Isolated myocyte contractile function is normal in postinfarct remodeled rat heart with systolic dysfunction

Area of Science:

• Cardiovascular Biology
• Cardiac Remodeling Research
• Myocardial Infarction Studies

Background:

• Postinfarction ventricular remodeling is a known complication.
• The mechanisms driving remote noninfarcted myocardium dysfunction remain unclear.

Purpose of the Study:

• To investigate serial changes in left ventricular (LV) structure and function post-myocardial infarction.
• To correlate global cardiac changes with myocyte structural and functional alterations in remote myocardium.

Main Methods:

• Serial assessment of global LV structure and function in rat hearts post-myocardial infarction (MI) and sham operations.
• Isolation and functional assessment of myocytes from remote LV and RV myocardium.
• Correlation of myocyte dimensions and function with global LV remodeling and dysfunction.

Main Results:

• MI rats exhibited significant cardiac remodeling, increased heart weight-to-body weight ratio, and elevated LV volumes.
• Global LV dysfunction was evident, with impaired pressure development.
• Isolated LV and RV myocytes showed significant lengthening and widening, correlating with LV volume and function changes.
• Despite structural changes, isolated myocytes displayed normal contractile function and Ca2+ handling.

Conclusions:

• Postinfarct remodeling primarily involves myocyte lengthening, not slippage.
• Normal contractile function of isolated remote myocytes suggests myocyte contractile abnormalities are not the primary cause of global dysfunction.
• Reduced myocyte mass and nonmyocyte factors (e.g., wall stress, altered geometry) are likely key contributors to postinfarct LV dysfunction.