HIV-infected patients may be more likely to have type 2 MIs

More than half of MIs among HIV-infected patients were classified as type 2 MIs that occurred in the setting of a mismatch between oxygen demand and supply, according to a longitudinal study.

Although estimates vary, the researchers said that type 2 MIs account for a minority of MIs in the general population.

Lead researcher Heidi M. Crane, MD, MPH, of the University of Washington, and colleagues published their results online Jan. 4 in JAMA Cardiology.

“Our results suggest that, in HIV-infected individuals, [type 1 MI] and [type 2 MI] may represent distinct clinical entities that require different approaches to prevention and treatment, as noted in the general population,” the researchers wrote. “To our knowledge, this study is the first to report a high proportion of [type 2 MIs] occurring among HIV-infected individuals.”

The researchers noted that MIs are typically classified into five types based on the underlying mechanism of myocardial ischemia. They defined type 1 MIs as those that “result spontaneously from instability of atherosclerotic plaque” and type 2 MIs as those that are “secondary to causes other than atherosclerotic plaque rupture, including hypotension, hypoxia, and stimulant-induced spasm, resulting in increased oxygen demand or decreased supply.”

For this analysis, they examined type 1 and type 2 MIs among HIV-infected patients who had an incident MI between Jan. 1, 1996, and March 1, 2014, at one of the following sites: The Johns Hopkins University, University of Alabama at Birmingham, University of California–San Diego, University of California–San Francisco, The University of North Carolina at Chapel Hill and the University of Washington. The patients were part of the Centers for AIDS Research Network of Integrated Clinical Systems Cohort.

During the study, 571 patients had definite or probable MIs, of which 50.4 percent were classified as type 2 and 49.6 percent were classified as type 1. The median age of patients was 49 years old, and 75.3 percent were males.

Patients with type 2 MIs were more likely to be younger than 40 years old, be female, be African American, not be receiving antiretroviral therapy, have an HIV transmission risk factor of injection drug use and have a low median CD4 cell count and a high HIV viral load.

Patients with type 1 MIs were more likely to receive a statin before having an MI and be current smokers. They also had higher mean total cholesterol, non-high-density lipoprotein cholesterol and low-density lipoprotein cholesterol levels.

The most likely causes of type 2 MIs were sepsis or bacteremia (34.7 percent of cases), vasospasm induced by use of cocaine or other illicit drugs (13.5 percent) and hypertensive emergency (9.7 percent). Other causes included respiratory failure, noncoronary cardiac conditions and hypotension.

The researchers mentioned the study had a few limitations, including that silent type 1 MIs could have been missed and type 2 MIs could have been missed in critically ill adults who did not have their cardiac biomarkers assessed. They also noted there are conflicting ideas on how to best categorize an event as a type 2 MI, although two physicians independently reviewed each case and a third physician settled any disagreements.

In addition, they said that it was unclear of the importance of applying ECG classifications to categorize type 2 MIs. They recommended that future research focuses on understanding the association between traditional and HIV-specific cardiovascular disease risk factors, the genetic predisposition to develop MI and potential interactions with antiretroviral therapy and the role of behavioral factors.

“These findings have important implications for studying MIs, understanding the higher MI rates, and determining whether the extent burden of MI can be reduced by modification of [cardiovascular disease] risk factors among HIV-infected individuals, particularly given the unknown role, if any, of atherosclerosis in [type 2 MIs],” the researchers wrote. “Understanding types of MI may help clarify unanswered questions regarding risk factors, risk scoring, and prognosis. Most important, these findings are important clinically, as [type 1 MIs] and [type 2 MIs] may require different approaches for prevention and treatment in HIV-infected individuals.”