Figure 7.

Inotropes vs myotropes in heart failure (HF).

During inotrope infusion in the normal heart, |ΔG_~ATP| decreases but stays above the value of 52 kJ/mol—a critical value for normal SERCA (sarcoplasmic reticulum calcium ATPase) function. SERCA is a major regulator of calcium homeostasis and contractility in the heart, and thus SERCA dysfunction may contribute to both diastolic dysfunction and loss of contractile reserve with increased work demand. In contrast, when inotropes are used in HF, myocardium starts at lower level of |ΔG_~ATP|; any further decrease will likely cross this threshold with resulting SERCA dysfunction and diastolic and systolic dysfunction. Given their energy-sparing properties, myotropes may increase contractility with no further worsening in ATP supply/demand mismatch. Created with BioRender.com.