Analysis of the Treatment of Acute Myocardial Infarction Using Ambulance Records in Japanese Cities

Abstract

he usefulness of recanalization therapy that includes thrombolytic therapy and emergency percutaneous transluminal coronary angioplasty (PTCA) for acute myocardial infarction (AMI) is recognized, 1 and this procedure is widely performed as a primary treatment. Decreases in the case-fatality rates from AMI from approximately 30% to 10% have been reported with this therapy. However, many more institutions that specialize in cardiology and offer these procedures are needed. Average rates of fatality within 28 days after AMI were 48% for males and 54% for females according to the multinational monitoring of trends and determinants in cardiovascular disease (MONICA) project (21 countries; age 35-64 years). 2 In spite of the usefulness of recanalization therapy, it has not been available for all eligible AMI patients worldwide. In the US, thrombolysis is considered the first line of therapy for AMI in suitable patients, but in a recent report it was used in only 70% of ideal candidates. 3 In Japan, the mortality rate for AMI is low compared with that in the US or European countries, and there is a concentration of specialty institutions in urban districts at which patients can conveniently receive emergency PTCA or percutaneous transluminal coronary recanalization (PTCR) treatment.Although many reports describe results of medical treatment at specific institutions, there have been few investigations to determine the actual treatment situation for patients in an entire area. In order to determine treatment strategies for AMI, we studied the ambulance records from Chiba City and Ichihara City, Japan. We perused the medical records of the admitting institutions for all patients arriving by ambulance with a diagnosis of AMI, reconfirmed the diagnoses, and ascertained the medical treatment given in the acute phase. We also determined the availability of equipment and personnel for cardiac care in the admitting institutions and the case-fatality rates. Based on this information, recommendations are made. Methods Study PopulationFrom all 1992 ambulance records (n=31,191) from the Fire Departments in Chiba City and Ichihara City, Chiba Prefecture, Japan, we determined that 401 patients were admitted to hospital for AMI. Thirteen patients were excluded because they were seen more than 2 weeks after the onset of symptoms. Of the remaining 388 patients admitted within 2 weeks after the onset of symptoms, we examined the medical records of the institutions to which the patients were finally admitted and treated, reconfirmed the diagnoses using MONICA criteria 4 and determined what medical treatments were given. Briefly, the criteria for definite AMI were: (1) definite ECG changes; (2) probable ECG changes and abnormal enzymes; (3) typical symptoms and abnormal enzymes; or (4) fatal case with the appearance of fresh myocardial infarction and/or recent coronary occlusion found at necropsy. There were 171 patients who fulfillled the criteria, which included 168 patients admitted alive (Fig 1). Because observation periods were differ...

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