SAN FRANCISCO — Respiratory syncytial virus itself, and not the bronchiolitis associated with the infection, appears to be the cause of the heart damage often seen in young children with the virus, according to a prospective study involving 74 children.
All 74 children were less than 12 months of age and were admitted to the hospital for bronchiolitis, Dr. Susanna Esposito explained in a poster at the Interscience Conference on Antimicrobial Agents and Chemotherapy.
Aside from their bronchiolitis, the children were healthy.
Investigators excluded children from the study if they had a chronic disease (including a chronic disorder of the pulmonary or cardiovascular system, chronic metabolic diseases, neoplasias, kidney or liver dysfunction, hemoglobinopathies, immunosuppression, and genetic or neurologic disorders) that increased the risk of complications of a respiratory infection.
The investigators from the University of Milan collected the specimens with nasopharyngeal swabs to detect respiratory syncytial virus (RSV) types A and B.
As it turned out, 35 patients (47%) tested positive for RSV infection, and the remaining 39 (53%) did not.
Patients with RSV had significantly more cardiac arrhythmias and a significantly greater degree of abnormal heart rate variability than those without RSV. For example, approximately 25% of the patients with RSV had cardiac arrhythmias, compared with about 5% of those without RSV. Approximately 60% of the patients with RSV exhibited abnormal heart rate variability, compared with approximately 40% of those without RSV.
The investigators found no differences between the two groups in pulse oximetry, chest radiography, respiratory involvement, or cardiac troponin I levels.
The heart involvement appeared to be related to an RSV viral load of 100,000 copies per milliliter or more, and not to drug use or the disease's severity.
“This last finding suggests that RSV can be the direct cause of the heart damage and that arrhythmias can be found also in children with very mild RSV bronchiolitis in whom pulmonary hypertension and lung damage are nonexistent or marginal,” the investigators wrote.
“This means that a careful heart evaluation has to be performed in all the children with RSV bronchiolitis, and that higher viral load is a risk factor for heart damage development,” Dr. Esposito and her associates wrote.
The investigators reported that they had no conflicts of interest.