Surgical Myectomy in Patients with Hypertrophic Obstructive Cardiomyopathy: Real-World Outcomes, Surgical Techniques and Pathways to Optimization

English Summary
Chapter 1 provided a general introduction and outline of the thesis, focusing on outcomes of surgical myectomy in patients with hypertrophic cardiomyopathy (HCM). HCM is characterised by unexplained left ventricular hypertrophy in the absence of other loading conditions such as hypertension or aortic stenosis. It is the most common inherited cardiovascular disease, with a prevalence of 1 in 200 to 1 in 500 individuals. The clinical phenotype is highly variable, ranging from asymptomatic individuals to those with exertional dyspnea, chest pain, syncope, or sudden cardiac death. HCM is typically diagnosed by echocardiography or cardiac magnetic resonance imaging, and may progress to hypertrophic obstructive cardiomyopathy (HOCM), characterised by dynamic left ventricular outflow tract (LVOT) obstruction. Invasive therapy is required when a resting or provoked LVOT gradient exceeds 50 mmHg and is refractory to pharmacological treatment. The primary objective of this thesis was to outline opportunities to strengthen the quality of care and evidence base for patients with HOCM undergoing surgical myectomy, guided by three questions: which treatments work best, which outcomes matter most, and how can knowledge be implemented in clinical practice.

Part I – Real-world Outcomes
Chapter 2 described clinical outcomes of surgical myectomy in twelve Dutch hospitals. Surgical myectomy relieved LVOT obstruction in 93% of patients, the 30-day reoperation rate was 2%, and 30-day mortality for isolated surgical myectomy was 0%. Female sex, more than two concomitant procedures, and treatment in low-volume hospitals were significantly associated with increased 30-day complication rates. These results should be considered hypothesis-generating, underscoring the need for larger study populations.

Chapter 3 described outcomes of surgical myectomy with concomitant aortic valve replacement in patients with HOCM and aortic valve stenosis — a combination rarely reported in the literature. The 30-day permanent pacemaker implantation rate was 13% and the perioperative ventricular septal defect rate was 1%.

Part II – Surgical Techniques
Chapters 4, 5, and 6 evaluated outcomes of surgical myectomy combined with three different mitral valve repair techniques: secondary chordal cutting, edge-to-edge repair, and anterior mitral leaflet extension. While outcomes were generally satisfactory across all techniques, the additional benefit of routine concomitant mitral valve repair remains uncertain. Nevertheless, specific mitral valve and subvalvular characteristics may guide the choice of adjunctive intervention, allowing mitral valve repair to be applied selectively rather than routinely.

Part III – Preoperative Planning
Chapter 7 evaluated cardiovascular magnetic resonance-based 3D-printed heart models as tools for preoperative planning and simulation training. In a pilot study of five models, surgeons reported feeling better prepared and more confident prior to surgery. Larger studies are needed to validate these findings.

Part IV – General Discussion
With the introduction of cardiac myosin inhibitors as a new treatment option for HOCM, procedural volumes for surgical myectomy are expected to decline. As volume is a key determinant of surgical expertise, this poses additional challenges for sustaining high-quality care. Novel strategies — including simulation training, centralisation, and national quality registries — are therefore essential to safeguard outcomes for patients undergoing surgical myectomy in the future.