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

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.

We aimed to investigate the prognostic value of the PA/Ao ratio in patients with cardiac ATTR.

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.

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).

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.