Tridimensional Ventricular Analysis of Arrhythmogenecity of Long QT Syndrome(Differential effect of intracoronary acetylcholine injection in clinical cases and experimental models)

Intracoronary administration of acetylcholine (Ach) induced QTc interval prolongation in all 14 patients with congenital long QT syndrome (LQTS) and torsade de pointes arrhythmia developed following premature ventricular beats in 5 of the patients. In the experimental models of LQT 2 and LQT 3, tridimensional repolarization mapping showed that three layers having a different electrophysiological character existed in the left ventricle; endocardial (End), midmyocardial M-cell (Mid) and epicardial layer (Epi). The refractory period estimated by the activation-recovery interval (ARI) in the Mid layer was longer than that at Epi/End layers, so marked transmural ARI dispersion was created especially between the Mid and Epi layers at the longer basic drive of 60 bpm. The marked transmural dispersion of repolarization was diminished when the pacing rate changed to 100 bpm. Different from the clinical LQTS patients, intracoronary Ach administration in the LQT models did not show any QTc interval prolongation at lower concentrations. Further, at higher concentrations (＞5μg) of Ach, the Epi layer showed greater ARI abbreviation rather than the Mid/End layers which resulted in greater transmural dispersion of repolarization, but no ventricular arrhythmia was induced.