All-Cause Mortality Rates Vary Among Type 2 Myocardial Infarction Phenotypes

Christian Mueller, MD

New findings suggest the prevalence of type 2 myocardial infarction (MI) was one-fourth that of type 1 MI, with tachyarrhythmia and hypertension responsible for more than two-thirds of type 2 MI cases among patients presenting to the emergency department with acute chest discomfort.

Further study data show type 2 MI and type 1 MI had comparable all-cause and cardiovascular mortality rates at 2 years.

“Patients with tachyarrhythmia or hypertension as their underlying trigger of [type 2] MI had a lower mortality than patients with hypotension, hypoxemia, or anemia as the underlying trigger,” wrote study author Christian Mueller, MD, Cardiovascular Research Institute Basel (CRIB), Department of Cardiology, University Hospital Basel, University of Basel.

Investigators explored the characteristics, management, and outcomes of patients with type 2 MI from the Advantageous Predictors of Acute Coronary Syndrome Evaluation (APACE) study. The ongoing, prospective study included 12 centers in 5 countries and consisted of adult patients presenting to the emergency department with acute chest discomfort.

Enrolled patients underwent clinical assessment, including standardized and detailed medical history with assessment of 34 predefined chest pain characteristics, vital signs, physical examination, 12-lead electrocardiography (ECG), continuous ECG rhythm monitoring, pulse oximetry, standard blood testing, and chest radiography.

Follow-up was performed by telephone or in written form 3, 12, and 24 months after hospital discharge. The multivariable Cox proportional hazards models with adjustments for age, sex, and comorbidities were used to evaluate the association of type 2 MI versus type 1 MI with 2-year all-cause and CV mortality.

From April 2006 - April 2018, a total of 6253 patients were eligible for inclusion, with a median age of 61 years and 2078 women (33.2%). Data show the final adjudicated diagnosis was type 2 MI in 251 patients (4.0%) and type 1 MI  in 1027 patients (16.4%)

Among the 251 patients with type 2 MI, the dominant underlying pathophysiological mechanisms were tachyarrhythmia (135 [53.8%]) and hypertension (47 [18.7%]).

Investigators observed 33 deaths (13.9%) in the type 2 MI group and 116 deaths (11.7%) in the type 1 MI group over 730 days. All-cause mortality and cardiovascular mortality were found comparable at 2 years (type 2 MI: adjusted HR, 1.0; 95% CI, 0.7 - 1.5; type 1 MI, adjusted HR, 0.7; 95% CI, 0.4 - 1.1).

Data show future type 2 MI was more likely to occur among patients with index type 2 MI compared to patients with index type 1 MI (adjusted hazard ratio [HR], 3.20; 95% CI, 1.37 - 7.50; P = .007). Moreover, future type 1 MI was more likely to occur among patients with index type 1 MI (adjusted HR, 2.98; 95% CI, 1.19 - 7.44; P = .02).

As the cumulative incidence of 2-year all-cause mortality differed among the different mechanisms provoking type 2 MI, the mortality of patients with tachyarrhythmia or hypertension as the underlying trigger of type 2 MI was lower than other mechanisms.

“This diversity also highlights that the immediate therapeutic approaches to T2MI must be highly individualized and focused on rapid reversal of the trigger,” Mueller wrote.

The study, “Characteristics and Outcomes of Type 2 Myocardial Infarction,” was published in JAMA Cardiology.