High dose oral amiodarone loading exerts important hemodynamic actions in patients with congestive heart failure.
OBJECTIVE
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.
Gottlieb
S S
SS
Department of Medicine, University of Maryland School of Medicine, Baltimore 21201.
Riggio
D W
DW
Lauria
S
S
Peters
R W
RW
Shorofsky
S R
SR
Cines
M
M
Froman
D
D
Gold
M R
MR
D000284:Administration, Oral; D000368:Aged; D000638:Amiodarone / Q000008:administration & dosage / Q000494:pharmacology*; D002407:Catheterization, Swan-Ganz; D004305:Dose-Response Relationship, Drug; D004562:Electrocardiography; D005260:Female; D006333:Heart Failure / Q000503:physiopathology*; D006439:Hemodynamics / Q000187:drug effects*; D006801:Humans; D008297:Male; D011669:Pulmonary Wedge Pressure / Q000187:drug effects; D013815:Thermodilution; D013997:Time Factors
D000638:Amiodarone