The role of left atrio-ventricular coupling index and left atrial ejection fraction in predicting onset of atrial fibrillation and adverse cardiac events in hypertrophic cardiomyopathy

Abstract

Background: Several predictors of atrial fibrillation (AF) onset in patients with hypertrophic cardiomyopathy (HCM) have been proposed, however, all of them showed limited accuracy. This study aims to assess the role of new echographic parameters in predicting AF onset and major adverse cardiovascular outcomes (cardiovascular death or heart transplantation).

Methods: Clinical and imaging data from 141 patients with HCM and without a history of AF were retrospectively analyzed over a 5-year period. Patients who developed AF during the study were compared to those who did not. The analysis focused on key atrial parameters, including the Left Atrial Contraction Index (LACI) and Left Atrial Ejection Fraction (LAEF). LACI was defined as the ratio of left atrial end-diastolic volume to left ventricular end-diastolic volume. Echocardiographic measurements were standardized using cardiac magnetic resonance (CMR) as the reference. Regarding statistical analysis, each significant continuous variable was categorized by identifying a cut-off value using the Youden index. Independent associations with outcomes and cumulative survival were assessed using Cox regression analysis.

Results: Thirty-five patients developed AF, at a mean time of 4 years. The HCM-AF group had significantly higher values of LACI, left atrial diameter (LAD), and left atrial minimum volume (LAVmin). A LACI > 43% on echocardiography and LACI > 44% on CMR showed the best performance in identifying patients at risk for AF. In multivariate analysis, an echocardiographic LAEF < 43% was independently associated with the occurrence of AF (HR 2.9, 95% CI: 1.2-6.9). Additionally, a LAD > 40.5 mm was independently associated with AF onset, with a hazard ratio of 2.5 (95% CI 1.1-5.5). Eleven patients experienced the composite outcome of cardiovascular death or heart transplant, and a LACI > 60% was associated with this outcome.

Conclusion: In patients with HCM, both LACI and LAEF were significantly associated with the occurrence of AF over a 4-year period, demonstrating higher sensitivity and specificity compared to other parameters. A LACI > 60% was also found to be associated with cardiovascular death or heart transplant in this population.

Keywords: Adverse outcome; Atrial fibrillation; Hypertrophic cardiomyopathy; Imaging; Predictor.

Fig. 1

ROC curves of echocardiographic variables in predicting AF occurrence (A-E) or non AF occurrence during the study period (F). A ROC curve LACI echo, B ROC curve LAVmin echo, C ROC curve LAD, D ROC curve LACI cmr, E ROC curve LAVmin cmr, F ROC curve LAEF echo. LACI: left atrioventricular coupling index, LAD: left atrium diameter, LAEF: left atrium ejection fraction; LAV min: minimal left atrium volume

Fig. 2

Survival Curve free from AF for LAEF (on the left) and for LAD (on the right). LAD: left atrium diameter; LAEF: left atrium ejection fraction

Fig. 3

ROC Curves for LACI and LAVmin in predicting HTx or death. LACI: left atrioventricular coupling index, LAV min: minimal left atrium volume

Fig. 4

Booster pump phase illustration. In this phase, the LA emptying (white dashed arrow) depends mainly on the strength of LA contraction (white arrows) and atrial afterload. These elements are sensibly expressed in the LACI

Fig. 5

Comparison of two patients from our cohort. On the left, a 56-year-old male with obstructive HCM, who remained free of AF until the most recent follow-up (3 years). His LACI was low, at 34%. On the right, a 54-year-old female with non-obstructive HCM, who developed her first episode of AF 18 months after baseline TTE. Her LACI was elevated, at 49%