TYPE 2 MI IN SOUTHERN ALBERTA: A DESCRIPTIVE ANALYSIS

Abstract

The concept of type 2 myocardial infarction (MI), or myocardial necrosis due to supply-demand mismatch, was introduced in 2007, causing contention and confusion for many clinicians. We aimed to gather data on a large, unselected population of patients with type 2 MI and to evaluate investigation, management and prognosis. All patients with a positive troponin over a 2-year period in the Calgary Health Region were identified. Chart review was performed and patients with explicit ACS diagnoses excluded, leaving only patients with troponin elevations presumably associated with type 2 MI. Follow up data were obtained through the use of the Alberta Provincial Project for Outcomes Assessment in Coronary Heart Disease (APPROACH) database and its linkage to the Alberta Bureau of Vital Statistics. From January 1, 2007 to December 31, 2008, 998 patients with a presumptive diagnosis of type 2 MI were identified, with the majority admitted to general practice or internal medicine services. Infrequent symptoms were recorded, with the most common symptom being shortness of breath. Despite the troponin elevation, ECG was not performed in 6%, and 1/3 did not have subsequent ECGs after an initial assessment. The most common ECG change identified was T wave changes (24.1%), with ST depression in 13.7% and ST elevation observed in 5.6% of diagnosed type 2 MI. Echocardiograms were performed in only 23.2%, CT PE in 6.2%, and nuclear myocardial perfusion imaging in 0.05%. No patient underwent cardiac catheterization. Evidence-based therapy was prescribed infrequently, with only 25.5% given ASA and 16.7% statin. Outcomes were poor, as demonstrated in the Table. Readmission rates were high at 13.5% at 30-days and 35.2% at 1-year. In this large unselected cohort of patients with presumptive diagnoses of type 2 MI, ECG changes were common, and investigations to rule out type 1 MI or ongoing underlying ischemia were uncommon. Outcomes for these patients were poor and readmission rates high. Further research is required to determine appropriate management of this important group of patients.