June 01, 2019
Results of a retrospective study assessing the frequency and implications of mitral valve surgery at the time of septal myectomy for hypertrophic cardiomyopathy in a national cohort suggest that concomitant mitral valve intervention is associated with increased risk.
"National practice patterns related to mitral valve surgery in patients with hypertrophic cardiomyopathy undergoing septal myectomy are unknown," says Kimberly A. Holst, M.D., Surgery, at Mayo Clinic's campus in Rochester, Minnesota. "The aims of this study were to assess the frequency of concomitant operative interventions ― specifically mitral valve repair or replacement ― at the time of septal myectomy in patients with obstructive hypertrophic cardiomyopathy, and to understand the implications of these interventions in a national cohort.
"There has been controversy regarding the surgical management of mitral regurgitation in patients with hypertrophic cardiomyopathy," says Dr. Holst. "Although mitral regurgitation due to systolic anterior motion frequently resolves with an adequate septal myectomy, some groups support concomitant mitral valve procedures at the time of septal myectomy to address regurgitation. Directed interventions on the mitral valve at the time of septal myectomy are often viewed as a safe and comprehensive option to address both the hypertrophied ventricular septum and mitral regurgitation. Recent studies, however, have highlighted an increase in late mortality rates in patients with hypertrophic cardiomyopathy after undergoing septal myectomy with mitral valve replacement compared with patients having isolated septal myectomy or mitral valve repair."
Dr. Holst, Hartzell V. Schaff, M.D., and a research team with Cardiovascular Surgery at Mayo Clinic's campus in Rochester, Minnesota, used the National (Nationwide) Inpatient Sample (NIS) to analyze surgical outcomes for a cohort of patients who underwent mitral valve surgery at the time of septal myectomy for hypertrophic cardiomyopathy from Jan. 1, 2003, through Dec. 31, 2014. Study results were published in Mayo Clinic Proceedings in 2019.
Data selection and analyses
Using the NIS, the research team identified 1,174 adults with a primary diagnosis of hypertrophic cardiomyopathy who underwent surgical septal myectomy during the study period; those patients were identified based on ICD-9-CM diagnosis code.
To assess the effect of concomitant procedures on outcomes of septal myectomy, all codes for any cardiac operation were reviewed and categorized into concomitant procedure type. Procedures that would be part of the typical operative experience or the result of operative complications were not considered concomitant procedures. Patients were assigned to mutually exclusive surgical groups by procedures performed.
Primary outcomes included prolonged length of stay (nine or more days) and in-hospital mortality. The research team compared patient factors across surgical groups and assessed associations with prolonged length of stay and in-hospital mortality.
Characteristics of the cohort
- Overall age was 54.4 ± 14.5 years (mean ± standard deviation).
- Male patients constituted 45% (529) of the cohort.
- Isolated septal myectomy was performed in 67% (786) of patients; the remainder had concomitant cardiac procedures ― most frequently mitral valve repair or replacement (21.9% or 257).
- Median length of stay was increased in those with concomitant mitral valve surgery (seven days) compared with isolated septal myectomy (six days).
- Overall hospital mortality was 2.9% (34) and lowest in those patients undergoing isolated septal myectomy.
- In otherwise isolated septal myectomy, mitral valve replacement increased likelihood of in-hospital death.
"Directed interventions on the mitral valve at the time of septal myectomy are often viewed as relatively safe and offer comprehensive approaches to address both hypertrophied ventricular septum and mitral valve," says Dr. Holst. "The important negative effect of mitral valve replacement on early mortality and hospital length of stay should be emphasized, however ― especially because mitral valve replacement has been considered an alternative treatment for patients with hypertrophic cardiomyopathy. Mitral valve replacement as treatment for hypertrophic cardiomyopathy adds the associated late morbidity of prosthetic valves, including increased risk of endocarditis, subsequent reoperation in the setting of bioprosthesis, and need for lifelong anticoagulation for mechanical prostheses.
"These results suggest that concomitant mitral valve intervention is associated with increased risk and support the need for increasing surgeon experience with septal myectomy for obstructive hypertrophic cardiomyopathy to further improve outcomes and access of patients to high-quality surgical care."
For more information
Holst KA, et al. Septal myectomy in hypertrophic cardiomyopathy: National outcomes of concomitant mitral surgery. Mayo Clinic Proceedings. 2019;94:66.
National (Nationwide) Inpatient Sample (NIS). Agency for Healthcare Research and Quality Healthcare Cost and Utilization Project.