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. 2007 Jan;12(1):59-63.
doi: 10.1111/j.1542-474X.2007.00139.x.

Significance of lead strength during exercise testing

George Polizos  1 , Myrvin H Ellestad
Affiliations

Significance of lead strength during exercise testing

George Polizos et al. Ann Noninvasive Electrocardiol. 2007 Jan.

Abstract

Background: The aim of the study was to evaluate the contribution of relative lead strengths to exercise-induced ECG changes (ST depression) to predict the degree of myocardial ischemia as compared to the angiograms. This was accomplished by comparing the magnitude of ST depression to the ST/R ratio. Studies have shown that the diagnostic strength of a lead is directly related to the R wave amplitude and that sensitivity is significantly improved.

Methods: Three hundred patients, who underwent treadmill exercise testing and coronary angiography revealing significant coronary narrowing (> or = 70% luminal diameter narrowing), were studied, along with 150 patients clear of significant coronary artery disease (<70% luminar diameter narrowing). Our goal was to determine the correlation between the relative lead strengths, using a constructed ST/R ratio, to exercise induced ECG changes (ST depression) to predict the presence of myocardial ischemia as compared to angiographic findings. Using a cutoff of 0.1 for the ST/R ratio, our data were compared to the sensitivity and specificity of 1.0 mm ST depression.

Results: Overall sensitivity was improved for the ST/R ratio (84% vs 78%), while specificity was slightly decreased (81% vs 92%) in comparison to standard ST depression. When differentiating between R wave amplitudes, those with R wave < or = 10 mm showed significantly improved sensitivity (88% vs 54%) and a minor decrease in specificity (90% vs 92%). In those with R wave > or = 20 mm, the sensitivity of ST depression was higher (88% vs 71%) but the ST/R ratio was much more specific (88% vs 46%). No significant difference was observed when differentiating between male and female patients.

Conclusion: We found that the correction of ST depression for R wave amplitude results in improved sensitivity in patients with low R waves and specificity in patients with very tall R waves (R > or = 20 mm).

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Figures

Figure 1
Figure 1
Leads used for measurement.
Figure 2
Figure 2
Sensitivity and Specificity according to R wave amplitude.
See this image and copyright information in PMC

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