Influence of the KCl concentration on rat sinus node recovery time in vitro

The influence of changes in the KCl concentration of the bath fluid ([KCl]o) on the corrected sinus node recovery time (CSNRT) was studied using the continuous pacing method (M1) and the method of stimulation with premature pulses (M2). M1 and M2 were compared in Krebs-Henseleit solution containing normal (4.6 mM), low (3.1 mM, LoKCl) and high (6.1 mM, HiKCl) [KCl]o. The results revealed that HiKCl increased CSNRT (P less than 0.01) and changed the prematurity-CSNRT relationship (P less than 0.01), whereas LoKCl did not change CSNRT. M1 and M2 were different (P less than 0.01) regardless of [KCl]o, except for pacing intervals near the spontaneous cycle length.