Abstract 12063: Characteristics and Outcomes of Patients Who Achieve High Workload (≥10 Metabolic Equivalents) at the Time of Treadmill Exercise Echocardiography

Abstract

Background: The functional capacity of patients referred for cardiac stress testing is of prognostic importance. Patients who achieve a high exercise workload (≥10 metabolic equivalents (METs)) tend to have a favorable prognosis. The diagnostic and prognostic utility of stress echocardiographic imaging for such patients is unclear.

Methods: We evaluated the clinical and exercise echocardiographic characteristics and outcomes of 7,236 patients who exercised ≥9 minutes on the Bruce protocol. End-points were all-cause and cardiovascular mortality. Variables associated with mortality were identified.

Results: Exercise echocardiograms were positive for ischemia 12% of the time. Extensive ischemia developed in 4% of patients. For patients with normal exercise echocardiograms, all-cause and cardiovascular mortality rates were 0.30% and 0.05% per-person year of follow-up, respectively. Patients with a fixed abnormality had a slightly worse prognosis than those who developed ischemia (Figure). For patients who developed extensive ischemia, all-cause and cardiovascular mortality rates were 0.84% and 0.25% per-person year of follow-up, respectively. The highest risk patients were those with extensive and severe resting wall motion abnormalities (n=58), whose all-cause and cardiovascular mortality rates were 2.65% and 0.76% per person-year of follow-up, respectively. Exercise echocardiographic variables did not identify sizable patient subgroups at risk of death and did not provide incremental prognostic information (c-statistic 0.74 versus 0.73 for the clinical plus exercise electrocardiogram model).

Conclusions: Patients who achieve ≥10 METs during exercise testing do not often develop extensive ischemic echocardiographic abnormalities. Although exercise echocardiographic findings provide some prognostic information, this is not of incremental value for these patients, who overall have an excellent short- and medium-term prognosis.