Oxygen pulse of cardiopulmonary exercise stress test helps on determining the behaviour of systolic volume measured by echocardiography in heart failure patients: a pattern is revealed

Abstract Patients with chronic heart failure (CHF) often experience a decline in their functional class, oxygen consumption (V2) and cardiac output (CO). Cardiopulmonary exercise testing with end-tidal gas analysis (CPET) is the gold standard for assessing this fitness. One of the most important hemodynamic variables at maximum exertion is stroke volume (SV) measured by echocardiography (ECO) under incremental workload, nevertheless, in this population its behaviour is unknown even though its established relation with oxygen pulse (2P) measured by CPET in healthy people. Our hypothesis is that the possible correlation between SV and 2P will allow us to define the inability of the heart muscle pump to compensate with its reserves in CHF at maximum exertion. We aimed to determine the correlation between 2P and SV in CHF patients, measured by combined ECO-CPET and to define the typical pattern of behavior in this population. Methodology quasi-experimental study of patients with diagnosis of chronic heart failure of any etiology underwent ECO-CPET on a treadmill, with non-invasive CO measurements at each stage of the incremental workload, alongside the variables of cardiorespiratory fitness (V2, heart rate HR, expired volume VE and ventilatory thresholds VT, VAT VT2). Categorical variables were expressed as proportions, and numerical variables were analyzed using measures of central tendency and dispersion according to the Shapiro-Wilk test. Correlation analysis was performed using Pearson's correlation coefficient between 2P (V2/HR) and SV. The behavior of CO, SV, 2P, HR and oxygen arterio-venous difference (2AVD) obtained by Fick’s equation at each stage of exercise was categorized to define the heart failure pattern. Results 30 CHF patients were included, 73.33% were men, mean age of 60.9 years (±2.18), average LVEF 32.4+-7.97, (95%CI 29.4-35.4), and average strain of -8.55 (95%CI -6.88,-10.2). Coronary artery disease and valvular heart disease were the most frequent causes; 23% had implantable devices and 86% were being treated with beta-blockers (Table). The baseline SV was on average lower than that of a patient without heart disease, and similarly, the exercise SV was on average at 45% of what a healthy subject achieves (maximum SV of 59.5+-24, 95%CI 8.42-10.9). A moderate direct correlation was found between SV and 2P ​​(r=0.50, p=0.004). Significant decreases in SV and CO were observed during exercise starting at VT2, along with chronotropic incompetence and a typical dome-shaped pattern due to low oxygen consumption with a rapid plateau and slow recovery in V2 kinetics (Figure). Conclusions The moderate correlation between peak 2P and SV suggests that these parameters are useful in assessing cardiac pumping capacity during exercise, complementing the typical pattern in patients with HFrEF.