Role of right ventricle and pulmonary hypertension on determining delta vo2/delta work rate flattening: insights from cardiopulmonary exercise test combined with exercise echocardiography

Background: several cardiovascular diseases are characterized by an impaired O2 kinetic during exercise. The lack of a linear increase of ΔVO2/ΔWork Rate (WR) relation, as assessed by expired gas analysis, is considered an indicator of abnormal cardiovascular efficiency. We aimed at describing the frequency of ΔVO2/ΔWR flattening in a symptomatic population of cardiac patients, characterizing its functional profile and testing the hypothesis that dynamic pulmonary hypertension and right ventricular contractile reserve play a major role. Methods and results: We studied 136 patients, with different cardiovascular diseases, referred for dyspnoea during effort. Cardiopulmonary exercise test (CPET) combined with simultaneous exercise-echocardiography were performed using a symptom-limited protocol. ΔVO2/ΔWR flattening was observed in 36 patients (Group A, 26.5% of population) and was associated with a globally worse functional profile (reduced peak VO2, anaerobic threshold 11.4±3.3 vs 13.8±4.4 mL/kg/min, O2 pulse 8.2±2.3 vs 10.9±3.1 mL/beata, impaired VE/VCO2). At univariate analysis, exercise EF, exercise mitral regurgitation, rest and exercise TAPSE, exercise systolic pulmonary artery pressure (SPAP) and exercise cardiac output (7.7±2 vs 9.0±2.8 L/min) were all significantly (p <0.05) impaired in Group A. The multivariate analysis identified exercise SPAP (OR 1.06; CI 1.01 -1.11; p= 0.011) and exercise TAPSE (OR 0.88; CI 0.8 -0.97; p= 0.013) as main cardiac determinants of ΔVO2/ΔWR flattening. Conclusion: In patients symptomatic for dyspnea, the occurrence of ΔVO2/ΔWR flattening reflects a significantly impaired functional phenotype whose main cardiac determinants are the impaired SPAP response and the reduced peak RV longitudinal systolic function. Flattening No flattening Univariate P value Multivariate P value Rest Peak Rest Peak Reast Peak Peak Peak VO2, mL/Kg/min -- 13.4±3.9 -- 18±6.6 -- <.0001 -- VE/VCO2 -- 33.2±8 -- 29.8±6.8 -- .02 -- LV EF, % 47±14 47±17 52±16 55±17 .12 .03 NS Mitral regurgitation ≥3/4+, % 14 39 14 20 .9 .025 .013 TAPSE, mm 20±5 22±5 22±5 25±6 .05 .0029 .011 SPAP, mmHg 37±17 61±19 33±14 51±18 .22 .0009 .013