Implications of Abnormal Exercise Electrocardiography With Normal Stress Echocardiography

Abstract

Importance: Patients with abnormal (positive) exercise electrocardiography, but normal stress echocardiography (+ECG/-Echo) are commonly encountered in clinical practice; however, the prognostic significance of this discordant result is unclear.

Objective: To determine whether patients with +ECG/-Echo have a higher rate of adverse clinical events and a poorer prognosis than patients with negative exercise ECG and normal stress Echo imaging (-ECG/-Echo).

Design, setting, and participants: Between January 1, 2000, and February 28, 2014, a total of 47 944 consecutive patients without known coronary artery disease who underwent exercise stress Echo at Duke University Medical Center were evaluated for inclusion in this observational cohort study. Data analysis was conducted from January 1, 2000, to December 31, 2016.

Interventions/exposures: Patients were categorized as having -ECG/-Echo, +ECG/-Echo, or +Echo (-ECG/+Echo and +ECG/+Echo).

Main outcomes and measures: The primary outcome was a composite end point of death, myocardial infarction, hospitalization for unstable angina, and coronary revascularization. Secondary outcomes included individual adverse events and downstream testing.

Results: After excluding submaximal tests and nondiagnostic ECG or stress imaging results, 15 077 patients (mean [SD] age, 52 [13] years; 6228 [41.3%] men) were classified by stress test results. Of these, 12 893 patients (85.5%) had -ECG/-Echo, 1286 patients (8.5%) had +ECG/-Echo, and 898 patients (6.0%) had +Echo. Through a median follow-up of 7.3 (interquartile range, 4.4-10.0) years, the composite end point occurred in 794 patients with -ECG/-Echo (8.5%), 142 patients with +ECG/-Echo (14.6%), and 297 patients with +Echo (37.4%). Death occurred in 425 patients with -ECG/-Echo (4.8%), 50 patients with +ECG/-Echo (5.9%), and 70 patients with +Echo (11.2%). Myocardial infarction occurred in 195 patients with -ECG/-Echo (2.2%), 31 patients with +ECG/-Echo (3.6%), and 59 patients with +Echo (8.7%). The addition of stress ECG findings to clinical and exercise data yielded incremental prognostic value. Patients with -ECG/-Echo imaging results had the least downstream testing (2.3%), followed by +ECG/-Echo (12.8%), and +Echo (33.6%) (P < .001).

Conclusions and relevance: The presence of +ECG results with normal stress Echo imaging may identify a population of patients who are at slightly increased risk for adverse cardiac events, which was not previously recognized. Further study is needed to determine whether these patients will benefit from intensification of medical management.

Figure 1.. Study Flow Diagram

ECG indicates electrocardiogram; Echo, echocardiogram.

Figure 2.. Cumulative Incidence of the Primary Composite End Point: Death, Myocardial Infarction, Hospitalization for Unstable Angina, and Coronary Revascularization

Cumulative incidence classified according to exercise electrocardiogram (ECG) and stress echocardiogram (Echo) results. Comparisons were significant at P < .001 using negative ECG and Echo (−ECG/−Echo) as the reference.

Figure 3.. Cumulative Incidence of Individual Major Adverse Cardiac Events

Cumulative incidence of individual end points for patients with negative electrocardiogram/negative echocardiogram (−ECG/−Echo) and positive ECG/negative Echo (+ECG/−Echo). Incidence of myocardial infarction, unstable angina, and coronary revascularization was significantly greater among patients with +ECG/−Echo.