Predicting Acute Myocardial Infarction in HIV-Positive Patients
Acute myocardial infarction rates are higher in HIV-positive patients; a new study out of the VA may help clinicians determine who’s most at risk.
For people diagnosed with human immunodeficiency virus (HIV), the most pressing concern is access to antiretroviral therapy (ART). ART has made great strides over the past few years and now enables HIV-positive patients to enjoy a much longer lifespan and avoid or delay the onset of AIDS by years, even decades. Once the virus is suppressed, however, other causes of illness and death may come to the fore. Acute myocardial infarction (AMI), for example, strikes HIV-positive individuals at a 50% to 75% higher rate than non-infected people after accounting for established risk factors.
To examine this issue and to determine whether AMI can be predicted to some degree, a group of researchers affiliated with various Veterans Affairs (VA) medical centers nationwide delved into information provided by the Veterans Aging Cohort Study (VACS), which tracked health data of veterans. The study team analyzed the records of 8,168 HIV-positive veterans who started ART during the period of 1996 to 2012, excluding anyone who had previously taken ART or who had known coronary artery disease before starting ART. The median age of the subjects was 46, almost 97% were male, and more than half (54.8%) were African American. The researchers noted the subjects’ baseline numbers, including HIV viral load, white blood cell count, and VACS index score, a score designed to assess general mortality risk that takes into account anemia, kidney disease, liver disease, and hepatitis C status in addition to HIV viral load and white blood cell count. They then assessed the subjects again starting six months after ART was initiated. The subjects were followed until they either suffered from AMI, died, had their last clinic visit at the VA, or until September 2012 if none of the previous applied. This time-updated assessment and baseline assessment were then used to create cumulative measures of the HIV viral load, white blood cell count, and VACS index score, leading to nine separate metrics: baseline HIV viral load, time-updated viral load, cumulative time-updated viral load, baseline white blood count, time-updated white blood count, cumulative time-updated white blood count, baseline VACS score, time-updated VACS score, and cumulative time-updated VACS score.
Out of these nine metrics, six had a significant association with AMI. Patients who had a baseline HIV viral load of more than 100,000 copies per milliliter saw a 41% increased risk of AMI. At any time during the study, patients with a viral load between 201 and 999 copies/mL had a 71% increased risk of AMI compared with patients whose viral load was 200 or below. The time-updated viral loads, even at higher levels, did not correlate with increased risk of AMI. However, the cumulative time-updated viral loads did correlate to increased AMI risk. Baseline white blood cell counts above 200 cells/mm3 were somewhat predictive of AMI, while the time-updated white blood cell counts were associated with AMI only when the counts were still below 200 cells/mm3. VACS scores at or below 50 at baseline showed an association with AMI, as did time-updated scores 55 and above. Cumulative time-updated VACS scores at all levels—high and low—were associated with AMI risk.
The researchers discovered that cumulative viremia—or the presence of virus in the blood—was notably associated with AMI while time-updated viremia was not. The time-updated VACS scores, however, were determined to be the greatest predictor of AMI and death in general rather than the other eight metrics. This is convenient, according to the study’s authors, because baseline measures for patients are not always available. “It suggests that a patient’s current status is much more important than how they got there or the duration of time they spent in a particular state,” they wrote.
The authors acknowledged that the study has limitations. Women were largely excluded. The specifics of the patients’ ART regimens were unknown. The study was based on administrative data and not direct observation. Although confident that their metrics can be used to predict AMI and mortality among HIV-positive individuals, the researchers are hoping that future studies can provide a more detailed view of cardiovascular risk in this population.
Laurie Saloman, MS, is a health writer with more than 20 years of experience working for both consumer and physician-focused publications. She is a graduate of Brandeis University and the Medill School of Journalism at Northwestern University. She lives in New Jersey with her family.