Left Atrioventricular Coupling Index (LACI) in Breast Cancer Patients Receiving trastuzumab

Background: trastuzumab therapy for HER2-positive breast cancer is associated with cardiotoxicity. The left atrioventricular coupling index (LACI) may serve as a sensitive biomarker of subclinical myocardial dysfunction. This study evaluates longitudinal LACI changes in breast cancer patients undergoing trastuzumab therapy.

Methods: In this prospective cohort, 41 female patients with breast cancer treated with trastuzumab underwent serial cardiac magnetic resonance imaging (CMR) at baseline, 6, 12, and 18 months. LACI was calculated as the ratio of left atrial end-diastolic volume (LAEDV) to left ventricular end-diastolic volume (LVEDV).

Results: Of the 41 patients (mean age 52±11 [SD] years; 56% received an anthracycline). One patient experienced trastuzumab-induced cardiotoxicity (TIC). Mean baseline left ventricular ejection fraction (LVEF) 68.0±5.9%; mean baseline left atrial ejection fraction (LAEF) (66.0±6.6%). LACI increased from 16.7±0.8% at baseline to 19±0.9% at 12 months (p=0.014), returning to baseline levels at 18 months (16.7±0.9%, p=1.000). No significant interaction (all p > 0.10) was detected between time and anthracycline use for LACI. No patients developed a decline in LVEF >10% or clinical heart failure during follow-up, despite significant temporal changes in LACI. LACI demonstrated significant inverse correlations with LAEF both at baseline (r = −0.69, p < 0.001) and at 12 months (r = −0.72, p < 0.001).

Conclusion: LACI increased during treatment and returned to baseline by 18 months. Its transient elevation was strongly associated with worsening LA function, supporting LACI as a marker of subclinical atrioventricular remodeling and uncoupling. Further studies should evaluate its role in longitudinal cardiac monitoring during trastuzumab therapy.