Rescuing the heart from the tornadoes of sudden cardiac death.

Sudden cardiac death (SCD) causes 4 to 5 million deaths each year globally. Electrical vortices (tornadoes or rotors) are the origin of ventricular fibrillation (VF), which often causes SCD. Cardiac electrical vortices have complex dynamics and have been shown in many mammalian species. During VF, the heart fails to contract suitably and is unable to pump blood. Once VF is initiated, drug treatments are ineffective and even make things worse. The only effective treatment is electrical shock to the ventricles. Our current understanding of VF mechanisms is fragmentary, hindering the development of personalized therapies. Yet recent insights into the roles of the most critical sarcolemmal ion channels in VF in controlling the excitation-recovery process provide hope. Substantial evidence indicates that the molecular interplay between the main cardiac sodium channel (NaV1.5) and the strong inward-rectifier potassium current (Kir2.1) controls cardiac excitability, wave propagation velocity, and rotor formation, as well as rotor stability and frequency during VF. Studies at the cellular, molecular, and ion channel levels are helping us understand how rotors generate the turbulence that characterizes VF, providing insights into how to prevent their initiation and identifying new therapeutic targets to avert premature death.