The accuracy of the electrocardiogram during exercise stress test based on heart size.

Department of Sport, Health & Exercise Science, University of Hull, Hull, United Kingdom.
PLoS ONE (Impact Factor: 3.53). 08/2011; 6(8):e23044. DOI: 10.1371/journal.pone.0023044
Source: PubMed

ABSTRACT Multiple studies have shown that the exercise electrocardiogram (ECG) is less accurate for predicting ischemia, especially in women, and there is additional evidence to suggest that heart size may affect its diagnostic accuracy.
The purpose of this investigation was to assess the diagnostic accuracy of the exercise ECG based on heart size.
We evaluated 1,011 consecutive patients who were referred for an exercise nuclear stress test. Patients were divided into two groups: small heart size defined as left ventricular end diastolic volume (LVEDV) <65 mL (Group A) and normal heart size defined as LVEDV ≥65 mL (Group B) and associations between ECG outcome (false positive vs. no false positive) and heart size (small vs. normal) were analyzed using the Chi square test for independence, with a Yates continuity correction. LVEDV calculations were performed via a computer-processing algorithm. SPECT myocardial perfusion imaging was used as the gold standard for the presence of coronary artery disease (CAD).
Small heart size was found in 142 patients, 123 female and 19 male patients. There was a significant association between ECG outcome and heart size (χ(2) = 4.7, p = 0.03), where smaller hearts were associated with a significantly greater number of false positives.
This study suggests a possible explanation for the poor diagnostic accuracy of exercise stress testing, especially in women, as the overwhelming majority of patients with small heart size were women.

  • [Show abstract] [Hide abstract]
    ABSTRACT: Significant gender differences have been found in performance of the exercise ECG for the identification of coronary artery disease. However, identical exercise ECG ST segment criteria have been used in men and women, which might contribute to the lower accuracy of these methods in women than in men. To assess the effect of gender-specific test partitions on relative performance of standard and heart rate-adjusted ST segment depression criteria in men and women, the exercise ECGs of 143 women and 477 men were examined. Non-gender-specific test partitions, selected to have matched specificities of 96% for each test method, were determined in all 283 normal subjects, and gender-specific test partitions with identical specificity were determined separately in the 52 normal women and 231 normal men; sensitivity of these criteria was then examined in the 91 women and 246 men with coronary disease. Standard ST segment depression criteria (0.1 mV of additional horizontal or downsloping ST segment depression at end exercise) with identical 96% specificity in the entire group of normal subjects and separately in women and men had a significantly lower sensitivity of 51% in women compared with 67% in men (P < .01). Among women, performance of the ST segment/heart rate (ST/HR) slope was more improved than that of the ST/HR index by the use of gender-specific criteria. Compared with the performance of non-gender-specific criteria, application of gender-specific ST/HR slope partitions with matched specificity of 96% resulted in a significant increase in sensitivity in women from 84% to 91% (P < .01), with no significant change in sensitivity in men (89% to 88%) and with no residual difference in sensitivity between men and women. Although the use of gender-specific ST/HR slope criteria significantly improved sensitivity in both men and women with respect to standard criteria (each P < .0001), the relative increase in sensitivity provided by heart rate adjustment was significantly greater in women than in men (40% versus 21%, P < .001). Similar gender differences in improvement in performance using gender-specific criteria for the ST/HR slope were observed when analysis of test performance was restricted to the detection of three-vessel coronary disease (50% versus 9%, P = .002). At high specificity, gender-specific test partitions improve sensitivity of the ST/HR slope for the identification of coronary disease in women, with no decrease in sensitivity in men. In contrast, gender-specific partitions do not change performance of standard test criteria, which is lower in women than in men. Accordingly, the relative benefit of heart rate adjustment by the ST/HR slope method is greater in women than in men. These findings support use of the ST/HR slope with use of gender-specific partitions for the identification and quantification of coronary artery disease in both men and women.
    Circulation 09/1995; 92(5):1209-16. · 14.95 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: This study was designed to evaluate the incremental prognostic value over clinical and exercise variables of rest thallium-201/exercise technetium-99m sestamibi single-photon emission computed tomography (SPECT) in women compared with men and to determine whether this test can be used to effectively risk stratify patients of both genders. To minimize the previously described gender-related bias in the evaluation of coronary artery disease in women, there is a need to identify a noninvasive testing strategy that is able to accurately and effectively risk stratify women. We identified 4,136 consecutive patients (2,742 men, 1,394 women) who underwent dual-isotope SPECT. The incremental value of nuclear testing was determined using both a stepwise Cox proportional hazards model and Kaplan-Meier survival analysis. Receiver operating characteristic curve analysis was performed to determine test discrimination for high risk patients in men and women. The patient population was followed up for 20 +/- 5 months for events (cardiac death or nonfatal myocardial infarction). During this time, 63 myocardial infarctions and 32 cardiac deaths occurred in the men, and 31 myocardial infarctions and 14 cardiac deaths occurred in the women. Nuclear testing significantly stratified both men and women irrespective of their rest electrocardiogram. Cox proportional hazards analysis revealed that nuclear testing added incremental prognostic value in both men and women after inclusion of the most predictive clinical exercise variables (overall chi-square 89 in men vs. 120 in women, p < 0.005). Kaplan-Meier survival analysis demonstrated that nuclear testing further stratified men and women with both intermediate to high and low prescan likelihoods of coronary artery disease (p < 0.005 for all). Receiver operating characteristic curve analysis demonstrated superior discrimination for the nuclear scan results in identifying high risk women than men (area under the curve: 0.84 +/- 0.03 vs 0.71 +/- 0.03 in men, p < 0005). The odds ratio comparing event rates in patients with women than in men, suggesting superior stratification using nuclear testing in women. Dual-isotope myocardial perfusion imaging yields incremental prognostic value in both men and women. This modality identifies low risk women and men equally well but relatively high risk women more accurately than relatively high risk men and, thus, is able to stratify women more effectively than men.
    Journal of the American College of Cardiology 08/1996; 28(1):34-44. · 15.34 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: We attempted to formally compare the diagnostic accuracy of thallium-201 single-photon emission computed tomographic (SPECT) myocardial perfusion imaging in men and women and the effect of chamber size on accuracy. The diagnostic accuracy of conventional exercise testing has been shown to be lower in women. Less is known about the relative accuracy of perfusion imaging. Because of smaller body size, women have a smaller heart size than men, a factor that may reduce accuracy. We identified 323 patients undergoing thallium-201 SPECT myocardial perfusion imaging who either had < 5% probability of coronary artery disease (CAD) by Bayesian analysis or who underwent cardiac catheterization within 60 days of stress testing. Patients with documented history of infarction, coronary artery bypass grafting, pathologic Q waves on the electrocardiogram, left bundle branch block or nonischemic cardiomyopathy were not included. We performed strict quantitative analysis, and receiver operating characteristic (ROC) curves were generated and the area under the curve was calculated for men and women. A size index was generated from the number of short-axis slices and average radius of each slice, and the group was classified as having a large or a small chamber size. The ROC areas of men and women with a large and a small chamber size were then compared. Diagnostic accuracy was lower in women than in men (ROC are 0.82 vs. 0.93, p < 0.05) despite similar values for peak heart rate and rate-pressure product and similar severity of CAD. There was a greater difference in accuracy between patients with a large versus a small chamber size (ROC area 0.94 vs. 0.73, p < 0.01) despite similar levels of exercise and severity of CAD. When we compared men and women in groups stratified by chamber size, we could not detect a significant difference between ROC area values of men and women (large: 0.94 men, 0.93 women, p = 0.77, power to detect difference in area of 0.15 = 91%; small: 0.79 men, 0.72 women, p = 0.58, power to detect difference in area of 0.15 = 35%). The diagnostic accuracy of thallium SPECT myocardial perfusion imaging is lower in women than in men. Most of the difference appears to be due to smaller left ventricular chamber size in women, although a small residual gender effect in smaller heart sizes cannot be entirely excluded. It is proposed that the most likely cause for this difference is the relatively greater effect of imaging blurring on smaller hearts.
    Journal of the American College of Cardiology 12/1996; 28(5):1214-9. · 15.34 Impact Factor

Full-text (2 Sources)

Available from
May 29, 2014