Obstructive HCM: Will Septal Reduction Zapping Hold Up?

Operators continued to make progress on an investigational septal reduction procedure for drug-refractory obstructive hypertrophic cardiomyopathy (HCM) at the Chinese center that pioneered the technique.

Among 200 patients, the 30-day major adverse clinical event rate was 10.5% with percutaneous intramyocardial septal radiofrequency ablation (PIMSRA), with the bulk of events related to pericardial effusions that declined over time with improved procedural planning and technique, reported Liwen Liu, MD, PhD, of Xijing Hospital, Fourth Military Medical University, and colleagues.

There were two deaths: one attributed to cardiogenic shock at 1 week — perhaps due to excessive radiofrequency ablation — and the other a sudden cardiac death at day 6 due to either ventricular or bradycardia arrhythmia, they noted in JAMA Cardiology.

The good news was that periprocedural conduction disturbances were low, with permanent right bundle branch block occurring in 2.5% of patients and resuscitated ventricular fibrillation occurring in 1.0%. There were no permanent pacemaker implantations after PIMSRA.

“These results are encouraging and support the design of a randomized clinical trial against well-established septal reduction therapies,” Liu’s group wrote.

Septal myectomy is limited by the availability of experienced surgical centers, whereas percutaneous alcohol septal ablation (ASA) relies on the patient having sufficiently sized septal perforator branches and poses a risk of damaging the conduction system.

Based on this study, PIMSRA’s “mortality and morbidity compare favorably with both of these alternatives,” commented Dana Roxana Bataiosu, MD, and Harry Rakowski, MD, both of Toronto General Hospital in Ontario.

However, the duo cautioned that the technique is technically challenging. The good results observed by Liu’s team may not necessarily be replicated elsewhere, they suggested in an accompanying editorial.

“As with the options that came before, the techniques need to be refined, made widely available, and stand the test of time, before the wire displaces patients who benefit from the scalpel or the catheter,” Bataiosu and Rakowski concluded.

Liu’s group had reported initial findings from the first 15 PIMSRA patients back in 2018.

“We now use preprocedural computed tomography angiography and intraoperative color Doppler flow imaging during needle insertion to determine the appropriate site of needle entry allowing us to minimize vessel injury. In the last 120 cases, no patient required mini thoracotomy to drain the pericardial effusion,” they noted.

For this study, Liu and colleagues analyzed consecutive obstructive HCM patients presenting to Xijing Hospital from 2016 to 2020.

Out of 1,314 potential PIMSRA candidates, 244 met criteria for high outflow gradients and drug-refractory symptoms. Ultimately, 40 underwent surgery or ASA following a heart team discussion, and four received treatment for significant coronary artery disease.

Of the 200 people included in the PIMSRA cohort, mean age was 47, and 62.5% were men.

By 90 days, maximal septal thickness was reduced from a mean of 24.0 mm to 17.3 mm (P<0.001), while left ventricular outflow tract gradients dropped from 79.0 mm Hg to 14.0 mm Hg (P<0.001).

At last follow-up (median 19 months), 96% of patients had New York Heart Association functional class I or II symptoms.

Liu and team acknowledged the importance of 5-year follow-up and serial imaging to assess the extent of myocardial scarring resulting from PIMSRA.