JRSM >
Volume 95, Number 11 >
Pp. 552-553
Department of Cardiac Surgery, St Mary's Hospital, Praed Street, London W2 1NY, UK
Correspondence to: Mr P Kumar, 43 Blenheim Gardens, Kingston, Surrey KT2 7BN, UK E-mail: pankajkumar66{at}hotmail.com
Atrial fibrillation is the commonest sustained cardiac arrhythmia, with a prevalence of about 10% in the over-70s1. The implications in terms of mortality, stroke and quality of life are of major concern. Patients have been successfully treated by surgical interruption of conduction pathways—the maze procedure. Lately a saline-irrigated radiofrequency probe, Cardioblate, has become available in the UK for this purpose.
CASE 1
A man aged 71 with rheumatic mitral disease and coronary artery disease had been in atrial fibrillation since the age of 22—i.e. for 49 years. He underwent off-pump triple coronary artery bypass grafting; then, after institution of cardiopulmonary bypass, the mitral valve was repaired with an annuloplasty ring and a modified maze procedure was performed with the irrigated radiofrequency probe. On discontinuation of cardiopulmonary bypass the heart was initially in nodal rhythm but soon the atria started beating and sinus rhythm was restored (Figure 1). The total ablation time was 5 minutes 8 seconds. The patient was in sinus rhythm four months post-operatively.
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CASE 2
A woman of 67 with rheumatic mitral stenosis had been in atrial fibrillation since the age of 45—i.e. for 22 years. She underwent mitral valve replacement together with a modified maze procedure with the irrigated radiofrequency probe. At the end of the procedure both atria were beating, with the heart in sinus rhythm. Total ablation time was 3 minutes and 22 seconds. She was in sinus rhythm when seen six months postoperatively.
COMMENT
The maze procedure, as usually practised, entails a series of incisions in the left and right atrium to achieve electrical isolation and block the re-entry pathway. Maze III is very effective, with sinus rhythm and atrial contractility restored long term in more than 90% of patients2. It is, however, a difficult and long procedure with substantial morbidity.
The radiofrequency probe offers a shorter and simpler procedure, creating a full-thickness burn in the atrium. By use of saline irrigation the tip is constantly cooled so that resistive heating is directed several millimetres below the surface. The depth of the lesion can be varied depending on the power applied, the irrigation speed, the electrode diameter, and the delivery time. Nakagawa et al.3 report that this method produces larger and deeper lesions than ‘dry’ radiofrequency ablation. This has advantages in terms of speed, but does entail a risk of injury to deeper structures: Mohr et al.4 reported oesophageal injury in 1.3%.
The success rate of the modified maze (restoration of sinus rhythm with atrial contractility) was reported by Sie et al.5 as 90% at one year, 86% at two years and 75% at three years5. Benussi et al.6 reported 77% at a mean follow-up of 11.6 months. To the best of our knowledge the maze III operation has not been compared directly with the modified maze.
We are now recruiting more patients to assess the efficacy of this approach. Whilst at present surgical ablation is being used in patients requiring cardiac surgery for other reasons, the method may in future be applicable to a wider group.
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