Type 2 myocardial infarction: clinical and demographic features, laboratory and instrumental associations

TL;DR: Type 2 myocardial infarction is diagnosed in a substantial proportion of MI patients and is independently associated with concomitant anemia, left bundle branch block, absence of ST-segment elevation, older age, and the echocardiographic absence of local hypo- and akinesia of the left ventricle.

Abstract: Background: Type 2 (T2) myocardial infarction (MI) is diagnosed in patients with acute coronary syndrome with increasing frequency. However, the information on etiology, pathogenetic mechanisms, instrumental and laboratory features is inconsistent. Purpose: to examine the clinical and demographic parameters, and results of routinely performed laboratory and instrumental test in patients with T2 MI and compare them with population characteristics of type 1 (T1) MI. Methods: We retrospectively included 450 consecutive patients admitted with acute MI diagnosed in accordance with the Third Universal Definition (2012) that underwent coronary angiography. T1 MI was diagnosed in the presence of intraluminal thrombus in the epicardial vessel, or absence of atherosclerotic plaque integrity with decreased myocardial blood flow (TIMI < 3). All other patients were classified as having T2 MI. We analyzed electronic medical records to obtain their data. Student’s t-test and chi-square methods were used to compare single variables in patients with T1 and T2 MI. Multiple logistic regression was then performed to establish independent association of studied parameters with the type of MI. Results: Type 2 MI was diagnosed in 175 (39%) patients and was associated with increasing age (p = 0.007) and female gender (p = 0.01). T2 MI patients more frequently present without ST segment elevation (p = 0.001) and have lower troponin values (p = 0.001). They also had more often had a previous MI (p < 0.001) and had undergone myocardial revascularisation (p = 0.002). The absence of obstructive coronary atherosclerosis was diagnosed in a small fraction of patients with T2 MI [12 (6.9%)]. Independent predictors of having T2 MI were the presence of anemia (p < 0.001), left bundle branch block (p = 0.019), the absence of ST-segment elevation (p = 0.001), age ≥ 70 years (p = 0.014) and the absence of local wall motion abnormalilties on echocardiography (p = 0.002). Conclusion: Type 2 myocardial infarction is diagnosed in a substantial proportion of MI patients and is independently associated with concomitant anemia, left bundle branch block, absence of ST-segment elevation, older age, and the echocardiographic absence of local hypo- and akinesia of the left ventricle.