Ankyrin-B reduction enhances Ca spark-mediated SR Ca release promoting cardiac myocyte arrhythmic activity

► Reduced Na and Ca transport but unaltered [Na]i and diastolic [Ca]i in AnkB+/− myocytes. ► Ca transients, SR Ca load and fractional SR Ca release are larger in AnkB+/− myocytes. ► Higher Ca spark frequency and unaltered total SR Ca leak in intact AnkB+/− myocytes. ► The bias towards Ca spark-mediated leak is due to different cytosolic RyR regulation. ► More coordinated RyR openings increase the propensity for Ca waves in AnkB+/− mice.