Radioisotopic assessment of peripheral and cardiac muscle involvement and dysfunction in polymyositis/dermatomyositis.

99mTc-pyrophosphate musculoskeletal imaging and 99mTc-red blood cell gated blood pool imaging were performed on 10 patients with documented polymyositis/dermatomyositis. Abnormal 99mTc-pyrophosphate uptake by peripheral muscles was found in 8 patients (6 mild, 2 marked). Cardiac uptake occurred in 5 patients and was 3+ in 2 with cardiovascular symptoms. These 2 patients also had abnormal EF on gated blood pool imaging. Patients without myocardial 99mTc-pyrophosphate uptake had normal EF. Patients with myocardial 99mTc-pyrophosphate uptake had abnormal wall motion, in proportion to the degree of uptake. Response to therapy and outcome were poorer in patients with marked scintigraphic changes. These findings suggest that the magnitude of 99mTc-pyrophosphate myocardial uptake may have prognostic implications in these patients.