AUTHOR INFORMATION

Section 1 of 11

Authored by Robin R Hemphill, MD, MPH, Associate Professor, Director, Disaster Preparedness, Department of Emergency Medicine, Vanderbilt University Medical Center

Coauthored by Michael A Huott, MD, Consulting Staff, Department of Emergency Medicine, Southwest Texas Methodist Hospital

Robin R Hemphill, MD, MPH, is a member of the following medical societies: American Academy of Emergency Medicine, American College of Emergency Physicians, and Society for Academic Emergency Medicine

Edited by Edmond Hooker, MD, Assistant Clinical Professor, Department of Emergency Medicine, University of Louisville, Wright State University; Francisco Talavera, PharmD, PhD, Senior Pharmacy Editor, eMedicine; Paul Blackburn, DO, Program Director, Department of Emergency Medicine, Maricopa Medical Center; Assistant Professor, Department of Surgery, University of Arizona; John Halamka, MD, Chief Information Officer, CareGroup Healthcare System, Assistant Professor of Medicine, Department of Emergency Medicine, Beth Israel Deaconess Medical Center; Assistant Professor of Medicine, Harvard Medical School; and Craig Feied, MD, FACEP, FAAEM, FACPh, Professor of Emergency Medicine, Georgetown University, Director, National Institute for Medical Informatics, Director, Federal Project ER One, Director, National Center for Emergency Medicine Informatics

Author's Email:	Robin R Hemphill, MD, MPH
Editor's Email:	Edmond Hooker, MD

eMedicine Journal, March 7 2006, VOLUME 7, Number 3

INTRODUCTION

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Background: Multifocal atrial tachycardia (MAT) is an irregular cardiac rhythm caused by at least 2 different sites of competing atrial activity.

Pathophysiology: MAT most often is found in the elderly patient with decompensated chronic lung disease and should be thought of as a hypoxic complication of underlying heart conduction pathology. However, other underlying causes may be present, such as congestive heart failure, sepsis, or methylxanthine toxicity. The effect of MAT on the heart conduction system may or may not lead to hemodynamic instability.

Frequency:

• In the US: MAT is believed to be quite common. Usually, the patient's underlying problem (eg, respiratory failure, sepsis, theophylline toxicity) takes therapeutic precedent. The condition is transient and resolves when the underlying condition improves.

Mortality/Morbidity:

• MAT is seldom life threatening. The overall clinical picture and symptoms improve when the underlying condition is addressed and MAT is controlled.

• Morbidity is difficult to quantify because the underlying disease is the primary determinant of complications.

Age: This is predominately a condition of the elderly patient with multiple medical problems.

CLINICAL

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History:

• Palpitations

• Shortness of breath

• Chest pain

• Lightheadedness

• Syncopal episode

• Symptoms may be transient

Physical:

• Pulse is rapid and irregular.

• Cardiac monitor and electrocardiograph (ECG) show an irregular rapid tachycardia, usually narrow-complex.

• It is often confused with atrial flutter or fibrillation.

• It usually does not cause hemodynamic instability.

• Cardiac and pulmonary physical findings reflect the underlying process.

• Respiratory adventitial sounds often are prominent.

Causes:

• Decompensated chronic lung disease

• Congestive heart failure

• Sepsis

• Methylxanthine toxicity

• Myocardial infarction

• Pneumonia

• Pulmonary embolism

• Hypokalemia

DIFFERENTIALS

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Atrial Fibrillation
Atrial Flutter

Other Problems to be Considered:

Narrow-complex tachyarrhythmias
Sinus tachycardia
Wide-complex tachyarrhythmias

WORKUP

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Lab Studies:

• Electrolytes

• Magnesium level

• Theophylline level (if patient is on this medication)

• Obtain other laboratory tests as clinically indicated (eg, CBC, cardiac markers, ABGs).

Imaging Studies:

• If the patient is unstable, a portable anteroposterior (AP) chest radiograph is indicated to check pulmonary and cardiac findings.

Other Tests:

• All patients are placed on pulse oximetry and a cardiac monitor.

• A 12-lead ECG with a rhythm strip is essential to make the diagnosis.

• MAT is suggested when 3 or more P wave morphologies are present.

• Varying P-P, PR, and R-R intervals may indicate MAT.

• The atrial rhythm of patients with MAT is 100-180 beats per minute.

• A narrow QRS complex is present unless there is a conduction delay.

TREATMENT

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Prehospital Care:

• Stabilize the acute situation as necessary.

• Provide oxygen, cardiac monitoring, and pulse oximetry.

• Establish IV access without delaying transport.

Emergency Department Care:

• Rapidly assess and stabilize the ABCs while providing simultaneous treatment. An upright sitting position usually is most appropriate.

• Obtain IV access with a large-bore catheter with isotonic sodium chloride solution at a to keep open (TKO) rate.

• Administer oxygen to maintain the saturation greater than 90%, but avoid excessive oxygen in patients with known significant COPD. This will avoid the theoretical problem of removing the hypoxic drive for ventilation, which can result in increased carbon dioxide retention.

• The need for tracheal intubation is dictated by the standard clinical indications.

• Establish cardiac monitor, blood pressure monitor, and pulse oximetry.

• Treat the underlying cardiopulmonary process, theophylline toxicity, or metabolic abnormality. Bronchodilators and oxygen should be administered for treatment of decompensated chronic obstructive pulmonary disease (COPD); activated charcoal and/or charcoal hemoperfusion is the therapy for theophylline toxicity.

• When magnesium sulfate is administered to correct hypokalemia, most patients convert to normal sinus rhythm (NSR).

• Specific antiarrhythmic therapy is not commonly indicated and the value of such therapy is not proven. Metoprolol has been shown to be somewhat effective in converting MAT to NSR, and verapamil effectively slows the ventricular rate, but it is less effective in conversion to NSR.

• Due to the multiple atrial foci, cardioversion rarely is successful.

• Avoid sedatives.

Consultations: A cardiologist may be of assistance with ECG interpretation and may be available for consultation if antiarrhythmic therapy is being considered.

MEDICATION

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Although specific drug therapy historically has not demonstrated great efficacy in treating MAT, several small reports describe effectiveness with the use of magnesium sulfate (with concomitant correction of hypokalemia), verapamil, and some beta-blockers.

Drug Category: Antiarrhythmics -- In conjunction with the correction of the underlying medical process, these agents may provide conversion to NSR or control of the ventricular rate.

Drug Name	Magnesium sulfate -- Considered by some the DOC. Maximum dose not well defined. Patient's deep tendon reflexes should be evaluated serially, as loss of reflexes is a signal to slow or halt the infusion of the drug.
Adult Dose	2 g IV over 60 s, followed by 1-2 g/h
Pediatric Dose	Not established
Contraindications	Documented hypersensitivity; heart block; Addison disease; myocardial damage; severe hepatitis
Interactions	Concurrent use with nifedipine may cause hypotension and neuromuscular blockade; may increase neuromuscular blockade observed with aminoglycosides and potentiate neuromuscular blockade produced by tubocurarine, vecuronium, and succinylcholine; may increase CNS effects and toxicity of CNS depressants, betamethasone, and cardiotoxicity of ritodrine
Pregnancy	A - Safe in pregnancy
Precautions	Magnesium may alter cardiac conduction leading to heart block in digitalized patients; monitor respiratory rate, deep tendon reflex, and renal function when administered parenterally; may produce significant hypertension or asystole; correct serum potassium to > 4 mEq/L

Drug Name	Verapamil (Calan, Covera-HS) -- During depolarization, inhibits calcium ion from entering slow channels or voltage-sensitive areas of vascular smooth muscle and myocardium.
Adult Dose	5-10 mg IV followed by a second dose 15-30 min later if the patient does not satisfactorily respond to the initial dose
Pediatric Dose	Not established
Contraindications	Documented hypersensitivity; severe CHF; sick sinus syndrome or second-degree or third-degree AV block; hypotension (<90 mm Hg systolic)
Interactions	Verapamil may increase carbamazepine, digoxin, and cyclosporine levels; coadministration with amiodarone can cause bradycardia and a decrease in cardiac output; when administered concurrently with beta-blockers may increase cardiac depression; cimetidine may increase verapamil levels; verapamil may increase theophylline levels
Pregnancy	C - Safety for use during pregnancy has not been established.
Precautions	Hepatocellular injury may occur; transient elevations of transaminases with and without concomitant elevations in alkaline phosphatase and bilirubin have occurred (elevations have been transient and may disappear with continued verapamil treatment); monitor liver function periodically

Drug Name	Metoprolol (Lopressor) -- Selective beta1-adrenergic receptor blocker that decreases the automaticity of contractions. During IV administration, carefully monitor blood pressure, heart rate, and ECG.
Adult Dose	Initially 5 mg IV q5min; not to exceed 15 mg
Pediatric Dose	Not established
Contraindications	Documented hypersensitivity; uncompensated congestive heart failure; bradycardia; asthma or severe COPD; cardiogenic shock; AV conduction abnormalities
Interactions	Aluminum salts, barbiturates, NSAIDs, penicillins, calcium salts, cholestyramine, and rifampin may decrease bioavailability and plasma levels of metoprolol, possibly resulting in decreased pharmacologic effects; toxicity of metoprolol may increase with coadministration of sparfloxacin, phenothiazines, astemizole, calcium channel blockers, quinidine, flecainide, and contraceptives; metoprolol may increase toxicity of digoxin, flecainide, clonidine, epinephrine, nifedipine, prazosin, verapamil, and lidocaine
Pregnancy	B - Usually safe but benefits must outweigh the risks.
Precautions	Beta-adrenergic blockade may reduce signs and symptoms of acute hypoglycemia and may decrease clinical signs of hyperthyroidism; abrupt withdrawal may exacerbate symptoms of hyperthyroidism, including thyroid storm; monitor patient closely and withdraw the drug slowly; during IV administration, carefully monitor blood pressure, heart rate, and ECG

FOLLOW-UP

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Further Inpatient Care:

• Most patients require admission to further manage their underlying cardiopulmonary diseases.

• These patients frequently are admitted to a monitored bed; however, the clinical scenario and the hemodynamic stability of the patient dictate disposition.

Further Outpatient Care:

• Patients who convert to NSR after treatment and stabilization of the underlying process or by specific antiarrhythmic therapy may be cautiously considered for discharge.

• In order to be discharged, the patient must be back to baseline, have no complicating factors, be able to accomplish activities of daily living, and be available for close follow-up care.

Transfer:

• For patients with theophylline toxicity, consider transfer to hospitals with hemoperfusion capabilities.

Deterrence/Prevention:

• Close and careful management is required because of the underlying complex cardiopulmonary medical conditions.

• Surveillance and replacement as appropriate of electrolyte and magnesium levels

• Careful monitoring of theophylline levels in order to avoid toxicity

Complications:

• Atrial thrombi with embolization and subsequent stroke

• Myocardial infarction from incongruous myocardial supply and demand

• Pulmonary emboli

Prognosis:

• Depends on the prognosis of any comorbid disease

MISCELLANEOUS

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Medical/Legal Pitfalls:

• Treating MAT as atrial flutter or fibrillation

• Treating MAT with aberrancy as ventricular tachycardia

• Utilizing cardioversion or defibrillation when not indicated

• Failure to simultaneously correct hypokalemia when giving magnesium sulfate

• Failure to address the underlying medical problem; becoming distracted by the cardiac rhythm

• Discharging patients without adequately treating underlying medical problems

TEST QUESTIONS

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CME Question 1: Which of the following is not a typical underlying medical condition often associated with multifocal atrial tachycardia (MAT)?

A: Decompensated chronic lung disease
B: Congestive heart failure
C: Digoxin toxicity
D: Methylxanthine toxicity
E: Pulmonary embolism

The correct answer is C: Digoxin toxicity typically leads to atrioventricular blocks, regularization of atrial fibrillation, or ventricular ectopy.

CME Question 2: What is the first line medical therapy for a patient with an ECG that demonstrates multifocal atrial tachycardia (MAT)?

A: IV procainamide
B: IV lidocaine
C: IV beta-blockers
D: Supportive therapy directed at the underlying process
E: IV magnesium

The correct answer is D: In treating MAT, the primary efforts are directed toward correcting the underlying decompensated medical condition, which often correct the MAT.

Pearl Question 1 (T/F): The most common cause of multifocal atrial tachycardia (MAT) is myocardial infarction.

The correct answer is False: The most common cause of MAT is decompensated chronic lung disease. Other causes include pneumonia, congestive heart failure, pulmonary embolism, myocardial infarction, diabetes, hypokalemia, and methylxanthine toxicity.

Pearl Question 2 (T/F): For treatment of multifocal atrial tachycardia (MAT), the recommended dose of IV magnesium is 2 g IV over 60 seconds, then 1-2 g/h.

The correct answer is True: The recommended dose is 2 g IV over 60 seconds, then 1-2 g/h. Patient`s deep tendon reflexes should be evaluated serially, as loss of reflexes is a signal to slow or halt the infusion of the drug.

Pearl Question 3 (T/F): Magnesium sulfate administered with potassium replacement is appropriate therapy for some patients with multifocal atrial tachycardia.

The correct answer is True: Several small reports describe effectiveness with the use of magnesium sulfate (with concomitant correction of hypokalemia), verapamil, and some beta-blockers. Provide potassium replacement to reach a serum potassium level of greater than 4 mEq/L.

Pearl Question 4 (T/F): Cardioversion is often useful in the treatment of multifocal atrial tachycardia (MAT).

The correct answer is False: Cardioversion should be avoided because it is usually ineffective in converting the multiple foci of MAT, and it may lead to rhythm degeneration.

BIBLIOGRAPHY

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• Arsura EL, Solar M, Lefkin AS, et al: Metoprolol in the treatment of multifocal atrial tachycardia. Crit Care Med 1987 Jun; 15(6): 591-4[Medline].
• Collier WW, Holt SE, Wellford LA: Narrow complex tachycardias. Emerg Med Clin North Am 1995 Nov; 13(4): 925-54[Medline].
• Hoffman JR, Votey SR: Tachyarrhythmias. In: Harwood-Nuss AL, Linden CH, Luten RC, et al, eds. The Clinical Practice of Emergency Medicine. 2nd ed. Philadelphia, Pa: Lippincott-Raven; 1996:609.
• Iseri LT, Fairshter RD, Hardemann JL, Brodsky MA: Magnesium and potassium therapy in multifocal atrial tachycardia. Am Heart J 1985 Oct; 110(4): 789-94[Medline].
• Levine JH, Michael JR, Guarnieri T: Treatment of multifocal atrial tachycardia with verapamil. N Engl J Med 1985 Jan 3; 312(1): 21-5[Medline].
• Stapczynski JS: Disturbances of cardiac rhythm and conduction. In: Tintinalli JE, Ruiz E, Krome RL, eds. Emergency Medicine: A Comprehensive Study Guide. 4th ed. New York, NY: McGraw-Hill; 1996:145.

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