The patients were treated between 1998 and 2019 at the Mayo Clinic in Rochester, Minnesota, Tufts Medical Center in Boston, and Fuwai Hospital in Beijing, China. Researchers reviewed data on 3,359 patients: 3,274 who received SM and 585 who had ASA.
Over a median of 6.4 years (IQR: 3.6-10.2 years), the 10 year all-cause mortality was 26.1% in the ASA group and 8.2% in the myectomy group, according to a report in the Journal of the American College of Cardiology by Dr. Hao Cui of the Mayo Clinic and colleagues.
Their analysis showed significant differences in the baseline characteristics of the patients, with rates of many risk factors increased in the ASA versus SM group. These included age (63.9 versus 53.7); renal failure (8.8% versus 0.9%); diabetes (12.7% versus 8.7%); coronary artery disease (27.5% versus 9.0%); use of calcium channel blockers (42.8% versus 35.1%); and hypertension (53.5% versus 44.3%). Septal thickness was 19mm versus 20 mm. In addition, males represented 46.8% of the ASA group and 56.2% of the SM group.
There were fairly similar rates of beta-blocker use (75% vs 79% in ASA vs SM groups, respectively); NYHA Class II (19.1% vs 15.4 %); NYHA Class III (78.5% vs 81.3%); and peak left ventricular outflow tract (LVOT) gradient (84 mmHG versus 85 mmHg).
Very few patients were in NYHA Class IV, and very few had extreme septal thickness >30 mm.
Variables independently associated with increased mortality included older age, NYHA Functional Class II-IV, chronic obstructive pulmonary disease (COPD), previous CVA, atrial fibrillation, renal failure, diabetes and greater septal thickness.
Unadjusted mortality was higher after myectomy, but after adjustment for age, sex, and comorbidities, the risk of mortality was higher after septal reduction by ASA (HR:1.68; 95% CI: 1.29-2.19; P < 0.001), according to the report. The researchers confirmed this finding by an additional propensity score matching analysis to address the imbalance in baseline characteristics.
As the mortality incidence was from prospectively maintained databases at each center, including linkage in the U.S. to LexisNexis Accurint, the authors used all-cause mortality as the primary outcome and did not differentiate for this analysis among causes of death, in particular sudden death or heart failure death, or use of pacemakers or automated implantable cardioverter defibrillators. Given the age distribution, it did not appear to include the highly publicized but rare (3/100,000) sudden death in athletes, who often die without warning signs or previous diagnosis, despite controversial "athletic" physicals and EKGs.
In describing the concerns that patients and physicians have when deciding which procedure to have, Dr. Cui and colleagues suggested that although SM has a <1% mortality risk at experienced center, "some clinicians advise ASA for older patients, because of perceived increased operative risk." In the adjusted model, however, mortality curves do not begin to diverge until the 3-year mark, which may be of significance when discussions with the elderly is appropriate, they noted. "In contrast, ASA is usually not recommended to very young patients because of the risk of heart block and pacemaker dependency as well as uncertainty regarding the long-term effects of the septal scar."
Dr. Mark Sherrid of NYU Langone Health in New York City and colleagues commented in an editorial on the "remarkably low postoperative mortality in the myectomy group (0.3%)." They discuss the newer techniques in lengthening surgical myectomy, along with repair of the mitral valve and release of the papillary muscle/chordal apparatus to improve anatomic overlap and gradients. "Ablation cannot address the pathology of mitral valve and papillary muscles," they write. "The more alcohol given, the greater the septal thinning, but the more frequent are side effects."
Dr. Sherrid, who directs NYU's Hypertrophic Cardiomyopathy Program, told Reuters Health in a follow-up email, "Cui et al was an observational study from a highly selected group of participating centers. Nevertheless, because at such centers alcohol ablation yields suboptimal relief of gradient and symptoms, and because, as shown, alcohol ablation is associated with higher mortality, it should not be considered a routine therapeutic choice for patients with medication-resistant obstructive HCM. We believe it should be reserved for those patients who have severe COPD, frailty, other causes of increased surgical risk, or limited life expectancy. The remaining large majority of patients should be referred to a center with surgical expertise."
The online publication of the new study coincides with the approval in the U.S. of the first new oral agent for symptomatic HCM, mavacamten.
"Another factor that will certainly be considered will be the cumulative cost of new agents, compared with the fixed cost of a low-mortality, definitive surgical procedure that provides excellent survival," Dr. Sherrid said.
SOURCE: https://bit.ly/3ylpoIt and https://bit.ly/38a3Zr5 Journal of the American College of Cardiology, online April 25, 2022.
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