J Thorac Cardiovasc Surg 2004;128:326-327
© 2004 The American Association for Thoracic Surgery
Ventral cardiac denervation: Is it truly an effective prophylaxis against atrial fibrillation after coronary artery bypass grafting?
Joseph Alex, MBBS, MRCS,
Mazhar Ur Rehman, MBBS, FRCS (CTh),
Levent Guvendik, MD, FRCS, FETCS
Department of Cardiothoracic Surgery, Castle Hill Hospital, Hull And East Yorkshire Hospitals NHS Trust, Hull, United Kingdom
To the Editor:
We read with interest the article by Melo and colleagues1 on ventral cardiac denervation (VCD) as a prophylaxis against atrial fibrillation (AF) after coronary revascularization. However, we wish to point out certain aspects of the methodology that may have affected the results. Post-CABG AF is paroxysmal in a large proportion of patients and does not always give rise to clinical symptoms. The fact that only 34% and 33% of the patients in their VCD and control groups, respectively, had continuous telemetry monitoring for 4 days would have significantly reduced the AF detection rate, the primary end point of the study. Although statistically nonsignificant, the mixture of different myocardial preservation strategies used (crystalloid cardioplegia, blood cardioplegia, and off-pump) effectively reduced the advantage of the large number of patients in the study.
We conducted a study between January 2002 and April 2003 (Table 1) in which we compared the incidence of AF among 70 consecutive patients undergoing primary CABG with that among 70 consecutive patients who underwent VCD (with the same technique described by Melo and colleagues1) in addition to primary CABG. All patients were operated by the same consultant surgeon with the same bypass method and myocardial preservation technique (antegrade-retrograde cold St Thomas' Hospital blood cardioplegia). All patients had continuous telemetry monitoring for 5 days after the operation. In contrast to the findings of Melo and colleagues,1 and despite the younger age of our patients, we found no significant difference in the incidence of AF between the two well-matched groups in our study.
Melo and colleagues1 failed to come up with a convincing reason for the claimed effectiveness of the technique. Anatomically, the route taken by autonomic nerves to the heart is highly variable2; a lesser but significant and variable proportion of autonomic nerves reaches the heart along the pulmonary veins and the back of the heart, so the actual denervation achieved in quantitative terms is not consistent or comparable between patients unless the innervation is mapped out before denervation. The inclusion of patients with diabetes (26% in the VCD group and 27% in the control group in their study and 16% and 13%, respectively, in our own study) and patients receiving ß-blockers (75% in the VCD group and 81% in the control group in their study and 69% and 72%, respectively, in our study) gives rise to additional problems. Many patients with diabetes already have partial denervation from preexisting autonomic neuropathy, and it is debatable how much additional denervation is achieved surgically with the technique. ß-Blockers themselves have antiarrhythmic effects and produce a state of near-total pharmacologic sympathetic denervation. Long-term ß-blockade causes ß-receptor hypersensitivity, necessitating reintroduction of ß-blockers after the operation. The reintroduction of ß-blockers in most cases in the postoperative period results in total cardiac sympathetic denervation and partial parasympathetic denervation, which raises questions about the whole hypothesis.
One can only meaningfully assess the effectiveness of the technique through a prospective, randomized multicenter trial excluding patients with diabetes and those receiving ß-blockers. Histologic quantification of the amount and type of nerve fibrils in the excised fat pads is also necessary.
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References
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- Melo J, Voigt P, Sonmez B, Ferreira M, Abecasis M, Robocho M, et al. Ventral cardiac denervation reduces the incidence of atrial fibrillation after coronary artery bypass grafting. J Thorac Cardiovasc Surg. 2004;127:511–515[Abstract/Free Full Text]
- Pauza D, Skripa V, Pauzienne N, Stropus R. Morphology, distribution and variability of the epicardial neural subplexus in the human heart. Anat Rec. 2000;259:353–382[Medline]
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