Garfinkel Alan
Department of Medicine (Cardiology), UCLA, Los Angeles, CA, USA.
J Electrocardiol. 2007 Nov-Dec;40(6 Suppl):S70-4. doi: 10.1016/j.jelectrocard.2007.06.011.
Cardiac electrical alternans is an alternating rhythm in the electrical properties of the heart, such as cellular action potential duration, conduction velocity, and/or intracellular calcium (Ca) concentrations. These alternations can initiate reentrant arrhythmias and can also break up ongoing reentry, creating ventricular fibrillation. Alternans can take several forms. The alternation in time can be uniform in space (concordant alternans) or can have regions that are out of phase with other regions (discordant alternans). Alternans can be driven by voltage instabilities (involving electrical restitution) or by Ca instabilities. In addition, the relation between voltage and Ca can be positive or negative. Anatomical factors can play a role in generating spatially discordant alternans, but there is also a critical role for instabilities that are dynamically generated and can only be understood as the response of a nonlinear medium to periodic excitation. This is especially true of spatially discordant alternans, the most deadly form. We will review the role of factors such as action potential duration, conduction velocity, and Ca, which interact with each other to produce alternans. Simulations of cardiac conduction support these conclusions, as do experiments in a variety of animal and human preparations.
心脏电交替是心脏电特性中的一种交替节律，如细胞动作电位持续时间、传导速度和/或细胞内钙（Ca）浓度。这些交替可引发折返性心律失常，也可终止正在进行的折返，从而导致心室颤动。电交替可呈现多种形式。时间上的交替在空间上可以是均匀的（一致电交替），也可以有与其他区域不同步的区域（不一致电交替）。电交替可由电压不稳定（涉及电恢复）或钙不稳定驱动。此外，电压与钙之间的关系可以是正相关或负相关。解剖学因素在产生空间不一致电交替中可能起作用，但动态产生的不稳定也起着关键作用，这种不稳定只能理解为非线性介质对周期性刺激的反应。对于最致命的空间不一致电交替形式来说尤其如此。我们将综述动作电位持续时间、传导速度和钙等因素的作用，这些因素相互作用产生电交替。心脏传导模拟支持这些结论，各种动物和人体实验的结果也是如此。
