The Selection of Cardiopulmonary Exercise Testing Protocols for Patients with Coronary Artery Disease

Abstract

Coronary artery disease (CAD) is the most common type of cardiovascular disease (CVD). Cardiorespiratory fitness (CRF), which can be measured using cardiopulmonary exercise testing (CPET), is a strong independent predictor of mortality. Maximal and submaximal exercise tests are commonly used to assess the CRF of patients in cardiovascular rehabilitation (CR) programs. Maximal exercise tests are performed until volitional exhaustion, whereas submaximal exercise tests are usually terminated at 85% of age-predicted maximal heart rate (HR). Over the past 75 years, several protocols have been developed for measuring CRF. However, most of these were created and validated in predominantly male populations (males = 85.7%, females = 14.3%). Due to anatomical and physiological differences between males and females, it should not be assumed that the most optimal maximal and submaximal exercise testing protocols would be the same for females and males. The overall aim of my thesis was to investigate the exercise testing practices in CR programs across Canada and the optimal maximal and submaximal exercise testing protocols for assessing peak V ̇ O2 in females and males with CAD. Study 1, TRADE, was an observational pan-Canadian survey to determine (i) which maximal and submaximal exercise testing protocols are most frequently used in CR programs across Canada; (ii) how many maximal and submaximal protocols are used at each CR centre; (iii) how many maximal and submaximal tests are completed per year; (iv) the number of times each maximal and submaximal protocol is used per year; (v) which healthcare professional is most often selecting the exercise testing protocol; and (vi) the decision making process and criteria used for selecting an exercise testing protocol. The TRADE survey was completed by 118 CR programs (30.4% of programs in Canada). Of the 85 centres (72.6%) which perform exercise testing, 13 (14.9%), 42 (49.4%), and 26 (29.9%) complete maximal, submaximal, and both maximal and submaximal exercise testing, respectively. The Bruce treadmill and 6-minute walk tests were the most frequently used maximal (82.1%) and submaximal (75.0%) exercise tests, respectively. It was estimated that 3,610 – 4,910 and 18,000 – 22,710 maximal and submaximal exercise tests, respectively, were performed annually across Canada. The Bruce test was used approximately 3,560 – 4,790 times per year and the 6MWT was used approximately 13,940 – 16,650 times per year. Physicians were the leading decision-makers, overseeing testing protocols in 38 of the 118 programs, and the most common criteria for selecting an exercise testing protocol included standard procedures developed by management (n = 18). Study 2, PACED, was a randomized single blind cross-over trial to determine if peak VO2 varied between different maximal and submaximal treadmill exercise testing protocols for females and males with CAD. Key secondary research questions examined: (i) how cardiometabolic responses and ratings of perceived exertion (RPE) compare between different maximal and submaximal protocols; (ii) how different increments of grade speed affect test duration for maximal and submaximal exercise tests; and (iii) the most common reason for test termination for maximal exercise tests for females and males with CAD. The study included 20 participants (7 females [age: 64 ± 7 years] and 13 males [age: 64 ± 8 years]). For females, there was a significant difference in peak VO2 across the protocols (F = 9.222, p = 0.001); however, the location of the difference in peak V ̇ O2 could not be identified, likely due to insufficient power as few females completed the modified Balke protocol. No difference in peak HR was observed across the protocols (F = 3.079, p = 0.425). Females appeared to achieve greater peak systolic BP during the modified Balke protocol (SBP: 190 ± 21 mmHg, F = 0.40, p = N/A) and higher peak blood lactate concentrations (5.2 ± 1.1 mmol/L, F = 1.395, p = N/A) using the Modified Balke protocol; yet, due to a small sample size, there was an insufficient power for this analysis. Females achieved a higher RPE using the UOHI Slow Ramp protocol (18 ± 3 points, F = 0.594, p< 0.05). For females, 67% cited speed as the primary reason for test termination for the modified Balke, 29% and 50% cited shortness of breath for the modified Bruce and UOHI Slow Ramp, respectively, and 33% cited musculoskeletal fatigue for the modified Naughton. For males, no difference in peak V ̇ O2 was observed across the protocols (F = 0.189, p = 0.75). Also, no differences in peak HR (F = 0.2023, p = 0.649), systolic BP (F = 1.015, p = 0.420), diastolic BP (F = 0.786, p = 0.524), blood lactate concentrations (F = 1.015, p = 0.409), or RPE (F = 1.701, p = 0.197) was observed across the protocols. For males, 20% cited speed as the primary reason for test termination for the modified Balke, while 28% cited muscuolskeletal fatigue for the modified Bruce, and 23% and 50% cited shortness of breath for the modifed Naughton and UOHI Slow Ramp, respectively. These thesis findings suggest that although the Bruce protocol is the most used maximal exercise testing protocol for measuring CRF in patients with CVD across Canada, the modified Naughton protocol should be used for females with CAD to achieve their highest peak VO2. These findings contribute to our understanding of how different CPET protocols can impact individual CRF and cardiometabolic responses in patients with CAD, though future studies should explore larger sample sizes to adequately (with sufficient sample sizes) capture these sex- specific responses.