Is it wise to discontinue milrinone (inotropic agent) in a patient with an RP Flex Impella (right ventricular support device)?

Management of Milrinone in a Patient with Impella RP Flex

It is generally advisable to continue milrinone in a patient with an Impella RP Flex device for right ventricular support, as discontinuation could lead to hemodynamic deterioration and compromise patient outcomes.

Rationale for Continuing Milrinone

Milrinone provides important inotropic support through phosphodiesterase-3 inhibition, which increases cardiac contractility while causing pulmonary and peripheral vasodilation 1. When used in conjunction with mechanical right ventricular support from the Impella RP Flex, these complementary mechanisms work together to optimize right ventricular function:

• Impella RP Flex: Provides mechanical circulatory support by pumping blood from the right atrium to the pulmonary artery, bypassing the failing right ventricle 2, 3
• Milrinone: Enhances cardiac contractility and reduces pulmonary vascular resistance, which is particularly beneficial for right ventricular function 1

Hemodynamic Considerations

The ACC/AHA guidelines specifically note that in patients with right ventricular failure, the concomitant use of agents that increase systemic afterload without increasing pulmonary vascular resistance (such as vasopressin or norepinephrine) may be needed to maintain RV perfusion during inodilator therapy with milrinone 4. This indicates that milrinone is considered appropriate therapy in the setting of right ventricular support.

When managing a patient with right ventricular failure requiring Impella RP Flex support:

1. Maintain euvolemia with a central venous pressure of 8-12 mmHg 1
2. Ensure adequate systemic blood pressure before relying solely on inotropic support 1
3. Consider vasopressor support (norepinephrine or vasopressin) to maintain systemic vascular resistance if needed 1
4. Monitor for complications of milrinone therapy, including:
   • Hypotension
   • Ventricular arrhythmias
   • Thrombocytopenia 1

Evidence from Clinical Experience

Recent studies have shown that patients with right ventricular failure requiring Impella RP support often benefit from concurrent inotropic therapy:

• In a single-center study of 22 patients with right ventricular failure treated with Impella RP Flex, 77% (17/22) were receiving inotropes before device support, suggesting that the combination therapy is common practice 3
• In the largest prospective study of patients with life-threatening right ventricular failure, patients received an average of 3.4 inotropes/vasopressors before Impella RP implant, with favorable survival outcomes 5

Important Monitoring Considerations

If continuing milrinone with Impella RP Flex:

• Maintain continuous ECG monitoring during infusion and for 1-2 hours after any dose adjustments
• Monitor daily laboratory values (electrolytes, BUN, creatinine)
• Perform regular hemodynamic assessments to evaluate response 1
• Adjust dosing based on renal function if needed 1

Potential Risks of Discontinuation

Abruptly discontinuing milrinone in a patient with right ventricular failure could lead to:

1. Sudden decrease in cardiac contractility
2. Increased pulmonary vascular resistance
3. Hemodynamic deterioration
4. Potential for clinical decompensation 4

The ACC/AHA guidelines specifically caution that "the decision to continue intravenous infusions at home should not be made until all alternative attempts to achieve stability have failed repeatedly" 4, suggesting that continuing inotropic support is preferred when needed for stability.

Conclusion

Based on the available evidence and guidelines, continuing milrinone in a patient with an Impella RP Flex is the preferred approach to maintain hemodynamic stability and optimize outcomes. Careful monitoring and potential addition of vasopressors to maintain adequate systemic blood pressure may be necessary to optimize the benefits of this combination therapy.