A 72-year-old woman with a history of rheumatic mitral stenosis presents with acute-onset atrial fibrillation with a rapid ventricular response (heart rate 140 bpm). She is haemodynamically unstable with systolic blood pressure 85 mmHg, cool extremities, and altered mental status. Her serum potassium is 3.2 mEq/L (normal 3.5–5.0), and ECG confirms AF with rapid ventricular rate. Which of the following is the most appropriate immediate management?

Explanation

## Critical Clinical Assessment This patient presents with **haemodynamic instability** secondary to rapid atrial fibrillation. The presence of **hypotension, altered mental status, and cool extremities** indicates **cardiogenic shock** and acute decompensation. ### Haemodynamic Stability Assessment | Clinical Feature | This Patient | Implication | |------------------|--------------|-------------| | **Systolic BP** | 85 mmHg | Hypotensive | | **Mental status** | Altered | Cerebral hypoperfusion | | **Extremities** | Cool | Poor peripheral perfusion | | **Heart rate** | 140 bpm | Severe tachycardia | | **Diagnosis** | AF with RVR | Haemodynamically unstable | **Key Point:** In **haemodynamically unstable patients with tachyarrhythmias**, pharmacological rate control is ineffective and delays definitive treatment. **Synchronized electrical cardioversion is the standard of care.** ### Why Cardioversion is Indicated **High-Yield:** The **ACLS guidelines** mandate synchronized cardioversion for any tachyarrhythmia causing haemodynamic instability, regardless of the rhythm. Pharmacological agents: - Have delayed onset (5–30 minutes) - May worsen hypotension (negative inotropic effects) - Do not restore sinus rhythm acutely - Delay restoration of perfusion **Clinical Pearl:** "Unstable = Shock" — any patient with signs of shock (hypotension, altered mental status, poor perfusion) requires immediate electrical therapy, not drugs. ### Management Algorithm for AF with RVR ```mermaid flowchart TD A[Atrial Fibrillation with RVR]:::outcome --> B{Haemodynamically stable?}:::decision B -->|No - Signs of shock| C[Correct electrolytes if time permits]:::action C --> D[Synchronized cardioversion]:::urgent D --> E[Sedation + 100-200 J biphasic]:::action E --> F[Sinus rhythm restored]:::outcome B -->|Yes - Stable| G{Rate control needed?}:::decision G -->|Yes| H[IV digoxin or beta-blocker]:::action H --> I[Monitor rate response]:::action ``` **Mnemonic: SHOCK** — **S**ynchronized cardioversion, **H**aemodynamic instability, **O**verride pharmacology, **C**ritical urgency, **K**eep sedation ready. ### Addressing the Hypokalaemia **Warning:** Hypokalaemia (K⁺ = 3.2 mEq/L) increases the risk of **torsades de pointes** and malignant arrhythmias during cardioversion. However, **do not delay cardioversion** to correct potassium — correct it **concurrently** or **immediately after** cardioversion is performed. Potassium repletion takes 30–60 minutes; the patient cannot wait. **Dosing:** IV potassium chloride 10–20 mEq over 30–60 minutes (via central line if possible) after cardioversion is initiated. [cite:ACLS Guidelines 2020; Harrison 21e Ch 235]