Radionuclide imaging of experimental myocarditis.

Abstract

SUMMARY The ability of 67Ga citrate and 99mTc pyrophosphate cardiac imaging to detect myocarditis was assessed in an experimental rabbit model. Twenty-three rabbits were imaged approximately 72 hours after infusion of i.v. norepinephrine. Diffuse cardiac uptake was found in 13 of 15 rabbits scanned with 67Ga. Tissue distribution studies documented significant myocardial uptake of 67Ga in those with positive scans. Precordial imaging and tissue distribution studies revealed no cardiac uptake in the eight rabbits scanned with 9mTc. Histologic examination of all 23 hearts revealed qualitatively similar, typical lesions of myocarditis. This study suggests that cardiac imaging with 17Ga may be useful in the detection of myocarditis.MYOCARDITIS, an inflammatory condition involving the heart, can lead to sudden unexpected death or severe congestive heart failure.1'3 Yet, its accurate detection is frequently difficult." 8 The clinical manifestations are often nonspecific," 3 and conventional diagnostic tests such as the ECG, serum cardiac enzymes and chest x-ray are insensitive as well as nonspecific.", 3,4 Recently, a brief clinical report5 and two experimental studies6' 7 have suggested that radionuclide cardiac imaging can detect the presence of myocarditis. In this report, we present the results of radionuclide cardiac imaging with 99mTc pyrophosphate and 67Ga citrate in an experimental model of myocarditis. Methods and MaterialsMyocarditis was created in 23 adult New Zealand white rabbits using a modification of the technique of Downing and Lee.8 Each rabbit was anesthetized with i.v. pentobarbital (30 mg/kg) and a 25-gauge butterfly needle was secured in a marginal ear vein. Norepinephrine was infused at a rate of 3 ,tg/kg/min for 100 minutes using a Harvard constant infusion pump. Radionuclide Imaging with 67Ga CitrateMyocardial imaging was performed in 15 rabbits 70-74 hours after the norepinephrine infusion. Five normal control rabbits were also imaged. All rabbits received 1.3 mCi of 67Ga citrate through a marginal ear vein 24 hours before cardiac imaging.After i.v. pentobarbital anesthesia, the rabbits were immobilized in the supine position. A single 10°left anterior oblique image of the heart was obtained using From Upon completion of in vivo imaging, each animal was sacrificed with a lethal dose of i.v. pentobarbital. The heart was excised intact, washed free of blood and clot, and weighed. The excised hearts from 10 of the rabbits were imaged again. Twenty-five thousand counts were obtained in each image. In each rabbit, the radioactivity content of heart and thigh muscle was individually assayed in a Capintec dose calibrator. Background counts were recorded and net counts were expressed in gCi/g of tissue.Radionuclide Imaging with "mTc Pyrophosphate Cardiac scintigrams were performed on eight additional rabbits 70-74 hours after norepinephrine infusion. All rabbits received 5 mCi of 99mTc pyrophosphate via a marginal ear vein, and 2-3 hours later, a single 10°left anterior oblique image of the cardiac ...

Contribution of alpha-adrenoceptor activation to the pathogenesis of norepinephrine cardiomyopathy.

“…To provide a more consistent and reproducible model, we have used a constant time base of 90 minutes. This is sufficient to produce extensive myofiber injury (Downing and Lee, 1978) readily identified by light microscopy and also by radionuclide cardiac imaging (Reeves et al, 1981). Moreover, measurements of cardiac function have revealed significant impairment of left ventricular performance when studied with afterload curves (Werner et al, 1980) or standard VF curves .…”

Myocardial gallium-67 imaging in dilated cardiomyopathy

“…Gallium-67 imaging has been successfully applied to imaging chronic inflammation in myocardial sarcoidosis (Forman et al, 1983) and pericarditis (O'Connell et al, 1980). In the experimental animal model of isoproterenol-induced myocarditis, gallium-67 uptake proved to be a sensitive technique for identifying active inflammation (Reeves et al, 1981). Chronic inflammatory diseases associated with cell-mediated immune responses such as interstitial pneumonitis (Niden et al, 1976), noninfectious interstitial nephritis (Wood et al, 1978), dermatomyositis (Smith et al, 1979), and rheumatoid arthritis (McCall et al, 1983) can be detected with 67Ga.…”