COMPARING A HIGH-DOSE DIPYRIDAMOLE SPECT IMAGING PROTOCOL WITH DOBUTAMINE AND EXERCISE STRESS-TESTING PROTOCOLS

Objective. To determine the safety, sensitivity, specificity, and accu racy of high-dose dipyridamole compared with treadmill and dobutamine stress imaging protocols. Background. Nuclear imaging studies using st andard dose dipyridamole provide similar results to those obtained whe n 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 em ission computed tomography (SPECT) protocols. Pharmacologic stress was performed in 85 people with the remainder under-going exercise testin g by Bruce protocol. In this study, 0.852 mg dipyridamole was used per kilogram body weight and was infused over a four-minute period. Resul ts from nuclear imaging were compared with those from coronary arterio grams. Results. The sensitivity and specificity of high-dose dipyridam ole 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 reverse d with aminophylline. The sensitivity and specificity of intravenous d obutamine was 100%, but it was used in a limited number of subjects. W hen patients were stressed by Bruce protocol the sensitivity was 92.5% and specificity was 42.8%. The differences were not attributable to i nadequate exercise duration. Conclusions. High-dose dipyridamole is sa fe and easily reversed with intravenous aminophylline. The sensitivity and specificity of dipyridamole and dobutamine stress testing were st atistically more accurate than results obtained with treadmill protoco ls when SPECT is used to image the heart. High-dose dipyridamole resul ted in greater changes in heart rate and blood pressure response than seen with standard-dose dipyridamole. Associated side effects can be e asily reversed with the administration of intravenous aminophylline wi thout significant complications. The sensitivity, specificity, and acc uracy of single photon emission computed tomography using high-dose di pyridamole are 100%, 88.9%, and 97.9%, respectively, for the overall p resence or absence of disease when compared with coronary arteriograph y. This is significantly (P <0.005) greater than that obtained by trea dmill nuclear imaging protocols, independent of imaging agent.