A specific inflammation of the heart muscle (myocarditis) is often triggered by the body’s immune response to a viral infection. However, it has now been discovered that the virus itself can damage the heart even before inflammation occurs.
A new study involving experts at the Virginia Tech Carilion School of Medicine examined acute heart infections and molecular changes in the infected heart before a significant immune response or severe cardiomyopathy occurs. The results are published in the specialist journal “Circulation Research”.
Inflammation of the heart muscle caused by adenoviruses
Myocarditis is an inflammation of the heart muscle and one of the main causes of sudden cardiac death in young adults, the researchers report. Up to 42 percent of cases of sudden cardiac death in young adults are due to myocarditis, with a viral infection being the most common cause.
Adenoviruses are known to be one of the main causes of myocarditis, but it has remained unclear how a viral infection can lead to sudden cardiac arrest, the research team continued.
“From a clinical perspective, our understanding of viral infection of the heart has focused on inflammation that causes problems with the frequency or rhythm of the heartbeat,” explains study author James Smyth in a press release.
Infection process examined
In their new study, the researchers examined the effects of the infection process on the heart in mice. They used the so-called mouse adenovirus type 3 and analyzed the consequences of acute heart infections and the molecular changes in the infected heart, even before a significant immune response or severe cardiomyopathy occurred.
The team identified an acute stage in which the virus infects the heart, even before the body’s immune response triggers inflammation. Before the tissue becomes inflamed, the virus lays the foundation for cardiac arrhythmias.
In this phase, the virus disrupts important components of the communication and electrical system of the heart at the beginning of the infection, the researchers explain.
Even before symptoms appear, the adenovirus infection creates conditions that disrupt the so-called gap junctions (special structures between neighboring heart cells that enable communication between these cells) and the heart’s ion channels.
The ion channels are involved in maintaining the ionic balance needed to produce normal patterns of electrical activity in the heart. They ensure that the heart beats properly, the experts add.
Imminent cardiac arrhythmias
When these communication bridges and so-called gatekeepers are disrupted by an adenovirus infection, the heart can develop irregular patterns of electrical activity called arrhythmias.
As a result, both the heart’s beating and its ability to pump blood are impaired, which can lead to heart problems, especially in people with an active infection, the researchers explain.
New treatment in sight?
In the future, targeted treatment of specific heart changes caused by viral infections could be used to significantly reduce the risk of heart problems in people with viral infections, the researchers hope.
Even if acute infections appear normal on MRI and echocardiography, when viewed at the molecular level they can indicate dangerous health consequences, the experts add.
As far as diagnostics are concerned, ways can now be sought to test blood for a biomarker of the serious problem, in order to detect an increased risk of cardiac arrhythmias through a simple blood test.
The new study shows completely new ways to diagnose and treat viral infections of the heart. Given the high incidence of virus-related myocarditis, which leads to sudden cardiac death, this finding is crucial, the experts conclude. (as)
