emergent surgery between January 1998 and June 2004 at Nayoro City General Hospital. In 16 patients, on-pump surgery was performed on the arrested heart, and in the other 15, on-pump surgery was performed on the beating heart. Early results were compared between the two groups.

RESULTS: Preoperative and perioperative patient characteristics revealed no significant differences between the two groups. Although there was no statistically difference between the two groups, the early mortality rates of on-pump arrested-heart coronary bypass grafting (31.3%) was higher than that of on-pump beating-heart coronary bypass grafting (13.3%). Postoperatively, the creatine kinase myocardial band value for the on-pump beating-heart group was significantly lower than that for the on-pump arrested-heart group (221 ± 200 IU/L versus 666 ± 540 IU/L, p = 0.008). The incidence of postoperative acute renal failure was significantly higher in the on-pump arrested-heart group than in the on-pump beating-heart group (p = 0.034). The durations of ventilator use and inotropic agent use were longer in the on-pump arrested-heart group than in the on-pump beating-heart group, though the differences were not statistically different (p = 0.152, p = 0.223).

CONCLUSIONS: On-pump beating-heart coronary artery bypass grafting has the possibility to eliminate intraoperative global myocardial ischemia and to be an acceptable surgical option for acute myocardial infarction associated with lower postoperative mortality and morbidity.

	Introduction

Top Abstract Introduction Patients and Methods Results Comment References

 
The early results of emergent coronary artery bypass grafting (CABG) for acute myocardial infarction have been reported to be poor. Percutaneous catheter intervention (PCI) is generally the first choice for treatment of acute myocardial infarction to immediately reperfuse the coronary flow. However, there are some cases requiring emergent surgical treatment, and in these cases the clinical results have been generally unacceptable because patients are often hemodynamically unstable owing to cardiogenic shock. Moreover, cardioplegic arrest during cardiopulmonary bypass can induce myocardial damage. Recently, in these situations, we have performed on-pump CABG on the beating heart, whereas in the past cases would have been treated with on-pump CABG on the arrested heart. We have now studied the results of on-pump beating-heart CABG for acute myocardial infarction and have evaluated the usefulness of this technique.

	Patients and Methods

Top Abstract Introduction Patients and Methods Results Comment References

 
Thirty-one patients with acute myocardial infarction, 23 men and 8 women with a mean age of 66 years (66.0 ± 11.8; range, 37 to 82), underwent emergent CABG between January 1998 and June 2004 at Nayoro City General Hospital. They all had already performed coronary angiograms by cardiovascular internist, and the decision for emergent operation was made before transferring to our department. The indications for emergent operation were failed or unsuccessful precutaneous coronary intervention in 16 patients, concomitance with a severe stenosis or aneurysm of the left main coronary artery in 7 patients, and severe three-vessel disease in 8 patients. Although the culprit vessel was the left anterior descending artery in all cases, there were 2 cases concomitant with the infarction of right coronary artery area from the findings of the electrocardiogram. The electrocardiogram indicated ST-segment elevation in leads V1 to V4 in all cases, and 2 cases were associated with ST-segment elevation in leads II and III and aVf.

In 16 patients, between 1998 and 2001, on-pump surgery was performed on the arrested heart; in 15 patients, between 2002 and 2004, on-pump surgery was done on the beating heart. The same surgeon performed the CABG in all cases.

Cardiopulmonary bypass was instituted by canulation of the ascending aorta and the right atrium, and a standard circuit with a hollow fiber membrane oxygenator and a centrifugal blood pump were used in both groups. In the on-pump arrested-heart CABG, after cardiopulmonary bypass was established, aortic cross clamp and cardiac arrest were induced with Young's solution. Myocardial protection was achieved by means of intermittent antegrade and retrograde cold blood cardioplegia after every anastomosis. A terminal warm shot was administered before declamping of the aorta at finishing of all distal anastomoses as a rule. In patients with aneurysm of the left main coronary trunk, declamping of the aorta was performed after transaortic suture of the left coronary ostium and proximal anastomosis on the ascending aorta. Patient body temperature was maintained at 28°C.

In the on-pump beating-heart CABG, total cardiopulmonary bypass was established, and body temperature was maintained at 36°C. Bypass grafting surgery was performed on the beating heart using a heart stabilizer and heart positioner. The left anterior descending artery was the first target vessel, the right coronary artery system the next, and the circumflex system the last. During anastomosing of the next graft, the bypass grafts that had already been sutured were unclamped and opened.

Urine output was measured every hour in the intensive care unit, and intravenous continuous infusion of the mannitol and furosemide cocktail was given to the patient with low urine output below 0.5 mL/kg an hour lasting for 3 hours. Continuous hemofiltration started when urine output did not increase or renal shutdown occurred in spite of mannitol and furosemide. Hemodialysis was introduced after the patient's hemodynamic state improved. The condition requiring hemofiltration or hemodialysis was defined as postoperative renal failure in this study.

We analyzed the clinical results, mortality rate, morbidity rate, and blood chemistry data between the two groups retrospectively.

Informed Consent
The Institutional Review Board of Nayoro City General Hospital approved this study, and waived the individual consent because this study was retrospective.

Statistical Analysis
Results are expressed as mean ± SD. Statistical analysis comparing the two groups was performed with an unpaired Student's t test for the means or with a ² test for the variables. Probability values less than or equal to 0.05 were considered significant.

	Results

Top Abstract Introduction Patients and Methods Results Comment References

 
The preoperative patient data analysis (Table 1) between the two groups demonstrated no significant differences in mean age, sex, comorbidities, clinical preoperative status, creatine kinase myocardial band (CK-MB) values, or duration between onset and operation.

	Comment

Top Abstract Introduction Patients and Methods Results Comment References

It has been demonstrated that keeping the heart beating is associated with less myocardial edema and better function [7]. As cardioplegic arrest can trigger intense inflammatory responses, aortic cross-clamping should be avoided in unstable patients in acute myocardial infarction. The avoidance of aortic cross-clamping and cardiac arrest can contribute to myocardial protection and eliminate intraoperative global myocardial ischemia. Our data show that CK-MB values in the on-pump beating-heart CABG are significantly lower than those in the on-pump arrested-heart CABG. It has previously been demonstrated that in the on-pump beating-heart CABG is a lower release of troponin Ic, which is a highly cardiac specific marker of tissue damage [8]. In the present study, the operative mortality was lower in the on-pump beating-heart CABG than the on-pump arrested-heart CABG, although the difference was not significant.

Renal failure is a frequent complication in patients who have experienced hemodynamic failure or undergone conventional cardiac surgery. Ascione and associates [9] have demonstrated that beating-heart CABG offers a low risk of systemic hypoperfusion during surgery and as a consequence superior renal protection, as demonstrated by a low incidence of postoperative renal complications. Prifti and colleagues [10] have also indicated that this technique offers better renal protection associated with fewer postoperative complications due to intraoperative hypoperfusion. Although renal failure requiring dialysis or hemofiltration was identified postoperatively in both groups in our series, the incidence was significantly lower in the on-pump beating-heart CABG group.

Another point to consider is the technical features of the on-pump beating-heart CABG technique. When fully assisting the heart with cardiopulmonary bypass, it is advantageous to place the graft on the circumflex artery area easier owing to the reduction in heart volume compared with off-pump CABG. Utilizing a heart stabilizer and positioner, which are routinely used in off-pump CABG, optimal exposure in the posterior and lateral fields of the heart can be obtained even in the beating heart. Borowski and colleagues [11] have indicated that the on-pump beating-heart technique can help avoid extreme upward retraction of the heart during revascularization of the circumflex artery branch, thus contributing to better myocardial protection. Although the likelihood of incomplete revascularization tends to increase in off-pump CABG [12], we can achieve complete revascularization with the on-pump beating-heart method.

Our results lead us to believe that on-pump beating-heart CABG offers the possibility to eliminate intraoperative global myocardial ischemia and is an acceptable surgical option for acute myocardial infarction associated with lower postoperative mortality and morbidity.

Limitations
Several limitations of this study need to be addressed. First, our investigation was retrospective. Second, as the patients undergoing conventional CABG were from a former series, whereas the beating-heart CABG was conducted during the most recent decade, a historical difference exists; however, the operations were performed by the same surgeon. Third, the number of patients in each group was small. Further studies will be necessary and are expected.

	References

Top Abstract Introduction Patients and Methods Results Comment References

 

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This Article Abstract Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Add to Personal Folders Download to citation manager Author home page(s): Yuichi Izumi Permission Requests Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Izumi, Y. Articles by Kimura, F. Search for Related Content PubMed PubMed Citation Articles by Izumi, Y. Articles by Kimura, F. Related Collections Coronary disease