Cardiovascular magnetic resonance-derived metrics as diagnostic markers for left ventricular outflow tract obstruction in hypertrophic cardiomyopathy.

BACKGROUND: This study aims to assess the utility of cardiovascular magnetic resonance (CMR)-derived measurements as diagnostic indicators for left ventricular outflow tract obstruction (LVOTO) in hypertrophic cardiomyopathy (HCM) patients, using Doppler echocardiography as the reference method.

METHODS: In this single-center retrospective cross-sectional study, adult HCM patients with transthoracic echocardiography and CMR within a 6-month time window were enrolled. Doppler LVOT gradient was measured both at rest and under provocative maneuvers. LVOTO was defined as a gradient ≥30 mmHg. The total cohort was randomly divided into a training (80%) and validation (20%) cohorts, maintaining the same proportions of patients with and without LVOTO in both cohorts. In CMR, all measurements were performed in the three-chamber balanced steady-state free precession cine images. CMR metrics were examined in relation to LVOTO by means of multivariable logistic regression models.

RESULTS: Four hundred forty-eight adult HCM patients (67% (301/448) males, median (25th-75th percentile) age 55 (45-62) years) were enrolled. LVOTO was present in 42% (186/448) HCM patients. For identifying LVOTO, a model including the minimum distance between the mitral leaflet tip and the interventricular septum indexed to body surface area (minimum MV-IVSi distance), left ventricular (LV) stroke volume, and signal intensity ratio LVOT/LV showed an outstanding discriminatory ability in the validation cohort with an area under the curve (AUC) of 0.91 (95% confidence interval (CI) 0.85-0.97). The univariable model of the minimum MV-IVSi distance showed an AUC of 0.88 (95%CI 0.81-0.95). An MV-IVSi distance ≤6.5 mm/m2 yielded a specificity of 94% and a positive predictive value of 89%, and >9.0 mm/m2, a sensitivity of 97% and a negative predictive value of 97%. The minimum MV-IVSi distance showed excellent intra- and inter-observer reproducibility with an intraclass correlation coefficient of ≥0.95.

CONCLUSION: CMR-derived parameters, particularly the minimum MV-IVSi distance, can accurately identify LVOTO in HCM patients and easily be integrated into a standard CMR analysis.