Evolution of Action Potential Alternans in Rabbit Heart during Acute Regional Ischemia

Figure 8

A schematic explaining the evolution of OAPA alternans during acute ischemia and its link with the intramural 2 : 1 conduction block. The traces of the optical and microelectrode recordings (ME1 and ME2) are labeled in black, blue, and red, respectively. The tips of the microelectrodes are located right under the pixel (black point) viewed by the CCD camera. Due to depth averaging effect the optical recording constitutes a weighted sum of signals originating at different depths and represented by ME1 and ME2. (a) Control, all recordings show 1 : 1 conduction and no alternans. (b) After 6 minutes of ischemia an area of 2 : 1 conduction block (shown in yellow) develops inside the ischemic region (shown in grey), while the subepicardial layer preserves normal 1 : 1 conduction. The summation of ME1 and ME2 results in OAPA alternans. (c) As ischemia progresses, the 2 : 1 block evolves into complete conduction block (black region) leading to simultaneous disappearance of the action potential from ME1 and the OAPA alternans.

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