CMR-derived pulmonary artery to aorta ratio as a predictor of adverse outcome in patients with cardiac transthyretin amyloidosis

Abstract Introduction Cardiac transthyretin amyloidosis (ATTR) represents a heart failure phenotype often accompanied by pulmonary hypertension. The pulmonary artery to aorta ratio (PA/Ao), as assessed on cardiac computed tomography or cardiac magnetic resonance (CMR), has demonstrated to indicate risk for adverse events in a variety of cardiovascular diseases, particularly in heart failure and pulmonary hypertension. However, its prognostic value in cardiac ATTR remains unknown. Aim We aimed to investigate the prognostic value of the PA/Ao ratio in patients with cardiac ATTR. Methods Data of consecutive patients diagnosed with cardiac ATTR undergoing CMR were prospectively collected. PA/Ao ratios were measured from CMRs using axial images (Figure 1A). Adverse outcome, defined as heart failure related hospitalizations and/or mortality, was recorded during follow-up. Results Among the 190 confirmed cardiac ATTR patients (mean age 76±11 years, 79% males), encompassing hereditary transthyretin (vATTR, n=22) and senile (wtATTR, n=168) types, the median pulmonary artery diameter was 28mm (IQR 25-31) and the median ascending aorta diameter was 35mm (IQR 33-39). Over the median follow-up period of 28 months (IQR 11-50 months), 84 (44%) patients experienced an adverse event. Kaplan Meier curves demonstrated an increased risk for adverse outcome in patients with PA/Ao ratios above the median of ≥0.8 (p<0.001 by log rank test, see Figure 1B). In univariate analysis, a high PA/Ao ratio was associated with adverse outcome (HR=10.3, 95% CI=2.59–41.1, p<0.001). When adjusted for age, sex, body mass index and right ventricular function, the PA/Ao ratio remained significantly related to adverse outcome (adj. HR=10.8, 95% CI=1.76–65.8, p=0.010). Conclusion A PA/Ao ratio ≥0.8 on CMR is associated with heart failure hospitalization and death in patients with cardiac ATTR. This threshold, notably lower than the commonly reported ≥1.0 in other patient populations, holds promise for future risk stratification.