Cardiac rehabilitation: A potential pathway for patients with peripheral artery disease

Krist Feka

doi:10.25907/01071

Peripheral artery disease (PAD) is an atherosclerotic condition characterised by stenosis or occlusion of the arteries in the lower limbs. Worldwide, PAD affects over 230 million adults, and its prevalence is projected to increase to 360 million by 2050. Peripheral artery disease is associated with walking impairment and reduced physical activity levels, which contribute to the already elevated cardiovascular mortality and morbidity. Supervised exercise is an effective therapy that is associated with improvements in walking capacity, physical activity levels, and cardiovascular disease risk factors in patients with PAD. Emerging evidence also suggests that supervised exercise therapy following lower limb revascularisation as a combined therapy approach can enhance clinical outcomes compared with revascularisation alone. However, access to dedicated exercise programs is very limited, and less than half of the vascular units worldwide have access to exercise services for the referral of patients with PAD. Cardiovascular rehabilitation (CR) programs are widely accessible worldwide (>5,700 programs) and have the potential to facilitate access to exercise therapy for patients with PAD. The overall aim of this PhD thesis was to facilitate the integration of people undergoing lower limb revascularisation for PAD into CR programs. Firstly, a scoping review was conducted to identify the characteristics, level of evidence, and quality of studies that have integrated patients with PAD into CR programs (Study One). Secondly, a randomised-controlled trial was undertaken which aimed to provide new knowledge and test the efficacy of a community-based CR program, compared with usual care, on walking capacity and quality of life following lower limb revascularisation for PAD (Study Two). Finally, a nationwide survey of Australian CR programs was undertaken which aimed to identify the proportion and characteristics of CR programs that accept PAD referrals, and perceived barriers and facilitators to the inclusion of patients with PAD (Study Three). In Study One, a comprehensive scoping review revealed a total of 21 studies that have integrated patients with PAD into CR programs. The majority of the studies were limited to single-arm or observational designs, and there were only two randomised-controlled trials. Most participants (N=2,784/4,095, 68%) were included in CR due to cardiac disease with a comorbidity of PAD. Only five studies fully adhered to current PAD exercise recommendations. While there were limited high-quality data, CR was associated with improvements in walking capacity and long-term mortality and morbidity rates. However, there were limited PAD-specific assessments and inconsistent outcome measures. There is a need for high-quality trials (randomised-controlled trials) to determine whether CR can serve as a viable option to facilitate access to exercise therapy for people undergoing lower limb revascularisation for PAD. In Study Two (randomised-controlled trial), 56 participants who had recently undergone (< 12 months from enrolment) lower limb revascularisation for PAD were randomised to either a 6-week community-based CR program or usual care. Cardiovascular rehabilitation resulted in significant improvements in maximum (marginal mean difference [MMD]: 22.4 m, 95% CI: 6.2 – 38.6 m, P = 0.008), and pain-free walking distance (MMD: 55.6 m, 95% CI: 8.7 – 102.6 m, P = 0.021) during the 6-minute walk test compared with usual care. Cardiovascular rehabilitation also improved maximum walking time (MMD: 289.5 s, 95% CI: 194.9 – 384.1 s, P < 0.001) during a graded treadmill walking test; but not pain-free walking time (P = 0.311). Compared with usual care, CR improved self-reported walking distance score (MMD: 13.9 %, 95% CI: -0.3 – 28.2 %, P = 0.055), stair-climbing score (MMD: 12.5 %, 95% CI: -0.9 – 25.9 %, P = 0.066), and brachial artery flow-mediated dilation (MMD: 1.3 %, 95% CI: -0.003 – 2.548 %, P = 0.051), although these differences were not statistically significant. Cardiovascular rehabilitation did not improve quality of life (intermittent claudication questionnaire score), cardiorespiratory fitness (peak oxygen uptake), physical activity levels (accelerometer-derived and self-reported), arterial stiffness (augmentation index, pulse wave velocity), or ankle-brachial index when compared to usual care. In Study Three (nationwide survey), a total of 438 Australian CR programs were identified and invited to participate. One-hundred and nine programs responded to the survey and 97 completed all questions. Most programs in Australia (N=65/109, 60%) accept PAD referrals. However, across all programs PAD referrals accounted for only 1.8% (N=493/27,776) of all referrals in the previous year. Across programs that accept patients with PAD, referrals due to PAD were also low and accounted for 2.4% (N= 336/14,284) of all referrals. The main barriers to the inclusion of patients with PAD in CR were lack of referrals (59%), lack of capacity (48%), and lack of staff (48%). The main facilitators included listing PAD as an inclusion criterion (73%), additional funding (71%), and education of CR staff on PAD care (68%). In summary, this PhD thesis highlights a missed opportunity for the integration of people with PAD into CR programs to facilitate access to exercise therapy following lower limb revascularisation. This thesis identified a lack of high-quality studies assessing the efficacy of CR following lower limb revascularisation for PAD. The second study of this thesis addresses this limitation by providing high-quality data on the efficacy of post-revascularisation CR, and reports that CR is effective in improving walking capacity compared with revascularisation alone. Lastly, the third study of this thesis reports that most CR programs accept patients with PAD; however, referral rates are very low. There is a clear need for stronger collaborations between CR programs and referral sources to establish a direct referral pathway to CR for patients with PAD.

Cardiac rehabilitation: A potential pathway for patients with peripheral artery disease

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