Clofilium prolonged flutter cycle length by 18% and terminated atrial flutter within 30-120 seconds, whereas acetylcholine decreased cycle length in a canine model.
Do acetylcholine and clofilium alter monophasic action potential duration and cycle length in a canine model of reentrant atrial flutter?
In a canine model of atrial flutter, agents that reduce action potential duration (acetylcholine) accelerate circus movement, while those that increase it (clofilium) slow and terminate flutter.
Monophasic action potentials (MAP) were recorded from canine atrium during reentrant flutter resulting from circus movement in atrial tissue above the tricuspid ring. A catheter and plaque contact electrodes were developed to record MAP from the epicardium or endocardium during sinus rhythm, paced rhythms, and flutter. The transmembrane action potential duration of tricuspid ring tissue also was studied in vitro. During flutter at cycle lengths of 140-160 ms, MAP showed incomplete repolarization. Pacing at comparable cycle lengths had a similar effect. Acetylcholine (10 micrograms/kg, i.v.) shortened MAP duration during pacing and, during flutter, decreased cycle length and increased MAP amplitude. Clofilium (500 micrograms/kg, i.v.) prolonged flutter cycle length by 18% and terminated the flutter within 30-120 s. During pacing at a cycle length of 300 ms, clofilium increased MAP duration and effective refractory period (ERP) by 30%. Transmembrane action potentials showed that clofilium (0.2 mg/L) modified only action potential duration. Conduction velocity was significantly decreased by clofilium during flutter but not during pacing at a cycle length of 300 ms. These data support the conclusion that in this model of flutter, the circus movement occurs in partially repolarized tissue. The circus movement can be accelerated by agents (acetylcholine) that reduce ADP, and slowed and terminated by agents (clofilium) that increase it.
Wu et al. (Thu,) conducted a other in Reentrant atrial flutter. Clofilium and Acetylcholine was evaluated on Monophasic action potential duration and flutter cycle length. Clofilium prolonged flutter cycle length by 18% and terminated atrial flutter within 30-120 seconds, whereas acetylcholine decreased cycle length in a canine model.