An angiotensin-mediated signaling pathway that contributes to a circulatory system process carried out by the heart, where the activated receptor transmits the signal via Gq-mediated activation of phospholipase C (PLC). PLC hydrolyses phosphatidylinositol 4,5-bisphosphate (PIP2) into the second messengers inositol-1,4,5,-triphosphate (IP3) and diacylglycerol (DAG). DAG activates protein kinase C (PKC), whilst IP3 binds intracellular receptors to induce the release of Ca2+ from intracellular stores.