Impact of atropine injection on heart rate response during treadmill exercise echocardiography: A double-blind randomized pilot study

We evaluated the effect of atropine on the heart rate (HR) response during treadmill exercise echocardiography. A potential limitation of treadmill exercise echocardiography is the requirement for postexercise imaging. Rapid recovery of HR and wall motion abnormalities may decrease test sensitivity. A double-blind randomized study was performed at a tertiary care center. Fifty-two patients (age, 63 ± 9 years) with known or suspected coronary artery disease were injected with either 0.5 mg of atropine or saline before treadmill exercise echocardiography. HR response during and after exercise was recorded. Atropine resulted in a greater increase in HR before exercise (increase of 15 ± 9 vs 5 ± 7 beats per minute, P < 0.0001) and a higher HR rate during the first 5 minutes of exercise (P < 0.05). In recovery, there was an exponential decrease in HR in both atropine and control groups. However, at the end of image acquisition (66 ± 15 seconds), the HR was higher in the atropine group (128 ± 21 vs 115 ± 19 beats per minute, P = 0.02) and remained higher throughout the 10-minute recovery period (P = 0.0015). Dry mouth was more common after atropine injection (P = 0.005); other side effects were similar. The extent and resolution of myocardial ischemia were comparable in both groups. Atropine injection before treadmill exercise echocardiography results in a higher HR during the acquisition of echocardiographic images; whether atropine could affect the diagnostic accuracy of tread mill exercise echocardiography requires further study.