Does varying extracellular potassium concentration affect APD restitution kinetics and ventricular fibrillation dynamics in isolated canine ventricles?
Increasing extracellular potassium alters APD restitution kinetics and can convert ventricular fibrillation to a periodic rhythm, highlighting the role of APD restitution in VF maintenance.
To test whether hyperkalemia suppresses ventricular fibrillation (VF) by reducing the slope of the action potential duration (APD) restitution relation, we determined the effects of the extracellular K(+) concentration (K(+)(o)) (KCl = 2.7-12 mM) on the restitution of APD and maximum upstroke velocity (V(max)) the magnitude of APD alternans and spatiotemporal organization during VF in isolated canine ventricle. As KCl was increased incrementally from 2.7 to 12 mM, V(max) was reduced progressively. Increasing KCl from 2.7 to 10 mM decreased the slope of the APD restitution relation at long, but not short, diastolic intervals (DI), decreased the range of DI over which the slope was >/=1, and reduced the maximum amplitude of APD alternans. At KCl = 12 mM, the range of DI over which the APD restitution slope was >/=1 increased, and the maximum amplitude of APD alternans increased. For KCl = 4-8 mM, the persistence of APD alternans at short DI was associated with maintenance of VF. For KCl = 10-12 mM, the spontaneous frequency during VF was reduced, and activation occurred predominantly at longer DI. The lack of APD alternans at longer DI was associated with conversion of VF to a periodic rhythm. These results provide additional evidence for the importance of APD restitution kinetics in the development of VF.
Koller et al. (Fri,) studied this question.