Heptanol in concentrations up to 1.2 mM slowed conduction but did not stop reentry or terminate tachycardia in a rabbit model of infarction with uniform anisotropic epicardial border zone.
Does heptanol terminate ventricular tachycardia in a rabbit model of infarction with uniform anisotropic epicardial border zone?
Heptanol, an uncoupler, failed to terminate ventricular tachycardia in a rabbit infarct model, suggesting drugs decreasing intercellular coupling may be ineffective for functional reentry caused by uniform anisotropy.
INTRODUCTION: The purpose was to study reentry in a rabbit model of infarction. METHODS AND RESULTS: A model of an infarct epicardial border zone was produced in Langendorff perfused rabbit hearts by freezing the inner two thirds of the left ventricular wall, allowing only a thin epicardial muscle layer to survive. Reentrant circuits causing stable ventricular tachycardia occurred in the surviving rim of epicardial muscle as shown by mapping impulse propagation with a 196-electrode array. The circuits were functional, and reentry did not occur around an anatomical obstacle. Slow conduction in the circuits was caused by the anisotropic properties of the epicardial muscle. Activation in the circuits was slow transverse to the long axis of the fiber bundles and rapid parallel to the long axis. Other features of the circuits, including orientation of the central functional line of block parallel to the fiber long axis, and an oval shape are also characteristic of anisotropic reentry. Since the slow conduction causing reentry is a result of poor transverse intercellular coupling, we determined whether the "uncoupler" heptanol would cause block in the circuits and terminate tachycardia. Heptanol in concentrations up to 1.2 mM slowed conduction in the transverse and longitudinal directions in the circuits and sometimes extended the central line of functional block. It did not, however, stop reentry because the reentrant impulse was still able to conduct around the ends of the block line. CONCLUSION: Drugs that decrease intercellular coupling may not be effective antiarrhythmic agents when uniform anisotropy causes functional reentry.
NASSIF. et al. (Thu,) conducted a other in Infarction and ventricular tachycardia. Heptanol was evaluated on Termination of tachycardia and block in reentrant circuits. Heptanol in concentrations up to 1.2 mM slowed conduction but did not stop reentry or terminate tachycardia in a rabbit model of infarction with uniform anisotropic epicardial border zone.