Prognostic value of the left ventricular mass index by magnetic resonance imaging in patients with hypertrophic obstructive cardiomyopathy undergoing septal myectomy

Research background Traditional risk factors for hypertrophic cardiomyopathy (HCM) have limited ability to predict poor survival outcomes in the medium to long term after surgical septal myectomy (septal myectomy) in patients with hypertrophic obstructive cardiomyopathy (HOCM) undergoing septal myectomy. Additionally, there is a lack of studies reporting the relationship between left ventricular mass index (LVMI), an index of ventricular remodeling in hypertrophic obstructive cardiomyopathy, and medium to long-term prognostic outcomes after septal myectomy. Research methods: From June 2011 to July 2016, 490 patients with HOCM who completed preoperative cardiac magnetic resonance (CMR) were retrospectively enrolled for mid- to long-term follow-up. The study's primary endpoint included all-cause death. Secondary endpoints included cardiac death and adverse cardiovascular events. Furthermore, CMR measures were applied to study the risk factors for mid- and long-term adverse endpoint events after septal myectomy treatment. Study results: 486 patients with HOCM completed follow-up and were included in the final analysis. Twenty-one patients (4.3%) died during follow-up (median 73.6, maximum 105.6 months), and 66 patients (16.3%) had an adverse cardiovascular event during follow-up. In the Cox proportional risk regression model, the most significant predictor of all-cause mortality after septal myectomy was CMR-LVMI (risk ratio 1.009, 95% confidence interval 1.003-1.015, P=0.018). In receiver operating characteristic (ROC) analysis, LVMI > Cutoffpredicted all-cause death analyzed separately by male and female subgruop(P<0.05). In Cox proportional risk regression models (incorporating age, maximum septal thickness, left atrial diameter, left ventricular end-diastolic dimension, left ventricular ejection fraction, LV outflow tract peak pressure, pulmonary hypertension, LGE positive and LVMI), the most significant predictor after surgical septal resection was LVMI measured by CMR (hazard ratio 1.025, 95% confidence interval 1.009-1.040, P=0.002). From ROC analysis, LVMI >cutoff accurately predicted the occurrence of all-cause mortality analysed separately by male and female (P<0.05). Additionally, K-M survival curve plots suggested that patients with HOCM above the LVMI threshold group had lower all-cause mortality-free survival (Log-rank: P=0.0.025), hear failure related mortality-free survival (Log-rank: P=0.0.014) in the medium to long term after septal myectomy. Conclusions An elevated preoperative left ventricular myocardial mass index suggests adverse ventricular remodeling and is an independent predictor of poor survival outcomes in patients with HOCM in the medium to long term after septal myectomy.