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J Thorac Cardiovasc Surg 2005;130:233-234
© 2005 The American Association for Thoracic Surgery
Letters to the Editor |
Department of Cardio-Thoracic Surgery, Glasgow Royal Infirmary, Glasgow, United Kingdom
To the Editor:
The article "Map-Guided Surgery for Atrial Fibrillation" by Nitta and associates
1
confirms and raises important issues. An adequately performed pulmonary vein isolation (PVI) cures most patients with intermittent atrial fibrillation (AF) but fails as an isolation procedure in patients with non–pulmonary vein (non-PV) foci and in those with continuous AF, in whom the PVs and the circuits they harbor become irrelevant to the maintenance of AF. In these patients the goal shifts from isolating the trigger to ablating the macroreentrant circuits. Although a left atrial (LA) procedure is mandatory, the real question is the following: When do we address the right atrium (RA)?
The identification of the transition from intermittent to continuous AF is crucial in determining the pattern of activation and the procedure needed. What was the relationship between the activation pattern and (1) the underlying structural heart disease and (2) the pattern (continuous or intermittent) and duration of AF?
The authors state that intraoperative mapping would be useful in determining the indications for simplified procedures for AF. Only 8 patients had PVI, although 21 had passive RA activation. This indicates that further refinement in technology is required before intraoperative mapping could really indicate the choice of procedure.
The success rates for AF between the 2 procedures are probably similar because the authors have been selective in the choice of patients for PVI. It will be interesting to speculate what the results would have been if these 13 patients also had simple LA procedures. Intraoperative mapping confirmed that most activation arose from the posterior LA, the appendage, and the PVs and justifies the use of LA procedures for such patients. It is useful to know the exact sites of activation in those with predominantly LA activation. Perhaps with further refinement in mapping techniques, it would be possible to develop abbreviated lesion sets even shorter than the ones that currently exist. For instance, it might not be necessary to ablate all PVs if only specific veins are involved.
The finding of activation from the LA appendage justifies appendage exclusion. The effect of this on appendage-sparing procedures needs to be analyzed. Did the authors ablate the appendage, even if it was not the focus of activation? If so, why?
Patients in the study with LA diameters exceeding 60 mm but with viable electrical activity were cured of AF. This suggests that (1) the presence of viable electrical activity is a greater predictor for AF conversion rather than LA diameter and (2) mapping is useful in predicting the probability of AF conversion in these patients.
The mapping time is acceptable, provided mapping reliably indicates the choice of procedure, and will reduce with the advent of more sophisticated systems. If similar maps could be obtained with a single LA electrode, then perhaps preoperative mapping would substantially reduce operative mapping time.
Thirteen of 21 patients with passive RA activation underwent the radial procedure because the pattern of atrial activation could not be completely determined in the intraoperative analysis. Have they really proved their point?
References
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