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Correspondence

Reply

CRSTI, 7777 Forest Ln, Suite A-323, Dallas, TX 75230

(Email: mmagee{at}csant.com).

To the Editor:

We appreciate the interest that Parolari and colleagues [1] have shown in our subanalysis of off-pump and on-pump coronary artery bypass grafting (CABG) in the PREVENT IV trial [2]. However, we take strong exception to the points made in their communication. Specifically, they suggest that our analyses and conclusions drawn from data collected from the PREVENT IV study are fallacious and misleading, rather preferring to conclude that we have manufactured "another brick in the wall of evidence" supporting reduced graft patency in off-pump coronary artery bypass (OPCAB). On the contrary, we believe that the data contained in the study is clear and definitive and that our conclusions are appropriate and fully supported by the data. In fact, the data clearly supports the conclusions in the abstract that the saphenous vein graft failure rate was 25% in both groups and that the 1-year clinical outcomes (MACCE) were better with off-pump than with on-pump CABG. As is clearly shown in Table 6, there was no statistical difference in the fraction of patients who experienced one or more vein graft stenosis or occlusion (0.46 vs 0.45; p = 0.75). The vein graft failure rates, as presented in the abstract and in Table 7, were similar in the on-pump and off-pump groups (25.3 vs 25.7%; p = 0.62). Table 8 shows predictors of graft failure, based on a multivariable analysis, and this included target artery quality, graft conduit type (vein, internal mammary artery, and so forth), patient weight, length of surgery, use of a sequential graft technique, and vein harvest technique (endoscopic vs open). Neither off-pump technique nor target artery location was associated with graft failure.

The only significant interactions with cardiopulmonary bypass use were seen with vein harvest technique and graft quality. For grafts harvested endoscopically compared with open, the probability of graft failure was higher if the surgery was performed off pump (odds ratio, 1.78 for off pump vs 1.27 for on pump). If a poor or fair quality graft was used (compared with a good graft), the probability of graft failure was higher if the surgery was performed off pump (odd ratio, 1.90 for off pump vs 1.23 for on pump). For the other characteristics associated with graft failure, the risk of graft failure was similar for on-pump and off-pump surgery. Specifically, Table 8 does not show a statistically significant independent influence of OPCAB on graft patency. After adjusting for differences in the previously listed significant predictors of vein graft failure, the odds of graft failure for on-pump versus off-pump patients was 0.82 (95% confidence interval, 0.67 to 1.00; p = 0.054).

The MACCE (death, stroke, MI) measured 1 year after CABG was statistically different between on-pump and off-pump groups (15.4% vs11.3%; p = 0.012). After adjusting for other factors that influence MACCE in this population (age, sex, smoking status, history of congestive heart failure, history of atrial fibrillation, number of grafts), the negative effect of being on pump versus off pump remained (hazard ratio, 1.31; 95% confidence interval, 1.01 to 1.69). As we fully acknowledged in the discussion, although MACCE at 1 year is 33% more likely if surgery is done on pump, the benefit of decreased MACCE with off-pump surgery at 1 year is no longer present 2 years after CABG. In our opinion, other patient factors, including progression or development of comorbid disease or progression of coronary artery disease, likely affect MACCE and graft patency to a greater degree than technical factors related to the surgical technique 2 years after CABG.

We strongly agree that cardiac surgeons must take responsibility for maximizing the efficacy and durability of CABG to insure that it remains a viable alternative in the available options for coronary revascularization. Rather than being "another brick in the wall" against off-pump surgery, this data further supports the overwhelming preponderance of evidence in the literature that OPCAB can achieve improved efficacy through decreased short-term morbidity and mortality without sacrificing durability or graft patency in appropriately selected and managed patients.

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1. Parolari A, Tremoli E, Biglioli P, Alamanni F. Off-pump coronary bypass surgery: another brick in the wall of reduced graft patency Ann Thorac Surg 2009;87:675-676(letter).[Free Full Text]
2. Magee MJ, Alexander JH, Hafley G, et al. Coronary artery bypass graft failure after on-pump and off-pump coronary artery bypass: findings from PREVENT IV Ann Thorac Surg 2008;85:494-499.[Abstract/Free Full Text]

This Article Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Email this article to a friend Similar articles in this journal Alert me to new issues of the journal Add to Personal Folders Download to citation manager Author home page(s): Mitchell J. Magee Michael J. Mack Permission Requests Citing Articles Citing Articles via Google Scholar Google Scholar Articles by Magee, M. J. Articles by Mack, M. J. Search for Related Content PubMed Articles by Magee, M. J. Articles by Mack, M. J. Related Collections Related Article