Left atrial dysfunction in different morphologic phenotypes of hypertrophic cardiomyopathy: a cardiac magnetic resonance feature tracking study

Background: Hypertrophic cardiomyopathy (HCM) exhibits substantial phenotypic heterogeneity; however, differences in left atrial (LA) function among morphological subtypes remain poorly characterized. Cardiac magnetic resonance feature tracking (CMR-FT) offers advanced capabilities for quantifying LA deformation, yet its application to the evaluation of subtype-specific LA mechanics remains limited. This study aimed to investigate LA functional impairment among HCM phenotypic subtypes using CMR-FT.

Methods: A total of 225 patients with HCM, divided into septal (n=153), apical (n=40), and concentric (n=32) subgroups, along with 68 age- and sex-matched healthy controls (HC), were retrospectively included from March 2023 to October 2024 at three tertiary hospitals. LA functional parameters, including reservoir strain (εs), conduit strain (εe), booster strain (εa), peak positive strain rate (SRs), peak early negative strain rate (SRe), and peak late negative strain rate (SRa), were obtained using CMR-FT. Statistical analyses included Chi-squared tests, one-way analysis of variance (ANOVA) with post hoc testing, linear regression, and intraclass correlation coefficients (ICCs).

Results: All HCM subgroups showed impaired LA strain parameters compared to HC [(εs, %): septal: 26.69±11.02, apical: 23.47±8.16, concentric: 21.30±6.53 vs. control: 46.43±13.73; (εe, %): septal: 12.36±6.42, apical: 10.87±4.28, concentric: 9.72±4.28 vs. control: 27.88±11.15; (εa, %): septal: 14.34±6.41, apical: 12.60±4.97, concentric: 11.58±5.56 vs. control: 18.55±6.04; all P<0.05]. The concentric HCM subgroup demonstrated more severe impairment in LA εs and εa than the septal subgroup (both P<0.05). Septal HCM showed significant correlations between all LA strain parameters and left ventricular ejection fraction (LVEF) and global longitudinal strain (LVGLS) (|r|≥0.324, all P<0.001); apical HCM demonstrated correlations between LA εs, εe, and the aforementioned LV function parameters (|r|≥0.373, all P<0.05); only LA εa correlated with LVEF and LVGLS in concentric HCM (|r|≥0.389, both P<0.05). CMR-FT showed excellent reproducibility for LA strain measurements in patients with HCM (all ICCs >0.75).

Conclusions: LA dysfunction varies across HCM phenotypes, with greater reservoir and booster impairment in concentric than septal HCM. These findings underscore the subtype-specific alterations in atrial mechanics and highlight the potential utility of CMR-FT for phenotypic characterization in HCM.