Multifocal Atrial Tachycardia

KEY FEATURES

ESSENTIALS OF DIAGNOSIS

• Heart rates up to 150 bpm

• Three or more distinct P waves in a single lead

• Variable P-P, P-R, and R-R intervals

• A majority (60–85%) of cases are associated with pulmonary disease

GENERAL CONSIDERATIONS

• Accounts for < 1% of all arrhythmias

• Chronic obstructive pulmonary disease exacerbation is the most common condition in which this arrhythmia is seen

• Respiratory failure, decompensated heart failure, and infection may precipitate the condition

• Hypokalemia, hypomagnesemia, and hyponatremia may be associated with this arrhythmia

• Pulmonary embolism, valvular heart disease, and postoperative state may rarely be associated with this arrhythmia

• Abnormal automaticity is the most likely mechanism, although triggered activity is also proposed

• Multifocal atrial tachycardia is often misdiagnosed as atrial fibrillation due to the irregularity in the R-R interval

CLINICAL PRESENTATION

SYMPTOMS AND SIGNS

• Most of the symptoms are related to the underlying cause

• Most patients are short of breath secondary to underlying lung disease

• Palpitations

• Chest pain

PHYSICAL EXAM FINDINGS

• Variable S₁

• Other findings relate to underlying cause

DIFFERENTIAL DIAGNOSIS

• Atrial fibrillation

• Atrial flutter

DIAGNOSTIC EVALUATION

LABORATORY TESTS

• CBC, basic metabolic panel

• Arterial blood gas analysis

• Cardiac biomarkers if there is a suspicion of myocardial infarction

• Chest x-ray and other investigation toward managing the underlying cause

ELECTROCARDIOGRAPHY

• ECG shows tachycardia with 3 or more distinct P waves in a single lead and variable P-P, P-R, and R-R intervals

IMAGING STUDIES

• Occasionally an echocardiogram may be used to assess right and left heart function

TREATMENT

CARDIOLOGY REFERRAL

• If patients are hemodynamically unstable

• If ventricular rate could not be controlled using conventional atrioventricular (AV) nodal blocking drugs

HOSPITALIZATION CRITERIA

• Most patients are hospitalized because of underlying respiratory failure

MEDICATIONS

• Treat the underlying cause (ie, respiratory failure)

• Verapamil is useful, 180–360 mg/day

• Cardiac selective beta blockers, such as metoprolol, may be used for ventricular rate control if tolerated

• Intravenous magnesium and potassium supplementation may convert a significant number to sinus rhythm

• Digoxin is usually not helpful and has the potential to initiate atrial tachycardia

• Theophylline and beta agonists should be titrated down to the least effective dose

THERAPEUTIC PROCEDURES

• In a rare patient, pacemaker implantation followed by AV nodal ablation may be required

MONITORING

• ECG monitoring in the hospital

DIET AND ACTIVITY