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a Division of Cardiovascular Surgery, The Texas Heart Institute at St. Luke’s Episcopal Hospital, Houston, Texas
b Division of Cardiopulmonary Transplantation, The Texas Heart Institute at St. Luke’s Episcopal Hospital, Houston, Texas
c Center for Surgical Innovation, The University of Cincinnati, Cincinnati, Ohio
Accepted for publication July 12, 2007.
* Address correspondence to Dr Cohn, The Texas Heart Institute at St. Luke’s Episcopal Hospital, MC 2–114A, PO Box 20345, Houston, TX 77225-0345 (Email: wcohn{at}heart.thi.tmc.edu).
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Abstract |
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Methods: We reviewed the charts of 498 consecutive patients who underwent orthotopic heart transplantation at a single institution during a 15-year period.
Results: Twenty-seven patients (5.4%) experienced POAF within 60 days of transplant. In 9 of these patients, POAF occurred within 2 weeks of a biopsy-proven transient rejection episode; excluding these patients from the analysis revealed a non–rejection-associated POAF rate of 18 of 489 patients (3.7%).
Conclusions: Despite the long ischemic times, extensive manipulation of the transplanted heart, and the postoperative administration of proarrhythmic inotropic agents that cardiac transplantation typically involves, this procedure is associated with a low incidence of POAF, particularly if patients in whom rejection and POAF were temporally related are excluded. These findings suggest that complete cardiac denervation and pulmonary vein isolation protect heart transplant recipients from POAF, thus supporting the notion that similar lesions may be useful in the treatment of other types of atrial fibrillation.
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Introduction |
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Since the introduction of the cut-and-sew Cox Maze III procedure for the treatment of AF, numerous variations of this operation have been introduced. Many of these use externally applied energy, including heat, cold, radiofrequency current, focused ultrasound, and laser light, to create the transmural atrial lesions intended to disrupt macro-reentry pathways. Most of these newer procedures involve creating only a subset of the classic lesion set described by Cox and colleagues [7, 8]. Although these lesion subsets are arguably incomplete, they have important advantages: they can often be made through small thoracotomies or even videoscopically, they are associated with a decreased risk of postoperative hemorrhage, and they can be created without cardiopulmonary bypass. Few data are available about the long-term results of these procedures; however, short-term follow-up studies suggest that many patients are converted to normal sinus rhythm by these limited-access, off-pump procedures [9].
Nonetheless, the validity of using limited lesion sets, including those that produce cardiac denervation and pulmonary vein isolation, is not universally accepted. For this reason, we examined the incidence of postoperative AF (POAF) after heart transplantation, which necessitates complete cardiac denervation and pulmonary vein isolation, to evaluate the effectiveness of these lesions in preventing AF.
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Material and Methods |
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Patients underwent electrocardiography once a day for the first 3 days after surgery, and they were kept on telemetry throughout their hospitalization. Additionally, in the absence of any complications or concerns, they underwent electrocardiography at least nine times (once for each of nine biopsies) during the first year after discharge, and then at least annually thereafter.
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Results |
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Of the 27 patients in whom POAF occurred, 14 had a documented episode of biopsy-proven transient rejection; 9 of the 14 had onset of AF within 2 weeks of the rejection episode, suggesting a possible association between the dysrhythmia and rejection. When these 9 patients were excluded, the rate of non–rejection-associated POAF was 18 of 489 patients (3.7%).
Of the 489 transplantations performed during this period that did not lead to rejection-associated POAF, 424 were performed with a biatrial technique in which left and right circumferential atrial suture lines are used, which preserves the posterior aspects of both native atria. The other 65 procedures involved a bicaval anastomotic technique in which the entire native right atrium is excised. The incidence of POAF for the two different techniques was 16 of 424 (3.8%) for biatrial and 2 of 65 (3.1%) for bicaval implantation; this difference was not significant (p = 0.78).
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Comment |
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Other studies of POAF in heart transplant recipients have found very different rates from what we found. Pavri and associates [11] found a high rate of POAF (16 of 88 patients, or 18.2%) in cardiac transplantation patients in the first 2 weeks after transplantation. At the other extreme, Khan and colleagues [12] found POAF in only 3 of 923 transplant recipients (0.3%) during a mean follow-up period of 7.5 years. Neither study differentiated between POAF episodes that were associated with rejection and those that were not. In contrast, Cui and coworkers [13], who found a POAF rate of 69 of 892 (7.7%) in transplant recipients during the first 2 weeks after operation, noted that 22 of these patients experienced a rejection episode during that 2-week period. If these patients are excluded, the non–rejection-related POAF rate drops to 47 of 870 patients (5.4%), which is close to our rate of 3.7%.
The extremely low incidence of POAF in our orthotopic heart transplantation patients (relative to that of coronary artery bypass grafting and valve surgery patients in other studies) supports the idea that certain lesions—ie, pulmonary vein isolation and cardiac denervation—have significant antiarrhythmic effects. This finding seems particularly significant given the long ischemic times, extensive manipulation of the transplanted heart, and the postoperative administration of proarrhythmic inotropic agents that the transplantation procedure typically involves. Counterbalancing these effects are the generally young age and structural normality of the transplanted hearts, as well as the routine postoperative use of steroids, which have a potent antiinflammatory effect. It is difficult to determine the relative contributions of these different effects, but our findings lend at least some support to the idea that denervation and pulmonary vein isolation may be useful for preventing AF.
Evidence for this possibility also comes from findings that cardiac autotransplantation, which causes the same type of denervation that allogeneic heart transplantation does, alleviates AF in patients with concomitant AF and mitral valve disease [14, 15]. Admittedly, cardiac autotransplantation is less invasive and involves shorter ischemic times than allogeneic transplantation does. However, all of these procedures were performed on persons who already had AF. In both studies, autotransplantation alleviated AF in nearly 90% of cases, suggesting that the denervation that results from autotransplantation successfully interferes with AF-promoting processes.
Inflammation caused by mechanical trauma or metabolic insult has been implicated as a mechanism in the development of AF. Multiple studies showing similar incidences of POAF in patients undergoing on-pump and off-pump coronary artery bypass grafting [16–20] support a role for inflammation caused by mechanical manipulation. One possible mechanism by which inflammation results in AF may be related to heterogeneity in tissue conduction in inflamed tissue.
Whether or not new posttransplantation AF arises from the suture lines is difficult to determine. It is hard to imagine, however, any electrical signal coming from outside the suture line having an impact on the transplanted heart, because the healing process almost assuredly creates a circumferential transmural scar.
Before June 2002, we performed biatrial anastomosis exclusively, retaining the back wall of the native right atrium. Since that date, we have used a bicaval technique, which results in more anatomic positioning of the transplanted heart. Interestingly, the incidence of POAF was not affected by this change in technique.
This study had some notable limitations. First, it was a purely retrospective review, so there were a variety of factors that we could not control, including patient selection and technical aspects of the transplantation procedure. However, this potential weakness may also have made our patients more representative of the general population of cardiac transplant recipients than they would have been had patient selection and operative factors been strictly controlled. Second, it is possible that some of our patients experienced brief episodes of POAF that were not recognized or recorded in the patients’ charts. However, our patients were kept on telemetry throughout the period of their hospitalization, so it is unlikely that in-hospital episodes of POAF were missed.
In conclusion, although there were many potential confounding factors in our study, our findings suggest that pulmonary vein isolation and cardiac denervation provide significant POAF prophylaxis in cardiac transplant recipients. These findings also suggest that more extensive cardiac denervation will improve the efficacy of limited-lesion-set approaches to the surgical treatment of AF.
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