Highlights
In this multicentre Dutch registry of 335 patients with hypertrophic obstructive cardiomyopathy, surgical myectomy produced marked early haemodynamic improvement, with the mean resting left ventricular outflow tract gradient falling from 61 ± 30 mmHg to 13 ± 12 mmHg.
Thirty-day adverse outcomes were not negligible: mortality was 5%, stroke 3%, ventricular septal defect 2%, and surgical reoperation 2%.
Low-volume hospitals performing fewer than 10 myectomy procedures per year had higher adjusted 30-day complication rates, with an odds ratio of 3.23 (95% confidence interval 1.43-8.09; P = .007).
Female sex and performance of at least two concomitant procedures were also associated with increased 30-day complications, underscoring the need for careful risk stratification and procedural planning.
Background
Hypertrophic cardiomyopathy is the most common inherited cardiomyopathy and is characterized by unexplained left ventricular hypertrophy, myocyte disarray, and a variable clinical course that ranges from asymptomatic disease to severe heart failure, atrial fibrillation, stroke, or sudden cardiac death. A substantial subgroup develops dynamic left ventricular outflow tract obstruction due to septal hypertrophy, systolic anterior motion of the mitral valve, and mitral-septal contact. In symptomatic patients with obstructive physiology despite guideline-directed medical therapy, septal reduction therapy becomes an important therapeutic option.
Surgical septal myectomy remains the reference invasive treatment for many patients with hypertrophic obstructive cardiomyopathy, particularly when anatomy is complex or when concomitant mitral, aortic, tricuspid, or coronary procedures are required. In experienced centers, myectomy can provide durable relief of obstruction, improved symptoms, and favorable long-term survival. However, outcomes are known to be operator- and center-dependent, and much of the best available evidence comes from high-volume expert programs. This creates an important evidence gap for real-world national practice, especially in healthcare systems where procedures are distributed across multiple hospitals with varying experience.
The study by Heeringa and colleagues addresses that gap by examining national registry data from the Netherlands. The central clinical question is highly relevant: when myectomy is performed across multiple centers, do outcomes vary according to procedural volume, and which patients are at highest risk for short-term complications?
Study Design and Methods
Design and data source
This was a multicentre observational registry study using data from the Netherlands Heart Registration. The investigators included all patients with hypertrophic obstructive cardiomyopathy who underwent surgical myectomy between 2012 and 2020 in 12 Dutch hospitals.
Population
The cohort comprised 335 patients. The study focused on individuals undergoing myectomy for obstructive hypertrophic cardiomyopathy, rather than the broader hypertrophic cardiomyopathy population. This distinction matters because operative risk, symptom burden, and treatment goals differ substantially between obstructive and non-obstructive disease.
Procedural categories
The operative case-mix was heterogeneous. Isolated surgical myectomy accounted for 22% of procedures, myectomy with one concomitant procedure for 54%, and myectomy with two or more concomitant procedures for 24%. This is clinically important because operative outcomes from isolated septal myectomy cannot be assumed to apply to combined procedures, which often involve more complex structural heart disease.
Endpoints
The study described 30-day clinical outcomes and evaluated factors associated with increased 30-day complication rates. Reported early postoperative outcomes included mortality, ventricular septal defect, stroke, and surgical reoperation. The investigators also assessed effectiveness in relieving left ventricular outflow tract obstruction and associated mitral valve abnormalities by comparing preoperative and postoperative echocardiographic parameters.
Statistical analysis
Multiple logistic regression analyses were used to identify factors associated with higher 30-day complication rates. A key exposure of interest was hospital procedural volume, with low-volume hospitals defined as performing fewer than 10 surgical myectomy procedures per year.
Key Findings
Procedural effectiveness
The most immediately reassuring finding is that surgical myectomy was highly effective in relieving obstruction. Mean resting left ventricular outflow tract gradient declined from 61 ± 30 mmHg before surgery to 13 ± 12 mmHg after surgery. Systolic anterior motion fell from 80% preoperatively to 8% postoperatively, and severe mitral regurgitation, defined as grade 3 or 4, declined from 31% to 6%.
These data strongly support the mechanical effectiveness of myectomy in restoring left ventricular outflow tract patency and correcting the pathophysiologic interplay between septal hypertrophy and mitral valve motion. The authors conclude that obstruction was effectively relieved in 93% of patients. For clinicians, this confirms that even in a multicentre real-world setting, surgery can achieve the intended anatomical and haemodynamic result in the vast majority of cases.
Thirty-day clinical outcomes
Against these strong efficacy signals, the early complication profile warrants careful attention. Thirty-day mortality was 5%, stroke occurred in 3%, ventricular septal defect in 2%, and surgical reoperation in 2%.
These event rates are higher than those often quoted from internationally recognized myectomy centers of excellence, where operative mortality in isolated cases is frequently reported at well below 1%. The difference likely reflects a combination of broader real-world case-mix, inclusion of concomitant procedures, and volume variation among hospitals. It also highlights a recurring issue in procedural cardiology and cardiac surgery: outcomes reported from expert centers may not fully capture what is achieved nationally when the procedure is decentralized.
Volume-outcome relationship
The study’s headline observation is the inverse relationship between hospital volume and 30-day complications. After adjustment, low-volume hospitals had a significantly higher 30-day complication rate, with an odds ratio of 3.23 and a 95% confidence interval of 1.43-8.09 (P = .007).
From a health-services perspective, this is a clinically meaningful signal. It suggests that myectomy may be one of those complex procedures for which accumulated institutional experience matters, not only technical skill in the operating room but also patient selection, imaging interpretation, perioperative care pathways, management of conduction disturbances, and multidisciplinary decision-making.
Other factors associated with complications
Two additional factors were associated with increased 30-day complication rates: female sex and the performance of at least two concomitant procedures. The association with multiple concomitant procedures is biologically and clinically plausible. More extensive surgery generally means longer cardiopulmonary bypass times, more challenging anatomy, increased bleeding risk, and greater postoperative complexity.
The finding regarding female sex is noteworthy and deserves careful interpretation. Women with hypertrophic cardiomyopathy are often diagnosed later in the disease course and may present at older ages, with more advanced symptoms or a different anatomical phenotype. It is also possible that sex-related differences in referral timing, body size, operative anatomy, or comorbidity burden contributed to the observed association. Registry-based analyses cannot fully disentangle these mechanisms, but the signal is important enough to justify deeper investigation.
Clinical Interpretation
How should clinicians interpret the efficacy data?
The reduction in left ventricular outflow tract gradient and the marked improvement in systolic anterior motion and mitral regurgitation are entirely consistent with the known mechanism of septal myectomy. For symptomatic obstructive hypertrophic cardiomyopathy that is refractory to medical therapy, surgery remains a highly effective definitive intervention, especially in patients with septal anatomy suitable for resection and in those requiring simultaneous correction of associated structural lesions.
In practical terms, these findings reinforce that myectomy should not be viewed narrowly as a gradient-lowering operation. It is often a broader reconstructive procedure that can normalize flow dynamics, reduce mitral-septal interaction, and improve secondary mitral regurgitation.
Why does procedural volume likely matter?
The apparent volume-outcome relationship fits the broader cardiovascular surgery literature. Myectomy is not a routine operation; it requires tailored septal resection guided by nuanced understanding of ventricular morphology, papillary muscle anatomy, mitral valve apparatus abnormalities, and intraoperative imaging. Centers that perform the procedure more frequently are more likely to develop dedicated multidisciplinary teams, standard postoperative pathways, and better recognition of complications such as complete heart block, residual obstruction, septal perforation, or ventricular septal defect.
That said, the authors appropriately advise caution. The total sample size was modest, the number of centers was limited, and residual confounding remains possible. Low-volume centers may have taken on more complex cases, or differences in referral patterns may have affected risk estimates. Even so, the magnitude of association is difficult to ignore.
Implications for referral pathways
For referring cardiologists, the study supports considering institutional experience when selecting a center for septal reduction therapy. This is already reflected in contemporary guidelines, which emphasize treatment at experienced hypertrophic cardiomyopathy centers and shared decision-making by multidisciplinary teams. The Dutch data add registry-based support for a more centralized model of surgical care, particularly for patients anticipated to need combined procedures.
Strengths of the Study
A major strength is the use of a national multicentre registry rather than a single high-performing institution. This makes the data more representative of routine practice and therefore more relevant to health-system planning. The inclusion of detailed clinical and echocardiographic outcomes also allows simultaneous evaluation of procedural success and perioperative safety.
Another strength is the explicit analysis of concomitant procedures. Many studies on myectomy focus on isolated operations, but in real-world practice, a large proportion of patients require additional valve or other cardiac surgery. By capturing this complexity, the study offers a more realistic picture of operative risk.
Limitations
Several limitations temper interpretation. First, the observational design precludes causal inference. Although low volume was associated with more complications, one cannot conclude definitively that centralization alone would eliminate the excess risk.
Second, the sample size was relatively limited for multivariable analysis, especially when subdivided by procedural complexity and hospital volume. Confidence intervals, while statistically significant for the primary volume finding, remain fairly broad.
Third, the abstract does not provide detailed baseline differences among hospitals or between men and women. Without granular information on age, symptom severity, septal thickness, comorbidities, frailty, arrhythmia burden, and operative specifics, residual confounding is likely.
Fourth, only 30-day outcomes are highlighted. For hypertrophic cardiomyopathy surgery, longer-term endpoints are highly relevant, including symptom status, recurrent obstruction, atrial fibrillation, pacemaker implantation, heart failure hospitalization, and survival.
Finally, the volume threshold of fewer than 10 procedures per year is clinically intuitive but somewhat arbitrary. Whether a different threshold would better discriminate risk remains uncertain.
Relation to Current Guidelines and Existing Evidence
Current American and European guidance already favors management of obstructive hypertrophic cardiomyopathy in experienced centers. The 2020 American Heart Association/American College of Cardiology guideline emphasizes referral to specialized hypertrophic cardiomyopathy centers for complex management decisions, including septal reduction therapy. The 2023 European Society of Cardiology cardiomyopathy guideline similarly supports evaluation in expert multidisciplinary settings.
The present study does not overturn those recommendations; rather, it gives them pragmatic support from contemporary registry data. It also complements the long-standing observational literature from major expert centers showing excellent long-term symptomatic and survival outcomes after myectomy. What this Dutch study adds is a reminder that procedural excellence may not automatically generalize across all hospitals.
Practice Implications
For clinicians, several practical messages emerge. First, surgical myectomy remains a highly effective treatment for relieving obstruction in carefully selected patients with hypertrophic obstructive cardiomyopathy. Second, the early risk profile appears meaningfully influenced by institutional experience and operative complexity. Third, women and patients requiring multiple concomitant procedures may merit particularly careful preoperative assessment and perioperative planning.
For hospitals and policymakers, the data raise an important service-delivery question: should myectomy care be more strongly centralized? While the study alone is not sufficient to mandate structural reform, it supports serious consideration of referral networks, center accreditation, case concentration, and minimum-volume standards.
Funding and Trial Registration
The abstract does not report specific funding information or a ClinicalTrials.gov registration number. As this was a registry-based observational study using the Netherlands Heart Registration, conventional interventional trial registration may not have been applicable.
Conclusion
This multicentre Dutch study provides a realistic view of contemporary surgical myectomy practice outside a single expert center. The procedure was highly effective at reducing left ventricular outflow tract obstruction and correcting associated mitral valve abnormalities. However, the 30-day complication burden was clinically relevant, particularly in hospitals performing fewer than 10 myectomies per year, in women, and in patients undergoing at least two concomitant procedures.
The central message is not that myectomy is unsafe; rather, it is that surgical success in hypertrophic obstructive cardiomyopathy depends on both technical efficacy and systems of care. These findings strengthen the case for experienced multidisciplinary programs, thoughtful referral patterns, and larger studies to refine volume thresholds and risk prediction.
Citation and References
Heeringa TJP, Hegeman RMJJ, Koop Y, El Mathari S, Hoogewerf M, Roefs MM, Smits KC, Laenens D, De Zan G, Cramer MJ, Guglielmo M, van der Harst P, Vaartjes I, Mokhles MM, Klein P, van der Kaaij NP. Surgical myectomy for hypertrophic cardiomyopathy: procedural volume and outcomes. European Heart Journal. 2026 May 21;47(20):2481-2493. PMID: 40878834. Available at: https://pubmed.ncbi.nlm.nih.gov/40878834/
Ommen SR, Mital S, Burke MA, Day SM, Deswal A, Elliott P, Evanovich LL, Hung J, Joglar JA, Kantor P, Kimmelstiel C, Kittleson M, Link MS, Maron MS, Martinez MW, Miyake CY, Schaff HV, Semsarian C, Sorajja P, et al. 2020 AHA/ACC Guideline for the Diagnosis and Treatment of Patients With Hypertrophic Cardiomyopathy. Journal of the American College of Cardiology. 2020;76(25):e159-e240.
Arbelo E, Protonotarios A, Gimeno JR, Arbustini E, Barriales-Villa R, Basso C, Bezzina CR, Biagini E, Blom NA, Charron P, et al. 2023 ESC Guidelines for the management of cardiomyopathies. European Heart Journal. 2023;44(37):3503-3626.