Factors related to vascular dynamics, such as vanishing platelet thrombi, are likely to play an important role in the genesis of myocardial ischemia and infarction, events rarely found in individuals with ET 2,3 . In this study, a case of anterior acute myocardial infarction (AMI) diagnosed in a patient with known ET is reported. The patient received thrombolytic therapy, followed by successful rescue coronary angioplasty (RCA). Case ReportA 48-year-old white male patient arrived at the Emergency Department (ED) of the Instituto do Coração (INCOR) complaining of chest pain consistent with coronary artery disease, which had started 3h before arrival at the ED. At the time of hospital admission, the physical examination showed no abnormal findings, with the exception of high blood pressure (180/120mmHg). The electrocardiogram showed an elevation of the ST segment in leads D 1 , aVL, and from V 1 to V 6 , consistent with extensive anterior AMI. Intravenous streptokinase was started with a 3h delay (representing the time interval between the development of the symptoms and the beginning of the infusion). There were no clinical criteria for myocardial reperfusion and the patient was classified as group II of the Killip-Kimball heart failure classification. Thus, RCA was started 9h after the beginning of the symptoms. The coronary angiography, performed according to the Judkins technique, showed an occlusion of the proximal third of the left anterior descending coronary artery (LAD), without any evidence of atherosclerotic lesions in the remaining arteries ( fig. 1). The RCA (balloon) of the LDA was successfully performed. The control angiography showed occlusion of the distal portion of the 2 nd marginal branch of the left circumflex artery (M2), as a result of the migration of a thrombus. This vessel was also dilated, with a successful outcome ( fig. 2).There were no incidents during hospitalization. CK-MB peaked at 244 U/l (normal range, up to 10 U/l) and the echocardiography performed 3 days after the coronary event showed a value of 59% for the ejection fraction of the left ventricle, septal hypokinesis, and akinesis of the apical wall.The patient reported high blood pressure for approximately the previous 20 years and use of amlodipine on an irregular basis. He denied other risk factors for coronary artery disease and reported that, 3 months before, he had suffered from self-limited chest pain with similar characteristics, pain of short duration unrelated to physical or emotional stress. The patient knew he suffered from ET 4 years earlier, when he was diagnosed with it by an expert, based on laboratory findings (platelet count, peripheral blood smear, and platelet aggregation tests) and confirmed by myelogram. He was not in use of any specific medication for ET. The platelet count was 1,100,000/mm 3 , without other significant abnormalities in white blood cell or red blood cell counts. The protein electrophoresis, the urine analysis, the chest films and the abdominal ultrasonography did not show any significant...

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