Left atrioventricular coupling index in hypertrophic cardiomyopathy: a new echocardiographic perspective

Background

Hypertrophic cardiomyopathy (HCM) is a clinically defined myocardial disease characterized by unexplained left ventricular hypertrophy, irrespective of genotype status, and is associated with complex atrioventricular interactions that contribute to diastolic dysfunction and clinical heterogeneity. The left atrioventricular coupling index (LACI), defined as the ratio of left atrial minimum volume to left ventricular end-diastolic volume, integrates atrial residual volume with ventricular filling capacity and may provide a novel echocardiographic perspective on atrioventricular interaction in patients with HCM.

Purpose

This study aimed to evaluate the clinical and echocardiographic characteristics associated with the LACI in patients with clinically defined HCM.

Methods

A total of 240 consecutive patients with clinically defined hypertrophic cardiomyopathy (left ventricular wall thickness ≥15 mm unexplained by loading conditions), diagnosed between March 2023 and November 2025, were included. The LACI was defined as the ratio of left atrial minimum volume to left ventricular end-diastolic volume measured by echocardiography. As no established LACI cut-off exists in HCM, patients were stratified according to the median LACI value (0.270) into two groups. Clinical, laboratory, and comprehensive echocardiographic parameters, including left atrial volumetric and strain indices, were compared, and the ESC sudden cardiac death risk score was calculated.

Results

Patients with LACI >0.270 were significantly older and more frequently exhibited an obstructive HCM phenotype, with higher resting and Valsalva left ventricular outflow tract gradients, compared with those with lower LACI values (all p<0.001). Genotype positivity did not differ between groups. Higher LACI was associated with greater myocardial hypertrophy, impaired diastolic relaxation, and smaller left ventricular end-diastolic and end-systolic volumes.

Patients with elevated LACI showed more advanced left atrial involvement, characterized by a higher left atrial volume index, increased left atrial maximum, minimum, and pre-atrial contraction volumes, and a reduced left atrial emptying fraction (all p<0.001).

In addition, higher LACI was associated with increased ESC sudden cardiac death risk scores and demonstrated a weak but significant positive correlation with SCD risk (Spearman r=0.216, p<0.001), suggesting an association with higher-risk clinical and echocardiographic profiles rather than a direct predictive role.

Conclusion

In clinically defined HCM, higher LACI values are associated with distinct clinical and echocardiographic profiles, including obstructive physiology, impaired diastolic function, left atrial dysfunction, and higher ESC sudden cardiac death risk scores, independent of genotype status. LACI may offer a simple echocardiography-based perspective for integrated assessment in HCM.For image description, please refer to the figure legend and surrounding text.