Mortality Rate in Type 2 Myocardial Infarction: Observations from an Unselected Hospital Cohort

Mortality in patients with type 2 myocardial infarction is high, reaching nearly 50 %. The excess mortality in type 2 myocardial infarction is likely caused by the nature of the myocardial infarction rather than patient co-morbidity.

Background
The classification of myocardial infarction into 5 types was introduced in 2007. The prognostic impact of this universal definition, with particular focus on type 2 myocardial infarction, has not been studied prospectively in unselected hospital patients.

Methods
During a 1-year period, all hospitalized patients having cardiac troponin I measured were considered. The diagnosis of a myocardial infarction was according to the universal definition, and specified criteria were used in the classification of type 2 myocardial infarction. Follow-up was at least 1 year, with mortality as the end point.

Results
A total of 3762 consecutive patients were studied, of whom 488 (13%) had a myocardial infarction. In 119 patients a type 2 myocardial infarction was diagnosed. After a median of 2.1 years (interquartile range, 1.6-2.5 years), 150 patients had died, with a mortality rate of 49% (58/119) in those with type 2 myocardial infarction and 26% (92/360) in those with type 1 myocardial infarction (P < .0001). In a multivariable Cox regression analysis the following variables were independently associated with mortality: current or prior smoker, high age, prior myocardial infarction, type 2 myocardial infarction, hypercholesterolemia, high p-creatinine, and diabetes mellitus. The multivariable-adjusted hazard ratio for type 2 myocardial infarction was 2.0 (95% confidence interval, 1.3-3.0). With shock as the only exception, mortality was independent of the triggering conditions leading to type 2 myocardial infarction.

Conclusions
Mortality in patients with type 2 myocardial infarction is high, reaching approximately 50% after 2 years. Further descriptive and survival studies are needed to improve the scientific evidence on which treatment of type 2 myocardial infarction is based.

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–Lotte Saaby, MD, Tina Svenstrup Poulsen, MD, PhD, Axel Cosmus Pyndt Diederichsen, MD, PhD, Susanne Hosbond, MD, Torben Bjerregaard Larsen, MD, PhD, Henrik Schmidt, MD, DMSc, Oke Gerke, MSc, PhD, Jesper Hallas, MD, DMSc, Kristian Thygesen, MD, DMSc, Hans Mickley, MD, DMSc

This article originally appeared in the April 2014 issue of The American Journal of Medicine.