Is the 10 m incremental shuttle walk test a useful test of exercise capacity for patients referred to cardiac rehabilitation?

BACKGROUND: Field exercise tests are a feasible alternative to the symptom-limited exercise test for measuring exercise capacity in patients attending cardiac rehabilitation. AIMS: To evaluate the criterion validity of the 10 m incremental shuttle walk test (ISWT) as a useful tool for measurement of exercise capacity for patients eligible for cardiac rehabilitation. METHODS: Fifteen patients eligible for cardiac rehabilitation completed a treadmill symptom-limited exercise test and two ISWTs with the order of testing randomised. Associations between the symptom-limited exercise test and the ISWT were explored and the ability of the ISWT to predict symptom-limited exercise test duration estimated. RESULTS: There was a moderate to high association ( r2 ⩾0.72) between ISWT duration and distance, and symptom-limited exercise test duration; and a moderate association between ISWT peak heart rate and end of test oxygen saturation and these outcomes on the symptom-limited exercise test (0.47⩽ r2 ⩽0.67). However, prediction of symptom-limited exercise test duration based on the ISWT produced wide 95% confidence intervals, for example, ranging from 9.1 to 16.3 minutes for an individual who completes the ISWT. Order of testing did not affect the results and the association between the ISWT and symptom-limited exercise test was similar for both the first (ISWT 1) and second test (ISWT 2) ISWT. CONCLUSIONS: The results provide support for the ISWT as a convenient field test of exercise capacity in a cardiac rehabilitation population, but not as a surrogate to predict symptom-limited exercise test duration for individuals. A single ISWT may provide as good an estimate of exercise capacity as repeating the test.

Prognostic Values of Symptom-Limited Exercise Test Early after Acute Myocardial Infarction

BACKGROUND: Uncomplicated myocardial infarction is often the harbinger of future cardiac events such as unstable angina, recurrent myocardial infarction or death. The prognostic utility of exercise test(pre-discharge low level exercise test) in patients recovering from acute myocardial infarction(AMI) has been documented by many studies. However there are few data of the safety and value of a symptom-limited exercise test early after AMI. We performed this study to assess the safety of test and the prevalence of abnormal response to symptom-limited exercise test and to determine the ability to predict future cardiac events. METHODS: The study group comprised 91 patients(male ; 73, Anterior infarction ; 43, Q-wave infarction ; 68, Thrombolysis ; 58, Age ; 57+/- years) with uncomplicated AMI. Symptom-limited exercise tests were performed before discharge(8.7+/-0.5 days after infarction) using modified Bruce protocol. Exercise test was considered positive if there was new > or =1mm horizontal or downsloping ST segment depression at 0.08sec after J point compared with baseline. The patients were followed for the development of new cardiac events. RESULTS: 1) The mean duration of exercise test was 14.2 min(range 4.3 - 21.5)and the mean workload(Metabolic Equivalents : METs) was 6.0 METs(range 2.1 - 17.0). There were no complications during exercise test and post-recovery phase. 2) There were positive test in 31 patients(34%), ST segment elevation in 10(11%), and inadequate blood pressure(BP) response in 10 patients(11%). 3) During the follow-up period(1-50 months, mean 12.5 months), 9 patients experienced post-myocardial infarction angina and revascularization therapy, respectively, and 1 patient had cardiac death and recurrent myocardial infarction, respectively. 4) The patients with cardiac events had a significantly higher degree in stenosis of infarct-related artery(90+/-3 vs 78+/-3, p<0.05) and lower systolic BP on peak exercise(136+/-7 vs 156+/-4, p<0.05). 5) The positive exercise test was associated with cardiac events in the follow-up period but ST-segment elevation, inadequate BP response, the use of thrombolytic agents, and non-Q wave infarction did not predict future cardiac events. CONCLUSIONS: The symptom-limited exercise tests early after acute myocardial infarction appear to be safe and will identify more patients with inducible myocardial ischemia relatively. The posive test can predict cardiac events and the prognosis of patients of this group can be improved with aggressive management and careful follow-up.