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Ann Thorac Surg 2003;78:755-756
© 2003 The Society of Thoracic Surgeons
Quebec Heart Institute, Hôpital Laval, 2725, Chemin Ste-Foy, Ste-Foy, PQ G1V 4G5, Canada
e-mail: rgea{at}hotmail.com
To the Editor:
We read with interest the article by Bucerius and coauthors concerning determinants of stroke after cardiac operations, and we congratulate them on the timely data collection and analysis.
At the Quebec Heart Institute, we recently focused on determinants of cerebral vascular accident (CVA) in a group of 10,000 patients undergoing coronary artery bypass grafting (CABG) [2]. Like Bucerius and colleagues, we found a stroke rate of around 2% with a significantly higher incidence in patients having operation on cardiopulmonary bypass (CPB) (2.1%) compared with those having off-pump CABG (OPCAB) (0.65%) (p < 0.005). After multivariate analysis, we identified seven preoperative and two perioperative determinants of CVA. Depressed left ventricular ejection fraction, previous stroke, and diabetes mellitus had the strongest impact. Intraaortic balloon pump requirement and transfusion rate were the sole operative determinants of CVA. The use of OPCAB did not have a protective effect against CVA. After accurate analysis and division into subgroups, we concluded that even a myocardial ischemia time of longer than 90 minutes and CPB longer than 120 minutes did not have an independent impact on CVA incidence [2].
Our findings are partially confirmed by a recent series by Ascione and associates [3] in which OPCAB was associated with a substantial, but not significant, protective effect against stroke. In contrast, in a smaller series of patients, Patel and colleagues [4] demonstrated a strong independent relationship between use of CPB and focal neurologic deficits.
As suggested by Bucerius and coauthors by univariate analysis, minimally invasive direct CABG (MIDCAB) procedures have a significantly lower stroke rate compared with conventional CABG on CPB, and there is no significant difference between OPCAB and conventional CABG stroke rates. After stepwise logistic regression, only an off-pump operation (including MIDCAB and OPCAB) is identified as a protective factor against CVA [1].
Although the authors wrote that "beating heart CABG is associated with a lower incidence of stroke and may therefore improve patient outcomes," we point out that the MIDCAB and OPCAB variables should be analyzed separately even in the multivariate model to better understand the true, independent impact of operative management on CVA occurrence. It is reasonable to believe that patients treated with MIDCAB have lower comorbid profiles including younger age and less coronary artery and peripheral vascular disease. Furthermore, limited revascularization performed during MIDCAB permits no aortic manipulation, causes minimal hemodynamic derangement, and results in shorter operating times. All of these factors could directly determine a lower occurrence of stroke in this already highly select group of patients. As presented by Bucerius and co-workers, the significantly lower CVA rate in the MIDCAB population seems undisputable; however, no conclusion can be drawn about the true benefits offered by the OPCAB approach in terms of protection against perioperative stroke. In this sense, aortic manipulation and sudden hemodynamic instability associated with highly comorbid profiles may play an important role in increasing the CVA rate even in OPCAB patients.
In conclusion, we believe that the real advantages of beating-heart coronary operations in terms of CVA prevention should be analyzed by excluding the highly select population of MIDCAB candidates. Only by focusing on a strict comparison between OPCAB and traditional CABG on CPB can we elucidate the real advantages of this innovative procedure and understand its theoretical superiority in either the overall population or in select subgroups of high-risk patients.
References
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