A 28-year-old man with infective endocarditis affecting the aortic valve develops acute severe aortic regurgitation with pulmonary oedema. He is in cardiogenic shock. What is the drug of choice for acute haemodynamic support in this patient?

Explanation

## Acute Aortic Regurgitation with Cardiogenic Shock **Key Point:** In acute severe aortic regurgitation (AR) with cardiogenic shock, dobutamine is the agent of choice because it combines positive inotropy (β₁ effect) with peripheral vasodilation (β₂ effect), reducing afterload while maintaining cardiac output—the ideal haemodynamic profile for AR. **High-Yield:** The pathophysiology of acute AR is critical: systolic blood pressure is maintained by increased LV contractility and stroke volume, but diastolic pressure falls due to regurgitation. Afterload reduction is essential; pure vasoconstrictors worsen the regurgitation fraction. **Clinical Pearl:** In acute AR, the goal is to reduce afterload and increase contractility simultaneously. Dobutamine achieves both: it increases contractility (β₁) and causes peripheral vasodilation (β₂), thereby reducing the regurgitant fraction and improving forward flow. ### Haemodynamic Profile Required in Acute AR | Parameter | Target | Rationale | | --- | --- | --- | | **Cardiac Output** | ↑ | Maintain perfusion | | **Afterload** | ↓ | Reduce regurgitant fraction | | **Heart Rate** | Moderate | Tachycardia shortens diastole, reduces AR time | | **Contractility** | ↑ | Compensate for LV dysfunction | ### Comparison of Inotropes in Acute AR | Agent | Inotropy | Chronotropy | Vasodilation | Vasoconstriction | Use in AR | | --- | --- | --- | --- | --- | --- | | **Dobutamine** | ↑↑ | ↑ | ↑↑ | — | **First-line** | | **Phenylephrine** | — | — | — | ↑↑↑ | **Avoid** (↑ afterload) | | **Noradrenaline** | ↑ | ↑ | — | ↑↑ | **Avoid** (↑ afterload) | | **Milrinone** | ↑ | ↑ | ↑↑ | — | Alternative if β-agonist intolerant | **Mnemonic:** DOBUTAMINE = **D**ecreased afterload + **O**ptimal inotropy + **B**eta-driven + **U**tility in AR **Warning:** Pure vasoconstrictors (phenylephrine, noradrenaline) increase afterload, which increases the regurgitant fraction and worsens pulmonary oedema. They are contraindicated in acute AR. ### Clinical Management Algorithm ```mermaid flowchart TD A[Acute severe AR + cardiogenic shock]:::outcome --> B{Haemodynamic goal?}:::decision B -->|Increase CO + Decrease afterload| C[Dobutamine]:::action B -->|Afterload reduction only| D[Nitroprusside/Nitroglycerin]:::action C --> E[Improves forward flow, reduces regurgitation]:::outcome D --> F[Adjunctive vasodilator therapy]:::outcome G[Pure vasoconstrictors]:::urgent --> H[Contraindicated - worsens AR]:::urgent ``` [cite:Harrison 21e Ch 282]