Cardiac mechanical efficiency is preserved in primary cardiac hypertrophy despite impaired mechanical function

Area of Science:

• Cardiology
• Physiology
• Biophysics

Background:

• Increased heart size (cardiac hypertrophy) is a significant risk factor for heart failure and mortality.
• Hypertension-induced cardiac hypertrophy often involves impaired mechano-energetics and cardiac efficiency, but the direct link remains unclear.

Purpose of the Study:

• To investigate the direct association between cardiac hypertrophy and cardiac mechano-energetics.
• To utilize isolated left-ventricular trabeculae from a rat model of primary cardiac hypertrophy.

Main Methods:

• Simultaneously evaluated energy expenditure (heat output) and mechanical performance (force, work) using microcalorimetry.
• Assessed energy expenditure related to cross-bridge and Ca2+ cycling (activation heat).
• Quantified mechanical and cross-bridge energy efficiency at varying preloads and afterloads.

Main Results:

• Cardiac hypertrophy led to increased cardiomyocyte size and impaired mechanical performance (lower force, shortening, work output).
• Reduced force production correlated with decreased energy expenditure in Ca2+ and cross-bridge cycling.
• Notably, both mechanical and cross-bridge energy efficiency remained unchanged despite hypertrophy.

Conclusions:

• Cardiac hypertrophy is directly associated with impaired contractile function.
• Energy efficiency is preserved in the presence of cardiac hypertrophy.
• Findings highlight the need to investigate metabolic and Ca2+ disturbances in cardiac mechanical and energetic impairment.