Abstract: A system delivers fibroblasts to a region of cardiac tissue at a location associated with a cardiac arrhythmia in a patient to form a conduction block in the region. A cardiac delivery system is coupled to a source the fibroblasts and delivers the fibroblasts to the location to form a conduction block. Substantial cardiac ablation is thus avoided. A contact member is shaped to correspond with a patterned region of tissue for delivering the fibroblasts along the pattern, such as linear, curvilinear, or circumferential patterns as required for treating particular arrhythmias. A pulmonary vein isolation assembly has an expandable or loop-shaped member cooperating with a needle array that delivers the fibroblast cells into a circumferential region of tissue engaged by the expandable member where a pulmonary vein extends from an atrium. Methods include providing the fibroblast cells as autologous cells in an injectable preparation.