Study Confirms Quality-of-Life Benefits of Myectomy in Obstructive HCM

Prospective SPIRIT-HCM trial demonstrates broad gains over 12-month follow-up

For the first time, septal myectomy has been shown in a prospective trial to improve quality of life (QoL) and functional capacity in patients with symptomatic obstructive hypertrophic cardiomyopathy (HCM).

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This finding, from a single-center, investigator-initiated Cleveland Clinic study known as SPIRIT-HCM, was reported in a featured science session at the American Heart Association’s virtual Scientific Sessions 2021.

“The primary goal of septal myectomy is to alleviate the symptoms and improve the quality of life in obstructive hypertrophic cardiomyopathy patients when medication is no longer effective,” says principal investigator Milind Desai, MD, MBA, Director of the Hypertrophic Cardiomyopathy Center and Director of Clinical Operations in Cleveland Clinic’s Heart, Vascular & Thoracic Institute. “However, its impact on quality of life, physical and social health has not been prospectively studied until now.”

Study design and cohort

The investigators prospectively assessed various metrics of QoL and functional capacity among patients with obstructive HCM who were scheduled to undergo septal myectomy at Cleveland Clinic from March 2017 to June 2020. Inclusion criteria were age 18 to 65 and fulfillment of class I or II indications for surgical relief of left ventricular outcome tract (LVOT) obstruction, consistent with current guidelines.

The primary endpoint of this single-arm study was an improvement of 5 or more points from baseline to 12-month postsurgical follow-up in the summary score of the Kansas City Cardiomyopathy Questionnaire (KCCQ), an established QoL metric in this setting. Prespecified secondary endpoints included KCCQ subscores as well as scores on other validated QoL instruments, 6-minute walk test results and various clinical measures.

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Among 560 patients who underwent surgery for obstructive HCM during the study period, 173 met inclusion criteria, agreed to participate and completed baseline evaluation. The cohort was predominantly male (62%), had a mean (± SD) age of 51 ± 11 years and had a high prevalence of obesity (66%).

The vast majority of patients underwent either isolated surgical myectomy (70%), myectomy with papillary muscle reorientation (18%) or myectomy with mitral valve repair (9%). There was one perioperative death (three weeks postoperatively) and no strokes, cardiac reoperations or cases of ventricular tachycardia or sudden cardiac death.

Results: Improvements across the board

Of the original cohort, 31 patients were lost to follow-up and six withdrew informed consent, leaving a final cohort of 136 patients who completed follow-up evaluation.

Among these patients, 125 (92%) achieved the primary endpoint of a ≥ 5-point improvement in KCCQ summary score, including 109 (80%) who achieved a large (> 20 point) improvement. Only 4% of patients had a worse score at 12-month follow-up, and the remaining 4% had no change in score. Improvements were independent of patients’ baseline New York Heart Association class.

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Other key findings included the following:

  • 117 patients (86%) reported good to excellent health status (KCCQ summary score ≥ 75) at follow-up.
  • Median KCCQ summary score improved from 50 (interquartile range [IQR], 37 to 66) at baseline to 96 (IQR, 86 to 100) at 12 months (P < 0.001).
  • The cohort’s median scores on all other QoL metrics — including scores on the Patient-Reported Outcomes Measurement Information System (PROMIS), the Duke Activity Status Index (DASI), the European QOL-5 dimensions (EQ-5D) and all KCCQ subscales — improved markedly from baseline to 12-month follow-up, as did 6-minute walk distance, measures of dyspnea and fatigue, peak LVOT gradient and N-terminal pro-BNP level (P < 0.001 for all). Significant improvements in the QoL measures were observed in more than 80% of patients.

Encouraging findings merit further exploration

“These findings demonstrate that septal myectomy in patients with symptomatic obstructive HCM significantly improves overall quality of life, physical and social health status, left ventricular outcome tract obstruction and functional capacity,” says co-investigator Steven Nissen, MD, Chief Academic Officer of Cleveland Clinic’s Heart, Vascular & Thoracic Institute.

Even so, the investigators note, the current study is limited by its lack of a control group, relatively short follow-up and single-center design, as well as the potential for surgery to exert a placebo effect in terms of a patient-reported QoL outcome.

Dr. Desai says the study’s encouraging QoL findings should be confirmed in additional studies with a more rigorous design. “Future studies should also explore which social demographic, clinical and physiological parameters are most strongly associated with improved health status from myectomy for obstructive HCM,” he concludes.