LAUSR

OBJECTIVES We compared the effectiveness of virtual 3-dimensional (3D) models with 2-dimensional (2D) transthoracic echocardiography (TTE) for evaluating the anatomy of the interventricular septum (IVS) and abnormal muscle bundles (AMBs) in planning septal myectomy (SM). METHODS Between January 2017 and July 2020, 103 consecutive symptomatic patients with hypertrophic cardiomyopathy underwent 2D TTE and cardiovascular magnetic resonance imaging in 49 (47.6%) or computed tomography angiography in 54 (52.4%) patients with 3D IVS modelling for SM planning. We evaluated maximal IVS thickness and location, length and thickness of AMBs. RESULTS The mean maximal IVS thickness by 2D TTE was 7.3 [standard deviation (SD) 4.8] mm less than that based on the 3D model analysis: 21.4 (SD 3.7) vs 28.6 (SD 5.5) mm, respectively (P < 0.001, 95% confidence interval 6.4-8.2). The planned volume of ideal SM was larger than that of performed SM: 26.2 (18.4-39.4) vs 10.3 (7.4-12.8) cm3, respectively (P < 0.001). The sensitivity and specificity of 2D TTE in diagnosing AMBs were 36.9% and 95%, and those of cardiovascular magnetic resonance and computed tomography angiography with 3D modelling were 97.1% and 100% for cardiovascular magnetic resonance and 98% and 100% for computed tomography angiography, respectively. AMBs occurred in 84 (81.6%) patients. No patient required mitral valve replacement. The 30-day mortality was 1 patient. There were 4 late non-cardiac deaths (3.9%) within 18.1 (standard error 1.32) months. CONCLUSIONS Anatomical analysis of the IVS and AMBs based on their virtual 3D models is highly effective for SM planning.