We present 2 cases of extended septal myectomy using low-cost 3-dimensional (3D) printed models of the interventricular septum with its fragment cut out mechanically or by initial 'virtual' myectomy. 3D prints exhibited excellent cardiac imaging and planning of the 'optimal' volume and shape of the resection, as well as intraoperative quality control of septal myectomy by filling a trough in the 3D-printed interventricular septum with excised myocardium.

Introduction The completeness of septal myectomy (SM) is the key to surgery of hypertrophic obstructive cardiomyopathy (HOCM), but its planning is still based on echocardiographic findings. The need to perform radical SM requires the development of new cardio-visualisation techniques for monitoring myectomy quality. Aim To improve results in centres treating few patients with HOCM using a new method of optimal SM with the help of 3-dimensional models to achieve an ‘ideal’ interventricular septum (IVS) thickness of 10–11 mm. Material and methods Between 2017 and 2018, 30 patients underwent optimal SM after computed tomography angiography, creation of a virtual 3-dimensional model of the IVS, computer-aided mapping, virtual SM and 3-dimensional printing of models of the ‘ideal’ IVS and the fragment to be removed. Results Initial isolated extended SM ( n = 29, 97%) was effective in 23/29 (79%) patients. Four non-fatal complications were observed. A permanent pacemaker was implanted in three patients. No patients required mitral valve replacement. The mean postoperative left ventricle (LV) resting systolic gradient was 7.5 ±4.4 mm Hg, and at the latest follow-up this value was 7.1 ±4.2 mm Hg. The average weight of the excised myocardium was 12.0 g (range: 5.8–22.5 g). At follow-up both volumetric and dimensional LV echocardiography parameters increased compared with preoperative values ( p ≤ 0.007). Conclusions The proposed optimal SM provides intraoperative monitoring of the shape and volume of the myocardium resected to achieve the ‘ideal’ IVS, true radicality and an increase in the volumetric and dimensional parameters of the LV.

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.

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