Exercise performance-based outcomes of medically treated patients with coronary artery disease and profound ST segment depression
Reference: Journal of the American College of Cardiology 2000; 36: 2140-45, http://content.onlinejacc.org/cgi/content/abstract/36/7/2140
Authors: CA Thompson, S Jabbour, RJ Goldberg, RYS McClean, BZ Bilchik, CM Blatt, S Ravid, TB Graboys
The following study was conducted by researchers at the Lown Cardiovascular Research Foundation.
Objectives: We sought to determine the relationship between exercise duration and cardiovascular outcomes in patients with profound (2 mm) ST segment depression during exercise treadmill testing (ETT).
Background: Patients with stable symptoms but profound ST segment depression during ETT are often referred for a coronary intervention on the basis that presumed severe coronary artery disease (CAD) will lead to unfavorable cardiovascular outcomes, irrespective of symptomatic and functional status. We hypothesized that good exercise tolerance in such patients treated medically is associated with favorable long-term outcomes.
Methods: We prospectively followed 203 consecutive patients (181 men; mean age 73 years) with known stable CAD and 2 mm ST segment depression who are performing ETT according to the Bruce protocol for an average of 41 months. The primary end point was occurrence of myocardial infarction (MI) or death.
Results: Eight (20%) of 40 patients with an initial ETT exercise duration 6 min developed MI or died, as compared with five (6%) of 84 patients who exercised between 6 and 9 min and three (3.8%) of 79 patients who exercised 9 min (p = 0.01). Compared with patients who exercised 6 min, increased ETT duration was significantly associated with a reduced risk of MI/death (6 to 9 min: relative risk [RR] = 0.25, 95% confidence interval [CI] 0.08 to 0.76; >9 min: RR = 0.14, 95% CI 0.04 to 0.53). This protective effect persisted after adjustment for potentially confounding variables. We observed a 23% reduction in MI/death for each additional minute of exercise the patient was able to complete during the index ETT.
Conclusions: Optimal medical management in stable patients with CAD with profound exercise-induced ST segment depression but good ETT duration is an appropriate alternative to coronary revascularization and is associated with low rates of MI and death.