Right ventricular coupling predicts cardiopulmonary fitness in cardiac transthyretin amyloidosis

Background: Wild-type transthyretin cardiac amyloidosis (ATTRwt) is an infiltrative disease leading to restrictive cardiomyopathy. We aimed to characterise exercise capacity in ATTRwt and to identify predictors of cardiopulmonary fitness, focusing on echocardiographic and clinical parameters. Methods: We studied 110 ATTRwt patients from a prospective single-centre registry (2020-2024) by cardiopulmonary exercise testing (CPET). Besides CPET, all patients underwent comprehensive clinical assessment including follow-up for mortality. In 32 patients follow-up CPET after 1 year was available. Results: In ATTRwt, reduced aerobic capacity (pVO2 16 [13–18] ml/kg/min), and ventilatory inefficiency (VE/VCO2 slope 35 [30–43]) were common. In the multivariable regression analysis, we identified TAPSE/sPAP ratio as predictive for pVO2 (p = 0.019) and ventilatory efficiency (p = 0.004), while left ventricular ejection fraction or measures of left ventricular hypertrophy were not predictive. Concordantly, TAPSE/sPAP ratio assessed at baseline predicted pVO2 at 1-year follow-up (p = 0.009). Furthermore, patients with a TAPSE/sPAP ratio below the median of 0.38 mm/mmHg presented a higher risk of all-cause death (p = 0.009). Conclusion: In ATTRwt the TAPSE/sPAP ratio, a marker of right ventricular coupling, was an independent predictor of aerobic capacity assessed by CPET, at baseline and after 1 year, highlighting the importance of right ventricular assessment for risk stratification.