J Thorac Cardiovasc Surg 2004;128:325-326
© 2004 The American Association for Thoracic Surgery
Reply to the Editor
Kathryn K. Collins, MD
University of California, San Francisco, 521 Parnassus, C-346, Box 0632, San Francisco, CA 94117 USA
The Fontan population is heterogeneous in terms of the underlying anatomy and number and nature of surgical interventions before the Fontan operation. Many factors are thought to be associated with the development of atrial arrhythmias in this group. Animal studies have suggested that surgical incision and extended suture lines are particularly likely to create an arrhythmogenic substrate.1-3 The more recent versions of the Fontan procedure (lateral tunnel or the extracardiac conduit) have had lower reported incidences of late atrial arrhythmias than the older types of Fontan operations.4 Long-term follow-up of the extracardiac conduit Fontan operation has not yet been reported with respect to arrhythmia, but Stamm and colleagues4 have recently shown that the lower incidence of atrial tachycardia in the lateral tunnel Fontan procedure persisted through a mean 10-year follow-up.4 One can interpret this finding to mean that the current Fontan techniques are in fact less arrhythmogenic then was initially projected when our study was undertaken. If so, placement of an interventional atrial incision to the lateral tunnel Fontan may not be warranted in every case, only for patients deemed at higher risk (eg, with a preoperative history of atrial tachycardia).
Although avoiding atrial manipulation and suture lines altogether has theoretic benefits, it is not practical in all cases. If atrial suture lines are required for the surgical intervention, then choosing to place or extend them in such a way to reduce the likelihood of atrial arrhythmias is warranted. Our interventional atrial incision to the lateral tunnel Fontan procedure was designed to transect potential arrhythmia circuits around the atriotomy or the right atrioventricular valve, the primary areas where atrial arrhythmias typically develop. It was designed to be simple, to be feasible in patients with varied anatomy, and to have low added risks for the patient. The location of the incision is inferior to the sinus node or the blood supply to the sinus node. The interventional incision will not act as a substrate for atrial arrhythmias because there is no atrial tissue surrounding the incision around which a tachycardia circuit could propagate; the incision is anchored on either end by the nonconducting boundaries of the atriotomy and the right atrioventricular annulus. In fact, treatment of atrial arrhythmias by the Fontan revision surgeries with the right atrial maze procedures are designed create conduction block by similar but more extensive means.5
I agree that early postoperative sinus node dysfunction is associated with the development of late sinus node dysfunction and late atrial tachyarrhythmias. In our clinical trial, we reported a high percentage of early sinus node dysfunction in both the control and intervention groups, with no statistically significant difference between the two groups. Thus the sinus node dysfunction seen in this study was not attributable to the interventional atrial incision.
Our study reported only the short-term outcomes of our interventional atrial incision for the prevention of intra-atrial reentrant tachycardia in the lateral tunnel Fontan population. We have learned that, in contrast to previous clinical and animal studies, inducible perioperative atrial arrhythmias were not especially common clinically in these patients. Following up our cohort to assess long-term arrhythmia prevalence will provide a useful addition to our knowledge of the arrhythmia substrate in the Fontan population.
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References
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- Gandhi SK, Bromberg BI, Rodefeld MD, Schuessler RB, Boineau JP, Cox JL, et al. Spontaneous atrial flutter in a chronic canine model of the modified Fontan operation. J Am Coll Cardiol. 1997;30:1095–1103[Abstract]
- Gandhi SK, Bromberg BI, Rodefeld MD, Schuessler RB, Boineau JP, Cox JL, et al. Lateral tunnel suture line variation reduces atrial flutter after the modified Fontan operation. Ann Thorac Surg. 1996;61:1299–1309[Abstract/Free Full Text]
- Rodefeld MD, Bromberg BI, Schuessler RB, Boineau JP, Cox JL, Huddleston CB. Atrial flutter after lateral tunnel construction in the modified Fontan operation: a canine model. J Thorac Cardiovasc Surg. 1996;111:514–526[Abstract/Free Full Text]
- Stamm C, Friehs I, Mayer JE, Zurakowski D, Triedman JK, Moran AM, et al. Long-term results of the lateral tunnel Fontan operation. J Thorac Cardiovasc Surg. 2001;121:28–41
- Deal BJ, Mavroudis C, Backer CL, Johnsrude CL, Rocchini AP. Impact of arrhythmia circuit cryoablation during Fontan conversion for refractory atrial tachycardia. Am J Cardiol. 1999;83:563–568[Medline]
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