Role of right ventricle and dynamic pulmonary hypertension on determining ΔVO2/ΔWork Rate flattening : insights from cardiopulmonary exercise test combined with exercise echocardiography

Background-Several cardiovascular diseases are characterized by an impaired O-2 kinetic during exercise. The lack of a linear increase of Delta oxygen consumption (VO2)/Delta Work Rate (WR) relationship, as assessed by expired gas analysis, is considered an indicator of abnormal cardiovascular efficiency. We aimed at describing the frequency of Delta VO2/Delta WR 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 as cardiac determinants.
Methods and Results-We studied 136 patients, with different cardiovascular diseases, referred for exertional dyspnoea. Cardiopulmonary exercise test combined with simultaneous exercise echocardiography was performed using a symptom-limited protocol. Delta VO2/Delta WR 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, O-2 pulse, impaired VE/VCO2). At univariate analysis, exercise ejection fraction, exercise mitral regurgitation, rest and exercise tricuspid annular plane systolic excursion, exercise systolic pulmonary artery pressure, and exercise cardiac output were all significantly (P<0.05) impaired in group A. The multivariate analysis identified exercise systolic pulmonary artery pressure (odds ratio, 1.06; confidence interval, 1.01-1.11; P=0.01) and exercise tricuspid annular plane systolic excursion (odds ratio, 0.88; confidence interval, 0.80-0.97; P=0.01) as main cardiac determinants of Delta VO2/Delta WR flattening; female sex was strongly associated (odds ratio, 6.10; confidence interval, 2.11-17.7; P<0.01).
Conclusions-In patients symptomatic for dyspnea, the occurrence of Delta VO2/Delta WR flattening reflects a significantly impaired functional phenotype whose main cardiac determinants are the excessive systolic pulmonary artery pressure increase and the reduced peak right ventricular longitudinal systolic function.