Type 2 MI Less Frequent Than Type 1 MI But Has Similar Long-term Outcome

Limited data exist defining optimal management strategies because T2MI is a heterogeneous entity with varying etiologies and triggers. Thus, these patients require individualized care. A major barrier is the absence of a uniform definition that can be operationalized with high reproducibility. Dr Tania Coscia and her team explored the characteristics, management, and outcomes of patients with type 2 MI from the Advantageous Predictors of Acute Coronary Syndrome Evaluation (APACE) study.

In a prospective cohort study, conducted at 12 emergency departments in five European countries, the researchers included 6,253 patients who presented with acute chest discomfort from 2006 to 2018. They assessed high-sensitivity cardiac troponin (hs-cTn) levels at a core laboratory, and final diagnoses of type I MI (T1MI) and T2MI were centrally adjudicated by two independent cardiologists, according to the Fourth Universal Definition of Myocardial Infarction. They determined that the diagnosis of T2MI required dynamic changes in hs-cTn level (as also seen in T1MI) and a clear trigger for ischemia (e.g., arrhythmia, hypoxemia, hypotension). They included patients with non-atherosclerotic coronary artery dissection or embolism, as well as coronary vasospasm in the T2MI group. The major outcome assessed was 2-year all-cause and cardiovascular mortality and subsequent T1MI and T2MI events. Follow-up was performed by telephone or in written form 3, 12, and 24 months after hospital discharge. They used multivariable Cox proportional hazards models with adjustments for age, sex, and comorbidities to evaluate the association of type 2 MI versus type 1 MI with 2-year all-cause and CV mortality.

Key findings of the study:

• Among 6,253 patients, the researchers observed T1MI in 1,027 patients (16.4%) and T2MI in 251 patients (4.0%). They further noted that the patients withT2MI were more likely to be female (35.9% vs 26.0%).
• They highlighted that the pathophysiologic mechanisms for T2MI included tachyarrhythmia (53.8%), hypertension (18.7%), anaemia (4.4%), bradyarrhythmia (4.0%), hypoxemia (3.6%), and hypotension (1.6%), as well as coronary vasospasm (5.6%), coronary dissection (1.2%) and coronary embolism (0.8%).
• They noted that the treatment for T1MI was more likely to include revascularization (75.2% for T1MI vs 3.6% for T2MI), dual antiplatelet therapy at discharge (76.3% vs 13.9%), and statin therapy at discharge (89.8% vs 53.8%), while fewer patients with T1MI were prescribed oral anticoagulation (13.5% vs 30.7%).
• They found that the two-year all-cause mortality was similar between T1MI and T2MI patients (13.9% vs 11.7%), as was 2-year cardiovascular mortality (7.6% vs 9.3%).
• Among patients with T2MI, they noted that those with hypoxemia, hypotension, or anaemia as the ischemic trigger had higher mortality than those with underlying tachycardia or hypertension.
• They observed that recurrent events were likely to be of the same type as the index event (adjusted hazard ratio for future T2MI in patients with index T2MI vs. T1MI, 3.20).

The authors concluded, "In this European cohort of patients presenting to emergency departments with chest pain, T1MI was more common than T2MI. Although all-cause and cardiovascular mortality were similar in the T1MI and T2MI groups, patients with T2MI due to hypoxemia, hypotension, or anaemia had higher mortality."

In a summary report, Dr Nicole Martin Bhave wrote, "Patients presenting with T2MI are heterogenous, particularly with regard to the fact that underlying coronary atherosclerosis may or may not be present. Those who have multiple chronic medical conditions such as kidney disease, diabetes, and heart failure are at particularly high risk for poor outcomes".

She further added, "The findings of this study cannot be extrapolated to patients with asymptomatic troponin elevation in the setting of medical stressors (i.e., nonischemic myocardial injury) or to critically ill patients."

For further information:

DOI: 10.1001/jamacardio.2022.0043

Keywords: Acute Coronary Syndrome, Anemia, Hypoxia, Anticoagulants, Arrhythmias, Cardiac, Bradycardia, Chest Pain, Coronary Angiography, Coronary Artery Disease, Coronary Vasospasm, Dissection, Embolism, Emergency Service, Hospital, Hydroxymethylglutaryl-CoA Reductase Inhibitors, Hypertension, Hypotension, Hypoxia-Ischemia, Brain, Myocardial Infarction, Myocardial Ischemia, Myocardial Revascularization, Patient Discharge, Platelet Aggregation Inhibitors, Secondary Prevention, Tachycardia, Troponin