Causes of oxygen supply-demand imbalance may offer prognostic value in type 2 MI
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Causes of MI such as hypoxemia and anemia, also tied to oxygen supply-demand imbalance, may confer greater 1-year all-cause mortality risk in patients with type 2 MI vs. type 1 MI, researchers reported.
However, other factors linked to oxygen supply-demand imbalance, including tachyarrhythmia and coronary mechanisms, conferred similar risk among patients with type 1 and type 2 MI, according to a secondary analysis of the High-STEACS trial published in JAMA Network Open.
“Tachyarrhythmia is the most common factor associated with oxygen supply-demand imbalance, occurring in half of all patients with type 2 myocardial infarction, and is associated with better outcomes. ... Systemic illnesses associated with type 2 myocardial infarction — anemia, hypoxemia, hypotension or severe hypertension — are less common, but patients with these illnesses as a factor associated with type 2 myocardial infarction share similar characteristics and have the highest rates of all-cause death,” Anda Bularga, MD, clinical research fellow at the British Heart Foundation Centre for Cardiovascular Science at University of Edinburgh, United Kingdom, and colleagues wrote. “Taken together, these findings suggest that for patients with type 2 myocardial infarction, it is important to distinguish the primary cardiac etiologic factors from those associated with hemodynamic stresses of a systemic illness to provide prognostic information.”
The High-STEACS trial
The present study is a secondary analysis of the step-wedged, cluster-randomized High-STEACS trial that assessed use of a high-sensitivity cardiac troponin I assay (Architect Stat, Abbott) with a 99th percentile diagnostic threshold for the diagnosis of MI in patients with suspected ACS at 10 secondary and tertiary care centers in Scotland.
As Healio previously reported, High-STEACS was the first trial testing the criteria used to diagnose MI but found to reduction in subsequent MI or CV death when using a lower diagnostic threshold for high-sensitivity cardiac troponin I.
Factors tied to oxygen supply-demand imbalance
This secondary non-prespecified analysis included 6,096 consecutive patients in High-STEACS with an adjudicated diagnosis of type 1 or type 2 MI (median age, 70 years; 43% women). The primary outcome was 1-year all-cause mortality based on factors tied to oxygen supply-demand imbalance in patients with type 2 MI.
Within this population, the most common factors tied to oxygen supply-demand imbalance in the setting of type 2 MI were tachyarrhythmia (55%), hypoxemia (20%), anemia (9%), hypotension (8%), severe hypertension (5%) and coronary mechanisms (3%).
At 1 year, all-cause mortality was observed in 15% of patients with type 1 MI and 23% of those with type 2 MI, according to the study.
Patients with type 2 MI due to hypoxemia (adjusted OR = 2.35; 95% CI, 1.72-3.18) and anemia (aOR = 1.83; 95% CI, 1.14-2.88) experienced greater likelihood for 1-year all-cause mortality compared with patients with type 1 MI.
Moreover, patients with type 2 MI attributed to tachyarrhythmia (aOR = 0.83; 95% CI, 0.65-1.06) or coronary mechanisms (aOR = 1.07; 95% CI, 0.17-3.86) experienced similar odds of 1-year all-cause mortality compared with those with type 1 MI.
“There is marked heterogeneity in referral to cardiology among patients with type 2 myocardial infarction, and the clinical implications of the different factors associated with type 2 myocardial infarction generate uncertainty,” the researchers wrote. “Although our knowledge of the clinical characteristics and outcomes among patients with type 2 myocardial infarction continues to evolve, we now require randomized clinical trials to determine the benefits or harms associated with investigation and treatment. Our findings have the potential to inform the selection of patients for future trials.”
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