A novel approach in the use of radiofrequency catheter ablation of septal hypertrophy in hypertrophic obstructive cardiomyopathy

Abstract

Objective: Alcohol septal ablation (ASA) is a therapeutic alternative to surgical myectomy in patients with hypertrophic obstructive cardiomyopathy (HOCM). However, the anatomical variability of the septal branch, risk of complete heart block, and late onset ventricular arrhythmias are limitations to its therapeutic usage. There is recent interest in the use of radiofrequency catheter ablation (RFCA) as a therapeutic option in HOCM. We aimed to assess the safety and efficacy of RFCA in the treatment of symptomatic HOCM.

Methods: Seven patients with symptomatic HOCM (mean age 43.7±15.6 years, five males), and significant left ventricular outflow tract (LVOT) gradient despite optimal drug therapy, underwent ablation of the hypertrophied interventricular septum. These patients had unfavorable anatomy for ASA. Ablation was performed under 3D electro-anatomical system guidance using an open irrigated tip catheter. The region of maximal LV septal bulge as seen on intracardiac echocardiography was targeted. Patients were followed up at 1, 6, and 12 months post-procedure.

Results: The mean baseline LVOT gradient by Doppler echocardiography was 81±14.8mm of Hg which reduced to 48.5±22.6 (p=0.0004), 49.8±19.3 (p=0.0004), and 42.8±26.1mm of Hg (p=0.05) at 1, 6, and 12 months respectively. Symptoms improved at least by one NYHA class in all but one patient. One patient developed transient pulmonary edema post-RFA. There were no other complications.

Conclusion: RFCA of the hypertrophied septum causes sustained reduction in the LVOT gradient and symptomatic improvement among patients with HOCM. Electroanatomical mapping helps to perform the procedure safely.

Keywords: Alcohol septal ablation; Hypertrophic obstructive cardiomyopathy; Left ventricular outflow tract; Radiofrequency ablation.

Fig. 1

CARTO-guided 3D anatomical map of LV with three pressure zones and radiofrequency ablation lesions. (A) The three pressure zones in 3-D CARTO LAO view with their corresponding pressure tracings. Yellow dots indicate the site of conduction system signals. The insert shows A-H-V signals (Site of left side His bundle). The gray color indicates the area of normal pressure zone with no difference in gradient observed in the pressure tracing. Pink zone reflects transition zone and purple, high pressure zone with corresponding pressure tracings. Note that in (B), the RF lesions (red dots) are delivered in the transition zone, away from the conduction system (yellow dots).

Fig. 2

Intracardiac echocardiographic images during radiofrequency catheter ablation. (A) Arrow shows that catheter tip is not in proper contact with septum. In this situation radiofrequency lesion delivery may not be effective. (B) Arrow shows firm contact of the catheter tip with the hypertrophied septum.

Fig. 3

LVOT gradient of individual patients at 1-month, 6-month, and 12-month followup.