Cardiology · Arrhythmias
The facts most likely to be tested
The hallmark ECG finding is an irregularly irregular rhythm with an absence of discrete P waves and a narrow QRS complex.
The CHA2DS2-VASc score is the gold standard for assessing thromboembolic risk to determine the necessity of long-term anticoagulation.
Hemodynamically unstable patients presenting with atrial fibrillation require immediate synchronized cardioversion.
Rate control is the preferred initial strategy for asymptomatic or minimally symptomatic patients, typically achieved with beta-blockers or non-dihydropyridine calcium channel blockers.
Rhythm control via catheter ablation or antiarrhythmic drugs is indicated for patients who remain symptomatic despite adequate rate control.
Transesophageal echocardiography (TEE) is mandatory to rule out left atrial appendage thrombus before attempting cardioversion in patients with atrial fibrillation of unknown duration or >48 hours.
Direct oral anticoagulants (DOACs), such as apixaban or rivaroxaban, are preferred over warfarin for stroke prophylaxis in patients with non-valvular atrial fibrillation.
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A 72-year-old male with a history of hypertension presents to the emergency department with palpitations and lightheadedness for the past 3 hours. Physical examination reveals an irregularly irregular pulse and a blood pressure of 115/75 mmHg. An ECG demonstrates an absence of P waves with a narrow QRS complex and a ventricular rate of 145 bpm. The patient has no history of valvular heart disease. His CHA2DS2-VASc score is calculated to be 3.
What is the most appropriate next step in management for this patient?
Rate control with a beta-blocker or non-dihydropyridine calcium channel blocker
The patient is hemodynamically stable, making rate control the appropriate initial management strategy per the CHA2DS2-VASc risk stratification and current guidelines.
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Etiology / Epidemiology
Most common sustained arrhythmia; associated with hypertension, CAD, and mitral stenosis.
Clinical Manifestations
Palpitations, fatigue, and irregularly irregular pulse; pulse deficit is a classic finding.
Diagnosis
ECG shows absent P waves and irregularly irregular R-R intervals.
Treatment
Rate control with beta-blockers or non-DHP CCBs; anticoagulation based on CHA2DS2-VASc score.
Prognosis
Major risk is ischemic stroke; requires long-term anticoagulation for high-risk patients.
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Epidemiology & Etiology
Prevalence increases significantly with age, particularly in patients with hypertension or heart failure. Common triggers include holiday heart syndrome (alcohol), hyperthyroidism, and post-operative states. Structural heart disease, specifically mitral valve disease, is a major predisposing factor.
Pertinent Anatomy
The pulmonary veins are the most common site of ectopic foci triggering the arrhythmia. The atrio-ventricular (AV) node acts as the gatekeeper, determining the ventricular rate based on its refractory period.
Pathophysiology
Characterized by multiple re-entrant circuits within the atria leading to chaotic electrical activity. The loss of the atrial kick reduces cardiac output by approximately 20-30%. Chronic remodeling leads to persistent electrical and structural changes, making sinus rhythm harder to maintain.
Clinical Manifestations
Patients often present with palpitations, dyspnea, or syncope, though many are asymptomatic. Physical exam reveals an irregularly irregular pulse and a pulse deficit between apical and peripheral heart rates. Acute hemodynamic instability (hypotension, altered mental status) requires immediate synchronized cardioversion.
Diagnosis
The ECG is the diagnostic gold standard, demonstrating absent P waves and irregularly irregular R-R intervals. A TTE (transthoracic echocardiogram) is essential to evaluate for structural heart disease and left atrial thrombus.
Treatment
Initial management focuses on rate control using beta-blockers (e.g., metoprolol) or non-DHP CCBs (diltiazem/verapamil). Do not use non-DHP CCBs in HFrEF. Anticoagulation is determined by the CHA2DS2-VASc score; a score of ≥2 in men or ≥3 in women generally mandates DOACs (e.g., apixaban).
Prognosis
The primary long-term concern is thromboembolism, specifically ischemic stroke. Patients must be monitored for bleeding risk using the HAS-BLED score before initiating long-term anticoagulation.
Differential Diagnosis
Multifocal Atrial Tachycardia: 3+ distinct P-wave morphologies
Atrial Flutter: sawtooth P-waves at 250-350 bpm
AVNRT: regular, narrow-complex tachycardia
Sinus Tachycardia: regular rhythm with visible P-waves
Wolff-Parkinson-White: delta wave on ECG