Why is epinephrine (adrenaline) beneficial for the right ventricle?

Epinephrine's Benefits for Right Ventricular Function

Epinephrine is superior for right ventricular support compared to other vasopressors due to its powerful β-adrenergic effects that enhance cardiac contractility while maintaining adequate perfusion pressure through its α-adrenergic effects. 1

Mechanism of Action

Epinephrine provides unique benefits for right ventricular (RV) function through:

• Balanced receptor activity: Acts on both α and β-adrenergic receptors, providing a three-fold mechanism to improve RV function 2:

  • Direct myocardial stimulation (positive inotropic action)
  • Increased heart rate (positive chronotropic action)
  • Peripheral vasoconstriction

• Enhanced contractility: Epinephrine is a more powerful cardiac stimulant than other inotropes like dobutamine, providing stronger β-adrenergic effects on the heart 3

• Improved systolic efficiency: Reinforces systolic efficiency without shortening diastole by:

  • Shortening systole
  • Decreasing myocardial resistance during diastole
  • Accelerating relaxation after contraction
  • Increasing filling pressure 3

Hemodynamic Effects on Right Ventricle

Epinephrine improves RV function through several mechanisms:

1. Improved RV contractility: Increases right ventricular ejection fraction (RVEF) by approximately 25% in patients with RV failure 4

2. Reduced RV end-systolic volume: Decreases right ventricular end-systolic volume index (RVESVI) without changing end-diastolic volume, indicating improved contractility 4

3. Enhanced RV stroke work: Significantly increases right ventricular stroke work index (RVSWI) by up to 76% in patients with RV failure 4

4. Improved ventricular-arterial coupling: Creates an upward vertical shift of the Frank-Starling relationship (RVSWI/RVEDVI) and an upward shift to the left of the pressure-volume relationship 4

5. Increased cardiac output: Improves cardiac index by approximately 20-24% in patients with severe septic shock and RV failure 4

Advantages Over Other Vasopressors

Epinephrine offers several advantages over other vasopressors for RV support:

• Superior to dobutamine: While dobutamine is primarily a β1-receptor stimulant that decreases systemic and pulmonary vascular resistance, it often requires combination with a vasopressor to maintain adequate perfusion pressure 1

• Comparable to norepinephrine with added benefits: In experimental models, both epinephrine and norepinephrine improve RV contractility, but epinephrine produces a more significant increase in cardiac output 5

• Better for acute RV failure: In acute RV failure, epinephrine improves RV contractility and increases cardiac output more effectively than pure α-agonists like phenylephrine 6

Clinical Applications

Epinephrine is particularly beneficial in:

1. Acute pulmonary embolism: The 2020 ESC guidelines note that epinephrine is used in cardiac arrest associated with pulmonary embolism 3

2. Septic shock with RV failure: Epinephrine improves RV function in patients with severe septic shock and RV failure by enhancing RV contractility 4

3. Cardiac arrest: The 2019 AHA guidelines recommend epinephrine administration during cardiac arrest (Class 1; Level of Evidence B-R), with 1 mg given every 3-5 minutes 3

Potential Limitations

Despite its benefits, epinephrine has some limitations:

• Post-resuscitation myocardial depression: As cardiac arrest duration increases, epinephrine becomes increasingly associated with post-ROSC myocardial depression 7

• Increased myocardial oxygen consumption: The β-adrenergic effects may increase myocardial work and potentially reduce subendocardial perfusion 3

• Tachycardia and arrhythmias: May be associated with a higher risk of tachycardia and arrhythmias compared to norepinephrine 3

Epinephrine remains a critical agent for supporting right ventricular function, particularly in acute settings where its balanced α and β effects provide immediate hemodynamic support while improving contractility of the failing right ventricle.