Cardiac Complications of Infections Due to Respiratory Syncytial Virus and Human Metapneumovirus: A Systematic Review and Pooled Analysis of Clinical Features

Respiratory syncytial virus (RSV) and human metapneumovirus (hMPV) are major causes of respiratory tract infections across different age groups. Although primarily regarded as respiratory pathogens, both viruses have been associated with cardiac complications, whose clinical spectrum remains incompletely characterized. We systematically reviewed published cases of RSV- and hMPV-associated cardiac involvement and compared their clinical characteristics and outcomes. PubMed, Scopus, and EMBASE were systematically searched for reports describing cardiac complications associated with laboratory-confirmed RSV or hMPV infection. Individual patient data were pooled and analyzed using descriptive and univariate analyses. Multivariable logistic regression was used to identify characteristics associated with hMPV versus RSV diagnosis, while multiple correspondence analysis (MCA) was performed to explore multivariate patterns of clinical presentation. Age-stratified sensitivity analyses were additionally performed. Overall, 102 cases were included, comprising 71 RSV (69.6%) and 31 hMPV (30.4%). hMPV cases were significantly older than RSV cases (41.5 years, interquartile range 3.5–63.0 vs. 1.5 years, interquartile range 0.2–31.0; p < 0.001) and had a higher burden of comorbidities. Myocarditis was the most frequently reported cardiac complication in both groups (87.1% hMPV vs. 74.6% RSV), followed by heart failure and pericarditis. ICU admission was more frequent among hMPV cases (96.8% vs. 77.5%; p = 0.034), whereas overall clinical outcomes did not significantly differ between groups. In exploratory multivariable analyses, dyspnea (aOR 16.280, 95% CI 1.370–193.475) and cough (aOR 6.059, 95% CI 1.062–34.552) were associated with hMPV diagnosis, whereas rhinorrhea (aOR 0.031, 95% CI 0.003–0.286) and lethargy/altered mental status (aOR 0.103, 95% CI 0.015–0.712) were associated with RSV diagnosis. ICU admission was also associated with hMPV diagnosis (aOR 11.033, 95% CI 1.125–108.173). These estimates were characterized by wide confidence intervals and should be interpreted cautiously. MCA showed substantial overlap between RSV and hMPV cases, without clear separation of their overall clinical presentation, while most between-group differences were attenuated in age-stratified analyses. In conclusion, both RSV and hMPV can be associated with a broad spectrum of potentially severe cardiac complications, with myocarditis representing the predominant reported manifestation. Despite some differences in demographic and clinical characteristics, their overall cardiac and clinical phenotypes substantially overlap. These findings support greater awareness of potential cardiac involvement during severe RSV and hMPV infections, while highlighting the need for prospective, systematically investigated cohorts to establish the incidence, mechanisms, and long-term outcomes of these complications.