Impact of right ventricular contractile reserve on exercise capacity in patients with heart failure: clinical application of low-load exercise stress echocardiography

Abstract

Abstract Background The peak oxygen uptake (VO2) evaluated by the cardiopulmonary exercise test (CPX) is an established marker of exercise capacity in patients with heart failure (HF). In particular, peak VO2 <14 ml/kg/min is used to be one of the criteria for heart transplantation. However, given exercise intolerance in patients with HF, it is difficult for refractory HF patients to reach sufficient exercise load. A recent report has highlighted significant impact of right ventricular (RV) function on mortality and urgent heart transplantation. Taken together, we hypothesized that the assessment of RV function was helpful to predict exercise capacity by using low-load exercise stress echocardiography (low-load ESE) in patients with HF. Purpose We evaluated whether RV dysfunction assessed by the low-load ESE determined a low peak VO2 <14 ml/kg/min in patients with HF. Methods We studied 67 consecutive hospitalized patients with HF (mean age, 65 years; 75% male; mean LV ejection fraction, 36%) who underwent ESE and CPX after stabilized HF condition, and the time interval of CPX and ESE tests was within 48 hours. CPX was performed using an upright cycle ergometer by a ramp protocol, while ESE was performed using ergometer in semi-supine position and the workload was generally increased by 25 watts every 3 minutes. The low-load ESE was defined as the 25 watts exercise. The increments of RV s' velocity at tricuspid annulus and RV strain in the free wall were considered as a preservation of RV contractile reserve. Among the study population, 26 patients were performed right heart catheterization and RV dP/dt/Pmax was estimated as an invasive marker of RV contractility. Results The achieved intensity of exercise was 50.4±21.0 watts, and all patients completed the low-load ESE. The invasive study showed that the change of RV s' velocity during the low-load ESE significantly correlated with RV dP/dt/Pmax (r=0.706, p<0.001). As shown in Figure, the non-invasive parameters of RV contractile reserve during the low-load ESE were significantly correlated with peak VO2 (RV s' velocity: r=0.787, p<0.001; RV strain: r=0.244, p=0.047). ROC analysis showed that the change of RV s' velocity during the low-load ESE correctly identified patients with peak VO2 <14 ml/kg/min (AUC=0.95, sensitivity 92.3%, specificity 85.2%). In terms of inter- and intra-observer variabilities, ICCs of the change of RV s' velocity were 0.86 and 0.96, and ICCs of the changes of RV strain were 0.63 and 0.70, respectively. Conclusion The change of RV s' velocity during the low-load ESE could determine exercise tolerance in patients with HF. The assessment of RV contractile reserve might be clinically useful to discriminate high risk HF patients. Figure 1 Funding Acknowledgement Type of funding source: None