Assessment of Oxygen Supply-Demand Imbalance and Outcomes Among Patients With Type 2 Myocardial Infarction
Authors: Bularga Anda , Taggart Caelan , Mendusic Filip , Kimenai Dorien M. , Wereski Ryan , Lowry Matthew T. H. , Lee Kuan Ken , Ferry Amy V. , Stewart Stacey S. , McAllister David A. , Shah Anoop S. V. , Anand Atul , Newby David E. , Mills Nicholas L. , Chapman Andrew R. ,   High-Sensitivity Troponin in the Evaluation of Patients with Suspected Acute Coronary Syndrome (High-STEACS) Investigators, Strachan Fiona E , Tuck Christopher , Doudesis Dimitrios , Sandeman Dennis , Adamson Philip D , Andrews Jack P M , Moss Alastair , Anwar Mohamed S , Hung John , Stables Catherine L , Vallejo Catalina A , Tsanas Athanasios , Marshal Lucy , Fujisawa Takeshi , Hautvast Mischa , McPherson Jean , McKinley Lynn , Fox Keith A A , Berry Colin , Walker Simon , Weir Christopher , Ford Ian , Gray Alasdair , Collinson Paul O , Apple Fred S , Reid Alan , Cruikshank Anne , Findlay Iain , Amoils Shannon , Maguire Donogh , Stevens Jennifer , Norrie John , Malo Jonathan , Fischbacher Colin M , Croal Bernard L , Leslie Stephen J , Keerie Catriona , Parker Richard A , Walker Allan , Harkess Ronnie , Wackett Tony , Armstrong Roma , Flood Marion , Stirling Laura , MacDonald Claire , Sadat Imran , Finlay Frank , Charles Heather , Linksted Pamela , Young Stephen , Alexander Bill , Duncan Chris 
Published: July 2022

Importance

Type 2 myocardial infarction occurs owing to multiple factors associated with myocardial oxygen supply-demand imbalance, which may confer different risks of adverse outcomes.

Objective

To evaluate the prevalence and outcomes of different factors associated with oxygen supply-demand imbalance among patients with type 2 myocardial infarction.

Design, Setting, and Participants

In this secondary analysis of a stepped-wedge, cluster randomized clinical trial conducted at 10 secondary and tertiary care hospitals in Scotland, 6096 patients with an adjudicated diagnosis of type 1 or type 2 myocardial infarction from June 10, 2013, to March 3, 2016, were identified, and the findings were reported on August 28, 2018. The trial enrolled consecutive patients with suspected acute coronary syndrome. The diagnosis of myocardial infarction was adjudicated according to the Fourth Universal Definition of Myocardial Infarction and the primary factor associated with oxygen supply-demand imbalance in type 2 myocardial infarction was defined. This secondary analysis was not prespecified. Statistical analysis was performed from July 7 to 30, 2020.

Intervention

Implementation of a high-sensitivity cardiac troponin I assay.

Main Outcomes and Measures

All-cause death at 1 year according to the factors associated with oxygen supply-demand imbalance among patients with type 2 myocardial infarction.

Results

Of 6096 patients (2602 women [43%]; median age, 70 years [IQR, 58-80 years]), 4981 patients had type 1 myocardial infarction, and 1115 patients had type 2 myocardial infarction. The most common factor associated with oxygen supply-demand imbalance was tachyarrhythmia (616 of 1115 [55%]), followed by hypoxemia (219 of 1115 [20%]), anemia (95 of 1115 [9%]), hypotension (89 of 1115 [8%]), severe hypertension (61 of 1115 [5%]), and coronary mechanisms (35 of 1115 [3%]). At 1 year, all-cause mortality occurred for 15% of patients (720 of 4981) with type 1 myocardial infarction and 23% of patients (285 of 1115) with type 2 myocardial infarction. Compared with patients with type 1 myocardial infarction, those with type 2 myocardial infarction owing to hypoxemia (adjusted odds ratio [aOR], 2.35; 95% CI, 1.72-3.18) and anemia (aOR, 1.83; 95% CI, 1.14-2.88) were at greatest risk of death, whereas those with type 2 myocardial infarction owing to tachyarrhythmia (aOR, 0.83; 95% CI, 0.65-1.06) or coronary mechanisms (aOR, 1.07; 95% CI, 0.17-3.86) were at similar risk of death as patients with type 1 myocardial infarction.

Conclusions and Relevance

In this secondary analysis of a randomized clinical trial, mortality after type 2 myocardial infarction was associated with the underlying etiologic factor associated with oxygen supply-demand imbalance. Most type 2 myocardial infarctions were associated with tachyarrhythmia, with better prognosis, whereas hypoxemia and anemia accounted for one-third of cases, with double the mortality of type 1 myocardial infarction. These differential outcomes should be considered by clinicians when determining which cases need to be managed if patient outcomes are to improve.

Trial Registration

ClinicalTrials.gov Identifier: NCT01852123