Abstract 20830: The Local Elevation of Extracellular Potassium Facilitates the Electrical Instability and Reentry Occurrence via Spatial Heterogeneity of the Action Potential Duration Restitution
Introduction: Accumulation of extracellular potassium ([K+]o) is one of the major consequences of acute ischemia. The systematic investigation of the role of K+ imbalance in arrhythmia induction is limited due to the rapidity of the electrophysiological changes after coronary artery occlusion.
Hypothesis: We used an experimental model of the regionally perfused rabbit heart to create the [K+]o heterogeneity and assess the hypotheses that a) conduction alternans lead to action potential (AP) alternans, conduction block and reentry, and b) spatial heterogeneity of action potential duration (APD) restitution due to high regional [K+]o results in AP instability and reentry induction.
Methods: After cannulation of the ascending aorta, the left marginal vein was cannulated separately and perfused with solution containing 4, 6, 8, 10 and 12 mM of K+. The heart was stimulated starting from a pacing interval (PI) of 400 ms down to 120 ms with steps of 5–50 ms. The Vm was mapped optically.
Results: The elevation of regional [K+]o slowed conduction at the area of regional perfusion (RP) and led to heterogeneous activation time distribution. At 8 mM of local [K+]o, the acceleration of the stimulation caused AP alternans within the RP area. The RP with 10 mM [K+]o promoted both AP alternans and 2:1 conduction block during PIs of 200 ms and shorter. The area of irregular electrical activity expanded with PI shortening. Analysis of propagation revealed three concurrent dynamics: regular when activation waves spread over tissue perfused with normal K+ (4 mM), alternating 2:2 rhythm near the border of [K+]o heterogeneity and 2:1 aperiodicity when propagation was within the high [K+]o area (10 mM). We did not observe conduction velocity alternans during propagation through the border zone. The elevation of [K+]o flattened APD restitution and shifted it towards shorter APD and a longer diastolic interval. The probability of arrhythmia induction varied depending on burst pacing rate and was significantly higher in hearts regionally perfused with 10 mM K+ (P<0.05).
Conclusions: We conclude that spatial heterogeneity of the APD restitution, which is created with regional elevation of [K+]o, is the mechanism related to AP instability, 2:1 block and reentry induction.
- © 2010 by American Heart Association, Inc.