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Statistical methods to improve the precision of the treadmill exercise test

Ralph A. H. Stewart, MD, FRACP^*, John Kittelson, PhD and I. Patrick Kay, FRACP^*

^* Department of Medicine, University of Otago, Dunedin, New Zealand
Department of Social and Preventive Medicine, University of Otago, Dunedin, New Zealand

View larger version (15K): [in a new window]   Figure 1 Data from a typical exercise test. (A) ST depression over time for all 12 ECG leads. (B) Lead with most ST depression and associated linear regression line used to estimate rate of increase in ST depression. ST depression was 1 mm at 5 min, but was not maintained for two consecutive measurements until 7.5 min.

View larger version (21K): [in a new window]   Figure 2 Sample size requirements are displayed when an average from one to six leads are used to measure ST segment depression during exercise. Results are presented for the rate of increase of ST depression (dashed line), ST depression at peak exercise (dotted line), and ST depression at equivalent sub-maximal exercise (solid lines). The influence of using only the longest equivalent sub-maximal exercise (one time point) and of averaging ST depression recorded from earlier 30-s ECGs is displayed for one to six time points.