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<100 bpm).54 The anatomic substrate of AVNRT is dual AV nodal physiology (Table 3). AVNRT is often well tolerated and is rarely life threatening. Patients will typically present with the sudden onset of palpitations and possibly with shortness of breath, dizziness, and neck pulsations. Syncope is a rare manifestation of AVNRT. AVNRT may occur spontaneously or on provocation with exertion, coffee, tea, or alcohol.

5.1 Acute Treatment: Recommendations

IIa C-LD 2.  Metoprolol is reasonable for ongoing management in patients with recurrent symptomatic MAT.226,229,230

See Online Data Supplements 7 and 8. Beta blockers are typically avoided in the presence of acute decompensated heart failure or in patients with severe (particularly bronchospastic) pulmonary disease. However, metoprolol has been used in small studies in patients with serious pulmonary disease after correction of hypoxia or other signs of acute decompensation. In these studies, intravenous or oral metoprolol resulted in conversion to sinus rhythm or achieved rate control, and oral metoprolol was used for maintenance therapy.226,230 Beta blockers are generally avoided in patients with severe conduction abnormalities or sinus node dysfunction.

Recommendations for Ongoing Management of Multifocal Atrial Tachycardia (Continued) COR LOE Recommendations

Recommendations for Acute Treatment of AVNRT COR LOE Recommendations

I B-R 1.  Vagal maneuvers are recommended for acute treatment in patients with AVNRT.82–84,234,235

See Online Data Supplement 10. For acute conversion of AVNRT, vagal maneuvers, including Valsalva and carotid sinus massage, can be performed quickly and should be the first-line intervention to terminate SVT. These maneuvers should be performed with the patient in the supine position. There is no “gold standard” for proper Valsalva maneuver technique, but in general, the patient raises intrathoracic pressure by bearing down against a closed glottis for 10 to 30 seconds, equivalent to at least 30 mm Hg to 40 mm Hg.82,84 Carotid massage is performed after absence of bruit has been confirmed by auscultation, by applying steady pressure over the right or left carotid sinus for 5 to10 seconds.83,84 Another vagal maneuver based on the classic diving reflex consists of applying an ice-cold, wet towel to the face85; in a laboratory setting, facial immersion in water at 10°C (50°F) has proved effective in terminating tachycardia, as well.86 One study involving 148 patients with SVT demonstrated that Valsalva was more successful than carotid sinus massage, and switching from 1 technique to the other resulted in an overall success rate of 27.7%.82 The practice of applying pressure to the eyeball is potentially dangerous and has been abandoned.

I B-R 2.  Adenosine is recommended for acute treatment in patients with AVNRT.42,51,91,236 See Online Data Supplements 9 and 10. Adenosine can be considered as both a therapeutic and diagnostic agent in narrow-complex tachyarrhythmias. It will acutely terminate AVNRT in approximately 95% of patients and will unmask atrial activity in arrhythmias, such as atrial flutter or AT.91,236

I B-NR 3.  Synchronized cardioversion should be performed for acute treatment in hemodynamically unstable patients with AVNRT when adenosine and vagal maneuvers do not terminate the tachycardia or are not feasible.94,208 See Online Data Supplement 10. Sinus rhythm must be promptly restored in patients with AVNRT who are hemodynamically unstable. The safety and effectiveness of cardioversion has been proven in patients with hemodynamically unstable SVT who had failed to convert with vagal maneuvers and intravenous pharmacological therapy.94

I B-NR 4.  Synchronized cardioversion is recommended for acute treatment in hemodynamically stable patients with AVNRT when pharmacological therapy does not terminate the tachycardia or is contraindicated.87,95

See Online Data Supplements 3 and 9. Synchronized cardioversion is highly effective in terminating SVT (including AVRT and AVNRT).94 Most stable patients with SVT respond to pharmacological therapy, with success rates of 80% to 98% for agents such as verapamil, diltiazem, or adenosine. In some resistant cases, a second drug bolus or higher dose of initial drug agent is often effective.87,96 Nevertheless, in rare instances, drugs may fail to successfully restore sinus rhythm, necessitating synchronized cardioversion. IIa B-R 1.  Intravenous beta blockers, diltiazem, or verapamil are reasonable for acute treatment in hemodynamically stable patients with AVNRT.96,237–240

See Online Data Supplement 10. Intravenous diltiazem and verapamil are particularly effective in converting AVNRT to sinus rhythm. These drugs should be used only in hemodynamically stable patients. It is important to ensure the absence of VT or pre-excited AF, because patients with these rhythms may become hemodynamically unstable and develop ventricular fibrillation if administered diltiazem or verapamil. Diltiazem or verapamil should also be avoided in patients with suspected systolic heart failure. Evidence for the effectiveness of beta blockers to terminate AVNRT is limited. In a trial that compared esmolol with diltiazem, diltiazem was more effective in terminating SVT.237 Nonetheless, beta blockers have an excellent safety profile, so it is reasonable to use them to attempt to terminate SVT in hemodynamically stable patients. IIb C-LD 1.  Oral beta blockers, diltiazem, or verapamil may be reasonable for acute treatment in hemodynamically stable patients with AVNRT.241,242

See Online Data Supplement 9. Overall, there are no data specifically studying the effect of oral beta-blocker monotherapy for the acute termination of AVNRT. However, 2 studies have demonstrated success with the combination of oral diltiazem and propranolol to terminate AVNRT or AVRT.241,242 Oral beta blockers have an excellent safety profile, and administration (particularly in patients without intravenous access) can be performed in conjunction with vagal maneuvers. IIb C-LD 2.  Intravenous amiodarone may be considered for acute treatment in hemodynamically stable patients with AVNRT when other therapies are ineffective or contraindicated.115 See Online Data Supplement 10. In a small cohort study, intravenous amiodarone was effective in terminating AVNRT.115 Long-term toxicity is not seen with intravenous amiodarone if given for a short period of time.

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