Washington: In a recent comparative study between men with and without HIV, it has been found that there is more variability of QT interval – in men living with the virus, which may contribute to the increased risk of sudden cardiac deaths. The study was published in the journal, 'Circulation.'
"The take-home message to patients and providers at this time is that it's still most important to treat early and control HIV infection with antiretroviral therapies, stick to therapy and continue to monitor virus levels," said lead author Amir Heravi, a medical student at the Johns Hopkins University School of Medicine.
"Also, people should work to reduce traditional cardiovascular disease risk factors by following a healthy diet, keeping fit, quitting smoking and treating diabetes to compensate for any additional burden of HIV on the heart," added Heravi.
The researchers believe that if they extend their findings then the physicians may eventually be able to use this measure of erratic electrical activity in the heart to more precisely assess a person's risk for sudden cardiac death, and identify ways to intervene to hopefully limit or stop risk.
According to Heravi, the increase in sudden cardiac death in people living with HIV was first substantially documented in 2012 in an HIV clinic in the San Francisco Bay area, but the biological roots of the increase have remained unclear.
In a bid to learn more, the Johns Hopkins researchers used data collected from the National Institutes of Health Multicenter AIDS Cohort Study (MACS), an ongoing 30-year study that follows the health of gay and bisexual men from four US cities. Specifically, they focused on medical information gathered from 534 men without HIV infection and 589 men living with HIV, of whom 83 per cent had undetectable levels of the virus in their blood as a result of antiretroviral therapy. Some 61 per cent of the men self-identified as white, 25 per cent as African American and 14 per cent as Hispanic or "other." Participants were an average age of 57, and those with HIV had been treated for the disease for approximately 13 years.
Each participant wore a portable electrocardiogram (ECG) "patch" device to continuously measure heart rhythms. The researchers analysed 3-4 days of data on the intervals between beats when the electrical signals that drive heart rhythms are not firing. This electrical relaxation phase, during which the heart is preparing to send another pulse for a new beat is known as the QT interval. Variations in the length of time of the QT interval between each heartbeat in each person are well documented, and greater variation is known to increase the risk for abnormal and sometimes fatal heart rhythms.
The researchers used a calculation that takes into account the heart rate and the QT interval ultimately to calculate the QT interval variability. Although a universal threshold between healthy and unhealthy levels hasn't yet been adopted, it's generally accepted that higher values translate to more heart disease and higher risk, the researchers say.
They found that compared to men without HIV, men with HIV had a more variable QT interval, 0.077 greater than what would be expected for their heart rate variability. Moreover, they found this variability was also linked to the amount of virus each man carried, as measured with a blood test. The men living with HIV, but with undetectable HIV virus had an average QT interval variability of just 0.064 greater than men without HIV, whereas men with higher levels of the virus had an average of 0.150 greater QT interval variability.
None of the participants experienced sudden cardiac death during the short study period. "As far as we know, our study looked at QT interval data measured during a longer period than any other," said senior study report author Katherine Wu, an associate professor of medicine at the Johns Hopkins University School of Medicine.
"This was thanks to the availability of the new portable ECG patches that we could now record and analyse the heartbeats long enough to detect these changes that were associated with HIV infection," Wu added.