In patients with HFpEF, 68% reached the lactate threshold at ≤40 W, and these patients were more likely to be female, anaemic, and have greater pulmonary vascular disease (all p < 0.01).
Observational (n=286)
What are the clinical and pathophysiological determinants of impaired submaximal fitness (lactate threshold ≤40 W) in patients with HFpEF?
Impaired submaximal fitness is common in HFpEF and is driven by distinct haemodynamic and ventilatory abnormalities during low-level exercise that are not apparent at maximal exertion.
Absolute Event Rate: 68% vs 32%
AIMS: Oxygen consumption at peak exercise is widely used to assess functional impairment in heart failure with preserved ejection fraction (HFpEF), but few patients exercise to this intensity in daily living. Alternative metrics that quantify submaximal fitness may provide more patient-centred evaluations, but the pathophysiology of submaximal exercise intolerance in HFpEF is unexplored. METHODS AND RESULTS: Patients with HFpEF underwent invasive haemodynamic cardiopulmonary exercise testing with blood lactate measurement during exercise to volitional fatigue. Lactate threshold (LT) was defined as the exercise workload at which arterial lactate exceeded >2.0 mmol/L, taken as a measure of submaximal fitness. Of patients with HFpEF (n = 286), 194 (68%) reached LT at a workload of 40 W or less (LT ≤40 W), while 92 (32%) reached a workload exceeding 40 W at LT (LT >40 W). As compared to LT >40 W, patients with LT ≤40 W were more likely to be female, anaemic, and had greater pulmonary vascular disease (all p < 0.01). During 20 W exercise, participants with LT ≤40 W had higher pulmonary artery pressure, biventricular filling pressures, minute ventilation and respiratory drive, higher perceived dyspnoea and fatigue ratings, greater arterial-venous oxygen content difference, despite similar cardiac output and oxygen delivery. At peak exercise, most of these differences were no longer apparent. Findings were replicated using non-invasively-measured workload at ventilatory threshold. CONCLUSIONS: Two-thirds of patients with HFpEF reach LT at workloads typical of activities of daily living. Patients with HFpEF and impaired submaximal fitness are more likely to be female, have greater pulmonary vascular disease and anaemia severity, and display greater haemodynamic, symptomatic, and ventilatory control abnormalities during low-level exercise, which are not apparent at maximal exertion. These findings have therapeutic implications and suggest a potentially important role for wider evaluation of submaximal fitness in addition to peak aerobic capacity.
Doi et al. (Wed,) conducted a observational in Heart failure with preserved ejection fraction (HFpEF) (n=286). Lactate threshold (LT) ≤40 W vs. Lactate threshold (LT) >40 W was evaluated on Proportion of patients reaching lactate threshold at a workload of 40 W or less. In patients with HFpEF, 68% reached the lactate threshold at ≤40 W, and these patients were more likely to be female, anaemic, and have greater pulmonary vascular disease (all p < 0.01).
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