Atrioventricular Nodal Reentrant Tachycardia

KEY FEATURES

ESSENTIALS OF DIAGNOSIS

• Heart rate typically 160–220 bpm, occasionally as slow as 120 bpm

• Most commonly a narrow QRS tachycardia

• Occasionally, retrograde P waves seen after the QRS complex or buried within the end of the QRS complex. Because of this, P waves not visible in 90% of cases

• Short RP tachycardia (RP interval shorter than PR interval)

• In atypical atrioventricular (AV) nodal reentrant tachycardia (< 20% of cases), long RP tachycardia (RP interval > PR interval) may be seen

GENERAL CONSIDERATIONS

• More common in females

• Polyuria not uncommon secondary to elevated atrial natriuretic peptide

• Age distribution is bimodal; initial episode during second decade of life, only to disappear and then reappear during the fourth and fifth decades

• Antegrade (slow pathway) and retrograde (fast pathway) limbs are within the AV node

• In atypical cases, fast pathway is antegrade limb

• Sudden death is reported in rare instances

CLINICAL PRESENTATION

SYMPTOMS AND SIGNS

• Rapid, regular pounding in the neck

• Palpitation

• Dizziness

• Occasionally syncope

• Polyuria

PHYSICAL EXAM FINDINGS

• Tachycardia: 120–220 bpm but usually > 160

• Occasionally hypotension

• Neck pulsations corresponding to the heart rate

• Tachycardia may occasionally terminate with vagal maneuver and carotid sinus pressure

DIFFERENTIAL DIAGNOSIS

• AV reentrant tachycardia

• Atrial tachycardia

DIAGNOSTIC EVALUATION

LABORATORY TESTS

• CBC, basic metabolic panel

ELECTROCARDIOGRAPHY

• ECG and rhythm strip usually show a narrow QRS complex tachycardia without p waves. When p waves are visible, they are seen near the end of the QRS complex (lead V1 is best) and usually a short RP (RP < PR) interval is noted

• Ambulatory cardiac monitoring to detect tachycardia

• Event recorder to detect tachycardia

IMAGING STUDIES

• In otherwise healthy patient, no imaging required, although echocardiography is commonly performed to exclude structural heart disease

DIAGNOSTIC PROCEDURES

• Invasive electrophysiology (EP) study to confirm mechanism of tachycardia and its suitability for ablation

TREATMENT

CARDIOLOGY REFERRAL

• EP referral is recommended for all patients, although some physicians may try medications initially

HOSPITALIZATION CRITERIA

• If the diagnosis is certain and posttermination ECG is normal, hospitalization is not required

MEDICATIONS

• Acute termination occurs with adenosine 6-mg or 12-mg bolus injection. Note that some atrial tachycardias are also adenosine sensitive

• Maintenance therapy includes beta blockers or calcium channel blockers to inhibit the slow pathway

• Class IC drugs may be used to inhibit the fast pathway; however, they are less commonly used due to ...