Lammers W J, Allessie M A, Bonke F I
Department of Physiology, University of Limburg, Maastricht, The Netherlands.
Am J Physiol. 1988 Dec;255(6 Pt 2):H1359-69. doi: 10.1152/ajpheart.1988.255.6.H1359.
In isolated superfused left atria of the rabbit, tachyarrhythmias became highly inducible with a decrease of the extracellular potassium concentration to 2.0 mM. The nature of the arrhythmias was determined with a high-resolution mapping system. In several cases, abnormal impulse formation was found, but the majority of arrhythmias (75%) was caused by a circus movement of the impulse. Furthermore, circus-movement tachyarrhythmias often degenerated into fibrillatory activity, and activation maps revealed the presence of multiple wavelets during this chaotic rhythm. The occurrence of reentrant arrhythmias may be caused either by an increase in inhomogeneity in conduction or by a shortening of the wavelength in low potassium. Inhomogeneity in conduction was determined by calculating the difference in activation times between neighboring electrodes. In low potassium, premature activation significantly increased the inhomogeneity index compared with slow rhythm (from 2.2 to 3.9; P less than 0.001) but was not significantly different from the inhomogeneity measured at normal potassium concentrations. Low potassium, however, did shorten significantly the wavelength of the impulse by approximately 40%. The increased inducibility of reentry in low potassium is therefore caused by a reduction of the length of the excitation wave and not by an increase in inhomogeneity in conduction.
在兔离体灌流左心房中，当细胞外钾浓度降至2.0 mM时，快速心律失常极易诱发。用高分辨率标测系统确定心律失常的性质。在几例中，发现了异常冲动形成，但大多数心律失常（75%）是由冲动的折返运动引起的。此外，折返性快速心律失常常演变为颤动活动，激动标测显示在这种紊乱节律期间存在多个小波。折返性心律失常的发生可能是由于传导不均一性增加或低钾时波长缩短所致。通过计算相邻电极之间激动时间的差异来确定传导的不均一性。在低钾时，与缓慢节律相比，过早激动显著增加不均一性指数（从2.2增至3.9；P<0.001），但与正常钾浓度时测得的不均一性无显著差异。然而，低钾确实使冲动波长显著缩短约40%。因此，低钾时折返易感性增加是由兴奋波长度缩短所致，而非传导不均一性增加所致。
