Submaximal exercise metrics: Looking prior to VO₂max : in Heart Failure.

Maximal oxygen uptake (VO₂max) remains the benchmark for cardiopulmonary exercise testing (CPET) in chronic heart failure (CHF). However, VO₂max and its surrogate, VO₂peak, often fail to capture the full spectrum of functional impairment, especially in patients unable to reach maximal effort. This review delineates submaximal CPET-derived metrics that offer valuable prognostic and diagnostic insights beyond VO₂max and are less dependent on peak effort. Guideline-endorsed parameters such as ventilatory anaerobic threshold (VAT) and the minute ventilation–carbon dioxide production slope (VE/VCO₂) are established tools for risk stratification and transplant evaluation. Emerging markers—including O₂ uptake efficiency slope (OUES), exertional oscillatory ventilation (EOV), O₂ pulse and cardiorespiratory optimal point (COP)—offer robust prognostic value in effort-limited populations. Additionally, O₂ uptake kinetics and extrapolated maximal oxygen consumption (EMOC) provide mechanistic perspectives on central and peripheral limitations, though their clinical integration remains early. Incorporating these submaximal metrics into composite risk models may enhance individualized care and improve outcomes in CHF.