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 O2 kinetic during exercise. The lack of a linear increase of Δ oxygen consumption (VO2)/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 as cardiac determinants.
Methods and Results—We studied 136 patients, with different cardiovascular diseases, referred for exertional dyspnoea. 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, O2 pulse, impaired VE/VCO2). At univariate analysis, exercise EF, exercise mitral regurgitation, rest and exercise tricuspid annular plane systolic excursion (TAPSE), exercise systolic pulmonary artery pressure (SPAP) and exercise cardiac output 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=0.01) and exercise TAPSE (OR 0.88; CI 0.80 -0.97; p=0.01) as main cardiac determinants of ΔVO2/ΔWR flattening; female sex was strongly associated (OR 6.10; CI 2.11 -17.7; p<0.01).
Conclusions—In patients symptomatic for dyspnea, the occurrence of ΔVO2/ΔWR flattening reflects a significantly impaired functional phenotype whose main cardiac determinants are the excessive SPAP increase and the reduced peak RV longitudinal systolic function.
- Received November 5, 2013.
- Accepted June 13, 2014.