CORRESPONDENCE: LETTERS TO THE EDITOR
Reply
Jennifer E. Cummings, MD,
Inderjit Gill, MD,
Rami Akhrass, MD,
MarkAlain Dery, MPH, DO,
Lee A. Biblo, MD, FACC and
Kara J. Quan, MD, FACC*
* Heart and Vascular Research Center, MetroHealth Campus, Case Western Reserve University, 2500 MetroHealth Drive, Cleveland, OH 44109 (Email: kquan{at}metrohealth.org).
We thank Dr. Bisleri and colleagues for their thoughtful review of our study, and we appreciate the opportunity to respond.
Although the sample size was small, our investigation was powered and sample size calculated using a moderate effect size prior to the initiation of the study; thus, this study had adequate power.
Their first concern addresses the use of perioperative beta-blockers in the entire population. The use of beta-blockers in coronary artery disease, especially following coronary artery bypass graft surgery (CABG), remains the standard of care (1,2). Withdrawal or withholding of these medications was therefore not considered.
Additionally, Dr. Bisleri and colleagues expressed concern in regard to bias in the significant amount of beta-blocker use (>90% compliance in both groups), selection of cardioplegia, and number of diabetic patients enrolled. Ours was a prospective randomized study. By randomizing the patients prior to their procedure, the possibility of bias was negated. As noted in our Table 1, no significant differences existed between groups in any patient characteristic (including cardioplegia type, diabetes, and beta-blocker use) (3).
Both groups demonstrated an equal number of diabetics, use of beta-blockers, and cold or warm blood cardioplegia. Therefore, the differences between the groups seen at the conclusion of the study cannot be attributed to any of these factors. As Dr. Bisleri and colleagues state, there was an equal number of diabetics in both groups (35% vs. 31%; p = NS) (3). Although this number of diabetic patients is higher than expected for the general population, we were evaluating bypass patients in whom a higher incidence of diabetes is expected. As there were no significant differences in the patient characteristics, the effect on atrial fibrillation seen at the conclusion of the study is separate and significant.
Finally, the concern that "off-pump" bypass surgery decreases a "well-known" risk of atrial fibrillation is relevant to our study. During "off-pump" bypass, there is no cross-clamp applied, and minimal if any anterior fat pad dissection occurs. We agree that this may be one of the factors reducing the risk of atrial fibrillation using this approach.
In summary, the prospective randomized design of our study should address the concerns of Dr. Bisleri and colleagues. We agree that this study generates many questions regarding the mechanism of postoperative atrial fibrillation, and we look forward to future studies. The reality is that the sample size was small and although the patients were randomized, dogmatic conclusions are not warranted, at least not yet.
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References
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- Eagle KA, Guyton RA, Davidoff R, et al. ACC/AHA 2004 guideline update for coronary artery bypass graft surgeryTask Force on Practice Guidelines (update of the 1999 guidelines). Circulation 2004;110:1168-1176.[Free Full Text]
- Eagle KA, Guyton RA, Davidoff R, et al. ACC/AHA guidelines for coronary artery bypass graft surgeryTask Force on Practice Guidelines (revision of 1991 guidelines). J Am Coll Cardiol 1999;34:1262-1347.[Free Full Text]
- Cummings JE, Gill I, Akhrass R, Dery MA, Biblo LA, Quan KJ. Preservation of the anterior fat pad paradoxically decreases the incidence of postoperative atrial fibrillation in humans J Am Coll Cardiol 2004;43:994-1000.[Abstract/Free Full Text]
Related Article
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Preservation of the anterior fat pad and incidence of postoperative atrial fibrillation following coronary surgery
- Gianluigi Bisleri, Tomaso Bottio, Jeffrey A. Morgan, and Claudio Muneretto
J. Am. Coll. Cardiol. 2005 45: 1308.
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