Genesis of phase 3 early afterdepolarizations and triggered activity in acquired long-QT syndrome.

ABSTRACT:

Background

Both phase 2 and phase 3 early afterdepolarizations (EADs) occur in long-QT syndromes, but their respective roles in generating arrhythmias in intact cardiac tissue are incompletely understood.

Methods and results

Intracellular Ca (Ca(i)) and membrane voltage (V(m)) were optically mapped in a quasi 2-dimensional model of cryoablated Langendorff-perfused rabbit ventricles (n=16). E-4031 (an I(Kr) blocker) combined with reduced extracellular K ([K(+)](o)) and Mg ([Mg(2+)](o)) prolonged action potential duration heterogeneously and induced phase 2 and phase 3 EADs. Whereas phase 2 EADs were Ca(i)-dependent, phase 3 EADs were not. The origins of 47 triggered activity episodes were attributed to phase 2 EADs in 12 episodes (26%) and phase 3 EADs in 35 episodes (74%). W

SUBMITTER: Maruyama M 

PROVIDER: S-EPMC3045276 | biostudies-literature | 2011 Feb

REPOSITORIES: biostudies-literature