Thrombotic events are a major complication of hypertrophic cardiomyopathy (HCM). There are only two available risk prediction models for thrombotic events, HCM Risk-CVA score and French HCM score developed by foreign scholars, yet the former one has been found to have limited predictive value in Chinese HCM patients.

To develop a risk prediction model for thrombotic events in Chinese patients with HCM.

A retrospective cohort study design was used. Five hundred and thirty-seven HCM patients who admitted to West China Hospital of Sichuan University from 2010 to 2018 were recruited. Post-discharge health status was collected by use of telephone follow-up or checking the treatment status recorded in the electronic medical record system once every 6 to 12 months until a composite thrombotic event (defined as the endpoint event) or death occurred or the determined thrombotic risk assessment day of this study (2019-12-31). Univariate and multvariate Cox regression analyses were applied to build a thrombotic risk prediction model, and its internal validation was tested in a resample using the bootstrapping technique.

Due to data missing, 24 cases were excluded, and the other 513 cases were finally included. During a median follow-up of 4.2 years (IQR: 1.3-6.2 years), thrombotic events occurred in 42 cases (8.18%), with an annual morbidity rate of 2.10%〔95%CI (1.47%, 2.73%) 〕. By multivariate Cox regression analysis, age, prior thrombotic event and left ventricular ejection fraction (LVEF) were identified (P<0.05) and used for constructing the formula of SAAE score (S=prior stroke and other thrombotic events, A=atrial fibrillation, A=age, E=LVEF) for predicting thrombotic events after being weighted based on the regression coefficient. Internal validation suggested that SAAE score could discriminate thrombotic events in the whole population {Harrell's C-index=0.773〔95%CI (0.688, 0.858) 〕}, with a calibration slope of 1.006, and could well discriminate 1-year, 3-year and 5-year thrombotic events (Harrell's C-index=0.790, 0.799, 0.735), with a good calibration ability. In addition, the SAAE score also performed well in distinguishing thrombotic events in patients with or without atrial fibrillation {Harrell's C-index=0.669〔95%CI (0.548, 0.791) 〕, 0.647〔95%CI (0.498, 0.795) 〕}, with good calibration ability. Besides that, SAAE score could partially discriminate 1-year, 3-year and 5-year thrombotic events in these two groups, with certain calibration ability. For three groups (whole study population, patients with/without atrial fibrillation), SAAE score could discriminate the risk of thrombotic events (either low, moderate or high) excellently. For the whole study population, SAAE score was better than HCM Risk-CVA score in distinguishing thrombotic events (P=0.013). Decision curve analysis showed the net benefit of SAAE score was better than HCM Risk-CVA score at different prediction time points (1, 3 and 5 years) .

This thrombotic events risk prediction model developed by us for Chinese HCM patients, namely SAAE score, could well stratify the risk of thrombotic events.