The usefulness of the tidal Volume difference(Peak-rest) as a prognostic indicator in patients with heart failure with reduced ejection fraction

Background The diaphragm is not only a crucial respiratory muscle but also plays a vital role in the cardiovascular system. It supports venous return to the right atrium and regulates heart rate variability and sympathetic activity. The capacity to increase the tidal volume of the lungs varies depending on the diaphragm's function. We hypothesized that the more severe the heart failure, the lower the diaphragm's functionality and, consequently, the less increase in tidal volume (TV). Thus, we proposed that the TV difference between peak exercise and rest during cardiopulmonary exercise testing (CPET) could predict prognosis in heart failure patients with reduced ejection fraction (HFrEF). Purpose To investigate whether ΔTV (Peak-rest) in milliliters helps in predicting prognosis in HFrEF patients. Methods We enrolled 136 HFrEF patients who underwent CPET, with data available on TV increase from rest to peak exercise point (ΔTV (Peak-rest) in milliliters). The primary endpoint was a combined outcome of all-cause mortality and heart failure hospitalization. Results During a median follow-up of 4.0 years (interquartile range: 2.4-5.3 years), we observed 56 combined events. The cutoff value for ΔTV (Peak-rest) in milliliters, defined by the median, was 714ml. Patients with ΔTV (Peak-rest) below 714ml exhibited a significantly higher event rate compared to those with ΔTV (Peak-rest) of 714ml or higher (Log-rank: p<0.001). This association remained significant even after adjusting for age and sex (HR: 0.27, P<0.001). Conclusions ΔTV (Peak-rest) in milliliters is a promising prognostic indicator in patients with HFrEF and could serve as a new tool for prognosis assessment in these patients.