Clinical Surrogates of Right Ventricular-Pulmonary Arterial Uncoupling

Purpose Right ventricular (RV) function is best represented by the ratio of RV contractility to pulmonary arterial (PA) load (RV-PA coupling). Gold standard measurement of RV-PA coupling, using multi-beat pressure-volume (P-V) loop to obtain the ratio of end-systolic elastance (Ees) to effective arterial elastance (Ea), is costly and invasive. Therefore, we sought to identify clinical surrogates of reduced Ees/Ea and RV-PA uncoupling. Methods We prospectively studied 35 patients suspected to have pulmonary hypertension (PH) with same day echocardiography, cardiac magnetic resonance imaging (CMR), right heart catheterization, and supine bicycle submaximal cardiopulmonary exercise testing. Multi-beat RV P-V loop measurements were also performed. Ees/Ea < 1.0 defined RV-PA uncoupling. Results Of 35 patients, 26 had resting PH while 9 did not (20/26 had group I PH). Average age was 57±13 years; 30 were women. Compared with baseline Ees/Ea ≥ 1.0, Ees/Ea <1.0 was associated with reduced RV ejection fraction (RVEF), stroke volume/end-systolic volume (SV/ESV), and resting and peak cardiac output, as well as higher RV afterload, all in line with RV-PA uncoupling. Commonly used measures of RV function and their correlation with RV-PA uncoupling are reported in Table 1. A novel metric, the ratio of change in end-systolic volume to change in end-systolic pressure (ΔESV/ΔESP) during submaximal exercise, predicted RV-PA uncoupling in both univariate as well as multivariate analysis adjusted for disease group and all other significant univariate predictors (P=0.009). Exercise ΔESV/ΔESP also had the best sensitivity and specificity for predicting RV-PA uncoupling (AUC 0.80; P=0.002). Conclusion Readily attainable clinical variables correspond to the gold standard Ees/Ea. We identified a novel parameter, exercise change in ΔESV/ΔESP, a marker of RV reserve, which had the best ability to predict RV-PA uncoupling. Future studies will investigate RV ΔESV/ΔESP and other markers of RV reserve. Right ventricular (RV) function is best represented by the ratio of RV contractility to pulmonary arterial (PA) load (RV-PA coupling). Gold standard measurement of RV-PA coupling, using multi-beat pressure-volume (P-V) loop to obtain the ratio of end-systolic elastance (Ees) to effective arterial elastance (Ea), is costly and invasive. Therefore, we sought to identify clinical surrogates of reduced Ees/Ea and RV-PA uncoupling. We prospectively studied 35 patients suspected to have pulmonary hypertension (PH) with same day echocardiography, cardiac magnetic resonance imaging (CMR), right heart catheterization, and supine bicycle submaximal cardiopulmonary exercise testing. Multi-beat RV P-V loop measurements were also performed. Ees/Ea < 1.0 defined RV-PA uncoupling. Of 35 patients, 26 had resting PH while 9 did not (20/26 had group I PH). Average age was 57±13 years; 30 were women. Compared with baseline Ees/Ea ≥ 1.0, Ees/Ea <1.0 was associated with reduced RV ejection fraction (RVEF), stroke volume/end-systolic volume (SV/ESV), and resting and peak cardiac output, as well as higher RV afterload, all in line with RV-PA uncoupling. Commonly used measures of RV function and their correlation with RV-PA uncoupling are reported in Table 1. A novel metric, the ratio of change in end-systolic volume to change in end-systolic pressure (ΔESV/ΔESP) during submaximal exercise, predicted RV-PA uncoupling in both univariate as well as multivariate analysis adjusted for disease group and all other significant univariate predictors (P=0.009). Exercise ΔESV/ΔESP also had the best sensitivity and specificity for predicting RV-PA uncoupling (AUC 0.80; P=0.002). Readily attainable clinical variables correspond to the gold standard Ees/Ea. We identified a novel parameter, exercise change in ΔESV/ΔESP, a marker of RV reserve, which had the best ability to predict RV-PA uncoupling. Future studies will investigate RV ΔESV/ΔESP and other markers of RV reserve.