The Use of Cardiopulmonary Stress Testing to Predict Poor Outcomes Post-Heart Transplantation

Abstract

<h3>Purpose</h3> Cardiopulmonary stress testing (CPX) has been used as a reliable marker for poor outcomes among patients with chronic heart failure. The utility of pre-transplant CPX to predict post heart transplant (HT) outcomes has not been evaluated. <h3>Methods</h3> We conducted an observational, retrospective, cohort study of all HT recipients who underwent a pre-HT CPX at a single center from 2013 to 2019. Measures of cardiovascular performance were evaluated including METs achieved, peak VO2, %-predicted peak VO2, VE/VCO2 slope, RER, and VO2/heart rate (HR). These were correlated to post-HT clinical outcomes including hospital length of stay (LOS), ICU LOS, need for mechanical circulatory support (MCS) (e.g. intra-aortic balloon pump or VA-ECMO), and death. <h3>Results</h3> 52 HT recipients were included (mean age 57 years, 67% male). All subjects underwent a CPX and subsequently received a HT within 139 ± 122 days. Subjects exhibited poor cardiovascular performance with 57% achieving a VE/VCO2 greater than 35 (average 37± 8), only 35% able to demonstrate greater than 6 METs, 58% with %-predicted peak VO2 less than 50, and 60% with VO2/HR of less than 11. Subjects with VE/VCO2 greater than 35 were older (60 years vs 49 years, p = 0.013) and had lower BSA (1.9 m2 vs 2.1 m2, p = 0.04). Ability to achieve greater than 6 METs was associated with less than 5-day ICU LOS (25% vs 10%, p=0.03) and a reduced need for MCS (2% vs 33%, p<0.001) (Fig. 1). A peak VO2 of greater than 14 ml/kg/min also was associated with a lesser need for MCS support (14% vs 43%, p=0.06). Patients with a VE/VCO2 slope of less than 35 were more likely to have a total LOS of less than 24 days (43% vs 25%, p=0.02). None of the CPX measures were associated with post-HT death. <h3>Conclusion</h3> Ability to achieve greater than 6 METs and a VE/VCO2 less than 35 were associated with positive post-HT clinical outcomes of reduced ICU LOS, reduced need for MCS, and reduced total hospital LOS. Pre-operative CPX measures may provide clinical utility in identifying subjects at risk for adverse post-HT outcomes.