McCue, Meghan C.

Our lab has demonstrated a lower cardiac output (Q) in patients with heart failure (HF) vs. controls (CTL) using acetylene rebreathing (ACET). This technique may be dependent on lung health, which is altered in HF. Therefore, we examined the relationship between Q from echocardiography (echo) and Q from ACET at rest and during exercise. Additionally, we examined the relationship between stroke volume (SV) estimated from O 2 pulse compared to SV by ACET (SV A ). 26 controls (CTL) and 18 HF patients with preserved ejection fraction (EF) completed an exercise test on a cycle ergometer. Lung conductance was measured by lung diffusion for carbon monoxide (DL CO ). Measures of Q (Q A , Acetylene rebreathe; Q E , transthoracic echo), heart rate (HR, 12‐lead ECG), and oxygen consumption (VO 2 , metabolic cart) were taken at rest and peak exercise. Stroke volume (SV) and O 2 pulse were calculated as Q/HR and VO 2 /HR, respectively. HF patients had lower DL CO compared to CTL (Rest: DL CO =11±0.5 vs 14±0.6 ml/min/mmHg, p<0.05). At rest and exercise, Q E was moderately correlated with Q A in CTL (Rest: r=0.47; Pk Ex: r=0.51, p<0.05) and HF (rest: r=0.47; Pk Ex: r=0.77, p<0.05). O 2 pulse was significantly related to SV A at rest and exercise in CTL (Rest: r=0.76; Pk Ex: r=0.81, p<0.05) and HF (Rest: r=0.81; Pk Ex: r=0.82, p<0.05). Cardiac function assessed via ACET is related to cardiac function by echo and O 2 pulse in patients with HF with preserved EF.

Purpose Oxygen pulse (O 2 pulse) is often used clinically as a surrogate for stroke volume during cardiopulmonary exercise testing; however, little data exists on the validity of this measure in patient populations (e.g. heart failure with preserved ejection fraction – HFpEF). Therefore, the purpose of this study was to examine the relationship between O 2 pulse and stroke volume (SV) measured using an accepted technique, echocardiography, at rest and during exercise. Methods Eighteen HFpEF (EF=62±1%) patients and 26 healthy controls (CTL) completed an exercise test on a cycle ergometer. Average measures of oxygen consumption (VO 2 , metabolic cart), heart rate (HR, 12‐lead ECG), and SV (transthoracic echocardiography) were taken at rest and peak exercise. O 2 pulse was calculated as VO 2 divided by HR. Results O 2 pulse was significantly correlated with SV at rest and at peak exercise in CTL (r=0.60 and r=0.55, p<0.05 for both respectfully). O 2 pulse was similarly significantly correlated with SV at rest in HFpEF (r=0.58, p<0.05) whereas this relationship demonstrated a trend at peak exercise (r=0.44, p=0.06). Conclusion Our results demonstrate a moderate relationship between O 2 pulse and SV measured using echocardiography in healthy control participants at rest and during exercise. There is a similar relationship at rest in patients with HFpEF; however, this relationship is less strong during exercise.