Before revision:  Here we present a mathematical model of  RyR and IP3R channel interaction which demonstrates that cytosolic IP3 is indeed capable of increasing the duty cycle of the calcium signal in the cardiomyocyte.
After revision:  Here we present a mathematical model of RyR and IP3R channel interaction which demonstrates that IP3-mediated Ca2+release in the cytosol is indeed capable of increasing the duty cycle of the calcium signal in the cardiomyocyte.