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patients with orthodromic AVRT can be directed at either the accessory pathway or the AV node, as both are key portions of the reentrant circuit. AV nodal–blocking agents may be contraindicated in patients at risk of rapid conduction down the accessory pathway during AF. Catheter ablation strategies target the accessory pathway, with high success rates. 6.1 Management of Patients With Symptomatic

Manifest or Concealed Accessory Pathways See Figure 14 for the algorithm for acute treatment of orthodromic AVRT and Figure 15 for the algorithm for ongoing management of orthodromic AVRT.

6.1.1 Acute Treatment: Recommendations

Recommendations for Acute Treatment of Orthodromic AVRT COR LOE Recommendations

I B-R 1.  Vagal maneuvers are recommended for acute treatment in patients with orthodromic AVRT.42,75,235,259

See Online Data Supplements 11 and 12. For acute conversion of orthodromic AVRT, 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 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 to 10 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 beneficial for acute treatment in patients with orthodromic AVRT.42,260,261

See Online Data Supplements 11 and 12. Adenosine is effective for conversion of orthodromic AVRT in 90% to 95% of patients, with minor and brief (<1 min) side effects occurring in approximately 30% of patients.42,260,261 Patients often have atrial or ventricular premature complexes immediately after conversion that, on occasion, may induce further episodes of AVRT. In this situation, an antiarrhythmic drug may be required to prevent acute reinitiation of tachycardia. Because adenosine may precipitate AF that may then conduct rapidly to the ventricle and even cause ventricular fibrillation, electrical cardioversion should be available.

I B-NR 3.  Synchronized cardioversion should be performed for acute treatment in hemodynamically unstable patients with AVRT if vagal maneuvers or adenosine are ineffective or not feasible.75,262,263

See Online Data Supplement 10. Synchronized cardioversion is highly effective in terminating AVRT.75 Cardioversion avoids complications associated with antiarrhythmic drug therapy and should be considered early in the management of hemodynamically unstable patients. Patients often have atrial or ventricular premature complexes immediately after cardioversion that, on occasion, may induce further episodes of AVRT. In this situation, an antiarrhythmic drug may be required to prevent acute reinitiation of tachycardia.

I B-NR 4.  Synchronized cardioversion is recommended for acute treatment in hemodynamically stable patients with AVRT when pharmacological therapy is ineffective or contraindicated.87,95

See Online Data Supplements 3 and 10. Synchronized cardioversion is highly effective in terminating SVT (including AVRT and AVNRT), and when the patient is stable, this is performed after adequate sedation or anesthesia.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 might prove effective.87,96 Nevertheless, in rare instances, drugs may fail to successfully restore sinus rhythm.

I B-NR 5. Synchronized cardioversion should be performed for acute treatment in hemodynamically unstable patients with pre-excited AF.75,94

See Online Data Supplement 10. Synchronized cardioversion is highly effective in terminating pre-excited AF.75 When AF occurs in patients with ventricular pre-excitation, if the accessory pathway has a short refractory period, this may allow for rapid pre-excited AV conduction; the resulting fast, often irregular, broadcomplex tachycardia is often unstable and may lead to ventricular fibrillation. It is therefore important to achieve early restoration of sinus rhythm in these patients. Patients often have atrial or ventricular premature complexes immediately after cardioversion that, on occasion, may induce AVRT or recurrent pre-excited AF.

I C-LD 6.  Ibutilide264 or intravenous procainamide265 is beneficial for acute treatment in patients with pre-excited AF who are hemodynamically stable. See Online Data Supplements 11 and 12. Small observational studies support the use of ibutilide or intravenous procainamide for the treatment of pre-excited AF in patients who are not hemodynamically compromised.264,265 Both medications can decrease ventricular rate by slowing conduction over the accessory pathway and have the additional benefit of possibly terminating AF.264,265

IIa B-R 1.  Intravenous diltiazem, verapamil42,260,266,267 (Level of Evidence: B-R ), or beta blockers268 (Level of Evidence: C-LD) can be effective for acute treatment in patients with orthodromic AVRT who do not have pre-excitation on their resting ECG during sinus rhythm. C-LD

See Online Data Supplements 11 and 12. Intravenous diltiazem or verapamil effectively terminate approximately 90% to 95% of AVRT episodes in patients without pre-excitation on their resting sinus-rhythm ECG, with drug-induced hypotension occurring in approximately 3% of patients.42,260,266,267 Intravenous beta blockers have not been studied in clinical trials; however, clinical experience suggests they are useful for terminating AVRT, with a low risk of associated complications.268

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