The Journal of Thoracic and Cardiovascular Surgery, Vol 109, Issue 5 899-904, Copyright © 1995 by The American Association for Thoracic Surgery and The Western Thoracic Surgical Association
NOTE: The fulltext of this article is not available online.
Electrophysiologic effects of procainamide, mexiletine, and amiodarone on the transplanted heart. Experimental study
L. Alvarez, C. Escudero, A. Torralba and I. Millan
Experimental Surgery Service, Clinica Puerta de Hierro, Madrid, Spain.
The effects of procainamide, mexiletine, and amiodarone on automaticity,
conduction, and refractoriness were studied in a model of heterotopic heart
transplantation in dogs that combined an innervated heart (recipient) and a
denervated transplanted heart (donor). After the surgical procedure, 500 mg
procainamide (n = 13), 200 mg plus 0.1 mg/kg per minute mexiletine (n =
10), or 150 mg amiodarone (n = 10) was administered intravenously. During a
baseline period and after drug administration, each heart was assessed for
atrioventricular interval; cycle length; sinoatrial conduction time;
atrioventricular node anterograde and retrograde block points;
atrioventricular node and ventricular antegrade effective refractory
periods; PR, QRS, and QT intervals on electrocardiogram; systemic arterial,
pulmonary arterial, central venous, and pulmonary capillary wedge
pressures; and cardiac output. In recipients, procainamide reduced cardiac
output, depressed sinus automaticity, slowed conduction time without
affecting the QRS interval, and prolonged the nodal and ventricular
refractoriness; in donor hearts, it depressed automaticity and prolonged
nodal refractoriness, but did not modify conduction or ventricular
refractoriness. Mexiletine only moderately depressed sinus automaticity in
recipient hearts; it did not affect the other parameters either in
recipient or transplanted hearts, nor did it alter the hemodynamic
situation. Amiodarone produced hypotension, reduced cardiac output, and
prolonged all the electrophysiologic intervals except the QRS interval in
recipient hearts. These changes were even more pronounced in the
transplanted hearts and led to extreme sinus bradycardia in four cases. Of
these three drugs, mexiletine appears to be the safest should treatment for
arrhythmias be necessary in transplant recipients.
