Cardiocyte contractile performance in experimental biventricular volume-overload hypertrophy

Area of Science:

• Cardiovascular Physiology
• Cellular Biology

Background:

• The right ventricle (RV) often tolerates volume overload better than the left ventricle (LV).
• Intrinsic differences in cardiac muscle cell (cardiocyte) contractile performance may explain this response.

Purpose of the Study:

• To determine if volume-hypertrophied RV and LV cardiocytes exhibit intrinsic differences in contractile performance.
• To investigate the cellular basis for differential ventricular adaptation to volume overload.

Main Methods:

• Isolated feline cardiocytes from a biventricular volume overload model (arteriovenous fistula) and controls were studied.
• Sarcomere shortening and relengthening properties were measured using laser diffraction.
• Cardiocyte function was assessed under varying superfusate viscosities.

Main Results:

• Volume overload significantly increased cardiac output and ventricular weight-to-body weight ratios in AVF cats.
• Despite hypertrophy, RV and LV cardiocytes from AVF cats showed normal contractile function and relengthening properties.
• No significant differences in sarcomere shortening or relengthening were observed between RV and LV cardiocytes, or between AVF and control groups.

Conclusions:

• Contractile dysfunction is not an inherent property of RV or LV cardiocytes hypertrophying due to volume overload with normal afterload.
• Cellular contractile performance is preserved in both ventricles under substantial volume loading.
• The study challenges the notion of intrinsic cellular differences in RV vs. LV adaptation to volume overload.