Numerous case reports and studies have now tied HHV-6 to myocarditis and cardiomyopathies. To further investigate this relationship, investigators from one of the top cardiology clinics in Europe performed a study to determine the outcome of patients discovered to have HHV-6 in their cardiac tissue during the initial biopsy screen. Unfortunately, most of the pathogens involved in cardiac disease cannot be found in the plasma and can only be detected reliably when identified within the heart tissue specimens. German cardiology clinics routinely perform endoscopic biopsies of patients with viral myocarditis and heart failure, and are thus in an excellent position to judge the impact of infections on these conditions. Clinics in the USA, on the other hand, rarely perform these biopsies.
IHC staining of HHV-6 proteins in interstitial cells.
In this study, endomyocardial biopsies (EMBs) from 73 cardiac patients were evaluated, and left ventricular ejection fraction (LV-EF) was determined using echocardiography.
The investigators (at Charite-Universitätsmedizin in Berlin) also performed follow-up biopsies after a median of 8.8 months. In the patients who had a resolution of HHV-6B infection, there was a significant improvement in ejection fraction. However, in those with persistent or new onset HHV-6 infection, left ventricular function progressively worsened, suggesting that HHV-6 infection can contribute to heart failure.
In 78% of the cases, HHV-6 infection resolved on its own and the LV-EF improved from an average of 54.9 to 60.7% (p<0.001). In the remaining 16 cases (22%) with persistent or new onset HHV-6, however, there was worsening of LV-EF from an average of 58.2 to 51.8 % (p<0.001).
Out of 521 total patients undergoing biopsies for inflammatory heart disease, 73 (14%) tested positive for HHV-6, with most of them HHV-6B (94.5%) rather than HHV-6A (5.4%). Dual infections with parvovirus B19 and HHV-6 were detected in 48% of the 73 HHV-6+ patients. The pattern of improvement after resolution, and subsequent worsening in the face of persistence was the same among patients with double infections. None of the patients included in the study had chromosomally integrated HHV-6.
The authors state that “HHV-6 may be a frequent cause of heart failure” and propose further studies to determine whether antiviral therapy can influence clinical outcome in cardiac patients.
For more information, read the full paper here.