Multifocal atrial tachycardia

8 Interesting Facts of Multifocal atrial tachycardia

1. Multifocal atrial tachycardia is a type of supraventricular tachycardia originating from multiple foci and characterized by:
   • Irregular atrial rate greater than 100 beats per minute; typically 110 to 180 beats per minute 
   • Organized P waves with at least 3 distinct wave morphologies in the same ECG lead 
   • Irregular P-P intervals and an isoelectric baseline between P waves 
2. Associated with underlying conditions, such as chronic obstructive pulmonary disease, hypoxia, pneumonia, theophylline or digoxin toxicity, hypokalemia, and hypomagnesemia 
3. Physical examination findings vary by underlying disease processes, but they include a rapid and irregular pulse
4. ECG confirms diagnosis 
5. Goal of treatment is restoring normal sinus rhythm and correcting or improving underlying pulmonary, metabolic, or cardiac conditions 
6. Medical therapy includes β-blockers and calcium channel blockers; metoprolol is first choice, with verapamil and diltiazem as alternatives 
7. Atrioventricular nodal ablation with cardiac pacemaker implantation is recommended for patients with refractory multifocal atrial tachycardia whose conditions are unresponsive to or intolerant of medical therapy 
8. Prognosis depends on severity of underlying conditions

Pitfalls

• Use of β-blockers is limited by transient hypotension and bronchospastic adverse effects, given that lung disease is commonly associated with multifocal atrial tachycardia 
• Differentiation of atrial fibrillation from multifocal atrial tachycardia is important because treatment differs for these conditions

Multifocal atrial tachycardia is a type of supraventricular tachycardia originating from multiple foci and characterized by:

Irregular atrial rate greater than 100 beats per minute; typically 110 to 180 beats per minute 

Organized P waves with at least 3 distinct wave morphologies in the same ECG lead 

Irregular P-P intervals and an isoelectric baseline between P waves 

Clinical Presentation

History

• Typically occurs in patients who are elderly or critically ill with advanced chronic pulmonary disease 
• Common symptoms
  • Palpitations
  • Lightheadedness
  • Anxiety
  • Dyspnea
  • Chest pain
  • Syncope
• Other findings
  • Symptoms or history of pulmonary disease (eg, chronic obstructive pulmonary disease)

Physical examination

• Findings are typically related to an underlying disease process (eg, chronic obstructive pulmonary disease)
• Rapid and irregular pulse
• Rapid oscillations or cannon waves noted in jugular vein examination

Causes

• Exact mechanism is unknown; may involve enhanced automaticity or triggered activity 

Risk factors and/or associations

Age

• Typically seen in elderly patients 

Other risk factors/associations

• Most common risk factors 
  • Underlying pulmonary disease 
    • Most commonly occurs in association with chronic obstructive pulmonary disease (Related: Exacerbation of chronic obstructive pulmonary disease)
    • Hypoxia
    • Pneumonia (Related: Community-acquired pneumonia in adults)
  • Cardiac disease (eg, valvular heart disease, heart failure) (Related: Heart failure)
  • Hypomagnesemia
  • Hypokalemia
• Less common risk factors
  • Theophylline toxicity 
  • Digoxin toxicity (Related: Digoxin, digitoxin, and other cardiac glycoside toxicity)
  • Sepsis
  • Diabetes mellitus (Related: Diabetes mellitus type 2 in adults)

How is Multifocal atrial tachycardia diagnosed?

• History and physical examination findings may be suggestive of underlying diseases, but they are not specific for multifocal atrial tachycardia
• ECG confirms the diagnosis 

Laboratory

• While no specific laboratory test exists to diagnose this condition, consider checking potassium and magnesium levels to evaluate for hypokalemia or hypomagnesemia, which are risk factors 

Functional testing

• 12-lead ECG 
  • Confirms diagnosis of multifocal atrial tachycardia; positive findings include:
    • Irregular rate greater than 100 beats per minute
    • Organized P waves with at least 3 distinct wave morphologies in the same ECG lead; each QRS complex is preceded by a P wave
    • Irregular P-P, PR, and R-R intervals
    • Isoelectric baseline between P waves
    • Some degree of atrioventricular block
    • Most P waves are conducted to the ventricles, usually with narrow QRS complexes

Differential Diagnosis

Most common

• Atrial fibrillation
• Atrial flutter with variable atrioventricular conduction
• Paroxysmal supraventricular tachycardia

Treatment Goals

• Convert to normal sinus rhythm
• Correct or improve underlying pulmonary, metabolic, or cardiac conditions

Admission criteria

Most patients require hospitalization to manage underlying cardiopulmonary diseases

Criteria for ICU admission

• Hemodynamic instability

Recommendations for specialist referral

• Refer to pulmonologist for management of underlying pulmonary disease
• Refer to interventional cardiologist if invasive intervention is planned
• Refer to cardiologist if antiarrhythmic therapy is being considered

Treatment Options

Management or correction of the underlying disorder may be sufficient for management of multifocal atrial tachycardia; however, if it is not successful or if the underlying disorder worsens, then medical management will be necessary, and some patients may need nodal ablation and pacemaker implantation 

Medical therapy 

• Metoprolol is the first choice for treatment of multifocal atrial tachycardia; however, use is limited because of adverse effects
• If metoprolol is contraindicated or not tolerated, calcium channel blockers (eg, verapamil, diltiazem) are recommended to decrease atrial contractility and slow atrioventricular nodal conduction
• If both metoprolol and calcium channel blockers fail, high-dose magnesium may be considered; use with caution in patients with renal failure
• Rate control therapy is generally effective for multifocal atrial tachycardia; therefore, antiarrhythmic agents (eg, amiodarone) are not recommended routinely

Provide electrolyte replacement for patients with associated hypokalemia or hypomagnesemia

Atrioventricular nodal ablation with cardiac pacemaker implantation is recommended for patients with refractory multifocal atrial tachycardia whose conditions are unresponsive to or intolerant of medical therapy 

Drug therapy

• β-blockers
  • Used for rate control and converting to normal sinus rhythm; first line therapy
  • Use is limited by transient hypotension and bronchospastic adverse effects, given that lung disease is commonly associated with multifocal atrial tachycardia 
  • Metoprolol 
    • IV
      • Metoprolol Tartrate Solution for injection; Adults: 5 mg IV bolus over 1 to 2 minutes; may repeat every 5 minutes to a maximum of 3 doses. Transition to oral therapy for maintenance.
    • Oral
      • Metoprolol Tartrate Oral tablet; Adults: 50 mg PO (or 25 mg PO if not tolerated) every 6 hours for 48 hours. Maintenance dose is 50 to 100 mg PO twice daily.
• Calcium channel blockers
  • Indicated if β-blockers are contraindicated or not tolerated
  • Decrease atrial contractility and slow atrioventricular nodal conduction
  • Verapamil 
    • Pretreatment with calcium gluconate 1 g IV, before administering verapamil, may prevent hypotension 
    • IV
      • Verapamil Hydrochloride Solution for injection; Adults: Initially, 5 to 10 mg (0.075 to 0.15 mg/kg) IV over at least 2 minutes. If no adequate response after 30 minutes, may give an additional 10 mg (0.15 mg/kg). Verapamil should not be used in patients with preexcitation, left ventricular systolic dysfunction, or decompensated heart failure.
    • Oral
      • Verapamil Hydrochloride Oral tablet; Adults: 120 to 320 mg/day PO, given in 3 to 4 divided doses.
  • Diltiazem 
    • IV
      • Diltiazem Hydrochloride Solution for injection; Adults: Initially, 0.25 mg/kg IV bolus over 2 minutes. After 15 minutes, 0.35 mg/kg over 2 minutes may be given. Individualize as needed. A 10 mg/hour IV infusion is started immediately after IV bolus. Some patients respond to lower doses (e.g., 5 mg/hour). Max: 15 mg/hour.
    • Oral
      • Diltiazem Hydrochloride Oral tablet; Adults: Initially, 30 to 60 mg PO 4 times per day. Increase up to 360 mg/day in 3 to 4 divided doses.
• Magnesium sulfate 
  • High-dose magnesium may be considered if other medications fail
  • Magnesium Sulfate Solution for injection; Adults: 1 to 2 g IV (or 15 to 30 mg/kg lean body weight) every 6 hours for 24 hours. After the first 24 hours, approximately 60 mg/kg/day may be given in divided doses or via IV drip for the next 2 to 5 days.
• Antiarrhythmics
  • Antiarrhythmic agents are not recommended routinely; often ineffective 
  • Amiodarone
    • Associated with conversion to normal sinus rhythm
    • May be considered if other options fail
    • Amiodarone Hydrochloride Solution for injection; Adults: 150 mg IV over 10 minutes, followed by 1 mg/minute continuous IV infusion for 6 hours then 0.5 mg/minute continuous IV infusion for 18 hours. After 24 hours, change to PO or consider decreasing rate to 0.25 mg/minute.

Nondrug and supportive care

Provide electrolyte replacement for patients with associated hypokalemia or hypomagnesemia

Procedures

Atrioventricular junction ablation and permanent cardiac pacemaker placement 

General explanation

• Radiofrequency catheter ablation of the atrioventricular node and bundle of His, followed by placement of pacemaker
• Typically performed by radiofrequency ablation in right atrium, near atrioventricular node
• Objective is to ablate the compact atrioventricular node, leaving a stable junctional escape rhythm
• Improves ventricular response
• Improves symptoms of tachyarrhythmia (eg, heart failure, syncope, shortness of breath) by restoring a regular heart rate
• Pacemaker must be monitored and anticoagulants may need to be continued

Indication

• For patients with persistent and symptomatic multifocal atrial tachycardia whose conditions are unresponsive to or intolerant of medical therapy

Contraindications

• Known atrial thrombus
• Presence of active systemic infection
• Mobile left ventricular thrombus
• Mechanical prosthetic heart valve

Complications 

• Sudden death (most common within 48 hours of ablation)
• Malignant dysrhythmia
• Cerebrovascular accident and transient ischemic attack
• Peripheral arterial embolism
• Congestive heart failure
• Myocardial infarction

Comorbidities

• Chronic obstructive pulmonary disease (Related: Stable chronic obstructive pulmonary disease)
  • Multifocal atrial tachycardia most commonly occurs in association with chronic obstructive pulmonary disease, especially during exacerbations (Related: Exacerbation of chronic obstructive pulmonary disease)

Monitoring

• Pacemaker function must be monitored by cardiologist

Complications

• Hemodynamic instability with rapid, uncontrolled multifocal atrial tachycardia
• Atrial thrombi with embolization, resulting in stroke (Related: Ischemic stroke)
• Pulmonary emboli (Related: Pulmonary embolism)
• Myocardial infarction (Related: Acute coronary syndromes)

Prognosis

• Depends on severity of underlying conditions
• Patients without structural heart disease and with only mild respiratory illness typically respond well to treatment and may have spontaneous resolution
• Among elderly patients, mortality is primarily caused by underlying cardiopulmonary conditions 
• Associated with high hospital mortality in critically ill patients 

Prevention

• Proper management of underlying diseases associated with multifocal atrial tachycardia may reduce risk

Sources

Schwartz M et al: Recognition and treatment of multifocal atrial tachycardia: a critical review. J Emerg Med. 12(3):353-60, 1994 Reference