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4.1.2 Ongoing Management: Recommendations

IIa B-NR 1.  Adenosine can be useful in the acute setting to either restore sinus rhythm or diagnose the tachycardia mechanism in patients with suspected focal AT.123,200,207

See Online Data Supplement 6. Adenosine is usually effective in terminating focal AT of a triggered mechanism but is not expected to be effective in reentrant focal AT.207 Transient suppression can be observed in automatic focal AT. The observation of transient AV block with persistent AT can be helpful in making the diagnosis and differentiating focal AT from AVNRT and AVRT. IIb C-LD 1.  Intravenous amiodarone may be reasonable in the acute setting to either restore sinus rhythm or slow the ventricular rate in hemodynamically stable patients with focal AT.205,206 See Online Data Supplement 6. The therapeutic effect of intravenous amiodarone in the acute setting is likely mediated via blockade of the beta receptors or calcium channels. Amiodarone may be preferred in patients with reduced ventricular function or with a history of heart failure. IIb C-LD 2.  Ibutilide may be reasonable in the acute setting to restore sinus rhythm in hemodynamically stable patients with focal AT.205,206 See Online Data Supplement 6. The effectiveness of ibutilide for treatment of focal AT is unclear. In 1 study, intravenous ibutilide terminated AT of single atrial morphology in 19 of 39 patients (38.8%), but the proportions of patients with focal AT and macroreentrant AT were not differentiated in this study cohort.206

Recommendations for Acute Treatment of Suspected Focal Atrial Tachycardia (Continued) COR LOE Recommendations

Recommendations for Ongoing Management of Suspected Focal Atrial Tachycardia COR LOE Recommendations

I B-NR 1.  Catheter ablation is recommended in patients with symptomatic focal AT as an alternative to pharmacological therapy.122–126,188,191–196,206

See Online Data Supplement 6. A large number of nonrandomized cohort studies on focal AT ablation have accumulated in the past 2 decades. In a 2012 ablation registry provided by 74 voluntary medical centers in Spain, AT was found in 333 of 11 042 of the ablation procedures performed.122 In experienced centers, when the AT can be induced in the laboratory, acute success rates above 90% to 95% have consistently been reported, with a complication rate of <1% to 2%.122,123,125,196 See Table 8 for a summary of ablation efficacy, complications, and rate of recurrence.

Although uncommon, focal AT-mediated cardiomyopathy should be recognized in patients presenting with heart failure, reduced ventricular function, and persistent tachycardia. In a case–control study of patients with AT, 10% of patients had evidence of cardiomyopathy.125 The tachycardia in patients with cardiomyopathy was incessant and slower than in the patients without cardiomyopathy (cycle lengths 502 ms and 402 ms, respectively). Normal ejection fraction was restored in 97% of patients after successful ablation.188

IIa C-LD 1.  Oral beta blockers, diltiazem, or verapamil are reasonable for ongoing management in patients with symptomatic focal AT.123,204,205

See Online Data Supplement 6. Data on long-term drug therapy of focal AT are limited to observational studies, and some studies did not provide clear inclusion criteria, so results for AT were combined with those for other mechanisms of SVT. Nevertheless, these drugs are moderately effective, with a low incidence of significant adverse effects.123,204,205,209–214 IIa C-LD 2.  Flecainide or propafenone can be effective for ongoing management in patients without structural heart disease or ischemic heart disease who have focal AT.209–213

See Online Data Supplement 6. Small case series studies reported that focal AT suppression was achieved with flecainide in most patients.209,210 In infants and children, propafenone is moderately effective in focal AT suppression during follow-up.213 Flecainide and propafenone are generally tolerated by patients with focal AT. Combinations of a class Ic drug with a beta blocker, diltiazem, or verapamil may improve overall efficacy rates. IIb C-LD 1.  Oral sotalol or amiodarone may be reasonable for ongoing management in patients with focal AT.188,211,215–219

See Online Data Supplement 6. Several studies reported moderate efficacies of oral sotalol or amiodarone in maintaining sinus rhythm in long-term treatment in children.188,211,215–219 Although most reports are in children, limited data suggest similar efficacy in adults.218 Because of the risk of proarrhythmia and other complications, before use of these drugs, a balance between anticipated benefit of focal AT suppression and potential adverse effects of these drugs should be carefully considered.

4.2 Multifocal Atrial Tachycardia

MAT is defined as a rapid, irregular rhythm with at least 3 distinct morphologies of P waves on the surface ECG. It may be difficult to distinguish MAT from AF on physical examination or even on a single ECG tracing, so a 12-lead ECG is indicated to confirm the diagnosis. On the ECG, the atrial rate is >100 bpm (or >90 bpm, as defined in at least 1 report220). Unlike AF, there is a distinct isoelectric period between P waves. The P-P, P-R, and R-R intervals are variable. The mechanism of MAT is not well established. Although it is assumed that the variability of P-wave morphology implies a multifocal origin, there are very few mapping studies of MAT.221 Similarly, the variability of the P-R interval may relate to decremental conduction through the AV node, as opposed to the origin of the P wave. Occasional responsiveness to verapamil suggests a triggered mechanism, but data are limited.222

MAT is commonly associated with underlying conditions, including pulmonary disease, pulmonary hypertension, coronary disease, and valvular heart disease,223 as well as hypomagnesemia and theophylline therapy.224 The first-line treatment is management of the underlying condition. Intravenous magnesium may also be helpful in patients with normal magnesium levels.225 Antiarrhythmic medications in general are not helpful in suppression of multifocal AT.226 Management often involves slowing conduction at the AV nodal level to control heart rate. Verapamil has been shown to have some efficacy in

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