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The occurrence of high-grade conduction disturbances after alcohol septal ablation (ASA) did not translate into worse long-term survival for people with obstructive hypertrophic cardiomyopathy (HCM), a registry study showed.

Among ASA procedures in the Euro-ASA registry, cases complicated by high-grade atrioventricular block requiring permanent pacemaker (PPM) implant were not associated with particularly worse New York Heart Association (NYHA) functional class and survival in patients followed for 5 years on average, according to a group led by Josef Veselka, MD, PhD, of Charles University and University Hospital Motol in Prague.

PPM implants tended to occur with more aggressive ASA, or when a higher dose of alcohol was used. As such, patients who had gotten a new PPM, compared with matched peers not needing one, were typically left with lower left ventricular (LV) outflow gradients (12 vs 17 mm Hg, P<0.01) and a lower need for reintervention via redo ASA or myectomy, Veselka's group reported in .

PPM recipients did have significantly lower LV ejection fractions at last follow-up (64% vs 66%, P=0.02).

"This highlights the difficult clinical choice between more ablation with better gradient reduction but a higher pacemaker rate," the authors said.

The choice is made no easier as long-term implications of PPM after ASA remain unclear, according to an by Andres Pineda, MD, of University of Florida College of Medicine-Jacksonville, and Andrew Wang, MD, of Duke University in Durham, North Carolina.

"Pacemaker implantation may be associated with significant early and late morbidity, such as lead or device malfunction and extraction, need for generator changes, device infections including infective endocarditis, and heart failure from right ventricular pacing," the duo wrote.

Nevertheless, the 5-year data for ASA appear reassuring.

"This report provides further evidence that with current techniques and in the hands of experienced operators, ASA provides excellent short- and long-term survival, which is at least comparable to septal myectomy and not adversely affected by the need of PPM implantation," Pineda and Wang wrote.

ASA and myectomy are the two main options for septal reduction therapy in people with obstructive HCM who have tried guideline-directed medical therapy.

In the spring, FDA formally opened the door to another medical option when the agency approved mavacamten (Camzyos), the first cardiac myosin inhibitor indicated for obstructive HCM. The caveat is that patients can only get mavacamten through a restricted program under a risk evaluation and mitigation strategy due to the drug's associations with reduced LV ejection fraction and systolic dysfunction.

was the large phase III trial that showed that mavacamten improved exercise capacity, LV outflow tract obstruction, NYHA functional class, and health status in obstructive HCM. Mavacamten users also had a lower need for septal reduction therapy in the subsequent VALOR-HCM study.

Septal reduction therapy continues to evolve as an investigational technique called percutaneous intramyocardial septal radiofrequency ablation is being developed at a Chinese center.

For the present study, Veselka and colleagues probed the Euro-ASA registry for ASA procedures performed from 1996 to 2021 in six European countries. The team found 1,814 people followed annually for 5 years on average, of whom 9.4% underwent PPM implantation in the first 30 days after the procedure.

Propensity score matching produced 139 pairs of PPM and non-PPM groups for comparison. Mean age was 60 years, and patients were roughly split between the sexes.

Before matching, however, the two groups differed significantly at baseline. PPM recipients tended to be older, have a higher prevalence of bundle branch block (BBB) before ASA, and have worse baseline function by the NYHA scale.

Independent predictors of PPM implant in the 30 days after ASA were NYHA class III/IV, older age, BBB before ASA, and increasing alcohol dose per 1 mL.

"In the past, it has been convincingly shown that certain factors play a key role in the risk of PPM implantation after ASA. Among the most important factors are preprocedural conduction abnormalities, especially a left BBB. Also, it has been demonstrated that the age of patients is a significant factor contributing to post-ASA conduction disturbances," the authors noted.

They acknowledged that the registry's lack of functional pacing data meant they could only assume, based on previous observations, that some patients were mostly independent of PPM pacing. Another limitation of the study was that the window of follow-up did not capture complications of PPM that can occur later.

The editorialists cautioned that there is potential for selection and reporting biases in the observational analysis, as well as a lack of standardized procedural techniques and independent echocardiographic core lab review.

In the absence of randomized controlled trials, however, the totality of the observational evidence thus far still supports "excellent outcomes" after ASA for HCM, Pineda and Wang maintained.

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