Low peak oxygen uptake in relation to total heart volume as an early marker of sub-clinical diastolic dysfunction.

Aims: Peak oxygen uptake (VO₂peak) is closely related to total heart volume (THV) in healthy individuals. This study aimed to investigate (i) the association between VO₂peak and THV in subjects with sub-clinical diastolic dysfunction, athletes, healthy controls, and patients with established heart failure with and without preserved ejection fraction (HFpEF and HFrEF), and (ii) whether VO₂peak/THV-index can distinguish between subjects with sub-clinical diastolic dysfunction, HFpEF, HFrEF, and healthy controls.

Methods and results: Seventy participants were included: 15 with sub-clinical diastolic dysfunction (defined as showing only 1-2 echocardiographic signs of diastolic dysfunction, not meeting clinical diagnostic criteria), 10 athletes, 15 healthy controls, and 30 heart failure patients (15 HFpEF and 15 HFrEF). VO₂peak was assessed by cardiopulmonary exercise testing and THV by cardiovascular magnetic resonance imaging. In sub-clinical diastolic dysfunction, THV was a weak determinant of VO₂peak (R ² = 0.41, P = 0.01), and even weaker in heart failure (R ² = 0.16, P = 0.03). However, THV strongly predicted VO₂peak in athletes and controls combined (R ² = 0.87, P < 0.0001). VO₂peak/THV did not distinguish healthy controls from sub-clinical diastolic dysfunction but could reliably discriminate between healthy controls and patients with heart failure.

Conclusion: Subjects with sub-clinical diastolic dysfunction may have an altered relationship between VO₂peak and THV, approaching that of patients with established heart failure. Thus, this proof-of-concept study indicates that sub-clinical diastolic dysfunction constitutes a group of patients that may be of interest to follow over time to prevent continued deterioration of cardiac function. Furthermore, the VO₂peak/THV ratio can be used to distinguish between healthy controls and overt heart failure.