Safety and efficacy of exercise testing with atropine in patients with recent uncomplicated ST elevation acute myocardial infarction

Background: Exercise testing (ET) remains the most accessible and widely used technique for the detection of coronary artery disease (CAD) and for the assessment of its severity. Failure to reach 85% of maximal predicted heart rate (MPHR) during exercise may render an ET nondiagnostic for ischemia detection in patients with recent uncomplicated ST elevation acute myocardial infarction (STEMI). We sought to investigate the injection of atropine in patients who fail to achieve 85% of age-predicted heart rate during ET, defining its safety and efficacy to raise heart rate to adequate levels as well as to determine its effect on ET interpretation. Methods: Between January 2005 and December 2008, we studied 1150 consecutive patients with recent uncomplicated STEMI (850 men and 300 women, mean age 59 ± 8 years) who were referred to a single exercise testing laboratory, prior to beginning a physical training program. In 450 patients (398 males and 52 females, mean age 61 ± 7 years) with a non-diagnostic test, the ET was repeated 1-2 days later, and during the test, 1-2 mg of atropine was administered to patients who were unable to continue because of fatigue before reaching minimal heart rate (HR), without an ischemic response. Results: mean HR before atropine injection was 129.5 ± 13.6 beats per minute (bpm), and it increased up to 147.3 ± 13.5 bpm after drug administration, with an incremental of 17.8 ± 6.9 bpm (p < 0.0001). The mean percentage of age-related HR achieved was 86.5% ± 6.1%. In 378 of these patients (84%), more than 85% of their aged-related HR ( 89.9% ± 4.1%) was attained. No major adverse effects occurred. The maximal heart rate (147.3 ± 3.5 versus 129.5 ± 13.6) and the double product (29378.7 ± 6342.7 versus 25798.3 ± 5328.5) were significantly greater after atropine (p < 0.0001, respectively). The increase in the maximal HR improved the detection of the electrocardiographic signs of exercise- induced myocardial ischemia (sensibility increased from 82.1% to 89.2%, specificity from 52.3% to 68.2%, and prognostic accuracy from 77.2% to 86.1%). Conclusion: Atropine added to ET in patients who cannot achieve their 85% age-related HR is safe and well-tolerated, and improves the prognostic accuracy in patients with recent uncomplicated STEMI. The combination with atropine increases the utility and the cost-effectiveness of ET.