Viral infections that make their way into the heart can cause a spectrum of damage to the cardiovascular system, depending on whether the infection is acute or chronic. Viruses causing respiratory illness like enteroviruses and influenza viruses can also affect the heart, causing a condition called viral myocarditis and leading to mild and even lethal cardiac injury.
Viral myocarditis is the leading cause of sudden unexpected death. Whether the condition is less severe for women or it just occurs less often, viral myocarditis most often affects men under the age of 40. It appears in two forms:
- 1. Acute
Often called “fulminant myocarditis,” this form of infection is short-lived and self-limiting. Although patients who fall to this kind of infection normally recuperate after their immune system clears the virus from their system, people with previous run-ins with “severely compromised” cardiac function may depend on a temporary left ventricular assist device until their heart is able to perform well enough on its own.
Like chronic inflammation can plague other parts of the body, it can also occur in the heart, causing a form of the disease called chronic myocarditis. As the heart muscle becomes increasingly inflamed, whether because of an ongoing viral infection or an autoimmune condition that targets proteins of the heart. After months or even years of chronic myocarditis, patients can develop a condition called dilated cardiomyopathy (DCM), a condition that usually impacts the left ventricle initially and moves to the atria (American Heart Association
). As the chambers of the heart stretch and grow thinner, the heart’s contractions grow abnormal and the heart becomes excessively and dangerously weak.
This condition sometimes requires a heart transplantation for a full recovery. Although other health problems can lead to dilated cardiomyopathy, 30 percent of all clinical cases stem from an original viral infection.
In a Current Pharmaceutical Design
review article, Sally A. Huber, PhD, from the University of Vermont Department of Pathology described an experimental animal model to first study the apparent sex bias in both acute and chronic myocarditis. Testosterone in males is thought to promote autoimmunity, increasing the chance that males will have a reaction to heart proteins that could cause myocarditis. On the other hand, the estrogen prominent in females actually suppresses viral infection and autoimmunity, making them less prone to myocarditis.
Huber found from her studies that eosinophils and other leukocytes infiltrate the myocardium during inflammation, but treating this penetration with immunosuppressive treatments is not only ineffective, it is harmful in this situation. Ultimately, clearance of the virus causing myocarditis would solve the condition, and suppressing the immune system would make clearing the virus virtually impossible.
Huber’s goal after writing this review is to find better therapeutic agents for treating viral myocarditis, and the animal model from her review article showed improved cardiac function in a clinical trial using interferon-beta to treat chronic viral infections causing myocarditis.
Source: Bentham Science Publishers