Left atrial strain identifies low-risk hypertrophic cardiomyopathy patients: a CMR study

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Abstract Background Hypertrophic cardiomyopathy (HCM) is associated with an increased risk of major adverse cardiovascular events (MACE), however, current risk stratification methods are imperfect. Left atrial global longitudinal strain (LA GLS) is an increasingly acknowledged predictive parameter, yet its potential role in HCM is not well defined. Purpose This study aims to investigate the prognostic role of cardiac magnetic resonance (CMR)-derived LA GLS for the occurrence of MACE in patients with HCM. Methods A retrospective, single-centre, CMR study of HCM patients was conducted. CMR images were analysed by two blinded investigators. LA GLS was derived from CMR two-chamber cine images by a semiautomatic method, and was categorized according to its median value. The endpoint was a composite of major adverse cardiovascular events (MACE), including all-cause death, sudden cardiac death (SCD), sustained and non-sustained ventricular tachycardias, appropriate implantable cardiac defibrillator shocks, heart failure hospitalization, syncope, stroke and new-onset atrial fibrillation. Cox regression analysis was performed. Results A total of 135 HCM patients were included, mean age was 57 years ± 17 and 41% were female. Average maximal wall thickness (MWT) was 17.7 ± 4.6 mm, 39% had left ventricular outflow obstruction (LVOTO) and 46% had positive late gadolinium enhancement (LGE). After a mean follow-up of 6.6 ± 3.4 years, 61 patients (45%) experienced the composite endpoint. Figure 1 shows the clinical and CMR differences according to the occurrence of MACE. LA GLS was significantly lower in patients with MACE compared to those without (26.4 ± 15% vs 30.4 ± 14%, p=0.046). Multivariate Cox regression analysis revealed that an LA GLS below the median value of 28.2% showed a tendency to be independently associated with MACE (HR 1.57, 95% CI: 0.877-2.814, p=0.128). Additionally, the presence of LGE (HR 2.2, CI: 1.233-3.801, p=0.007) and an left ventricular ejection fraction (LVEF) < 50% (HR 5.4, 95%, CI: 1.451-19.831, p=0.012) were also independently associated. Among low risk HCM patients (LVEF > 50%, MWT < 30 mm, absence of LGE and/or LVOTO), LA GLS demonstrated an additional prognostic role: those with an LA GLS above the median value exhibited a more favourable prognosis (Figure 2A-D). In fact, among patients considered at low risk according to the European Society of Cardiology HCM risk score (< 4% risk of SCD at 5 years) (n = 83), LA GLS < 28.2% (HR 2.6, 95% CI:1.037-6.461, p=0.042) and LVEF < 50% (HR 15.1, 95% CI: 2.877- 79.530, p=0.001) remained the only variables independently associated with MACE. Conclusions CMR-derived LA GLS is a predictor of outcomes in HCM beyond established imaging prognostic factors. Particularly, LA GLS appears to be useful in risk-stratifying low risk HCM patients: those with a normal LA GLS show a favourable prognosis. If confirmed in larger studies, LA GLS could be used to individualise HCM management.