Autoimmune myocarditis is not associated with left ventricular systolic dysfunction.

Area of Science:

• Cardiology
• Immunology
• Animal Models

Background:

• Experimental autoimmune myocarditis (EAM) is a key animal model for studying myocarditis pathophysiology.
• Previous studies yielded conflicting results, necessitating further investigation into cardiac dimensions and function during EAM.
• Serial echocardiography was employed to track changes throughout the disease course.

Purpose of the Study:

• To investigate the temporal changes in murine heart dimensions and left ventricular (LV) systolic function during experimental autoimmune myocarditis (EAM).
• To clarify discrepancies in previous research regarding EAM's effects on cardiac structure and function.

Main Methods:

• EAM was induced in male Balb/c mice using a fragment of the α-myosin heavy chain.
• Transthoracic echocardiography was performed on days 0, 7, and 21 post-immunization in both healthy and EAM-affected mice.

Main Results:

• EAM led to reduced LV systolic function and increased LV internal diameter (LVIDd, LVIDs) by day 7.
• By day 21, EAM induced significant LV wall thickening (e.g., LVAWDd increased 1.3-fold) but normalized LV systolic function compared to controls.
• Increased LV thickness correlated strongly with myocarditis severity in histopathological assessments.

Conclusions:

• EAM progression involves initial LV dilatation followed by ventricular hypertrophy.
• LV systolic function recovered by day 21 in EAM mice.
• Age significantly impacts echocardiographic parameters, underscoring the need for age-matched controls in rodent echocardiography studies.