Assessment of Oxygen Supply-Demand Imbalance and Outcomes Among Patients With Type 2 Myocardial Infarction: A Secondary Analysis of the High-STEACS Cluster Randomized Clinical Trial

Abstract

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.

Conflict of interest statement

Conflict of Interest Disclosures: Dr Wereski reported receiving grants from the British Heart Foundation during the conduct of the study and grants from the Medical Research Council outside the submitted work. Dr Shah reported receiving personal fees from Abbott Diagnostics to the institution during the conduct of the study. Dr Anand reported receiving a consultancy fee from AbbVie Ltd outside the submitted work. Dr Mills reported receiving grants and personal fees from Abbott Diagnostics and Siemens Healthineers and personal fees from Roche and LumiraDx outside the submitted work. No other disclosures were reported.

Figures

Figure 1.. Trial Population

UDMI indicates Universal Definition of Myocardial Infarction.

Figure 2.. Factors Associated With Oxygen Supply-Demand Imbalance in Type 2 Myocardial Infarction (MI)

A, Cumulative incidence curve for the primary outcome of all-cause death at 1 year. B, Kernel density plot showing the distribution of maximal high-sensitivity cardiac troponin I concentrations (ng/L [to convert to micrograms per liter, multiply by 0.001]) according to adjudicated diagnosis and factors associated with oxygen supply-demand imbalance in type 2 myocardial infarction (MI).

Figure 3.. Outcomes According to the Factors Associated With Myocardial Infarction

A, Cumulative incidence curves for the primary outcome of all-cause death at 1 year. B, Cumulative incidence curves for the secondary outcomes of myocardial infarction or cardiovascular death. C, Cumulative incidence curves for noncardiovascular death. The “coronary mechanisms” category includes patients with myocardial infarction owing to coronary artery plaque rupture or erosion (type 1) and coronary artery dissection, embolism, or vasospasm (type 2); the “systemic illnesses” category includes patients with myocardial infarction in response to an acute systemic illness, such as anemia, hypotension, hypoxemia, and severe hypertension. Patients with myocardial infarction owing to primary tachyarrhythmia comprise the “tachyarrhythmias” category.