Ann Thorac Surg 2002;74:249-251
© 2002 The Society of Thoracic Surgeons
Case report
Coexistence of sinus rhythm and segmental atrial fibrillation after maze procedure
Yasushi Matsumoto, MD*a,
Go Watanabe, MDb,
Masamitsu Endo, MDa,
Hisao Sasaki, MDa,
Fuminori Kasashima, MDa
a Department of Cardiovascular Surgery, National Kanazawa Hospital, Kanazawa, Japan
b Department of Surgery I, Kanazawa University School of Medicine, Kanazawa, Japan
Accepted for publication October 20, 2001.
* Address reprint requests to Dr Matsumoto, Department of Cardiovascular Surgery, National Kanazawa Hospital, 1-1 Shimoishibikicho, Kanazawa 920-8650, Japan
e-mail: matumoto{at}kinbyou.hosp.go.jp
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Abstract
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We present the case of an 80-year-old man with chronic atrial fibrillation associated with mitral regurgitation. The atrial fibrillation was successfully treated with the maze procedure combined with mitral valve replacement. The electrophysiological data are also reported. Recordings of sinus rhythm and intraatrial activity demonstrated the coexistence of sinus rhythm and fibrillation of both atria. This finding indicates that the sinus node was protected from segmental atrial fibrillation by entrance block, and this, in turn, is evidence of the efficacy of the maze procedure.
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Introduction
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The maze procedure was initially designed by Cox [1] as a surgical treatment of atrial fibrillation (AF). Restoration of sinus rhythm with the maze procedure reestablishes normal electrical activation of the atrium and its mechanical function, reduces the chances of thromboembolic complications, and improves hemodynamics. In the maze procedure, multiple incisions are made in and cryocoagulation is carried out on both atrial walls, but the conduction route for depolarization arising from the sinus node is preserved. Theoretically, prevention of AF depends on the blockade of the atrial lines of conduction, ie, the resultant masses of atrial tissue are too small to sustain reentrant multiple depolarizations. However, electrophysiological evidence supporting this theory is rare. We present the case of a patient who underwent the maze procedure and in whom intraatrial recordings demonstrated the coexistence of sinus rhythm and segmental AF.
An 80-year-old man experienced dyspnea with palpitations at rest and consulted a cardiologist at our hospital. An electrocardiogram revealed AF, a chest roentgenogram showed cardiomegaly and pulmonary congestive changes, and echocardiography performed at the same time revealed severe mitral regurgitation. On the basis of these findings, the patient was hospitalized. He had a history of persistent palpitations that began in his early 60s. Cardiac catheterization after recovery from congestive heart failure revealed mitral regurgitation (Seller’s grade 4) resulting from tendon rupture with mild pulmonary hypertension.
Operation was performed through a median sternotomy. Cardiopulmonary bypass was established between the ascending aorta and both venae cavae. With the patient under tepid hypothermia, the aorta was cross-clamped. During cardioplegic arrest, the mitral valve was replaced with a 29-mm Mosaic mitral bioprosthesis (Medtronic, Inc, Minneapolis, MN); the posterior leaflet was preserved. Subsequently, the modified maze procedure described by Kosakai and colleagues [2] was performed.
The patient’s recovery was uneventful, and restoration of sinus rhythm was obtained immediately after operation. Postoperative transesophageal echocardiography demonstrated return of contractility to both atria. No anticoagulant was administered, and no recurrence of AF has been detected to date, ie, 18 months postoperatively.
Twelve months after operation, the patient agreed to undergo an electrophysiological examination to evaluate postoperative sinoatrial function and conduction. The electrophysiological studies were performed after digitalis had been withheld for 3 days (no other antiarrhythmic drug had been given). Four quadripolar 6F USCI catheters with a 10-mm interelectrode distance were introduced percutaneously into the femoral vein (three catheters) and right internal jugular vein (one catheter) and were positioned in the high right atrium, His bundle, coronary sinus, and right ventricle. Sinus cycle length was 660 ms. The longest corrected sinus node recovery time was 363 ms after pacing at a cycle length of 400 ms, and the sinoatrial conduction time as measured by the Strauss method was 126 ms. Sinoatrial function was preserved.
The two distal poles of the catheter placed in the high right atrium in close proximity to the sinus node recorded the coexistence of a distinct atrial electrogram with a cycle length of 660 ms (sinus rhythm) and a localized irregular atrial potential with an average cycle length of 203 ms (Fig 1),
whereas the two proximal poles of the same catheter recorded only sinus activity. Simultaneously, the distal poles of the catheter positioned in the coronary sinus recorded atrial activity suggestive of AF (average cycle length, 190 ms) (see Fig 1). Rapid atrial pacing resulted in transient capture of the area where distinct atrial potential (sinus rhythm) was recorded, but it did not influence the respective atrial sites in which localized atrial potential was recorded. The sinus rhythm remained constant throughout pacing, and neither tachycardia nor AF was induced. To evaluate the reproducibility of our findings, the catheters were left in situ until the following day, when another electrophysiological examination was performed. The recordings were consistent with those of the previous study.
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Fig 1. The two distal poles of the catheter positioned in the high right atrium (HRA) in close proximity to the sinus node recorded the coexistence of a distinct atrial electrogram (cycle length, 660 ms) and a localized irregular atrial potential (arrowheads). Simultaneously, the distal poles of the catheter positioned in the coronary sinus (CS) recorded atrial activity suggestive of atrial fibrillation (arrows).
(HBE = His bundle; RV = right ventricle; A, H, and V atrial, His, and ventricular potentials, respectively.)
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Comment
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In 1962, Moe [3] postulated that AF was based on multiple reentrant wavelets occurring in random order in the atrium. Cox [1] developed the maze procedure as a method to exploit such a mechanism. A number of modifications of the maze procedure have been developed and used in the management of AF [2, 4]. In these procedures, appropriately placed atrial incisions and cryocoagulation interrupt the conduction routes of the most common reentrant circuits and direct the sinus impulse from the sinoatrial node to the atrioventricular node along a specified route.
Although many reports have described the clinical outcomes of these procedures, electrophysiological evaluation is rare. In one patient, intraatrial recordings demonstrated the coexistence of sinus rhythm and localized atrial potential in both atria. These findings were located in a well-defined area, and their reproducibility was confirmed. We believe that this is one of the first reports of the observation of atrial dissociation and dissimilar atrial rhythm with intraatrial electrode catheter recordings after the maze procedure. In addition, only a few reports [5, 6] have presented such findings in patients with sick sinus syndrome and atrial flutter/fibrillation.
Coexistence of sinus activity with AF of the right and left atria suggests that masses of atrial tissue surrounding the sinus node were protected by entrance block. Although we do not know whether the entrance block in and around the sinus node is caused by an anatomical or physiological barrier, it probably is related to the considerable fibrosis and fatty degeneration resulting from the incisions and cryocoagulation of the maze procedure. During the early postoperative period, a new reentrant circuit can develop or an ectopic focus can be activated because the effective refractory period of the atrium shortens. This probably is the result of a combination of factors, including local tissue edema, pericarditis, surgical trauma, and elevated levels of circulating catecholamines. In one patient, electrophysiological examinations were performed 12 months postoperatively, and therefore, the findings appear to indicate that the maze procedure was effective.
Although we were unable to determine whether the localized potentials we observed were caused by ectopic focus or reentry, we think that our findings in this patient will be of interest to those concerned with the theoretical basis of the maze procedure.
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References
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- Cox J.L. The surgical treatment of atrial fibrillation. IV. Surgical technique. J Thorac Cardiovasc Surg 1991;101:584-592.[Abstract]
- Kosakai Y., Kawaguchi A.T., Isobe F., et al. Modified maze procedure for patients with atrial fibrillation undergoing simultaneous open heart surgery. Circulation 1995;92(Suppl 2):359-364.[Abstract/Free Full Text]
- Moe G.K. On the "multiple wavelet" hypothesis of atrial fibrillation. Arch Int Pharmacodyn Ther 1962;140:183-188.
- Nitta T., Lee R., Schuessler R.B., Boineau J.P., Cox J.L. Radial approach: a new concept in surgical treatment for atrial fibrillation I. Concept, anatomic and physiologic bases and development of a procedure. Ann Thorac Surg 1999;67:27-35.[Abstract/Free Full Text]
- Zipes D.P., Dejoseph R.L. Dissimilar atrial rhythms in man and dog. Am J Cardiol 1973;32:618-628.[Medline]
- Gomes J.A., Kang P.S., Matheson M., Gough W.B., Jr, El-Sherif N. Coexistence of sick sinus rhythm and atrial flutter-fibrillation. Circulation 1981;63:80-86.[Abstract/Free Full Text]
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Abstract
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