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J Thorac Cardiovasc Surg 1998;115:1391
© 1998 Mosby, Inc.

LETTERS TO THE EDITOR

Regarding the surgical ablation of the sinus node

To the Editor:

The surgical treatment of supraventricular arrhythmias has virtually disappeared since the advent of radiofrequency catheter ablation in the electrophysiology laboratory. A finite number of patients still require surgical intervention in the rare event of unsuccessful catheter ablation, exemplified by the brief communication published by Esmailzadeh and associates. ¹

Although we never published our experience as a case report, we performed a surgical ablation of the sinoatrial node and high right atrium, before the appearance of radiofrequency ablation in our institution, using epicardial cryoablation without cardiopulmonary bypass in a Jehovah's Witness with documented sinus node reentrant tachycardia. We achieved total ablation of spontaneous electrical activity in the sinus node and high right atrium in positions 2, 13, 14, 15, 16, and 17 on a Wyndham grid ² using a 15 mm flat-face cryoprobe through which nitrous oxide circulated at –60° C from a Frigitronics cardiovascular surgical system (CCS-100, Frigitronics of Connecticut, Inc., Shelton, Conn.). Atrial pacing was not possible from the ablated areas. The results persisted 3 years after the ablation on follow-up electrophysiology studies.

We were able to achieve effective cryoablation of right atrial tissue on the beating heart despite potential heat transfer to the endocardial surface from circulating blood by compression of the target tissue between the cryoprobe and a wooden template placed inside the atrium through a purse-string suture directly underneath the cryoprobe. Compression of atrial tissue between the cryoprobe and the endocardial template produced thermal isolation of the target tissue by displacing warm blood away from the endocardium. This technique permitted transmural freezes lethal to atrial myocardium.

We subsequently published experiments that not only verified the principle of thermal isolation of target tissue, but also revealed subtleties of technique essential to ensure reproducible lethal freezes. ³ These included the following observations:

1. The temperature of the cryoprobe does not reflect the transmural tissue temperature unless the tissue is isolated from the circulation.
   
2. A line pressure of at least 600 psi ensures more rapid freezes and a greater chance of the tissue actually reaching –60° C.
   
3. Any break in the fusion between the tissue and the cryoprobe results in an immediate rise in tissue temperature, which does not decrease with prolongation of the freeze; the tissue must be thawed completely and refrozen.
   
4. Fusion can be made stronger if pressure is applied to the tissue between the cryoprobe and the template before freezing begins. Pressure reduces the tissue thickness and may reduce autoinsulation of the tissue by crystallizing tissue fluid simply by squeezing the fluid from the target area.
   
5. Delrin buffering material (E. J. du Pont de Nemours & Co., Inc., Wilmington, Del.) proved to be a significantly more effective insulator of tissue from the warming effect of underlying fluid than wood.
   

This case report and experimental evaluation demonstrate that surgical ablation of right atrial arrhythmias, although infrequently performed, can be accomplished by epicardial cryoablation, without cardiopulmonary bypass, provided thermal isolation of the target tissue can be accomplished and the principles of cryoablation are observed.

Centinela Hospital Medical Center555 East Hardy St., Inglewood, CA 9030112/8/89294

References

1. Esmailzadeh B, Bernat R, Winkler K, Meybehm M, Pfeiffer D, Kirchhoff PG. Surgical excision of the sinus node in a patient with inappropriate sinus tachycardia. J Thorac Cardiovasc Surg 1997;114:861-4.[Free Full Text]
   
2. Wyndham CRC, Arnsdorf MF, Levitsky S, et al. Successful surgical excision of focal paroxysmal atrial tachycardia. Circulation 1980;62:1365-72.[Abstract/Free Full Text]
   
3. Lee ME. Epicardial cryoablation of myocardial tissue using endocardial thermal isolation. Mt Sinai J Med 1992;62:357-61.
   

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This Article 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 Similar articles in PubMed Alert me to new issues of the journal Add to Personal Folders Download to citation manager Author home page(s): Myles Edwin Lee Permission Requests Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Lee, M. E. Search for Related Content PubMed PubMed Citation Articles by Lee, M. E.