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patients with MAT who do not have ventricular dysfunction, sinus node dysfunction, or AV block227,228; although diltiazem has not been studied, it may provide a class effect with similar mechanism to verapamil. Beta blockers can be used with caution to treat MAT in the absence of respiratory decompensation, sinus node dysfunction, or AV block.229,230 Amiodarone has been reported to be useful in 1 report.231 Cardioversion is not useful in MAT.223

4.2.1 Acute Treatment: Recommendation

4.2.2 Ongoing Management: Recommendations 5 Atrioventricular Nodal Reentrant Tachycardia

See Figure 12 for the algorithm for acute treatment of AVNRT and Figure 13 for the algorithm for ongoing management of AVNRT. AVNRT is the most common SVT. It is usually seen in young adults without structural heart disease or ischemic heart disease, and >60% of cases are observed in women.49 The ventricular rate is often 180 bpm to 200 bpm but ranges from 110 bpm to >250 bpm (and in rare cases, the rate can be

Miscellaneous

Ivabradine 5 mg BID 7.5 mg BID Phosphenes, AF •  Concomitant drugs that can exacerbate bradycardia

•  Contraindicated in decompensated HF •  Contraindicated if BP <90/50 mm Hg •  Contraindicated in severe hepatic impairment •  Hypertension •  Ivabradine is a substrate of CYP3A4 (major) •  Avoid use with concomitant strong CYP3A4 inhibitors (boceprevir, clarithromycin, indinavir, itraconazole, lopinavir/ritonavir, nelfinavir, ritonavir, saquinavir, telaprevir, posaconazole, voriconazole) •  Avoid use with strong CYP3A4 inducers (carbamazepine, phenytoin, rifampin, St. John’s wort) •  Avoid use with diltiazem, verapamil, grapefruit juice

Note: For this reference table, drugs are presented in alphabetical order within the drug classes, not by COR and LOE. *When 1 drug is used in combination with other drugs, appropriate dosing adjustments should be made with consideration of at least additive effects during dosage titration. All potential drug–drug interactions and adverse reactions are not included in this list. For a more detailed list of drug interactions and adverse responses, clinicians should consult additional resources; for example, www.crediblemeds.org may be consulted for potential prolongation of the QT interval. †QTc calculation used the Bazett’s Formula in most clinical studies. ‡Recommended given in conjunction with a beta blocker or nondihydropyridine calcium channel antagonist. AF indicates atrial fibrillation; AV, atrioventricular; BID, twice daily; BP, blood pressure; CrCl, creatinine clearance; ECG, electrocardiogram/electrocardiographic; HF, heart failure; INR, international normalized ratio; LV, left ventricular; QD, once daily; QID, 4 times a day; QTc, corrected QT interval; SA, sinoatrial; SVT, supraventricular tachycardia; TID, 3 times a day; and WPW, Wolff-Parkinson-White.

Table 7.  Continued

Drug Initial Daily Dose(s) Maximum Total Daily

Maintenance Dose Potential Adverse

Effects Precautions (Exclude or Use With Caution) and Interactions

Recommendations for Ongoing Management of Multifocal Atrial Tachycardia COR LOE Recommendations

IIa B-NR 1.  Oral verapamil (Level of Evidence: B-NR ) or diltiazem (Level of Evidence: C-LD) is reasonable for ongoing management in patients with recurrent symptomatic MAT.227,230 C-LD

See Online Data Supplement 8. Long-term management of MAT frequently involves slowing of the ventricular response because arrhythmia termination is often not achievable. Verapamil has the advantage of not exacerbating pulmonary disease. Although it would be expected for diltiazem to have a similar effect, data on its use in patients with MAT are lacking. These drugs should not be used in patients with severe conduction abnormalities or sinus node dysfunction because those conditions can be exacerbated with these agents.

Recommendations for Acute Treatment of Multifocal Atrial Tachycardia COR LOE Recommendation IIa C-LD 1.  Intravenous metoprolol229 or verapamil232,233 can be useful for acute treatment in patients with MAT.

See Online Data Supplement 7. The mechanism of MAT can involve triggered activity, and treatment with intravenous verapamil can terminate the arrhythmia with moderate success. In 1 small study, intravenous verapamil converted MAT in 8 of 16 patients treated.233 Alternatively, intravenous verapamil may acutely slow the ventricular response to MAT. The major potential side effect is hypotension.233 The relatively cardioselective beta blocker metoprolol can also work by slowing the ventricular rate in MAT. Beta blockers are typically avoided in patients with severe underlying pulmonary disease, particularly those with bronchospasm; both beta blockers and verapamil are typically avoided in the presence of acute decompensated heart failure and/or hemodynamic instability.

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