title: Proarrhythmic effect of blocking the small conductance calcium activated potassium channel in isolated canine left atrium.
abstract: BACKGROUND
  Small conductance calcium activated potassium (SKCa) channels are voltage insensitive and are activated by intracellular calcium. Genome-wide association studies revealed that a variant of SKCa is associated with lone atrial fibrillation in humans. Roles of SKCa in atrial arrhythmias remain unclear.
  
  
  OBJECTIVE
  To determine roles of SKCa in atrial arrhythmias.
  
  
  METHODS
  Optical mapping using the isolated canine left atrium was performed. The optical action potential duration (APD) and induction of arrhythmia were evaluated before and after the addition of specific SKCa blockers-apamin or UCL-1684.
  
  
  RESULTS
  SKCa blockade significantly increased APD₈₀ (188 ± 19 ms vs 147 ± 11 ms; P<.001). The pacing cycle length thresholds to induce 2:2 alternans, and wave breaks were prolonged by SKCa blockade. Increased APD heterogeneity was observed after the SKCa blockade, as measured by the difference between the maximum and the minimum APD (39 ± 4 ms vs 26 ± 5 ms; P<.05), by standard deviation (12.43 ± 2.36 ms vs 7.49 ± 1.47 ms; P<.001), or by coefficient of variation (6.68% ± 0.97% vs 4.90% ± 0.84%; P<.05). No arrhythmia was induced at baseline by an S1-S2 protocol. After SKCa blockade, 4 of 6 atria developed arrhythmia.
  
  
  CONCLUSIONS
  SKCa blockade promotes arrhythmia and prolongs the pacing cycle length threshold of 2:2 alternans and wave breaks in the canine left atrium. The proarrhythmic effect could be attributed to increased APD heterogeneity in the canine left atrium. This study provides supportive evidence of genome-wide association studies showing association of KCNN3 and lone atrial fibrillation.
authors: Krannert Institute of Cardiology and Division of Cardiology, Indiana University, Indianapolis, Indiana 46202, USA.
authors: Chia-Hsiang
authors: CH
authors: Hsueh
authors: Po-Cheng
authors: PC
authors: Chang
authors: Yu-Cheng
authors: YC
authors: Hsieh
authors: Thomas
authors: T
authors: Reher
authors: Peng-Sheng
authors: PS
authors: Chen
authors: Shien-Fong
authors: SF
authors: Lin
mesh_terms: D000818:Animals; D001145:Arrhythmias, Cardiac / Q000503:physiopathology*; D001281:Atrial Fibrillation / Q000503:physiopathology; D015153:Blotting, Western; D004285:Dogs; D022062:Electrophysiologic Techniques, Cardiac; D055106:Genome-Wide Association Study; D006325:Heart Atria / Q000503:physiopathology*; D066298:In Vitro Techniques; D008297:Male; D051640:Small-Conductance Calcium-Activated Potassium Channels / Q000187:drug effects*; D056969:Voltage-Sensitive Dye Imaging
chemical_list: D051640:Small-Conductance Calcium-Activated Potassium Channels
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