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Endocardial radiofrequency ablation for hypertrophic obstructive cardiomyopathy

Acute results and 6 months´ follow-up in 19 patients

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.

Myocardial Disease


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. 

Conclusion:

There are some limitations inherent in all pilot studies. Despite MRI and Carto fusion images was recommended, apparently only 5 (26%) patients had MRI images available. In order to identify possible conduction or arrhythmic complications patients were fitted with a 8 days ECG Holter system. There is no specific mention related the presence of ventricular arrhythmias (in particular non-sustained ventricular tachycardia) during admission or during follow-up. One of the main objections to alcohol ablation has been the possible pro-arrhythmic effects of the myocardial scar. As the authors recall in the paper, cardiometabolic test (with gas exchange measurements) and other echocardiographic measurements (assessment of the effect of diastolic dysfunction and SAM) would have added value to the study.

References


  1. Lawrenz T, Kuhn H. Endocardial radiofrequency ablation of septal hypertrophy. A new catheter-based modality of gradient reduction in hypertrophic obstructive cardiomyopathy. Z Kardiol. 2004;93:493–9.
  2. Faber L, Seggewiss H, Welge D, Fassbender D, Schmidt HK, Gleichmann U, Horstkotte D. Echo-guided percutaneous septal ablation for symptomatic hypertrophic cardiomyopathy: 7 years of experience. Eur J Echocardiography. 2004; 5: 347-355
  3. Faber L, Welge D, Fassbender D, Schmidt HK, Horstkotte D, Seggewiss H. One-year follow-up of percutaneous septal ablation for symptomatic hypertrophic obstructive cardiomyopathy in 312 patients: predictors of hemodynamic and clinical response Clin Res Cardiol. 2007;96:864 –73.
  4. Woo A, Williams WG, Choi R, Wigle ED, Rozenblyum E, Fedwick K, Siu S, Ralph-Edwards Anthony, Rakowski H. Clinical and echocardiographic determinants of long-term survival after surgical myectomy in obstructive hypertrophic cardiomyopathy. Circulation. 2005; 111: 2033-2041
  5. Firoozi S, Elliott PM, Sharma S, Murday A, Brecker SJ, Hamid MS, Sachdev B, Thaman R, McKenna WJ. Septal myotomy-myectomy and transcoronary septal alcohol ablation in hypertrophic obstructive cardiomyopathy. A comparison of clinical, haemodynamic and exercise outcomes. Eur Heart J. 2002;23:1617-24
  6. Maron BJ, Nishimura RA, McKenna WJ, Rakowski H, Josephson ME, Kieval RS. Assessment of permanent dual-chamber pacing as a treatment for drug-refractory symptomatic patients with obstructive hypertrophic cardiomyopathy. A randomized, double-blind, crossover study (M-PATHY). Circulation. 1999; 99: 2927-33.
  7. Alam M, Dokainish H, Lakkis NM. Hypertrophic obstructive cardiomyopathy-alcohol septal ablation vs. myectomy: a meta-analysis. Eur Heart J. 2009;30(9):1080-7
  8. Agarwal S, Tuzcu EM, Desai MY, Smedira N, Lever HM, Lytle BW, Kapadia SR. Updated meta-analysis of septal alcohol ablation versus myectomy for hypertrophic cardiomyopathy. J Am Coll Cardiol. 2010; 55(8):823-34.

Notes to editor


Presented by Dr. Gonzalo de la Morena and Dr. Juan Gimeno,
Department of Cardiology, University Hospital Virgen Arrixaca,
Murcia, Spain
The content of this article reflects the personal opinion of the author/s and is not necessarily the official position of the European Society of Cardiology.

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