Objectives: The purpose of this study was to use invasive monitoring to analyze the hemodynamic effects of both a large single dose and a 48-h loading regimen of amiodarone in patients with severe heart failure.
Background: Amiodarone is frequently used as an antiarrhythmic agent in patients with congestive heart failure, but the impact of this agent on cardiac function remains controversial. Recent successful experience with a rapid oral load of amiodarone makes invasive testing of the hemodynamic effects of oral amiodarone in such patients now feasible.
Methods: After baseline hemodynamic assessment (using balloon-tipped pulmonary artery catheters) and electrocardiographic measurements, 16 patients received 12.5 mg/kg body weight of amiodarone orally. Hemodynamic measurements were obtained hourly for 4 h. Patients then received this dose an additional seven times over the next 2 days. Hemodynamic variables and QRS, QT and PR intervals were measured after 48 h of treatment.
Results: Vasodilation was seen between 1 and 3 h after drug administration. Systemic vascular resistance decreased 326 +/- 135 dynes.s.cm-5, cardiac index increased 0.24 +/- 0.08 liters/min per m2 and mean arterial pressure decreased 6 +/- 3 mm Hg (mean +/- SEM, all p < 0.05). After 48 h of amiodarone administration, heart rate decreased 23 +/- 3 beats/min (p < 0.005), stroke volume increased 9 +/- 3 ml (p < 0.005), cardiac index decreased 0.23 +/- 0.09 ml/min per m2 (p < 0.05), pulmonary capillary wedge pressure increased 4 +/- 1 mm Hg (p < 0.01), right atrial pressure increased 3 +/- 1 mm Hg (p < 0.005) and QT and PR intervals were markedly prolonged (p < 0.01).
Conclusions: Although the first dose caused vasodilation, a complete loading regimen of amiodarone produced a decreased heart rate with elevated filling pressures and decreased cardiac index.