The cardiorespiratory and vascular adaptations to a routine UK exercise based cardiac rehabilitation programme

Nichols, Simon J.

Abstract

Introduction: Recent data suggests that UK cardiac rehabilitation (CR) programmes do not substantially improve cardiorespiratory fitness (CRF) or patient survival. The exercise dose prescribed as part of a routine CR programme may be insufficient. The aims of the thesis were to (i) investigate whether a routine UK CR exercise training programme could improve peak oxygen consumption (VO₂peak) and, (ii) reduce carotid intima-media thickness (CIMT) progression in patients with coronary heart disease (CHD) and, (iii) determine whether higher exercise training doses prescribed to patients with CHD through a tele-monitoring system elicit superior VO₂peak improvements compared to routine CR alone.

Study One: We recruited n=34 patients (85.3% male; age 62.1 ± 8.8 years; body mass index [BMI] 29.5 ± 4.5 Kg·m⁻²) who had recently been diagnosed with CHD. n=22 patients formed an exercise training group (TG) and undertook an eight week (16 session) low to moderate intensity (40-70% peak heart rate reserve), routine CR exercise training programme. n=12 patients declined routine CR and were assigned to a non- exercise control group (CG). Patients in the training group were followed up after completing their exercise training programme. Controls were followed up approximately 8 to 10 weeks after their initial visit (visit 2). Both groups were followed up 12 months later. VO₂peak change was determined in all patients via “gold standard” maximal cardiopulmonary exercise testing (CPET) using the modified Bruce treadmill protocol. C-IMT progression was also determined using B-mode ultrasound.

In the UK, submaximal exercise tests such as cycle ergometry are typically used to assess CRF change following CR. Submaximal cycle ergometry (intensities up to 70% heart rate reserve) was used to estimate changes in CRF. Submaximal cycle ergometry showed a mean improvement of 1.64 METs (95% CI 1.20 to 2.09 METs; p<0.001). However, “gold standard” maximal CPET showed that this equated to no significant change in VO₂peak (Δ change: 0.12 ml·kg⁻¹·min-1; 95% CI -1.00 to 1.24 ml·kg⁻¹·min⁻¹). No VO₂peak improvement was detected in controls (Δ change: 0.15ml·kg⁻¹·min⁻¹; 95% CI -1.37 to 1.66 ml·kg⁻¹·min⁻¹; p=0.978). VO₂peak remained unchanged after 12 months amongst patients in the TG (Δ -0.94 ml·kg⁻¹·min⁻¹; range -6.09 to 2.10 ml·kg⁻¹·min⁻¹; p=0.846). Controls experienced C-IMT progression in the right lateral aspect of their common carotid artery (CCA) at the end of the eight week CR period (Δ change: 0.070 mm; range -0.060 to 0.200 mm; p=0.038). Patients in the TG experienced C-IMT reduction in the left lateral aspect of their CCA between CR programme completion and their 12 month follow-up (Δ change: 0.054 mm; range -0.160 to 0.020 mm; p=0.015).

Study Two: We recruited n=50 healthy volunteers (60% male; age 26.2 ± 5.0 years; BMI 24.6 kg·m⁻² ) to examine the intra and inter-operator variability of automated c-IMT measurements when taken by novice operators. Two novice operators performed serial bilateral C-IMT ultrasound measurements using the CardioHealth Station (Panasonic Biomedical Sales Europe BV, Leicestershire, UK). Immediate inter-operator variability was determined by comparing operators’ initial measurements. Immediate retest variability was determined by comparing consecutive measurements (<10 minutes apart). Longer-term variability was determined by comparing operators’ initial measurements to a third set of measurements conducted one week later. Bland-Altman analysis and intraclass correlations were conducted. The limits of agreement (LoA) for immediate inter-operator variability were -0.063 to 0.056 mm (mean bias -0.003 mm). Operator 1’s immediate retest intra-operator LoA were -0.057 to 0.046 mm (mean bias was -0.005 mm). Operator 1’s intra-operator LoA at one week were -0.057 to 0.050 mm (mean bias -0.003 mm). Operator 2’s LoA were similar to those of operator 1. Novice operators produce acceptable short-term and one week inter- and intra-operator C-IMT measurement variability in healthy, young to middle aged adults using the Panasonic CardioHealth Station.

Study Three: We recruited n=27 patients with a diagnosis of CHD (88.9% male; age 59.5 ± 10.0 years; BMI 29.6 ± 3.8 kg·m⁻²). VO₂peak change was quantified in n=10 patients receiving routine CR plus personalised exercise training based on maximal CPET data delivered via a bespoke tele-monitoring device. VO₂peak change was also determined in n=17 patients receiving routine CR only. CPET was performed using a 25W stepped cycle ergometry protocol. The combination of routine CR and a bespoke exercise training programme significantly increase VO₂peak (Δ change: 2.08 ml·kg⁻¹·min⁻¹; 95% CI 1.88 to 3.97 ml·kg⁻¹·min⁻¹; p=0.014) compared to routine CR alone (Δ change: -0.29 ml·kg⁻¹·min⁻¹; 95% CI -1.75 to 1.16 ml·kg⁻¹·min⁻¹; p=0.841).

Conclusions: An eight week (16 session) low to moderate intensity (40-70% peak heart rate reserve) CR exercise training programme, typical of many programmes in the UK, does not improve direct measurements of VO₂peak on treadmill or cycle ergometer protocols. Current assessment methods utilising submaximal exercise testing may be overstating the effect of CR exercise interventions on CRF. Current UK recommendations for exercise training doses may also be inadequate. Data within study three indicates that a minimum of 13 sessions over a 12 week period may be required to improve VO₂peak. Limited evidence indicates that routine CR with structured exercise training may attenuate C-IMT progression compared with usual care control participants. This anti-atherosclerotic effect may be related to lower coronary risk factors and better adherence to other secondary prevention measures. Overall, higher exercise training doses and personalised exercise prescription derived from maximal CPET data appeared necessary for attaining significant CRF improvements in patients with CHD.

Citation

Nichols, S. J. (2015). The cardiorespiratory and vascular adaptations to a routine UK exercise based cardiac rehabilitation programme. (Thesis). University of Hull. Retrieved from https://hull-repository.worktribe.com/output/4218451

• Thesis Type: Thesis
• Deposit Date: Aug 23, 2016
• Publicly Available Date: Feb 23, 2023
• Keywords: Sports sciences
• Public URL: https://hull-repository.worktribe.com/output/4218451
• Additional Information: Department of Sport, Health and Exercise Science, The University of Hull
• Award Date: Dec 1, 2015