Cardiac function and chronotropic sensitivity to beta-adrenergic stimulation in sepsis

Area of Science:

• Cardiovascular Physiology
• Sepsis Pathophysiology
• Myocardial Function

Background:

• Cardiovascular response to sepsis involves hormonal and neural modulation.
• Sepsis can alter myocardial function and sensitivity to adrenergic stimulation.

Purpose of the Study:

• Investigate intrinsic myocardial performance in sepsis.
• Assess myocardial sensitivity to beta-adrenergic stimulation during sepsis.

Main Methods:

• Used an animal model of sepsis with bacteremia, normal blood pressure, and elevated heart rate.
• Studied intrinsic myocardial contractile function using isolated, perfused working heart preparations.
• Assessed chronotropic responses to isoproterenol in Langendorff perfused hearts and isolated right atria.

Main Results:

• Intrinsic myocardial contractile function was depressed in septic animals.
• Septic hearts showed elevated basal heart rates.
• Chronotropic sensitivity to isoproterenol was increased in septic hearts, with a lower EC50.
• Maximal heart rate response to isoproterenol was not significantly different from controls.

Conclusions:

• Sepsis depresses intrinsic myocardial function despite adequate in vivo cardiac performance.
• Myocardial sensitivity to beta-adrenergic stimulation is increased in sepsis.
• These findings highlight complex cardiovascular adaptations during sepsis.