Can triggered arrhythmias arise from propagation of Ca²⁺ waves between cardiac cells?

Intracellular Ca²⁺ overload can induce regenerative Ca ²⁺ waves that activate inward current in cardiac myocytes, allowing the cell membrane to achieve threshold. The result is a triggered extrasystole that can, under the right conditions, lead to sustained triggered arrhythmias. In this review, we consider the issue of whether or not Ca²⁺ waves can travel between neighboring myocytes and if this intercellular Ca ²⁺ diffusion can involve enough cells over a short enough period of time to actually induce triggered activity in the heart. This review is not intended to serve as an exhaustive review of the literature summarizing Ca ²⁺ flux through cardiac gap junctions or of how Ca²⁺ waves move from cell to cell. Rather, it summarizes many of the pertinent experimental studies and considers their results in the theoretical context of whether or not the intercellular propagation of Ca²⁺ overload can contribute to triggered beats and arrhythmias in the intact heart.