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Alcohol septal ablation (ASA) was safe and effective for younger obstructive hypertrophic cardiomyopathy (HCM) patients in a study with long-term data, leading investigators to call for a broadened indication for the procedure.

ASA patients ages 50 years and younger had (0.3% versus 20%, P=0.03) and pacemaker implantation rates (8% versus 16%, P<0.001) than those of their peers over 65, reported Max Liebregts, MD, of St. Antonius Hospital in the Netherlands, and colleagues.

The younger patients shared the same 1% annual odds of adverse arrhythmic events with older groups (P=0.90). However, functional recovery was more likely in the younger group. During 5.4 years' follow-up, 95% of young patients studied reached New York Heart Association functional class I or II, compared with 81% among those 65-years-and-older (P<0.001), according to the study published in the June 12 issue of JACC: Cardiovascular Interventions.

HCM guidelines from the American College of Cardiology Foundation/American Heart Association (ACCF/AHA) currently reserve ASA for older patients and those with serious comorbidities, giving the procedure a Class III indication ("harm") for younger patients who can have surgical myectomy instead.

Based on these data, "we propose that the indication for ASA can be broadened to younger patients," wrote Liebregts' group.

"Although the present study, a comparison of outcomes of ASA among different age groups, does not provide a direct comparison of outcomes after ASA and myectomy in younger patients, it provides reassuring data regarding the efficacy and safety of ASA in such patients," commented Michael A. Fifer, MD, of Boston's Massachusetts General Hospital, writing in an .

The younger the patient, the lower the annual death rate (1% versus 2% for middle-age group versus 5% for older group, P<0.01), they found.

Young patients who required a higher volume of alcohol for the procedure were more likely to die in a given year (1.4% who got 2.5 mL or more versus 0.6% who got less, P=0.03). Independent factors linked to mortality in this group:

• Increased age (HR 1.09, 95% CI 1.02-1.17)
• Female sex (HR 3.03, 95% CI 1.28-7.18)
• More alcohol injected during ASA (HR 1.55, 95% CI 1.04-2.30)
• Residual left ventricular outflow tract gradient (HR 1.01, 95% CI 1.00-1.02)

But as centers gain experience in the procedure, alcohol volumes may already be dropping, the authors suggested, noting that patients injected with 2.5 mL or more ethanol were treated 5 years earlier on average. "This trend of decreasing volumes of alcohol over the years is seen in most ASA studies and may thus further improve survival rates in young patients following ASA in the future."

Despite his concerns -- about pacemaker implantation in younger patients, and the use of higher doses of ethanol when encountering greater septal thickness -- Fifer agreed that it was time for ASA to move into lower age groups.

"The present study provides the most robust data to date regarding the outcomes of ASA in younger patients, precisely the type of data that were missing at the time of writing of the ACCF/AHA and European Society of Cardiology guidelines."

"Given the favorable outcomes of ASA in this age group, and the unavailability of high-volume myectomy programs in many geographic regions, the time has come to liberalize the indication for ASA in younger patients. A reassessment of the ACCF/AHA guideline in particular would be timely," the editorialist urged.

The observational study by Liebregts and colleagues included 1,197 consecutive patients with HCM (mean age 58 years, 49% women) who got ASA for severe left ventricular outflow tract obstruction despite optimal medical therapy. Participants were enrolled at seven tertiary centers in Europe from 1996 to 2015.

Older patients were more likely to be in New York Heart Association functional class III or IV before the ASA procedure, while there were more young patients with implantable cardioverter defibrillators and multiple risk factors for sudden cardiac death.

The authors acknowledged that greater alcohol use may be linked to the potential confounding factor of septal thickness, but they said they performed an analysis showing that was not the case (not included in the paper).

Other limitations included the study being underpowered for analysis in those 35 and younger and the lack of statistical adjustment for percutaneous technique.