ABSTRACT
Abstract Background Cardiopulmonary Exercise Testing (CPX) is essential for the assessment of exercise capacity for patients with Chronic Heart Failure (CHF). Respiratory gas and hemodynamic parameters such as Ventilatory Efficiency (VE/VCO2 slope), peak oxygen uptake (peak VO2), and heart rate recovery are established diagnostic and prognostic markers for clinical populations. Previous studies have suggested the clinical value of metrics related to respiratory gas collected during recovery from peak exercise, particularly recovery time to 50% (T1/2) of peak VO2. The current study explores these metrics in detail during recovery from peak exercise in CHF. Methods Patients with CHF who were referred for CPX and healthy individuals without formal diagnoses were assessed for inclusion. All subjects performed CPX on cycle ergometers to volitional exhaustion and were monitored for at least five minutes of recovery. CPX data were analyzed for overshoot of respiratory exchange ratio (RER=VCO2/VO2), ventilatory equivalent for oxygen (VE/VO2), end-tidal partial pressure of oxygen (PETO2), and T1/2 of peak VO2 and VCO2. Results Thirty-two patients with CHF and 30 controls were included. Peak VO2 differed significantly between patients and controls (13.5 ± 3.8 vs. 32.5 ± 9.8 mL/Kg*min−1, p < 0.001). Mean Left Ventricular Ejection Fraction (LVEF) was 35.9 ± 9.8% for patients with CHF compared to 61.1 ± 8.2% in the control group. The T1/2 of VO2, VCO2 and VE was significantly higher in patients (111.3 ± 51.0, 132.0 ± 38.8 and 155.6 ± 45.5s) than in controls (58.08 ± 13.2, 74.3 ± 21.1, 96.7 ± 36.8s; p < 0.001) while the overshoot of PETO2, VE/VO2 and RER was significantly lower in patients (7.2 ± 3.3, 41.9 ± 29.1 and 25.0 ± 13.6%) than in controls (10.1 ± 4.6, 62.1 ± 17.7 and 38.7 ± 15.1%; all p < 0.01). Most of the recovery metrics were significantly correlated with peak VO2 in CHF patients, but not with LVEF. Conclusions Patients with CHF have a significantly blunted recovery from peak exercise. This is reflected in delays of VO2, VCO2, VE, PETO2, RER and VE/VO2, reflecting a greater energy required to return to baseline. Abnormal respiratory gas kinetics in CHF was negatively correlated with peak VO2 but not baseline LVEF.
ABSTRACT
Objective:To analyze the value of minute ventilation to carbon dioxide production slope (VE/VCO 2 slope) combined with peak systolic blood pressure (SBP) in predicting prognosis for patients with chronic heart failure (CHF). Methods:A total of 170 patients with CHF who visited the Cardiac Rehabilitation Center of Tongji Hospital Affiliated to Tongji University and completed cardiopulmonary exercise test from March 2007 to December 2018 were enrolled in the study. The clinical data, cardiopulmonary exercise testing results and follow-up information of patients were collected to explore the predictors of all-cause mortality in patients with CHF.Results:The median follow-up time was 647 (182-1 764) days. All-cause death occurred in 34 patients. Compared with surviving patients, the proportion of diabetes and angiotensin-converting enzyme inhibitor/angiotensin Ⅱ receptor blocker (ACEI/ARB) use in fatal patients was significantly higher ( P<0.01). The VE/VCO 2 slope and peak SBP*VE/VCO 2 in the fatal patients were significantly higher, and the peak oxygen consumption (peak VO 2) was lower than those in the surviving patients ( P<0.01). The areas under the receiver operating characteristic curve (AUC) of VE/VCO 2 slope and peak SBP*VE/VCO 2 in predicting all-cause mortality in patients with CHF were 0.648 ( P=0.008) and 0.681 ( P=0.001), respectively; the optimal thresholds were >40.95 ( P=0.008) and > 5 423.50 mmHg (1 mmHg=0.133 kPa, P=0.006), the sensitivity was 0.559 and 0.588, and the specificity was 0.728 and 0.735, respectively. Multivariate Cox regression analysis showed that after adjusting for age, gender, diabetes and ACEI/ARB use, VE/VCO 2 slope ( HR=2.12, P=0.036) and peak SBP*VE/VCO 2 ( HR=2.42, P=0.016) were independent risk factors for all-cause mortality in patients with CHF. Conclusion:Compared to the traditional index VE/VCO 2 slope, a novel index peak SBP* VE/VCO 2 provides a relatively better predictive value for all-cause death of CHF patients.