Prognostic value of left atrial strain in patients with stage II light-chain cardiac amyloidosis receiving cardiac magnetic resonance imaging: a prospective cohort study

Background: The prognostic significance of left atrial (LA) dysfunction in cardiac amyloidosis is being increasingly acknowledged, but its importance in stage II light-chain cardiac amyloidosis (AL-CA) remains unclear. This study aimed to determine the prognostic value of LA strain in stage II AL-CA. Methods: Patients with stage II AL-CA who underwent cardiac magnetic resonance at Peking Union Medical College Hospital between January 1, 2015, and October 31, 2021, were consecutively enrolled in this cohort study. Telephone and clinical follow-ups were conducted monthly. The primary endpoints were all-cause mortality, and the secondary endpoints were the combination of all-cause mortality and cardiac progression. Cox regression and Kaplan-Meier survival analyses were performed to identify associations between variables and outcomes. Results: We included 131 patients with stage II AL-CA [61% male; median age 59 years; interquartile range (IQR), 51-65 years]. Among these patients, 37 (28%) reached the primary endpoint (all- cause mortality), and 52 (40%) reached the secondary endpoint (median follow-up 28 months; IQR, 10-50 months). Serum biomarker N-terminal pro-B-type natriuretic peptide and LA strain were significantly associated with the outcomes (all P values <0.05). In the multivariable models, reduced LA booster strain remained associated with a higher risk of all-cause mortality [hazard ratio (HR) 0.64, 95% confidence interval (CI): 0.42-0.96; P=0.031] and the secondary endpoint (HR 0.68, 95% CI: 0.49-0.93; P=0.015). The metrics of cardiac function that showed superior accuracy in predicting the risk of mortality were LA reservoir strain [concordance index (C-index) 0.72; 95% CI: 0.64-0.80] and LA booster strain (C-index 0.71; 95% CI: 0.64-0.80). The addition of LA booster strain to established prognostic predictors improved the discrimination and goodness of fit (P<0.001). Conclusions: LA booster strain is an independent prognostic indicator in stage II AL-CA and is superior to metrics of LV function. LA strain has potential clinical value as an early prognostic marker and may aid in identifying underdiagnosed patients with poor prognosis.