Synchronization of Spontaneous Calcium Release Waves Among Myocytes in Intact Heart Determines the Magnitude of Delayed Afterdepolarizations and Triggered Activity

Intracellular Ca waves occur as the result of spontaneous Ca release (SCR) during Ca overload. Ca waves activate Na-Ca exchange, causing delayed afterdepolarizations (DAD) which can achieve threshold and produce triggered extrasystoles. It is not known how these single cell events depolarize enough myocytes in intact heart to produce a triggered beat. We combined experimental observations with computer simulations to explain how SCR synchronization among myocytes brings a critical tissue mass to threshold.