Prognostic value of a new cardiopulmonary exercise testing parameter in chronic heart failure: oxygen uptake efficiency at peak exercise — comparison with oxygen uptake efficiency slope

Abstract

Introduction:A growing body of evidence shows the prognostic value of oxygen uptake effi ciency slope (OUES), a cardiopulmonary exercise test (CPET) parameter derived from the logarithmic relationship between O 2 consumption (VO 2 ) and minute ventilation (VE) in patients with chronic heart failure (CHF). Objective: To evaluate the prognostic value of a new CPET parameter -peak oxygen uptake effi ciency (POUE) -and to compare it with OUES in patients with CHF. Methods: We prospectively studied 206 consecutive patients with stable CHF due to dilated cardiomyopathy -153 male, aged 53.3±13.0 years, 35.4% of ischemic etiology, left ventricular ejection fraction 27.7±8.0%, 81.1% in sinus rhythm, 97.1% receiving ACE-Is or ARBs, 78.2% beta-blockers and 60.2% spironolactone -who performed a fi rst maximal symptom-limited treadmill CPET, using the modified Bruce protocol. In 33% of patients an cardioverterdefi brillator (ICD) or cardiac resynchronization therapy device (CRT-D) was implanted during follow-up.Peak VO 2 , percentage of predicted peak VO 2 , VE/VCO 2 slope, OUES and POUE were analyzed. OUES was calculated using the formula VO 2 (l/min) = OUES (log 10 VE) + b. POUE was calculated as pVO 2 (l/min) / log 10 peakVE (l/min). Correlation coeffi cients between the studied parameters were obtained. The prognosis of each variable adjusted for age was evaluated through Cox proportional hazard models and R2 percent (R2%) and V index (V6) were used as measures of the predictive accuracy of events of each of these variables. Receiver operating characteristic (ROC) curves from logistic regression models were used to determine the cut-offs for OUES and POUE. Results: pVO 2 : 20.5±5.9; percentage of predicted peak VO 2 : 68.6±18.2; VE/VCO 2 slope: 30.6±8.3; OUES: 1.85±0.61; POUE: 0.88±0.27. During a mean follow-up of 33.1±14.8 months, 45 (21.8%) patients died, 10 (4.9%) underwent urgent heart transplantation and in three patients (1.5%) a left ventricular assist device was implanted. All variables proved to be independent predictors www.revportcardiol.org

Overshoot of the Respiratory Exchange Ratio during Recovery from Maximal Exercise Testing in Kidney Transplant Recipients

“…This is defined as a further increase in VO 2 during recovery compared with the values observed at peak exercise [9,10], which has been found with a variable prevalence among cardiac patients and also in association with a worse prognosis [20]. A concomitant overshoot of the cardiac output in patients with heart failure has been described by other authors, suggesting that the VO 2 overshoot could be explained by a paradoxical increase in the stroke volume, probably due to a decrease in the peripheral vascular resistances after stopping exercise [9,11]. The authors also hypothesized that the increased stroke volume could be distributed to skeletal muscles to repay the oxygen deficit or that it could depend on a relatively slow decline of catecholamines at the end of exercise.…”

“…This is represented by a transitory increase in VO 2 during the first part of recovery and has been attributed to a paradoxical increase in the stroke volume due to a reduction in systemic vascular resistances. Speculations have been made about whether this impaired relationship between the stroke volume and vascular resistances could be due to a slow decrease in the adrenergic tone or to the repayment of the accumulated O 2 deficit [10,11].…”

Cardiopulmonary Exercise Testing for Preoperative Evaluation: What Does the Future Hold?

“…Although encouraging, the data supporting the prognostic value of OUES is limited to date due to a lack of appropriately powered prospective studies and warrants further investigation. The OUES displays prognostic value in patients with HF [49][50][51] and coronary artery disease (CAD) [52,53] and has been shown to be responsive to physical training in patients with CAD [54,55].…”

Who needs a transplant and when?

“…Novel biomarkers such as hs-CRP and soluble ST2 may provide additional risk stratification [55,57]. There have been many studies assessing CPET indices apart from peak VO 2 , such as ventilator efficiency, peak oxygen uptake efficiency, exercise oscillatory ventilation and others for risk stratification [58][59][60][61].…”