Effect of metoprolol in acute coxsackievirus B3 murine myocarditis.

Recent studies suggest that beta-adrenergic blocking agents show promise in the management of cardiomyopathies; however, their role in acute myocarditis is unknown. One hundred 3 week old mice were infected with coxsackievirus B3 and were given either metoprolol (n = 50) or normal saline solution (n = 50) intraperitoneally for 10 days. Twenty mice from each group were observed for mortality for 30 days. Of the remaining 60 mice, 10 from each group were killed on day 3, 6 or 10 and examined for heart viral titers and pathologic changes. Mortality rate in the metoprolol group was 60% compared with 0% in the saline group (p less than 0.005). Viral titers on day 10 of infection were 10(2.6 +/- 0.2) median tissue culture infective dose for the metoprolol group versus 10(2.1 +/- 0.1) for the saline group (p less than 0.05). Whereas pathologic changes at days 3, 6 and 10 of infection were similar in both groups, on day 30 of infection, inflammation, necrosis and mineralization scores (mean +/- SEM) were 1.1 +/- 0.3, 2.1 +/- 0.4, 2.2 +/- 0.5 for the metoprolol group versus 0.3 +/- 0.1, 0.4 +/- 0.3, 0.4 +/- 0.3 for the saline group, respectively (p less than 0.01). Six noninfected mice received metoprolol intraperitoneally for 10 days; there was no mortality during 30 days of observation. In conclusion, metoprolol administration exerts deleterious effects in acute coxsackievirus B3 murine myocarditis.