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traditional heart failure management and those awaiting heart transplants . To date , over 22,000 VADs have been implanted in North America , with more than 2,500 of these devices being implanted annually [ 18 ]. Cardiopathies in general represent a significant percentage of mortality and morbidity in the population , and they are among the primary contributors to disability andreducedqualityoflife [ 19 , 20 ]. A VAD patient can maintain haemodynamic control and adequate perfusion ; however , the functional deterioration caused by their underlying condition results in severe symptoms during exertion , hindering the completion of certain tasks .
In this regard , CR is a multidisciplinary set of interventions , one of which is physical exercise [ 21 ]. The improvement in functional capacity provided by CR reduces symptoms , hospitalisations , and complications associated with heart disease [ 21 , 22 ]. Designing a CR programme with the correct EP is indicated for VAD patients [ 4 ].
The CR programmes reviewed in these seven studies implemented cardiopulmonary exercise testing ( CPET ) or field tests like the 6-minute walk test ( 6MWT ) to observe the physiological response to exercise before and after CR in VAD patients . These tests are considered the gold standard for EP [ 4 ] astheyare objective and traceable over time . Moreover , their results reflect cardiorespiratory fitness , understood as the integrated capacity to transport oxygen , under adequate cardiopulmonary function , and the ability of muscle cells to utilise this oxygen [ 23 ].
Exercise intensity or workload prescriptions are derived from peak indices of various physiological variables , with the most commonly used being the percentage of maximum workload ( Wmax %), as used by Schmidt et al . [ 15 ], the percentage of maximum heart rate ( HRmax %), the percentage of peak oxygen consumption ( VO 2 peak %), the percentage of heart rate reserve ( HRR %), and maximum oxygen consumption ( VO 2 max ) [ 23 ], chosen by other authors . Given space , resource , and equipment constraints , HRmax % and HRR % are often the preferred reference values for prescribing intensities in outpatient CR programmes [ 23 ]. It is also advisable to continuously monitor physical effort and perceived dyspnoea , as these reflect the patient ’ s response to the intervention and serve as subjective indicators of progression in exercise intensity [ 24 ]. These measurements have proven to be applicable to VAD populations [ 23 ].
Exercise parameters such as intensity , frequency , duration , and volume physiologically impact the body by inducing changes in the cardiovascular system , such as increased stroke volume , improved cardiac output , reduced peripheral vascular resistance , and maintenance of adequate blood cell populations . In the respiratory system , it improves respiratory muscle function , facilitates proper breathing patterns , and enhances lung volumes and capacities , thus benefiting oxygen transport to tissues [ 25 ]. Additionally , skeletal muscle effects of CR include greater muscle fibre recruitment , increased capillary density , enhanced mitochondrial expression , stimulation of anabolic signals , and profiles of type I and type IIa muscle fibres , with a reduction in type IIb fibres , resulting in an adequate oxygen extraction capacity [ 25 , 26 ], ultimately leading to an increase in VO 2 .
Studies by Moreno et al ., Kerrigan et al ., Scaglione et al ., Alvarez Villela et al ., Schmidt et al ., and Marko et al . favoured aerobic exercise [ 11 – 16 ], supported by clinical practice guidelines [ 4 , 6 ]. Traditionally , this training has been conducted under a moderate-intensity continuous training ( MICT ) modality [ 27 , 28 ], with two studies opting for this modality : Kerrigan et al . [ 11 ] and Marko et al . [ 16 ]. In contrast , four studies , Moreno et al . [ 12 ], Scaglione et al . [ 13 ], Alvarez Villela et al . [ 14 ], and Schmidt et al . [ 15 ], preferred the high-intensity interval training ( HIIT ) modality , a more contemporary strategy .
On the other hand , MICT is characterised by maintaining the same exercise intensity for a prolonged period . The European Association of Preventive Cardiology defines this intensity as a range between 40 % and 69 % of VO 2 max , 55 % and 74 % of HRmax , or 40 % and 69 % of HRR [ 29 ]. Meanwhile , HIIT involves training at high intensities for short periods , 90 % of VO 2 max , with longer recovery periods at lower intensities [ 23 ].
There is limited scientific evidence regarding the most recommended modality for CR services in VAD patients . In heart failure and coronary artery disease patients , HIIT has demonstrated physiological benefits related to VO 2 max and VO 2 peak [ 30 ], which are indicators of improved cardiorespiratory fitness and an adequate response to cardiometabolic demands [ 23 ]. CR programmes implementing HIIT have shown greater increases in VO 2 peak % at 4 weeks compared to MICT ; however , when following up on this variable after a year , HIIT is slightly superior to MICT to the point where they can yield similar VO 2 peak % results [ 31 ]. This situation may coincide with the results of Moreno et al . [ 12 ], whose study lasted 12 weeks with a frequency of 3 sessions per week . Other studies with similar frequency , duration , and HIIT modality are those proposed by Kerrigan et al . [ 11 ], Alvarez Villela et al . [ 14 ], and Schmidt et al . [ 15 ], demonstrating changes in physiological variables , although not compared with MICT populations . Marko et al . [ 16 ] used both modalities , with a greater emphasis on MICT .
Interventions in VAD patients can be performed in both inpatient and outpatient settings , should be individualised , prescribed with a prior CPET , continuously monitored , and followed-up on patient perception [ 4 ]. As noted by Alvarez Villela et al . [ 14 ], in studies with small populations , HIIT application in VAD patients has shown positive results in improving physiological variables within a few weeks , with a frequency of 3 sessions per week [ 14 ]. Significant differences have been identified in favour of HIIT for VO 2 peak compared to MICT , but no differences have been found in 6MWT and patient perception scales [ 14 ]. Further research is necessary to establish precise indications in CR protocol designs .
Incorporating muscle strengthening exercises is considered in CR designs for VAD patients [ 4 ], with the 1RM test recommended beforehand to prescribe workloads , and the training should involve approximately 11 – 14 repetitions . Marko et al . [ 16 ] and Schmidt et al . [ 17 ] demonstrated that muscle strength training can be applied to VAD patients , increasing skeletal muscle strength . Overall , the benefits of CR can manifest in patients as adaptations to moderate to intense physical activities , providing sufficient quality to perform various daily tasks , with a perceived reduction in physical effort and dyspnoea , representing an optimal complement for VAD patients .
Only the study by Marko et al . [ 16 ] reported a single complication associated with EP , characterised by sustained