CORRESPONDENCE: LETTER TO THE EDITOR
Catheter Ablation After Mitral Replacement
Ganesh Shanmugam, MS, MCh, FRCS*
* Department of Cardiothoracic Surgery, Glasgow Royal Infirmary, Glasgow, United Kingdom (Email: sgunpat{at}hotmail.com).
Lang et al. (1) report their experience of transcatheter ablation of atrial fibrillation (AF) in patients with mitral valve prostheses (MVP). The investigators claim that patients in both groups were at the extreme end of the spectrum of atrial disease. However, more patients (a total of 14) had paroxysmal AF than did those with chronic AF; this does not necessarily constitute the extreme end of the disease. Did the researchers note any significant differences in the incidences of AF recurrences between those who had paroxysmal and those who had chronic AF?
Lang et al. (1) conclude that the outcomes are similar to those of standard patients undergoing catheter ablation, yet the 73% (75% in controls) sinus conversion rate falls far short of the results achieved by current surgical techniques. The need for subsequent intervention for atrial tachycardia (AT) and recurrent AF was pretty high. Given that AF circuits are unstable, what was the incidence of peri-procedural AF in these patients?
Moreover, the lines of ablation varied within as well as between the groups. Was this variation based on the findings of mapping? It would have been interesting to know what the findings of the mapping were in terms of the sites of the triggers. Given that the lines of ablation were different in these patients, how did the investigators compare the incidences of AF recurrence and AT between the two groups?
Although most studies have concentrated on the conversion to sinus rhythm, AT is emerging as a troublesome complication of most forms of intervention. It is significant that the incidence of AT was 29% in the MVP group, particularly considering that all patients in this group had specific lines of ablation to preclude AT!
Surgical scarring as a cause of AT in these patients is not a tenable explanation as none of them had preablation AT. It is more likely to be a consequence of the inability to create an adequate block at the mitral isthmus owing to the fear of damaging the prosthesis. It is well recognized that the creation of incomplete lines of block will facilitate macro-reentrant arrhythmias. This rate of sinus conversion and prevention of AT is then contingent on our ability to close the mitral isthmus adequately within these patients, without damaging the prosthesis. We clearly need to refine the ablation technique to address this issue.
None of these patients had a preprocedural diagnosis of AT, suggesting that AT was a consequence of the ablation. Are we then merely replacing one arrhythmia with another? Evidently we need to address this issue.
Notwithstanding these limitations, Lang et al. (1) are to be congratulated for achieving good results in a unique group of patients who are difficult to treat. Ostensibly, the number of such patients will be reduced in the future, as most of these patients will now have AF ablation, concomitant to mitral repair or replacement.
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1. Lang CC, Santinelli V, Augello G, et al. Transcatheter radiofrequency ablation of atrial fibrillation in patients with mitral valve prostheses and enlarged atria: safety, feasibility, and efficacy J Am Coll Cardiol 2005;45:868-872.[Abstract/Free Full Text]
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