A 58-year-old woman with a history of paroxysmal atrial fibrillation (AF) presents to the emergency department with palpitations and dyspnea for 2 hours. Vital signs: HR 165/min, BP 88/54 mmHg, RR 28/min, SpO₂ 90% on room air. Lung auscultation reveals bibasal crackles. ECG confirms AF with rapid ventricular response. Troponin is negative. What is the most appropriate immediate next step in management?

Explanation

## Clinical Assessment: Haemodynamically UNSTABLE AF-RVR This patient presents with **haemodynamic instability** secondary to AF-RVR: - **Hypotension:** BP 88/54 mmHg (systolic < 90) - **Hypoxia:** SpO₂ 90% on room air - **Pulmonary edema:** Bibasal crackles (acute heart failure) - **Tachypnea:** RR 28/min - **Rapid ventricular rate:** 165/min **Key Point:** When AF-RVR causes haemodynamic compromise (shock, acute pulmonary edema, altered consciousness), the immediate management is **synchronized DC cardioversion**, NOT rate control agents. ## Why Cardioversion in This Case? | Finding | Significance | Action | |---------|-------------|--------| | **Systolic BP < 90 mmHg** | Cardiogenic shock from rapid rate | **Cardioversion indicated** | | **SpO₂ < 92% with crackles** | Acute pulmonary edema / heart failure | **Cardioversion indicated** | | **Negative troponin** | No acute MI; haemodynamic instability is rate-related | Cardioversion will resolve instability | | **Paroxysmal AF history** | Suggests structural heart is normal; rate is the problem | Cardioversion likely to restore sinus rhythm | ## Mnemonic: UNSTABLE AF — Immediate Cardioversion **U** – Urgent symptoms (syncope, severe dyspnea, chest pain) **N** – No time for drugs (haemodynamic collapse) **S** – Shock or pulmonary edema **T** – Troponin negative (not ACS-related) **A** – Arrhythmia (AF-RVR) is the cause **B** – Backup: sedate with propofol/midazolam + fentanyl **L** – Load paddles and deliver synchronized shock **E** – Expect sinus rhythm restoration ## Cardioversion Technique ```mermaid flowchart TD A[AF-RVR with Haemodynamic Instability]:::urgent --> B[Establish IV access]:::action B --> C[Obtain 12-lead ECG confirmation]:::action C --> D[Sedate with Propofol 1-2 mg/kg IV]:::action D --> E[Apply defibrillator pads in anterolateral position]:::action E --> F[Select SYNCHRONIZED mode]:::decision F -->|Correct| G[Start at 100-120 J biphasic]:::action G --> H{Sinus Rhythm Restored?}:::decision H -->|Yes| I[Initiate anticoagulation & rate control]:::action H -->|No| J[Increase to 150-200 J, repeat]:::action J --> K{Sinus Rhythm Restored?}:::decision K -->|Yes| I K -->|No| L[Consider IV Amiodarone, then retry]:::action ``` **Clinical Pearl:** Always use **SYNCHRONIZED** cardioversion for AF (not unsynchronized/defibrillation). Synchronized delivery avoids the vulnerable period of the cardiac cycle and reduces risk of VF. **High-Yield:** Propofol is preferred for sedation in haemodynamically unstable patients because it has minimal myocardial depression at lower doses and provides amnesia. Etomidate is an alternative if propofol is contraindicated. ## Why NOT the Other Options? 1. **Intravenous diltiazem 20 mg bolus:** While diltiazem is excellent for rate control in **stable** AF-RVR, it is **contraindicated in haemodynamic instability**. Diltiazem causes vasodilation and negative inotropy, which would worsen hypotension and cardiogenic shock in this patient. Rate control agents are ineffective when the patient is in shock. 2. **Oral flecainide 200 mg:** Flecainide is a Class IC antiarrhythmic used for **rhythm control in stable AF**, not acute haemodynamic instability. Oral drugs have slow onset and are ineffective in shock. Additionally, flecainide has negative inotropic effects and is contraindicated in patients with reduced ejection fraction or acute heart failure. 3. **Intravenous furosemide 40 mg followed by rate control:** While this patient has pulmonary edema, **diuretics alone will not resolve the underlying problem**—the rapid ventricular rate is driving the heart failure. Furosemide is a temporizing measure but delays definitive treatment. In haemodynamic instability from AF-RVR, cardioversion is the definitive and immediate treatment; diuretics are adjunctive only after rate/rhythm is controlled. ## Post-Cardioversion Management 1. **Anticoagulation:** Initiate unfractionated heparin (UFH) or low-molecular-weight heparin (LMWH) immediately. If AF duration > 48 hours or unknown, perform transesophageal echocardiography (TEE) to exclude left atrial appendage (LAA) thrombus before cardioversion. 2. **Rate control:** Once sinus rhythm is restored, initiate a beta-blocker (e.g., metoprolol) or calcium channel blocker to prevent AF recurrence. 3. **Underlying cause:** Investigate for thyroid disease, structural heart disease (echocardiography), and electrolyte abnormalities. **Key Point:** The sequence in haemodynamically unstable AF is: **Cardioversion → Anticoagulation → Rate/Rhythm Control → Investigate Cause**.