Mortality Post Septal Ablation and Myectomy for HCM

Abstract & Commentary

By John P. DiMarco, MD, PhD

Source: Leonardi RA, et al. Meta-analyses of septal reduction therapies for obstructive hypertrophic cardiomyopathy: Comparative rates of overall mortality and sudden cardiac death after treatment. Circ Cardiovasc Interv. 2010;3:97-104.

Sudden cardiac death is a feared complication of hypertrophic cardiomyopathy (HCM). Therapies to reduce the incidence of sudden cardiac death have included implantable defibrillators and surgical- and catheter-based approaches to reduce obstruction by septal reduction. The long-term effects of septal-reduction therapies on sudden cardiac death have not been well described. In this paper, Leonardi et al performed a meta-analysis of the effects of septal reduction in 19 series that used alcohol septal ablations and eight studies that used surgical myomectomy. Studies that included sudden-death outcomes were selected for inclusion.

Surgical myomectomy results included data from 1,887 patients operated on between 1963 and 2005. The alcohol septal ablation results covered data from 2,207 patients who underwent the procedure between 1996 and 2007. Patients who underwent surgical myomectomy tended to be younger, had a slightly greater septal-wall thickness and a long mean duration of follow-up. In the myomectomy patients, there were 250 all-cause deaths and only 45 sudden cardiac deaths during follow-up, while among the patients who underwent alcohol septal ablation, there were 121 all-cause deaths and 26 sudden cardiac deaths. With adjustment for the number of patient years of follow-up, the all-cause mortality rate for surgical myomectomy was 1.8% per patient year vs. 2.1% per patient year for the alcohol septal ablation patients. The sudden cardiac death rate per patient year was 0.3% in the surgical myomectomy group vs. 0.4% in the alcohol septal ablation group. After adjustment for available baseline characteristics, the odds ratios for treatment effect on all-cause mortality and sudden cardiac death were 0.28 and 0.32 favoring alcohol septal ablation. Effects of the two procedures on New York Heart Association functional class were similar. More patients undergoing alcohol septal ablation required a new permanent pacemaker. ICD implantation post-procedure was uncommon in both cohorts.

The authors conclude that both surgical myomectomy and alcohol septal ablation result in similarly low rates for all-cause mortality and sudden cardiac death in patients with obstructive HCM. There does not appear to be an increase in arrhythmic potential with alcohol septal ablation. In fact, after adjustment for clinical variables, rates of all-cause death and sudden death were lower with alcohol septal ablation.

Commentary

Prevention of sudden death in patients with obstructive HCM remains a challenge. Some HCM patients have either no or only mild symptoms of congestive heart failure despite significant left ventricular hypertrophy, spontaneous nonsustained VT or histories of syncope. These patients are probably best managed with ICD implantation since there would be no symptomatic benefit from a septal reduction procedure. There are significant problems with aggressive use of ICD implants in these patients. Unfortunately, many HCM patients are young, the absolute annual sudden death rate is relatively low and the complication rate with implantable defibrillators is relatively high. Therefore, the data presented here that both alcohol septal ablation and surgical myomectomy result in both hemodynamic improvement and low rates of post procedure sudden cardiac death are encouraging. The data suggest that ICD therapy can be avoided in patients without prior arrhythmias who have successful septal reduction by either technique. However, it must be remembered that both the alcohol septal ablation and the surgical myomectomy series reported here came from very experienced centers. When referring patients with obstructive HCM for septal reduction, the physician should consider the experience of the center and know that they achieve good outcomes. Only if the procedural morbidity and mortality are low, can similar excellent results be anticipated.