Different techniques have been proposed for treatment of outflow tract obstruction in hypertrophic cardiomyopathy, surgical myectomy being the one with longer experience. Echo-guided septal alcohol ablation has gained popularity in the last 15 years achieving similar numbers and comparable results to surgery in experienced centres.
In this interesting paper published earlier this year the authors report the results of the first series of 19 cases treated with a new technique, the endocardial radiofrequency ablation. This technique was first reported back in 2004 by the same authors.
The left or right ventricular septum was ablated using an irrigating-tip ablation catheter in 9 patients and 10 patients respectively. An average of 31 (range 13-50) pulses were given in target area of 2 cm2. This was guided by MRI and Carto fusion images. Mean total CK after procedure was 415 U/L, with a CKmb 77 U/L and troponin I of 11 ng/ml.
Patients were evaluated at 6 months with echocardiography, bicycle ergometer and 6-min walk test. A mild but significant reduction in thickness was evidenced (pre: 22.6 ± 3.7 mm vs post: 21.4 ± 3.4 mm, p=0.046). Significant (60%) reduction in baseline and provoked and sustained gradients was achieved. Baseline gradient went from 78 ± 30 to 26 ± 22 mmHg, and exercise gradient went from 157 ±37 to 64 ± 44 mmHg. The 6-min walking distance increased significantly from 412 ± 129 m to 471 ± 139 m after 6 months, (p = 0.019); and NYHA class improved from 3.0 ± 0.0 to 1.6 ± 0.7 (p = 0.0001).
There were some complications. Complete atrioventricular block requiring permanent pacemaker implantation occurred in 4 patients (21%) and 1 patient had a cardiac tamponade. Authors concluded that endocardial radiofrequency ablation is a new alternative option to alcohol and myectomy for treatment of obstruction in hypertrophic cardiomyopathy. Dr. Lawrenz and colleagues suggested that the benefit of radiofrequency ablation, rather than thickness reduction, is related to the induction of a local contraction disorder at the septum.
Endocardial radiofrequency ablation for the treatment of obstruction constitutes a very original and attractive approach when other established options are not available. The development of new technological tools such as the MRI and Carto fusion imaging and the new irrigated catheters have made this possible. All 19 patients in this study were offered and refused myectomy and some of them (8) had an alcohol septal ablation procedure performed (ineffective) or failed (not suitable branches, collaterals, etc).
The experience of this collection of cases from 3 different centres is valuable but there are some issues that should be answered in a larger and more structured study. The election of the approach (right versus left) in this study was based on operator or case by case decision. Pre and post ablation bundle branch blocks were not recorded. One might think that part of the benefit from left sided ablation could be related to LBBB induction after procedure? The magnitude of gradient reduction with endocardial radiofrequency presented in this study is inferior to that reported for myectomy and alcohol septal ablation and it is comparable to that of DDD pacing. The rate of permanent pacing is high (21%) similar to first alcohol ablation series.
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