高钾时心室肌电-机械交替活动的分析

Analysis of the electromechanical alternans of ventricular muscleduringhyperkalemia

高钾（１２ｍｍｏｌ／Ｌ）条件下，突然增快刺激频率（１ＨＺ－４Ｈｚ），豚鼠乳头肌发生两轮２：１电－机械交替（ＥＭＡ）。第一轮ＥＭＡ历时约２２－３０ｓ宽的动作电位（ＡＰ）马低的收缩力（Ｆｃ）相对应。间隔性ＡＰ脱落期发生在两轮ＥＭＡ之间，历时约４－６ｍｉｎ。第二轮ＥＭＡ期间，高宽的ＡＰ与高的Ｆｃ相对应。ＡＰ交替消失时Ｆｃ交替也随之消失。第二轮ＥＭＡ历时２２－３４ｍｉｎ（２６±５ｍｉｎ，ｎ＝７），奎尼丁（１μｇ／ｍｌ）显著增强第二轮ＥＭＡ，异搏定（０．５μｇ／ｍｌ）则相反。提示高钾诱发的ＥＭＡ可能与Ｎａ＋，Ｃａ２＋离子流有关。

Two sets of 2:1 electromechanicalalternans (EMA)wereobserved in isolated guinea pig papaillary muscles exposed tohyperkalemia (12mmol/L)-Tyrode’s solution withrapid pacing (4Hz).Theprolonged durationof action potential(APD)were associated with low contractile force in the first set EMA which usually lasted for 22-30 second.The discontinuous actionpotential dropping phase occurred between the first and the second sets of EMA and usually lasted for 4-6 min During the secondsetof EMA which lastedfor22-34ming bothprolonged and high action potentials were associated with high contractile force .Themechanicalalternans died awaywith disappearanceof the electrical alternans Quinidine caused amarked augmentation inthesecond EMA set , but verapamilattenuated it 。The results suggested that hyperkalemiainduced EMAmight be associatedwith Na+and Ca2+current