A machine learning-based penalized Cox proportional hazards model comprising routinely available clinical and cardiac MRI variables showed strong performance (C index, 0.75) for major adverse cardiac event prediction in patients with hypertrophic cardiomyopathy.
Key Findings
Results
The CoxNet machine learning model demonstrated favorable performance for MACE prediction in HCM patients.
C index of 0.75 (95% CI: 0.65, 0.83)
Model was developed using a penalized Cox proportional hazards model with elastic net regularization (CoxNet)
Model training used 200 iterations of stratified subsampling cross-validation with 80% training and 20% testing splits
33 clinical, genetic, echocardiography, and cardiac MRI variables were included as candidate predictors
Results
The CoxNet model performance was similar to, though numerically higher than, the 2014 European Society of Cardiology sudden cardiac death risk model.
ESC model C index was 0.67 (95% CI: 0.57, 0.75)
CoxNet C index was 0.75 (95% CI: 0.65, 0.83)
The difference between models was not statistically significant (P = .07)
The ESC model is an established comparator specifically designed for sudden cardiac death risk stratification in HCM
Results
Key predictors of MACE in the CoxNet model included apical aneurysm, left ventricular end-systolic volume indexed to body surface area, extensive late gadolinium enhancement, native T1 z score, and male sex.
Apical aneurysm was identified as a top predictor
Extensive late gadolinium enhancement was among the key cardiac MRI-derived predictors
Native T1 z score, a cardiac MRI tissue characterization metric, was identified as a key predictor
Left ventricular end-systolic volume indexed to body surface area was a key functional predictor
Male sex was identified as a key demographic predictor
Methods
The study cohort consisted of 604 HCM patients who underwent cardiac MRI evaluation over a period from September 2015 to December 2022.
Mean age was 52 years ± 15 (SD)
417 of 604 patients were male
Median follow-up was 3.0 years (IQR, 1.9–4.2 years)
This was a retrospective cohort study design
Cardiac MRI protocol included balanced cine steady-state free precession, native T1 and T2 mapping, and late gadolinium enhancement
Methods
MACEs were defined as a composite outcome of cardiovascular death, resuscitated sudden cardiac death, or heart failure hospitalization.
The composite endpoint incorporated three distinct serious cardiac outcomes
This composite MACE definition was used as the primary endpoint for model development and evaluation
The outcome definition combined mortality and morbidity endpoints relevant to HCM prognosis
Conclusions
Cardiac MRI features were highlighted as important contributors to risk stratification in HCM.
Three of the five key predictors (apical aneurysm, extensive late gadolinium enhancement, native T1 z score) were cardiac MRI-derived features
The authors concluded that 'key variables highlight the impact of cardiac MRI features on risk stratification'
Native T1 mapping and late gadolinium enhancement represent tissue characterization techniques routinely available on cardiac MRI
What This Means
This research suggests that a machine learning approach can accurately predict which patients with hypertrophic cardiomyopathy (HCM) — a condition where the heart muscle becomes abnormally thick — are at high risk of serious cardiac events such as cardiovascular death, cardiac arrest, or hospitalization for heart failure. Researchers developed a model using 33 variables drawn from routine clinical assessments, genetic testing, echocardiography (ultrasound of the heart), and cardiac MRI scans in 604 patients followed over a median of three years. The model performed well, with a discrimination score (C index) of 0.75, meaning it correctly ranked higher-risk patients above lower-risk patients about 75% of the time.
The most important predictors identified by the model were features detectable on cardiac MRI: the presence of an apical aneurysm (a bulge at the tip of the heart), extensive late gadolinium enhancement (a marker of scar tissue in the heart muscle), and native T1 z score (a measure of heart tissue composition). The size of the heart's left ventricle at its smallest point and male sex were also key predictors. The model performed similarly to the widely used European Society of Cardiology risk calculator, though no statistically significant difference was found between them.
This research suggests that incorporating cardiac MRI data into machine learning models could improve how clinicians identify HCM patients most in need of close monitoring or preventive treatments, such as implantable defibrillators. The fact that all variables used were already routinely collected in clinical practice makes this type of model potentially practical to implement without requiring additional testing.