For a more detailed list of drug drug interactions, clinicians should consult additional resources. If hypotension is a consideration, a slow infusion of diltiazem (2.5 mg/min) or verapamil (1 mg/min) for up to 20 minutes may lessen the potential for QTc calculation used the Bazett s Formula in most clinical studies. Patients should be observed with continuous ECG monitoring for at least 4 h after infusion or until QTc has returned to baseline. The infusion should be stopped as soon as the arrhythmia is terminated or in the event of sustained or nonsustained ventricular tachycardia or marked prolongation of QT or corrected QT interval. AF indicates atrial fibrillation; AV, atrioventricular; BID, twice daily; COR, Class of Recommendation; HF, heart failure; INR, international normalized ratio; IV, intravenous; LOE, Level of Evidence; LV, left ventricular; PVC, premature ventricular contraction; QTc, corrected QT interval; SA, sinoatrial; SVT, supraventricular tachycardia; and WPW, Wolff-Parkinson-White. Table 6. Continued Drug Initial Dose Subsequent or Maintenance Dose Potential Adverse Effects Precautions (Exclude or Use With Caution) and Interactions Recommendations for Acute Treatment of Suspected Focal Atrial Tachycardia COR LOE Recommendations I C-LD Intravenous beta blockers, diltiazem, or verapamil is useful for acute treatment in hemodynamically stable patients with focal See Online Data Supplement 6. Intravenous beta blockers, diltiazem, or verapamil is recommended to treat focal AT. During EP study, propranolol or verapamil is moderately effective in either terminating the focal AT or slowing the ventricular rate in approximately 30% to 50% of the patients.204,205 Although these agents are relatively safe, close monitoring is recommended during intravenous drug therapy to evaluate for hypotension or bradycardia. I C-LD 2. Synchronized cardioversion is recommended for acute treatment in patients with hemodynamically unstable focal AT.94,208 See Online Data Supplement 6. 