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28/01/2026
Atrial Fibrillation in Acute Care: Clinical Approach Algorithm
Atrial fibrillation is a common arrhythmia in acute care, associated with palpitations, dyspnea, chest pain, or decompensated heart failure. Diagnosis should begin with ECG confirmation and a detailed clinical history, assessing symptom duration, medications, comorbidities, and red flags, as well as screening for reversible causes (electrolyte or acid–base disturbances, infection, hyperthyroidism, alcohol/stimulants).
This algorithm proposes a structured approach to atrial fibrillation, defining criteria for hemodynamic instability, guiding the choice between rhythm and rate control, and indicating when to anticoagulate. It helps identify patients who warrant further work-up and urgent intervention, optimizing resources and avoiding unnecessary procedures.
Podcast transcript
Initial assessment (ECG)
Patient with tachycardia and suspected atrial fibrillation. The first step is to confirm the diagnosis with a 12-lead ECG. Once AF is confirmed, define the treatment strategy, starting with the identification of reversible secondary causes.
Reversible secondary causes
Screen for electrolyte or acid–base disturbances, pericarditis, myocarditis, hyperthyroidism, sepsis, anaemia, gastrointestinal bleeding, hypothermia, or drug toxicity. Also consider decompensated heart failure, acute coronary syndrome, and hypovolaemia. If any cause is identified, treat the underlying condition.
Hemodynamic stability and red flags
If no reversible cause is found, the therapeutic decision centres on rhythm vs rate control. First, assess hemodynamic stability. Instability presents with systolic BP < 90 mmHg associated with altered mental status, chest pain, dyspnoea, or presyncope/syncope. Other red flags include acute ischaemia with ST-segment changes, elevated cardiac biomarkers, or decompensated heart failure.
Accessory pathway and specialist support
If the patient is hemodynamically unstable, request specialist support. Do the same when an accessory pathway is suspected—e.g., wide, bizarre, or polymorphic QRS complexes; history of Wolff–Parkinson–White; or a delta wave on prior ECGs.
Treatment strategy: rhythm vs rate
In stable patients, choose between rhythm and rate control. Rate control is generally favoured in patients >65 years, with hypertension, without heart failure, those preferring this approach, refractory to prior antiarrhythmics, or minimally symptomatic. Rhythm control can be considered when significant symptoms persist despite adequate rate control.
Cardioversion and episode duration
The decision to perform pharmacological or electrical cardioversion depends on AF duration. If <48 hours, cardioversion can be considered directly. If >48 hours or unknown, a minimum of 3 weeks of effective anticoagulation is required, or alternatively, a transoesophageal echocardiogram to exclude intracardiac thrombus. Recent stroke/TIA, peripheral thromboembolism, mechanical valve, or rheumatic heart disease contraindicate immediate cardioversion without prior anticoagulation.
Rhythm control: drugs and exclusions
If rhythm control is chosen and no exclusion criteria are present (second/third-degree AV block, prolonged QT, hypokalaemia, pregnancy, or severe renal/hepatic impairment), antiarrhythmics such as amiodarone, flecainide, propafenone, or sotalol may be used. In structural, ischaemic, or valvular heart disease, or with LV hypertrophy, avoid flecainide and propafenone; prefer amiodarone or sotalol. In heart failure, amiodarone is usually the drug of choice.
Rate control: LVEF-dependent
When opting for rate control, selection depends on left-ventricular ejection fraction. If LVEF <40%, use low-dose beta-blockers (e.g., metoprolol) and consider adding digoxin. With preserved LVEF, beta-blockers, non-dihydropyridine calcium-channel blockers (diltiazem or verapamil), or digoxin can be used alone or in combination.
Chronic anticoagulation
After initial control, start maintenance therapy (rhythm or rate) according to the chosen strategy. In all cases, assess thromboembolic risk and the need for long-term anticoagulation based on the CHA₂DS₂-VASc score.
Shared decision-making and follow-up
Therapy should be individualised, considering symptoms, comorbidities, contraindications, and the patient’s informed preference. Ensure an appropriate follow-up plan after discharge.
Related algorithms
Clinical cases
Clinical cases — Atrial fibrillation
Case 1 — Recent-onset AF, stable patient
Male, 45, no relevant history, palpitations for 12 hours. ECG: atrial fibrillation, HR 140 bpm, no signs of ischaemia. BP 125/75 mmHg, no dyspnoea, no HF. No prior anticoagulation. What is the most appropriate next step?
- Start anticoagulation for 3 weeks and only then consider cardioversion
- Start aspirin 150–300 mg/day
- Immediate cardioversion (electrical or pharmacological), followed by anticoagulation according to CHA₂DS₂-VASc
- Rate control only with IV diltiazem
Show answer
c) Immediate cardioversion (<48 h), followed by an anticoagulation decision according to thromboembolic risk.
Rationale: In AF of <48 h duration and a stable patient, it is acceptable to cardiovert without prior anticoagulation; ensure post-cardioversion anticoagulation according to CHA₂DS₂-VASc and bleeding risk. A 3-week delay is required when duration is >48 h or unknown.
Case 2 — AF with pre-excitation (suspected accessory pathway)
Female, 28, rapid irregular palpitations; ECG: irregular tachyarrhythmia with variable wide QRS; prior records show a delta wave. Haemodynamically stable. What is the best initial therapeutic option?
- IV adenosine bolus
- IV diltiazem
- IV amiodarone loading
- IV procainamide (or electrical cardioversion if the patient deteriorates)
Show answer
d) IV procainamide (or immediate electrical cardioversion if unstable).
Rationale: In AF with an accessory pathway, avoid AV-node blockers (adenosine, verapamil/diltiazem, digoxin and, in many protocols, IV amiodarone) due to the risk of facilitating conduction via the pathway and degeneration to VF. Agents that slow conduction in the accessory pathway (e.g., procainamide or ibutilide) are preferred; if instability occurs, perform immediate electrical cardioversion.
Rationale: In AF with an accessory pathway, avoid AV-node blockers (adenosine, verapamil/diltiazem, digoxin and, in many protocols, IV amiodarone) due to the risk of facilitating conduction via the pathway and degeneration to VF. Agents that slow conduction in the accessory pathway (e.g., procainamide or ibutilide) are preferred; if instability occurs, perform immediate electrical cardioversion.
Case 3 — AF >48 h/unknown duration: pre-cardioversion strategy
Male, 72, with hypertension and diabetes (CHA₂DS₂-VASc = 3), intermittent palpitations for “several days,” no precise record. ECG: AF, HR 110 bpm; stable. What is the correct approach before elective cardioversion?
- Immediate cardioversion without anticoagulation because he is haemodynamically stable
- Start a DOAC and maintain effective anticoagulation for ≥3 weeks before cardioversion (or TOE to exclude thrombus and cardiovert earlier)
- Start aspirin monotherapy for 3 weeks
- Prophylactic heparin for 24 h and then cardioversion
Show answer
b) Effective anticoagulation for ≥3 weeks (or a TOE-guided strategy).
Rationale: With duration >48 h or unknown, cardioversion requires anticoagulation for ≥3 weeks, or a strategy using trans-oesophageal echocardiography to exclude thrombus before cardioversion. Continue post-cardioversion anticoagulation according to CHA₂DS₂-VASc.
Rationale: With duration >48 h or unknown, cardioversion requires anticoagulation for ≥3 weeks, or a strategy using trans-oesophageal echocardiography to exclude thrombus before cardioversion. Continue post-cardioversion anticoagulation according to CHA₂DS₂-VASc.
FAQ
Frequently Asked Questions about Atrial Fibrillation (AF) in Acute Care
1) How is AF diagnosed in the emergency setting?
Diagnosis is confirmed with a 12-lead ECG, showing disorganised atrial activity (no clear P waves) and irregularly irregular RR intervals. In an irregular tachyarrhythmia with a wide QRS, suspect an accessory pathway until proven otherwise.
2) What are the signs of haemodynamic instability?
Hypotension (SBP < 90 mmHg), altered mental status, chest pain/ischaemia, severe dyspnoea or decompensated heart failure. In these cases, prioritise electrical cardioversion and specialist support.
3) When should I choose rhythm control versus rate control?
In stable patients, rate control is generally preferred (e.g., age > 65 years, comorbidities, mild symptoms). Rhythm control is appropriate when significant symptoms persist despite adequate rate control, in recent-onset AF, or when rapid functional recovery is desired.
4) How does AF duration guide cardioversion?
If duration is < 48 hours, immediate cardioversion can be considered. If > 48 hours or unknown, it requires effective anticoagulation for ≥ 3 weeks or a TOE-guided strategy to exclude thrombus before cardioversion.
5) Who should receive anticoagulation and for how long?
Decide based on the CHA₂DS₂-VASc score. After cardioversion, maintain anticoagulation for at least 4 weeks and, long-term, according to thromboembolic and bleeding risk. Aspirin does not replace anticoagulation in AF.
6) What should be avoided if an accessory pathway (pre-excited AF) is suspected?
Avoid drugs that block only the AV node (e.g., adenosine, verapamil/diltiazem, digoxin). Prefer agents acting on the accessory pathway (e.g., procainamide) or electrical cardioversion if unstable.
7) How do I choose rate-contr
Authorship and updates
Filipe Cerca, MD
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2024 ESC Guidelines para a abordagem da fibrilhação auricular (página oficial ESC).
Van Gelder IC, et al. 2024 ESC Guidelines for the management of atrial fibrillation. Eur Heart J.
AHA Clinical Update – 2023 AF Guideline (slide set de síntese).
NICE NG196 (2021): Atrial fibrillation – diagnosis and management.
Sakthivel R, et al. Atrial fibrillation and pre-excitation: risks e manejo (FA com via acessória).