[Predictive value of 99m-Tc-Sn(II) methylene diphosphonate in the study of acute myocardial infarction].

Myocardial scintigraphy with 99mTc-Sn (II)-Methylenediphosphonate (MDP) was performed in 90 patients with proven acute myocardial infarction (AMI), and in 37 subjects with acute chest pain of a different etiology, during the first five days after the onset of their illness. The procedure was 82.2% sensitive, 86.5% specific, and 83.5 accurate for the diagnosis of AMI. Based on the usual clinical, electrocardiographic and biochemical criteria, the likelihood of AMI in this population was of 70.9% before the scintigraphic test. Application of Bayes' Theorem showed an increase in the likelihood of AMI, from 70.9% to 93.7%, when myocardial scintigraphy was positive, an incremental ruling-in-gain of 22.8%. A normal scintigraphy, on the other hand, reduced the likelihood of AMI, from 70.9% to 33.4%, an incremental ruling-out gain of 37.5%. It is concluded that myocardial scintigraphy with MDP is an important clinical procedure for the study of patients with acute chest pain: a positive test tends to confirm AMI, while a normal image, although it reduces the likelihood of this disease, is not particularly helpful in ruling it out.