The incremental shuttle walk test (ISWT) is a valid, reliable submaximal exercise test used in the assessment of patients prior to cardiac rehabilitation (CR). Simultaneous electrocardiogram (ECG) measurements would provide important information on the safety of the test, and adequacy of subsequent cardiac risk stratification. Risk stratification is recommended to assess patients’ suitability for cardiac rehabilitation. For example, ST-segment depression >2 mm from baseline during testing would place a person in a high-risk category. However, such ECG measurements are rarely undertaken in clinical practice. The aim of the study was to investigate the incidence of ECG changes during an ISWT, and report on the possible impact of these findings on subsequent cardiac risk stratification.
A retrospective case note review was undertaken for the year 2017. Baseline clinical characteristics from eligible patients were gathered including those with ischaemic heart disease, heart failure, transplant and valve replacement, along with ECG measurements during the ISWT. The impact of ECG findings on cardiac risk stratification was calculated, based on risk stratification developed by the American Association of Cardiovascular and Pulmonary Rehabilitation. The safety of the ISWT was measured by the absence of major ECG changes.
Data were gathered for 295 patients. Minor ECG changes were identified during the ISWT in 189 patients (64.1%), with no major changes. The presence of silent myocardial ischaemia (ST-segment depression) had an impact on cardiac risk stratification in 27 patients. There was a statistically significant positive association between ST-segment depression with cardiac risk stratification (p<0.001).
In conclusion, the ISWT is safe in terms of ECG changes. The impact of ECG findings on cardiac risk stratification is significant and worthy of further consideration.
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