Multifocal atrial tachycardia is most often asymptomatic. However, patients typically have symptoms related to their underlying condition. Therefore, this arrhythmia is often found incidentally on the routine electrocardiogram or on a cardiac telemetry monitor. Studies show most people do not report palpitations or symptoms of syncope or pre-syncope. Once a diagnosis is made, a thorough history should be obtained with a focus on commonly associated conditions including cardiac and pulmonary diseases. On physical exam, most patients will have an elevated heart rate and an irregularly irregular rhythm. Most patients are hemodynamically stable, however, due to the association with underlying conditions, it is sensible to conduct a general assessment for signs of cardiopulmonary disease, especially since this arrhythmia can trigger decompensation of underlying cardiac and pulmonary disease.

Multifocal atrial tachycardia should be suspected in patients with tachycardia and irregularly irregular rhythm. Given its association with underlying medical conditions, it should also be suspected in patients with cardiac and pulmonary disease. Diagnosis is not clinical, but is made with electrocardiogram and can be made using the following diagnostic criteria. The electrocardiogram should show an atrial rate of greater than 100 beats per minute (although some suggest using a threshold of 90 beats per minute) with three or more discrete P wave morphologies in the same lead, not including that originating from the sinoatrial node. Furthermore, there should be irregular PP intervals, and the baseline should be isoelectric between P waves. Other findings that are commonly seen, but are not diagnostic include irregular PR and RR intervals. Variation in PR intervals has not been included in the diagnostic criteria because the PR interval varies with the length of the preceding RP interval.[11]

A diagnosis of multifocal atrial tachycardia does not typically warrant any additional workup, other than workup required for any underlying conditions. However, if arrhythmia persists despite the treatment of underlying medical conditions it may be worth checking a complete blood count and serum chemistry for signs of infection, anemia, or electrolyte abnormalities such as hypokalemia and hypomagnesemia. 

Other diagnoses that may present with similar findings on electrocardiogram that should be included in the differential diagnosis include sinus tachycardia with frequent premature atrial contractions (this would have regular PP intervals), atrial flutter with variable AV node conduction (this would have regular PP intervals and flutter waves), atrial fibrillation (this would not have discrete P-wave morphologies), and wandering atrial pacemaker which would have a heart rate less than 100 beats per minute).

The treatment of multifocal atrial tachycardia should focus on treating underlying medical conditions. Most episodes of multifocal atrial tachycardia resolve with the treatment of underlying conditions. Specific treatment is indicated if the patient develops symptomatic decompensation of their underlying cardiac or pulmonary disease or in the rare setting of persistent symptomatic arrhythmia despite adequate treatment of underlying conditions. If treatment is indicated, therapy should begin with first correcting underlying electrolyte abnormalities with the repletion of potassium to maintain greater than 4 mEq/L and magnesium greater than 2 mEq/L. Studies have shown magnesium suppresses ectopic atrial activity and can be beneficial even if magnesium levels are within the normal range. Once electrolyte abnormalities have been corrected, possible treatment options include non-dihydropyridine calcium channel blockers, beta-blockers, and atrioventricular (AV) node ablation. Studies have found no role for antiarrhythmic agents, cardioversion, or anticoagulation.

In the absence of underlying pulmonary disease, the first-line agent is beta-blockers. A beta-blockers act to suppress ectopic foci by reducing sympathetic stimulation and decreasing conduction through the atrioventricular node, thereby slowing the ventricular response.  Studies have found an average decrease in heart rate of 51 beats per minute and 79% of patients reverted to sinus rhythm.  Most patients did not need beta-blocker therapy long term as studies found long-term therapy was needed in only 25% of patients.  Caution should be used in patients with an underlying pulmonary disease such as COPD and patients with decompensated heart failure due to the increased risk for bronchospasms and decreased cardiac output.  Furthermore, beta-blockers should be avoided in patients with atrioventricular blocks unless a pacemaker has been implanted.

In the presence of underlying pulmonary disease, the first-line agent is a non-dihydropyridine calcium channel blocker such as verapamil or diltiazem. These agents act to suppress atrial rate and decrease conduction through the atrioventricular node, thereby slowing the ventricular rate.  Studies have found an average reduction in the ventricular rate of 31 beats per minute and 43% of patients reverted to sinus rhythm. Caution should be used in patients with preexisting heart failure or hypotension due to negative inotropic effects and peripheral vasodilation.  Similarly, calcium channel blockers should also be avoided in patients with atrioventricular blocks unless a pacemaker has been implanted.

In select cases of refractory multifocal atrial tachycardia, AV node ablation has been performed. Studies have found an average reduction in the ventricular rate of 56 beats per minute with adequate control of ventricular response in 84% of patients.  However, AV node ablation creates a complete heart block and requires the placement of a permanent pacemaker. 

• Decompensated chronic lung disease

• Coronary artery disease

• Heart failure

• Valvular heart disease

• Diabetes mellitus

• Hypokalemia

• Hypomagnesemia

• Postoperative state

• Pulmonary embolism

• Pneumonia

While most patients with multifocal atrial tachycardia are hemodynamically stable, it is a poor prognostic sign in the setting of an acute illness. Studies have shown a 60% in-hospital mortality and mean survival of just over one year.

MAT is best managed by an interprofessional team, including cardiology nurses. In general, MAT is benign and usually resolved if the offending agent or disease is managed.  Therapies that have not been found to have a role in the treatment of multifocal atrial tachycardia include antiarrhythmics, cardioversion, or anticoagulation. Studies have found most cases of multifocal atrial tachycardia will resolve without specific antiarrhythmic therapy. Antiarrhythmics such as quinidine, procainamide, lidocaine, and phenytoin have yet to be proven successful. Furthermore, digitalis has also not been shown to have any benefit. Cardioversion has not been shown to be effective in converting to sinus rhythm and should not be used in the treatment of multifocal atrial tachycardia. While one study found 55% of patients with multifocal atrial tachycardia developed atrial fibrillation or atrial flutter, current guidelines do not support the use of anticoagulation.[12][13][14]