Atriofascicular Tachycardia (Mahaim Tachycardia)

KEY FEATURES

ESSENTIALS OF DIAGNOSIS

• Wide QRS tachycardia (left bundle branch block and superior-axis morphology)

• Diagnosis confirmed at electrophysiologic study

• Progressive decrease in atrioventricular (AV) conduction through the pathway (anterograde decremental conduction)

• Coexistence with AV nodal reentrant tachycardia and other accessory pathways

GENERAL CONSIDERATIONS

• These pathways do not conduct retrogradely

• Antidromic tachycardia is the most common clinical tachycardia

• Minimal preexcitation during sinus rhythm

• More preexcitation during right atrial than lateral coronary sinus pacing (differential pacing)

• Earliest ventricular activation during tachycardia occurs at the right ventricular apex

• Atriofascicular pathways course along the right atrial free wall at the level of the tricuspid annulus and insert distally into right bundle branch

• Fasciculoventricular pathways give rise to fixed preexcitation and serve as bystanders during reentrant tachycardia

• Retrograde right bundle branch block prolongs the tachycardia cycle length

• Intermittent retrograde right bundle branch block causes long, short fluctuating cycle length of the tachycardia

• Mahaim pathway potentials and mechanical compression with the ablation catheter leading to loss of conduction are successful sites for ablation

CLINICAL PRESENTATION

SYMPTOMS AND SIGNS

• Palpitations

• Presyncope

• Syncope

PHYSICAL EXAM FINDINGS

• When associated with congenital heart disease (Ebstein’s anomaly), features of tricuspid regurgitation may be present

DIFFERENTIAL DIAGNOSIS

• Ventricular tachycardia

• Supraventricular tachycardia with aberrancy

DIAGNOSTIC EVALUATION

LABORATORY TESTS

• CBC, basic metabolic panel

ELECTROCARDIOGRAPHY

• During sinus rhythm, ECG may appear normal because of negligible preexcitation

• During tachycardia, ECG may resemble ventricular tachycardia

  • – If the patient has structurally normal heart, Mahaim tachycardia should be in the differential diagnosis

• Holter monitoring to document rhythm disturbances

IMAGING STUDIES

• Echocardiogram if there is an associated murmur to identify Ebstein’s anomaly

DIAGNOSTIC PROCEDURES

• Electrophysiologic study to confirm mechanism of tachyarrhythmias and establish diagnosis

TREATMENT

CARDIOLOGY REFERRAL

• All patients with an episode of symptomatic supraventricular tachycardia should be referred to a cardiologist

HOSPITALIZATION CRITERIA

• Symptomatic tachycardia, particularly syncope

• When ventricular tachycardia cannot be excluded

THERAPEUTIC PROCEDURES

• Radiofrequency (RF) ablation of the pathway

SURGERY

• Rarely required

MONITORING

• ECG monitoring in the hospital

DIET AND ACTIVITY

• No specific restrictions

• General healthy lifestyle

ONGOING MANAGEMENT

HOSPITAL DISCHARGE CRITERIA

• Twenty-four hours after RF ablation

FOLLOW-UP