Total Ca2+ handling for E-C coupling in the whole heart: an integrative analysis

Area of Science:

• Cardiovascular Physiology
• Biophysics
• Cardiac Metabolism

Background:

• Excitation-contraction (E-C) coupling is crucial for heart function, involving complex calcium (Ca2+) handling.
• Quantifying total Ca2+ handling and associated energetic costs in a beating left ventricle (LV) remains challenging with conventional methods.

Purpose of the Study:

• To develop and validate a novel integrative analysis method to assess total Ca2+ handling in the beating LV.
• To determine the oxygen (O2) cost of Ca2+ handling and contractility (Emax) in the LV.
• To evaluate futile Ca2+ cycling and Ca2+ reactivity of Emax.

Main Methods:

• Developed an integrative analysis utilizing internal Ca2+ recirculation fraction (RF) and O2 consumption (V(O2)) for Ca2+ handling.
• Obtained RF from postextrasystolic potentiation decay constant.
• Calculated O2 cost of Emax from V(O2) at varying Emax levels.

Main Results:

• The developed equation successfully calculated total Ca2+ handling, ranging from 30 to 110 micromol/kg, varying with Emax and pathology.
• The method enabled assessment of futile Ca2+ cycling and Ca2+ reactivity of Emax in a beating LV.
• These crucial parameters for understanding cardiac pathophysiology are not accessible through traditional techniques.

Conclusions:

• A novel integrative method provides quantitative insights into total Ca2+ handling and its energetic implications in the beating LV.
• This approach allows for the assessment of futile Ca2+ cycling and Ca2+ reactivity, offering new avenues for investigating cardiac disease.
• The method holds significant potential for advancing our understanding of the pathophysiology of Ca2+ handling in the heart.