Cardiomyocytes are excitable cells that can generate and propagate excitations; excitability is a
fundamental characteristic of these cells, which is reflected by action potential, the changes of transmembrane
potential as a function of time, orchestrated by ion channels, transporters, and cellular proteins. The electrical
excitation evoked in muscles must be transformed into mechanical contraction through the so-called excitationcontraction
coupling mechanism, and the proper contraction of cardiac muscles then drives pumping of blood to
the body circulation. Arrhythmias are electrical disturbances that can result in irregular heart beating with
consequent insufficient pumping of blood. Arrhythmias are often lethal, constituting a major cause for cardiac
death, particularly sudden cardiac death, in myocardial infarction and heart failure. Recent studies have led to the
discovery of microRNAs (miRNAs) as a new player in the cardiac excitability by fine-tuning expression of ion
channels, transporters, and cellular proteins, which determines the arrhythmogenicity in many conditions. This
review article will give a comprehensive summary on the data available in the literature. The basics of cardiac
excitability are first introduced, followed by a brief introduction to the basics of miRNAs. Then, studies on
regulation of cardiac excitability by miRNAs are described and analyzed.
