Disclosed are compositions, methods and systems for preventing or treating cardiac dysfunction, particularly cardiac pacing dysfunction by genetic modification of cells of targeted regions of the cardiac conduction system. In particular, a bio-pacemaker composition is delivered to cardiac cells to increase the intrinsic pacemaking rate of the cells, wherein the bio-pacemaker composition increases expression of a channel or subunit thereof that produces funny current and a T-type Ca.sup.2+ channel or subunit thereof, and expresses one or more molecules that suppresses the expression of the wild type potassium channel.