Left atrial and ventricular functional parameters by cardiovascular magnetic resonance for phenotyping hypertrophic...

Hypertrophic cardiomyopathy (HCM) is classified into obstructive (HOCM) and nonobstructive (HNOCM) phenotypes with distinct clinical implications. This study aimed to evaluate the diagnostic and prognostic value of left atrial (LA) and left ventricular (LV) functional parameters derived from cardiovascular magnetic resonance (CMR) for differentiating between the two subtypes, and to explore their prognostic value for predicting major adverse cardiovascular events (MACEs).

We retrospectively enrolled 173 participants (132 HCM patients, and 41 healthy controls). Cine imaging was utilized to acquire cardiac chamber dimensional and volumetric measurements. LV and LA strain parameters were assessed using feature tracking and fast long-axis methods. Multivariate logistic regression and receiver operating characteristic (ROC) analyses were applied to identify discriminative markers between HOCM and HNOCM. MACEs (all-cause death, sudden cardiac death, heart failure hospitalization, stroke, and new-onset atrial fibrillation) were recorded over a median follow-up of 969 days, with survival analyses performed using Kaplan-Meier (KM) curves.

Compared with HNOCM, patients with HOCM exhibited significantly impaired basal longitudinal strain (BLS, -14.26%±3.90% vs. -16.44%±4.82%, P=0.020), along with higher torsion, left ventricular mass index (LVMi), left ventricular end-diastolic volume index (EDVi), maximum ventricular wall thickness (MVWT), and left atrial maximum volume index (LAVi_max) (all P<0.05). These parameters demonstrated modest discriminative power for differentiating HOCM from HNOCM [area under the curve (AUC) range, 0.632-0.761, all P<0.05]. A combined model incorporating LVMi, torsion, and LAVi_max yielded improved diagnostic performance (AUC =0.828). During follow-up, 40 patients (30.3%) experienced MACEs. Impaired BLS independently predicted MACEs in the overall HCM cohort (AUC =0.773), as well as in HNOCM (AUC =0.780) and HOCM (AUC =0.737) subgroups (all P<0.05). KM analysis demonstrated significantly higher event rates in patients with BLS above corresponding thresholds (log-rank P<0.001).

CMR-derived BLS is a robust and independent predictor of MACEs in HCM, with this association likely driven predominantly by heart failure-related events rather than all components of the composite endpoint. Although additional LA and LV functional parameters provide complementary value for phenotypic differentiation, BLS emerges as a clinically practical marker for risk stratification across the HCM spectrum.