A new transapical beating-heart septal myectomy (TA-BSM) procedure is a safe and efficient septal reduction treatment for patients with hypertrophic obstructive cardiomyopathy (HOCM), according to new first-in-human data. The study, published online Monday and in the Aug. 15 issue of the Journal of the American College of Cardiology, reports that the novel TA-BSM procedure appears to be less technically demanding and easier to disseminate as a valuable alternative to conventional SM – adding that compared with conventional surgical septal myectomy (SM), TA-BSM provides real-time evaluation to guide resection while reducing surgical trauma. The research team, led by Jing Fang, MD, PhD, and Yani Liu, MD, PhD, from the Huazhong University of Science and Technology, Wuhan, China, noted that the prevalence of hypertrophic cardiomyopathy is estimated to be more than 1 in 500 in the general population – with HOCM affecting approximately 70% of these patients with hypertrophic cardiomyopathy. “Although pharmaceutical and septal ablation therapies are effective for some HOCM patients, surgical SM remains the criterion standard for the treatment of HOCM owing to its safety, efficacy, competence for heterogeneity, and favorable long-term outcomes,” said the team – adding that standard SM is performed by creating a rectangular trough in the hypertrophic septum bulging into the left ventricular outflow tract (LVOT) under cardiopulmonary bypass. However, highly efficient SM with a low mortality rate has largely been confined to a few high-volume centers globally, they said. Septal myectomy limitations Fang and colleagues noted that multiple limitations hamper the widespread use of SM to address the high prevalence of HOCM, adding that a major problem for the procedure is that “it is difficult to precisely determine the thickness and extent of the ventricular septum to be resected in an arrested heart through the narrow operative window permitted by the transaortic approach.” “Generally, whether sufficient myectomy has been accomplished can be assessed only when the heart resumes beating. Therefore, it is technically demanding to adequately abolish LVOT obstruction while preventing iatrogenic complications,” they said, adding that difficulties are even more pronounced in pediatric patients with a small aortic annulus. Furthermore, they added that surgical risks associated with median sternotomy and cardiopulmonary bypass render conventional SM prohibitive for elderly and morbid patients, while combined transaortic and transapical approaches are needed for some patients with midventricular obstruction or long-segment hypertrophy, “which further complicates the procedure and increases risks.” Novel procedure The team noted that the drawbacks of conventional SM and the advantages of transapical interventions motivated them to develop the novel TA-BSM procedure, “enabled by an innovative beating-heart myectomy device (BMD) that we invented.” They explained that visualization of SM under a real-time echocardiography-implemented cross-sectional view of the left ventricular (LV) geometry obviates the necessity for sternotomy. “We report here a first-in-human clinical trial of TA-BSM using this BMD at our institution, aimed at demonstrating the feasibility, safety, and efficacy of this novel technique for treating HOCM,” said the authors, noting that before enrollment, all patients underwent standard assessments, including transthoracic echocardiography (TTE) and cardiac magnetic resonance (CMR), while preoperative transesophageal echocardiography (TEE) was performed for patients with unclear mitral problems to exclude primary native valvular pathologies. First-in-human data A total of 47 patients with HOCM, aged 12 to 77 years, were enrolled into the single-center, single-arm, first-in-human, investigator-initiated registry study. The novel TA-BSM procedure was performed via mini-thoracotomy with the use the new BMD device under echocardiographic guidance, and without the use of cardiopulmonary bypass. The primary outcome measure was procedural success, defined by resting/provoked LVOT gradient <30/50 mm Hg and residual mitral regurgitation (MR) grade ≤1+ (of 4+) at 3-month follow-up. “Of the 46 patients who were followed for 3 months, 42 achieved procedural success,” said the team, reporting that the maximal LVOT gradient decreased from 86 mm Hg (interquartile range [IQR]: 67-114 mm Hg) at baseline to 19 mm Hg (IQR: 14-28 mm Hg) at 3 months. Additionally, an MR grade of ≤1+ was reported in three patients at baseline and in 45 patients at 3 months, they said. “One patient died on postoperative day 10 owing to device-unrelated reasons,” noted the team, adding that other major adverse events included one delayed ventricular septal perforation and one intraoperative left ventricular apical tear. The authors concluded that the novel TA-BSM procedure is a safe and efficient minimally invasive procedure for septal reduction of heterogeneous HOCM – adding that compared with conventional SM, TA-BSM provides real-time evaluation to guide resection while reducing surgical trauma. “TA-BSM appears to be less technically demanding and easier to disseminate as a valuable alternative to conventional SM, thus making septal reduction therapy available to the majority of eligible HOCM patients,” they said, adding that further research is now needed to characterize patients with HOCM who would benefit from TA-BSM as an alternative to SM, alcohol septal ablation or myosin inhibitor medication therapy. Procedural promise Writing in an accompanying editorial, Hartzell V. Schaff, MD, from the Mayo Clinic, Rochester, Minnesota, and Hao Cui, MD, PhD, from the Beijing Institute of Heart, Lung, and Blood Vascular Diseases, noted that this initial clinical trial had “successful outcomes,” with one early death (2%), one iatrogenic ventricular septal defect (VSD) requiring urgent repair (2%), and one instance of apical injury requiring sternotomy for repair (2%). The editorialists added that while the emphasized advantage of avoiding cardiopulmonary bypass “will undoubtedly have cachet with patients and some clinicians,” it is also important to recognize that extracorporeal circulation for cardiac surgery is extremely safe and reliable. Furthermore, they noted that an important consideration in selecting a surgical approach is that transaortic myectomy through a sternotomy allows simultaneous correction of associated cardiac problems, including degenerative mitral valve disease, obstructive coronary artery disease, bridging of the left anterior descending artery, and atrial fibrillation. “In our practice, associated procedures are performed in more than 30% of patients,” they said. However, they concluded that the novel device and surgical approach for TA-BSM may be an important step in expanding surgery for septal reduction therapy. “A clear advantage of performing myectomy on a beating heart is the real-time hemodynamic assessment of the adequacy of septectomy,” they said, noting that larger studies from multiple sites will be necessary to understand to what extent the learning curve and case volume affect outcomes. “The procedure promises to provide a less painful and more rapid recovery for patients compared with transaortic myectomy performed via sternotomy. Thus, future investigations of the safety and efficacy of myectomy by the beating heart transapical approach should also focus on quantifying postoperative patient experience,” they added. Sources: Fang J, Liu Y, Zhu Y, et al. First-in-Human Transapical Beating-Heart Septal Myectomy in Patients With Hypertrophic Obstructive Cardiomyopathy. J Am Coll Cardiol 2023;82:575-586. Schaff HV, Cui H. Septal Myectomy. An Evolving Therapy for Obstructive Hypertrophic Cardiomyopathy. J Am Coll Cardiol 2023;82:587-589. Image Credit: iushakovsky – stock.adobe.com