Abstract
We have optically mapped the spatiotemporal patterns of the spread of excitatory waves during "tachycardia-like excitation" in the isolated rat atrial preparation. The tachycardia-like excitation with a regular cycle length of 250 - 450 ms was evoked by regular pacing (0.5-1 Hz) applied with a bipolar electrode. The events lasted for various time periods (a few sec - longer than 10 min) and often terminated spontaneously. Multiple-site optical recording methods, using a voltage-sensitive merocyanine-rhodanine dye (NK2761) and a multi-element (12 × 12 or 16 × 16) photodiode array, were employed to simultaneously monitor action potentials from many sites in the atrium. The spread of excitation was assessed optically, and we mapped the conduction patterns of the excitatory waves. These maps indicate that, during the event of tachycardia-like excitation, the excitatory waves often propagated in a quasi-circular pathway which surrounded "blocked areas" including the ostium of the superior vena cava, suggesting the establishment of the macro re-entry. The blocked area was generated by the stimulation pulse applied shortly after the spontaneous excitation, and then the excitatory wave started to rotate around the blocked area. The blocked area was often maintained during the event of tachycardia-like excitation. In some cases, instable blocked areas were also observed. [Jpn J Physiol 54 Suppl:S98 (2004)]
