Adding objectivity to submaximal exercise testing by assessment of heart rate recovery – A healthy volunteer study (search)

Abstract

Introduction Pre-operative exercise testing is widely used to assess perioperative risk. ‘Maximal’ tests, such as Cardiopulmonary Exercise Testing, are not always well tolerated. To overcome this sub-maximal exercise tests (SET) are increasingly being utilised. Though potentially better tolerated, results may be dependent on patient motivation and effort. Measuring heart rate recovery (HRR) after SETs could potentially add objectivity. Quantifying HRR by calculating the difference between HR on exercise cessation and at one/two minutes into the recovery period (HRR1/HRR2) has been widely described(1). This study sought to assess the influence of SET effort level on the reproducibility of HRR and evaluate the reproducibility of novel methods for quantifying HRR. Methods Thirty-four healthy volunteers underwent three, six-minute SETs on a cycle ergometer. Individuals on beta-blockers or with contraindications to exercise testing were excluded. The first test was used to familiarise the volunteer with the test protocol and was undertaken at 20% of predicted maximum wattage (Wmax). The following two tests were delivered in a randomised order at 40% or 60% Wmax. Data on HRR was collected for 5-minutes on test cessation. Area under the (HR vs time) curve (AUC) and an effort corrected version of AUC (EC-AUC) were derived as novel indices of HRR. To ascertain the reproducibility of HRR indices, the intra-class correlation coefficient (ICC) and paired t-tests were estimated. Eight volunteers returned for a second day of exercise testing to determine the test-retest reliability. Results The median age of the study population was 39 (range; 22-72) with 15% of the population possessing chronic co-morbidities. The ICC for HRR1 was 0.15 (95%CI; 0-0.43). For HRR2 the ICC was 0.35 (0-0.68). The novel AUC method achieved an ICC of 0.61 (0.27-0.8). EC-AUC achieved an ICC of 0.46 (0.14-0.69). The test-retest reliability of HRR1 at 40% and 60% Wmax was 0.16 (0-0.79) and 0 (0-0.74) respectively. For HRR2 the test-retest reliability at 40% and 60% Wmax was 0 (0-0.7) and 0.2 (0-0.83). For AUC the test-retest reliability at 40% and 60% was 0.79 (0.26-0.95) and 0.55 (0-0.9). The test-retest reliability of EC-AUC at 40% and 60% was 0.65 (0.02-0.92) and 0.44 (0-0.87). Discussion HRR1/HRR2 demonstrated poor reproducibility across differing effort levels, suggesting they are influenced by level of exertion. The AUC methods displayed moderate reproducibility across and between the differing effort levels and may therefore be a superior way to quantify HRR post SET.