Clinical Drug Experience Knowledgebase

The administration of intravenous non-dihydropyridine calcium channel blockers such as diltiazem for patients presenting in atrial fibrillation with rapid ventricular response, without evidence of pre-excitation, are recommended first-line therapies by the American Heart Association.1 Hypotension warrants careful consideration in the treatment of atrial fibrillation with a rapid ventricular response. Hemodynamic stability is a continuum, however, and rate control is often vital, particularly in patients who are refractory to electrical cardioversion [or who have underlying conditions such that tachycardia is not well tolerated]. Diltiazem has been utilized in dosing such as 2.5 mg/min in those with decreased blood pressure and atrial fibrillation with elevated ventricular rate.2 Lim et al. in 2002 demonstrated the effectiveness of a slow infusion of diltiazem 2.5 mg/min to a maximum of 50 mg to control rate in supraventricular tachycardia.

The study of the slow infusion of diltiazem has been limited to supraventricular tachycardia. No literature exists evaluating the efficacy of such a gradual infusion in atrial fibrillation or atrial flutter, rhythms affecting 2.7 million to 6.1 million Americans.1,3 It can be reasoned that a gradual infusion of diltiazem will minimize side effects, predominantly hypotension, and perhaps even demonstrate efficacy in alleviating hypotension due to decreased stroke volume from excessive tachycardia. The proposed benefits of an infusion, as compared to a bolus, would allow for the termination of an infusion as soon as rate control is achieved thus limiting the potential for hypotension. With current evidence-based literature validating the superiority of non-dihydropyridine calcium channel blockers and questions surrounding present recommendations of weight based intravenous dosing, the authors suggest an inquiry into the utility of a gradual infusion of diltiazem for initial rate control in patients presenting with atrial fibrillation or flutter with or without hypotension related to excessive tachycardia.

This is a prospective, randomized, double blind investigation to compare the effectiveness of standard IV (intravenous) push diltiazem at 0.25 mg/kg (to a maximum of 25 mg) over 2 minutes, with a potential repeat dose of 0.35 mg/kg if the initial dose is not effective versus a slow infusion of 50 mg of IV diltiazem diluted in 50 mL of 0.9% normal saline (NS) administered over 20 minutes. The investigators anticipate the data to be collected over the course of 2-3 years. These methods of diltiazem administration are already accepted practices at our institution and are consistent with current approved product labeling and professional judgment based upon clinical experience, and therefore the investigators do not foresee any additional risk to patients enrolled in our proposed study. In either treatment group, should hypotension or other clinical evidence of poor systemic perfusion, no additional IV diltiazem, or additional administration of a diltiazem infusion will be administered. The primary outcome measured will be the efficacy of treatment as defined by the obtainment of a heart rate of <110 beats/minute within 30 minutes of drug administration. Secondary outcomes evaluated will include the need for additional medications to achieve rate control including the need for repeat diltiazem bolus at 0.35 mg/kg, electrical cardioversion, admission, allergic reactions, and side effects including, but not limited to, systolic blood pressure less than 90 mmHg or bradycardia with heart rate less than 60 bpm.