In older patients with cardiovascular (CV) conditions, frailty is a common comorbidity. Systematic reviews estimate the prevalence of frailty in older heart failure patients to be 44.5%, and pooled prevalence of frailty in ischaemic heart disease to be 19% in adults over age 60 (ranging from 4% to 61%) [1,2]. Patients with heart disease and frailty would benefit from cardiac rehabilitation (CR), but the authors of this paper note that we still lack established training interventions for frail patients. This lack is despite the EAPC Cardiac Rehabilitation Section call to action on frailty and cardiac rehabilitation in 2017 , in which the need to identify frailty and determine the effects of CR interventions on course and prognosis of frail patients was emphasised.
In this paper the authors discuss and review the evidence for blood-flow restricted resistance training (BFR-RT) as an innovative training modality that addresses the need to maintain or increase muscle strength in frail individuals unable to participate in usual moderate-to-vigorous intensity resistance training. BFR-RT is conducted with pneumatic torniquets to occlude venous blood flow and cause peripheral hypoxia in the muscle distal to the occlusion. Using BFR-RT with low loads suitable for frail individuals induces greater gains in muscle strength as the ensuing anaerobic processes and accumulation of specific metabolites mimic high load resistance training.
The authors review five studies addressing the safety of low load BFR-RT in patients with ischaemic heart disease or hypertension, and three studies addressing efficacy in ischaemic heart disease, heart failure or cardiac surgery. The authors conclude that low load BFR-RT is safe but advocate a lower volume of RT (< 15 repetitions/set), shorter breaks between sets (< 90 seconds) and wider cuffs to minimise cardiovascular risk. They note that studies have shown benefit of the technique (interventions between 6 and 12 weeks) in muscle strength and walk distance among others, compared to baseline and control interventions. The caveat is that these studies are small with sample sizes less than 40 individuals, although more data are available in studies of healthy adults.
The paper provides a proposal and recommendations for implementation of low load BFR-RT as part of exercise-based CR for frail patients with cardiovascular conditions. Low load BFR-RT is a promising modality of gaining muscle strength and improving the function of patients with both heart disease and frailty. However, as noted in the paper well-designed studies with larger samples are needed.