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 imaging agent.
Determination of the severity of coronary artery disease (CAD) by single photon emission computed tomography (SPECT) imaging has previously been shown to have greater sensitivity, specificity, and accuracy when performed with pharmacologic stress using dobutamine than by standard dose dipyridamole (SDD) or exercise stress testing (EST) prior to SPECT imaging. The use of lung to heart (L:H) ratios has been shown to be valuable in determining the presence or absence of left main (LM) or triple vessel (3V) CAD. No such work has been previously reported for dobutamine. Twenty-one patients were studied using dobutamine (n = 7) or EST (n = 14). These results were compared with results from Part II of this series of studies using high-dose dipyridamole (HDD) pharmacologic stress. In this study, patients underwent L:H ratio analysis following injection of 3 mCi of Tl-201, this provides sufficient time for thallium clearance from the blood pool. Results of the L:H ratios were compared with the results of coronary arteriographic (CA) evaluation. Patients who were "stressed" via EST demonstrated statistically greater (p = 0.001) L:H ratios in patients with LM/3V CAD when compared with patients who had 0-2 significantly stenosed coronary arteries. Patients stressed with dobutamine demonstrated lower L:H ratios (p = NS) in patients with LM/3V CAD than was seen for patients with 0-2 V CAD. Patients stressed with dobutamine had statistically (p = 0.05) lower L:H ratios than did similar patients stressed with EST. Increased L:H ratios following EST and HDD, as shown previously in Part II of this series, provide excellent markers for LM/3V CAD following Tl-201 injection. The presence of "normal" L:H ratios in patients with LM/3V CAD following dobutamine stress may suggest the presence of "stunned" or "hibernating" myocardium. The presence of "decreased" L:H ratios following dobutamine after HDD or EST has already shown an increased L:H ratio, might suggest a marker for myocardial viability that deserves further investigation.
Determination of the severity of coronary artery disease (CAD) by single photon emission computed tomography (SPECT) imaging has previously been shown to have greater sensitivity, specificity, and accuracy when performed with pharmacologic stress using high-dose dipyridamole (HDD), than by standard dose dipyridamole (SDD) or exercise stress (EST) prior to SPECT imaging. The use of lung-to-heart (L:H) ratios has been shown to be valuable in determining the presence or absence of left main (LM) or triple vessel (3V) CAD. Fifty-four patients were studied; HDD (n = 40) or EST (n = 14) was used for the study. These patients underwent L:H ratio analysis, in which anterior views were used 5-10 minutes after the injection of 3 mCi of T1-201. Results of the L:H ratios were compared with the diagnosis of epicardial CAD, as determined by coronary (CA) arteriography. Patients who were "stressed" using either HDD or EST demonstrated statistically greater (p < 0.001) L:H ratios if they had LM/3V CAD when compared with patients who had 0-2 significantly stenosed coronary arteries. Though L:H ratios were greater when HDD pharmacologic stress was used, there was no statistical (p = NS) differences between the two groups. Increased L:H ratios with HDD and EST provide excellent markers for LM/3V CAD using T1-201 imaging. Coupled with previously reported SPECT data, the use of HDD shows promise for increasing the diagnostic accuracy of SPECT imaging.
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