Abstract 2599: The Diagnostic Accuracy of the Exercise Electrocardiogram Based on Heart Size
Introduction: Multiple studies have shown that the exercise ECG is less accurate in women, primarily due to the high prevalence of false-positive tests. No definitive explanation for the lowered specificity has been established conclusively. However, there is evidence to suggest that the heart size can affect diagnostic accuracy of stress nuclear testing.
Objective: The purpose of this study is to assess the diagnostic accuracy of the exercise ECG based on heart size.
Methods: We evaluated 2,142 (1,219 women, 923 men) consecutive patients who were referred to nuclear stress testing at New York Methodist Hospital. Patients were divided into two groups: small heart size defined as end diastolic volume (EDV) <65 mL (Group A) and normal heart size defined as EDV >65 mL (Group B). Patients with pathological Q waves, LBBB, LVH, or WPW were excluded. The diagnostic accuracy of the exercise ECG was determined by using SPECT myocardial perfusion imaging as the gold standard.
Results: There were 384 patients (338 women, 46 men) who met criteria for a small heart. There was no significant differences between Group A and B in medication use, symptomatology or risk factors. The exercise ECG had a significantly higher false positive rate in Group A (specificity-69%, PPV-34%) as compared to Group B (specificity-82%, PPV-58%); p <0.001. There was no difference in sensitivity or NPV (Group A: 55%, 84%; Group B: 61%, 84%, respectively).
Conclusion: The exercise ECG has a higher false positive rate in patients with small heart size. The overwhelming majority of patients with small heart size are women. This study suggests a possible explanation for the poor diagnostic accuracy of stress testing in women.