Is there a specific inotrope or vasopressor that selectively works on the right ventricle?

No Single Inotrope or Vasopressor Selectively Works on the Right Ventricle

There is no inotrope or vasopressor that selectively acts only on the right ventricle—all agents affect both ventricles systemically. However, certain agents have more favorable effects on right ventricular (RV) function by reducing pulmonary vascular resistance (PVR) without compromising systemic vascular resistance (SVR), making them preferred choices for RV failure.

Preferred Agents for Right Ventricular Support

Inotropes with Favorable PVR Effects

The most RV-friendly inotropes are those that have neutral or beneficial effects on PVR 1:

• Milrinone is particularly advantageous for RV failure because it reduces PVR through pulmonary vasodilation while increasing cardiac contractility 2. As a phosphodiesterase-3 inhibitor, it works by increasing intracellular cAMP, causing relaxation of pulmonary vascular smooth muscle 2.

• Dobutamine has neutral effects on PVR and increases cardiac contractility through β1-receptor stimulation 1. It is often preferred over milrinone due to its shorter half-life, which allows for more rapid titration in the face of potential hypotension 1.

• Epinephrine also has neutral or beneficial effects on PVR and can be used in RV failure 1.

Critical Caveat: Systemic Hypotension

A major pitfall with both milrinone and dobutamine is their tendency to cause systemic vasodilation and hypotension 1, 2. This is particularly problematic in RV failure because:

• RV coronary perfusion occurs during both systole and diastole 1
• If PVR exceeds SVR (i.e., systolic pulmonary artery pressure > systolic systemic arterial pressure), RV ischemia results 1
• The fundamental principle is maintaining SVR > PVR at all times 1, 2

Strategy to Offset Hypotension

Replacement-dose vasopressin should be added to offset the drop in SVR without increasing PVR 1, 2. This is particularly important in septic patients or those with liver disease where vasopressin deficiency is common 1.

Inhaled Nitric Oxide: The Most RV-Selective Therapy

Inhaled nitric oxide (iNO) at 20 parts per million is the closest option to RV-selective therapy because it:

• Acutely decreases PVR and improves cardiac output 1
• Has no detrimental effect on SVR—this is its most important advantage 1
• Directly unloads the failing RV 1
• Improves oxygenation through ventilation-perfusion matching 1

Important Warnings About iNO

• Rebound pulmonary hypertension can occur upon weaning, particularly without replacement pulmonary vasodilator therapy 1
• Start or restart a phosphodiesterase inhibitor (like milrinone or sildenafil) when weaning iNO 1
• Risk of methemoglobinemia at sustained high doses 1

Agents to Avoid or Use Cautiously

Dopamine at infusion rates >7 mcg/kg/min increases PVR and should be avoided in RV failure 1. This makes it a poor choice when RV afterload reduction is the goal.

Clinical Algorithm for RV Failure Management

1. Ensure SVR > PVR as the primary hemodynamic goal 1, 2
2. Start iNO at 20 ppm for immediate PVR reduction without SVR compromise 1
3. Add dobutamine or milrinone for inotropic support, with preference for dobutamine due to shorter half-life 1
4. Add replacement-dose vasopressin if systemic hypotension develops to maintain SVR 1, 2
5. When weaning iNO, transition to oral phosphodiesterase inhibitor 1
6. Avoid high-dose dopamine (>7 mcg/kg/min) 1

Key Monitoring Parameters

• Maintain systolic systemic arterial pressure > systolic pulmonary arterial pressure 1
• Target mean arterial pressure ≥65 mmHg 1
• Monitor for arrhythmias with all catecholamines 3
• Use invasive hemodynamic monitoring (central venous pressure, mixed venous oxygen saturation) to guide therapy 1