A 68-year-old man with acute anterior wall myocardial infarction (STEMI) undergoes primary PCI. Post-intervention angiography shows TIMI 3 flow in the LAD. However, 2 hours later, he develops hypotension (BP 82/50 mmHg), elevated JVP, clear lung fields, and reduced urine output. Troponin I is markedly elevated. Echocardiography shows severe RV dysfunction with preserved LV ejection fraction. What is the most appropriate immediate management?

Explanation

## Clinical Context: Right Ventricular Infarction and Cardiogenic Shock This patient has **RV infarction** complicating acute MI: hypotension + elevated JVP + clear lungs (preserved RV afterload sensitivity) + RV dysfunction on echo. ### Distinguishing RV Infarction from LV Failure | Feature | RV Infarction | LV Failure | |---------|---------------|----------| | JVP | Elevated | Elevated | | Lung fields | Clear | Congested (crackles) | | Mechanism of hypotension | Preload-dependent (RV stroke volume ↓) | Pump failure (LV EF ↓) | | Troponin elevation | Present (RV myocardium infarcted) | Present (LV myocardium infarcted) | | Echo findings | RV dysfunction, normal/preserved LV EF | LV dysfunction, ↓ EF | | Fluid response | Improves (restores preload) | Worsens (pulmonary edema) | **Key Point:** RV infarction is **preload-dependent**. The RV cannot generate adequate stroke volume without sufficient venous return. Diuretics and vasodilators are contraindicated; fluids are therapeutic [cite:Harrison 21e Ch 297]. ### Pathophysiology of RV Infarction ```mermaid flowchart TD A[RV coronary occlusion<br/>usually RCA]:::outcome --> B[RV myocardial necrosis]:::outcome B --> C[RV contractility ↓]:::outcome C --> D[RV stroke volume ↓]:::outcome D --> E[Right atrial pressure ↑<br/>JVP elevated]:::outcome E --> F[LV preload ↓<br/>septal shift]:::outcome F --> G[LV stroke volume ↓]:::outcome G --> H[Systemic hypotension]:::urgent H --> I{Management?}:::decision I -->|Fluids| J[Restore preload → RV SV ↑]:::action I -->|Diuretics| K[Preload ↓ → Shock worsens]:::urgent ``` ### Correct Management Strategy **High-Yield:** RV infarction management follows the "fluid-first" approach: 1. **Aggressive IV fluid resuscitation** (500 mL bolus over 10–15 minutes) - Restores RV preload - Improves RV stroke volume - Increases LV preload via septal shift - Often resolves hypotension and restores perfusion 2. **If hypotension persists after fluids** → add **dobutamine** - Positive inotropy (enhances RV contractility) - Mild vasodilation (reduces afterload) - Preferred over norepinephrine in RV infarction (norepinephrine increases afterload, worsening RV function) **Clinical Pearl:** The classic teaching is "fluids are the inotrope of choice in RV infarction." Aggressive fluid resuscitation alone resolves hypotension in ~50% of cases. If additional support is needed, dobutamine is preferred because it improves contractility without increasing afterload [cite:Harrison 21e Ch 297]. ### Why NOT Other Agents in RV Infarction | Agent | Why NOT | Consequence | |-------|---------|-------------| | Nitroglycerin | Reduces preload | Worsens RV stroke volume | | Furosemide | Reduces preload | Worsens RV stroke volume | | Norepinephrine | Increases afterload | RV cannot overcome increased resistance; worsens shock | **Warning:** Diuretics and nitrates are CONTRAINDICATED in RV infarction. They reduce preload, which the RV desperately needs to generate adequate stroke volume.