January 27, 2017
Half of all myocardial infarctions (MIs) in a large U.S. HIV cohort were type 2 MIs, which are rare in the general population. Sepsis, bacteremia and recent illicit drug use explained most type 2 MIs, and the type 2 group differed from the type 1 group in cardiovascular risk and certain demographics.
Much research indicates that MI rates are higher with than without HIV infection. But these studies usually rely on unadjudicated MI outcomes and do not distinguish between the two MI types. Type 1 MIs result from atherosclerotic plaque instability, while the much rarer type 2 MIs reflect a mismatch between oxygen demand and supply, for example, with severe hypotension.
CNICS Cohort investigators conducted this study to measure rates of type 1 and 2 MIs in this HIV population, to compare patients with type 1 and type 2 MIs and to identify causes of type 2 MIs. The analysis included CNICS members from six sites who had an MI between January 1996 and March 2014. Researchers retrospectively identified MIs by searching the CNICS data repository for clinical diagnoses or indicative coronary interventions. Two expert physician adjudicators reviewed relevant data to verify MI diagnosis, to assign MI type and to identify causes of type 2 MIs.
Compared with patients who had a type 1 MI, those with a type 2 MI included a higher proportion who were younger than 40 (16.3% versus 8.8%), women (28.1% versus 19.1%), African American (70.1% versus 43.1%), not receiving antiretroviral therapy (46.5% versus 25.1%) and with drug injecting as their HIV transmission risk (37.2% versus 21.5%). A higher proportion of type 2 patients had a latest CD4 count below 200 cells/mm3 (44.4% versus 26.0%), and a lower proportion had a viral load below 400 copies/mL (44.1% versus 59.9%). Mean total cholesterol was lower in the type 2 group (167 versus 190 mg/dL), as was mean low-density lipoprotein cholesterol (87 versus 108 mg/dL). The type 2 group was less likely to use a statin (19.4% versus 32.6%) or to smoke (40.3% versus 50.0%). Average 10-year Framingham risk score was lower among type 2 patients (8 versus 10). All of these differences were statistically significant.
The most frequent causes of type 2 MI were sepsis or bacteremia (34.7%), vasospasm due to use of cocaine or other illicit drugs (13.5%) and hypertensive emergencies (9.7%).
The researchers concluded that HIV-positive people with type 2 MIs had fewer traditional cardiovascular risk factors than those with type 1 MIs. But the type 2 group was younger and had more advanced HIV infection than the type 1 group. The investigators believe their results suggest that, in people with HIV infection, type 1 and 2 MIs "may represent distinct clinical entities that require different approaches to prevention and treatment, as noted in the general population." The 50% type 2 incidence in this HIV population far exceeds the 2% to 26% rate reported in the general population.
Mark Mascolini writes about HIV infection.
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