Comparing a high-dose dipyridamole SPECT imaging protocol with dobutamine and exercise stress testing protocols. Part II: Using high-dose dipyridamole to determine lung-to-heart ratios

Abstract

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.