Background: The study aimed to investigate the prevalence, phenotypic characteristics and predictors of atrial fibrillation (AF) in patients presenting with light-chain (AL) or transthyretin (ATTR) cardiac amyloidosis (CA).
Methods: Clinical, biochemical and echocardiographic data of patients presenting with CA between 2005 and 2020 were retrospectively collected. CA staging was based on established biomarker systems. Binomial logistic regression was run to analyze the effects of clinical variables on the likelihood of AF.
Results: The study included 133 patients (53% AL, 41% wild-type (wt) ATTR-CA, 6% hereditary(h) ATTR-CA). Mean age was 71 years and 80% were male. AF was diagnosed in 64 (48%) patients (28% in AL-CA, 80% in wtATTR, 13% in hATTR). Patients with AF were older, more likely to have wtATTR-CA, exhibited more severe symptoms and carried a significantly higher burden of comorbidities. AF patients had lower left ventricular ejection fraction (47 vs. 53%, p < 0.005), higher left atrial volume index (54 vs. 46 ml/m2, p = 0.007), higher pulmonary artery pressure (42 vs. 31 mmHg, p = 0.008) and worse tricuspid annular plane systolic excursion values (17 vs. 20 mm, p = 0.01). Mitral regurgitation of at least moderate severity was also more frequent in the AF group (56 vs. 25%, p < 0.001). Higher ATTR-CA stage was associated with a higher proportion of patients with AF (p<0.001). Higher AL-CA stage was associated with lower AF rates (p<0.001). Three predictor variables were identified statistically significant for AF in a multivariate logistic regression model with 81.5% classification accuracy: AL type (OR 0.1, CI 0.01-0.29, p = 0.001), eGFR (OR 0.9, CI 0.93-0.99, p = 0.03) and BMI (OR 1.3, CI 1.07- 1.66, p = 0.01). ATTR amyloidosis was associated with a 10-fold higher risk of AF. During one-year follow-up only one episode of ischemic stroke was reported in this cohort.
Conclusion: AF affects nearly half of all patients with ATTR- or AL-CA. Patients presenting with AF have more severe symptoms, more depressed systolic function and a higher burden of comorbidities. ATTR type of amyloidosis is the strongest predictor of AF and justifies prospective screening for occult AF in this population.