Heart muscle performance after experimental viral myocarditis

Area of Science:

• Cardiology
• Virology
• Pathology

Background:

• Idiopathic cardiomyopathy may have viral antecedents.
• Coxsackie virus B3 is a known cause of myocarditis.

Purpose of the Study:

• To investigate late structural and functional consequences of experimental coxsackie virus B3 myocarditis.
• To determine the impact of age at inoculation on the persistence of myocardial dysfunction.

Main Methods:

• Myocarditis was induced in 12- and 22-day-old hamsters using coxsackie virus B3.
• Isometric contractility (peak developed tension) and muscle mechanics were assessed at various time points post-inoculation.
• Glycerinated muscle preparations were used to evaluate contractile protein function.

Main Results:

• Inoculation at 12 days led to significant depression in peak developed tension (17-43%) at 18 and 90 days post-inoculation, with reduced muscle stretch requirement.
• Inoculation at 22 days resulted in a 15% depression in peak developed tension at 18 days, with 50% less tension in glycerinated muscles.
• Myocardial function recovered by 90 days in hamsters inoculated at 22 days, but persistent dysfunction was observed in those inoculated at 12 days.
• No differences from controls were noted at 180 days post-inoculation for either age group.

Conclusions:

• Acute coxsackie virus B3 myocarditis can cause persistent alterations in myocardial contractility and compliance.
• Age at the time of viral infection significantly influences the recovery and long-term sequelae of myocarditis.
• Younger hamsters (12 days) inoculated with coxsackie virus B3 exhibit prolonged myocardial dysfunction compared to older hamsters (22 days).