A low CD4 cell count is associated with an increased risk of
heart attack for patients with HIV, US investigators report in the online
edition of the Journal of Acquired Immune
Deficiency Syndromes. Even after taking into account traditional risk
factors for cardiovascular disease, a CD4 cell count under 200 cells/mm3
was associated with a significantly increased risk of incident heart attack.
“Our data reinforce the emerging hypothesis that treatment
of HIV infection decreases the risk of cardiovascular disease”, write the
High of rates of cardiovascular disease are seen in patients
with HIV. A number of reasons have been suggested for this including a high
prevalence of traditional risk factors such as smoking, the side-effects of HIV
treatment, and the inflammatory effects of infection with the virus.
The large SMART treatment interruption study showed that a
CD4 cell count below 350 cells/mm3 was associated with an increased
risk of cardiovascular disease, and patients with traditional risk factors for
such illnesses are especially encouraged to start HIV treatment before their
CD4 cell count falls to this level. However, other research has yielded inconsistent
findings about the relationship between CD4 cell count and heart attack risk.
Therefore, researchers in Boston wished to gain a firmer
understanding of the relationship between CD4 cell count and viral load and
heart attack risk.
They analysed heart attack rates in 6517 HIV-positive
patients who received care between 1998 and 2008. Analyses were conducted to
see if CD4 cell count and viral load were associated with an increased risk of
heart attack, independent of traditional risk factors and the use of HIV
A total of 273 patients (4%) experienced a heart attack.
These were older than those who did not have a heart attack (54 vs. 46), and more
likely to high blood pressure (57% vs. 25%), diabetes (28% vs. 16%), high
lipids (33% vs. 29%), smoking (55% vs. 50%), kidney disease (14% vs. 7%), and a
history of coronary heart disease (35% vs. 9%) – all traditional risk factors
for heart disease.
In addition, those who had a heart attack were more likely
to have a CD4 cell count below 200
cells/mm3 (41% vs. 25%), or a viral load above 100,000 copies/ml
(20% vs. 10%).
The investigators’ first set of statistical analysis showed
that a CD4 cell count below 200 cells/mm3 doubled the risk of heart
attack (OR, 2.00; 95% CI, 1.48-2.71, p < 0.0001). A viral load above 100,000
copies/ml was also associated with a significant increase in the risk of heart
attack (OR, 2.23; 95% CI, 1.37-3.65, p = 0.001).
By contrast, a viral load below 400 copies/ml was associated
with a 44% reduction in the risk of heart attack (p = 0.003).
The investigators repeated their analysis, this time
controlling for traditional risk factors.
A CD4 cell count below 200 cells/mm3 remained
significant (OR, 1.74%; 95% CI, 1.07-2.81, p = 0.02). In addition, the
investigators found that each 50 cell/mm3 increase in CD4 cell count
significantly reduced the risk of heart attack (p = 0.002).
However, the significant relationship between viral load and
heart attack risk disappeared.
But further analysis that took into account traditional risk
factors for heart attack, but excluded CD4 cell count, showed that a viral load
above 100,000 copies/ml was associated with a significant increase in heart
attack risk (OR, 2.16; 95% CI, 1.26-3.69, p = 0.01), and a viral load below 400
copies/ml was protective against the risk of a heart attack (p = 0.02).
“We demonstrate that decreased CD4 cell count is
significantly associated with an increased risk of myocardial infarction and is
second only to hypertension in terms of its effect size as a risk factor”,
comment the investigators. They add that a CD4 cell count below 200 cells/mm3
was a much more important risk factor for heart attack than treatment with any
antiretroviral drug. Indeed, the investigators failed to find a significant
relationship between any antiretroviral and an increased risk of heart attack.
They conclude, “treatment of HIV infection to improve
immunological function is likely to be an important component of cardiovascular
prevention for patients with HIV.”