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Ambulatory blood pressure monitoring shows that 15% of HIV patients had undiagnosed high blood pressure
Michael Carter, 2011-08-11 13:50:00
Approximately 15% of HIV-positive patients had undiagnosed hypertension, Spanish investigators report in the online edition of the Journal of Acquired Immune Deficiency Syndromes.
However the study also found that 39% of patients diagnosed with high blood pressure during a normal clinic appointment had what is called "office hypertension" - raised blood pressure due to stress - rather than persistently elevated blood pressure.
Researchers at Madrid’s La Paz hospital used 24-hour blood pressure monitoring to assess the true prevalence of hypertension in patients who had raised blood pressure during clinical monitoring.
“A major strength of our study is the strict methodology used for BP [blood pressure] measurement and the use of ABPM [ambulatory blood pressure monitoring] for diagnosis of HTN [hypertension].”
Family history, older age, and greater exposure to HIV therapy with risk factors for elevated blood pressure.
Cardiovascular disease is now a major cause of illness and death in patients with HIV. Hypertension – or high blood pressure – is a risk factor for cardiovascular disease, but its prevalence and risk factors in HIV-positive patients are poorly understood.
Therefore investigators designed a prospective study involving 310 patients attending routine care.
They were concerned that the stressful environment of HIV clinics could mean that their patients’ blood pressure measurements obtained during routine care are not always accurate. Indeed, an acknowledged clinical syndrome is called isolated office blood pressure.
Consequently, all the investigators’ patients had their blood pressure monitored during routine clinic visits. This involved both seated and standing tests.
Patients with hypertension (blood pressure above 140/90 mmHG) were offered 24-hour ambulatory blood pressure monitoring. This test allows blood pressure and cardiac function to be monitored outside the clinical environment, during the performance of routine, day-to-day activities.
Most of the patients were white males, and their average duration of HIV infection was ten years. The majority (71%) were taking antiretroviral therapy.
Overall, 20 patients (7%) had a prior diagnosis of hypertension. Monitoring in the clinic showed that an additional 44 patients (14%) had blood pressure above 140/90 mHG). When these figures were added together, the prevalence of hypertension in the study population was 21%.
Ambulatory monitoring confirmed the diagnosis of hypertension in 26 of the patients who had isolated office hypertension. The investigators therefore calculated that the true prevalence of hypertension in their patients was 15%.
Patients with hypertension were older than those with healthy blood pressure (48 vs. 41 years, p < 0.001), had longer duration of HIV infection (13 vs. 9 years, p = 0.001), and had a lower nadir CD4 cell count (149 vs. 203 cells/mm3, p = 0.008). Patients with high blood pressure were also more likely to have lipoatrophy (46% vs. 26%, p = 0.008), and to be taking HIV therapy (87% vs. 68%, p = 0.008).
Analysis that controlled for potentially confounding factors showed three independent risk factors for hypertension:
Older age (each additional year increased the risk by 8%; OR = 1.08; 95% CI, 1.03-1.12; p < 0.001).
Family history of hypertension (OR = 2.24; 95% CI, 1.09-4.59; p = 0.027).
Number of antiretroviral regimens (OR = 1.2; 95% CI, 1.07-1.34; p = 0.001).
“The number of antiretroviral regimens could be an indirect measurement of ART duration and cumulative drug-related toxicity,” comment the investigators.
Female sex was associated with a significantly lower risk of hypertension (OR = 0.27; 95% CI, 0.09-0.81; p = 0.02).
Further analysis showed that 60% of patients who underwent 24-hour monitoring had abnormal cardiac patterns, and in 17% of patients these were extreme. CD4 cell counts were significantly higher in patients with normal cardiac rhythms than those with altered patterns (612 vs. 425 cells/mm3, p = 0.017).
The investigators acknowledge that their study has a number of limitations, including the small sample size. Nevertheless, they conclude, “using ABPM, HTN prevalence in HIV-infected patients is lower than previously reported…non-invasive BP monitoring could be useful to confirm HTN diagnosis and help make better decisions regarding treatment in hypertensive subjects.”
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