Comparing a High-Dose Dipyridamole SPECT Imaging Protocol with Dobutamine and Exercise Stress Testing Protocols

Abstract

Objective. To determine the safety, sensitivity, specificity, and accuracy of high-dose dipyridamole compared with treadmill and dobutamine stress imaging protocols. Background. Nuclear imaging studies using standard dose dipyridamole provide similar results to those obtained when treadmill stress is used. Recently dobutamine tomography and planar imaging with high-dose dipyridamole have been shown to improve nuclear imaging results. Methods. One hundred fifty-nine patients were imaged with thallium, teboroxime, or sestamibi per standard single photon emission computed tomography (SPECT) protocols. Pharmacologic stress was performed in 85 people with the remainder under going exercise testing by Bruce protocol. In this study, 0.852 mg dipyridamole was used per kilogram body weight and was infused over a four-minute period. Results from nuclear imaging were compared with those from coronary arteriograms. Results. The sensitivity and specificity of high-dose dipyridamole was 100% and 88.9%, respectively, which is statistically greater (P < 0.005) than that achieved when patients were stressed by treadmill. Side effects with the higher dose of dipyridamole were easily reversed with aminophylline. The sensitivity and specificity of intravenous dobutamine was 100%, but it was used in a limited number of subjects. When patients were stressed by Bruce protocol the sensitivity was 92.5% and specificity was 42.8%. The differences were not attributable to inadequate exercise duration. Conclusions. High-dose dipyridamole is safe and easily reversed with intravenous aminophylline. The sensitivity and specificity of dipyridamole and dobutamine stress testing were statistically more accurate than results obtained with treadmill protocols when SPECT is used to image the heart. High-dose dipyridamole resulted in greater changes in heart rate and blood pressure response than seen with standard-dose dipyridamole. Associated side effects can be easily reversed with the administration of intravenous aminophylline without significant complications. The sensitivity, specificity, and accuracy of single photon emission computed tomography using high-dose dipyridamole are 100%, 88.9%, and 97.9%, respectively, for the overall presence or absence of disease when compared with coronary arteriography. This is significantly (P < 0.005) greater than that obtained by treadmill nuclear imaging protocols, independent of imaging agent.