Optical Mapping of Tachycardia-Like Excitation Evoked by Pacing in the Isolated Rat Atrium

Abstract

Multiple-site optical recording of membrane potential activity using a voltage-sensitive dye was employed to monitor action potentials in the rat atrium. Electrical pacing at 1 Hz evoked the events of tachycardia-like excitation (TE).Key words: multiple-site optical recording, tachycardia-like excitation, pacing.Optical methods for monitoring membrane potential activity using fast voltage-sensitive dyes, which have several advantages over more conventional electrophysiological techniques, have provided a powerful tool for the mapping studies of excitation spread under arrhythmic conditions [1,2]. These studies are indispensable for understanding the mechanism(s) of the generation and the maintenance of cardiac arrhythmias, in which reentry and/or abnormal automatism may take part.We have been using optical methods with merocyanine-rhodanine dyes and a multiple-element photodiode array. Formerly, we optically assessed the ontogenetic development of the conduction pattern of excitations in early embryonic hearts [1]. We have also mapped the excitation spread pattern in adult hearts [3][4][5]. In a previous study [4,5], using a voltage-sensitive merocyanine-rhodanine dye together with a 16 × 16 or 12 × 12 element photodiode array, we optically mapped the excitation spread in the isolated rat atrial preparation during the abnormal state of atrial rhythm, which we named tachycardia-like excitation (TE), evoked by electrical stimulation. During TE, the action potentials occur at a much faster rate than in the normal condition, and the physiological pacemaker does not work. We demonstrated that the reentry mechanism took part in most of the TE. We also demonstrated the excitation spread during the initiation phase of TE evoked by tetanus stimulation (5-10 Hz).On the other hand, we have reported that TE can be evoked by regular electrical pacing at 0.5-1 Hz [4,5]. However, the mapping of its initiation phase evoked by pacing has been difficult because TE's initiation is unpredictable during the course of regular pacing. Fortunately, we could evoke several events of TE by pacing stimulation in a preparation and succeeded in recording them by means of a continuous multiple-site optical recording. We report here the conduction patterns of the excitatory wave during the event of TE evoked by regular pacing stimulation at 1 Hz in the isolated rat atrium.Some results presented herein have been communicated in a preliminary abstract [6].The experimental methods were the same as those described in the previous papers [4,5]. Adult rats (Wistar strain, 400-800 g) of both sexes were anesthetized by inhalation of ether. The hearts were quickly removed and bathed in an ice-cold bathing solution. The right atrial preparations including the sinus node area, caval area, and atrial septum were isolated, and the lateral wall of the right auricle was incised. The preparations were attached, positioning the endocardial side upward, to the silicone bottom of a chamber by pinning it with tungsten wires. The preparations were kept i...

Optical Mapping Analysis of the Spatiotemporal Pattern of Experimental Tachyarrhythmia in Improved Isolated Rat Atrium Preparation

“…For the suppression of optical artifacts resulting from contractile movements, 2,3-butanedione monoxime (BDM: 10-20 mM) was added to the bathing solution. In the previous reports [3][4][5], no systematic changes were observed in the conduction of excitation in BDM-containing solution.…”

“…We optically mapped the spread of excitation in the intact isolated rat right atrial preparation during an abnormal state of atrial rhythm, which we termed "tachycardia-like excitation", evoked by electrical stimulation [3][4][5]. During this event, the occurrence of the excitatory waves shows a much faster rate than that in the normal condition, and the physiological pacemaker does not work.…”

Cytochalasin D as the Depressant of Contraction for the Optical Monitoring of Action Potentials in Isolated Rat Atrium

“…For the optical recording of the cardiac action potential, this chemical was first applied to canine ventricular muscle [7], then to the heart of developing chick embryos [8], and perfused mouse and rat hearts [9,10]. We used this chemical in isolated rat atrial preparations and evaluated its validity in the optical recording of action potentials.Some of the results presented herein have been communicated in a preliminary abstract [11].The experimental methods were the same as those described in previous papers [3][4][5]. Adult rats (Wistar strain: 400-800 g) of both sexes were anesthetized by the inhalation of ether.…”

“…Using a voltage-sensitive merocyanine-rhodanine dye together with a 16 × 16 or 12 × 12 element photodiode array, we recorded optical action potentials (i.e., action potential-related optical signals) simultaneously from many sites, and optically mapped the excitation spread in isolated rat atrial preparations during the abnormal state of atrial rhythm, which we named "tachycardia-like excitation" (TE), evoked by electrical stimulation [3][4][5][6]. During TE, the action potentials occur at a much faster rate than in the normal condition, and the physiological pacemaker does not work.…”

“…The experimental methods were the same as those described in previous papers [3][4][5]. Adult rats (Wistar strain: 400-800 g) of both sexes were anesthetized by the inhalation of ether.…”