In 125 adult male Wistar rats: (i) either with one month old MI (n=110) and treated with growth factors (GFs, n=59) or vehicle (V, n=51) or (ii) sham operated (SO, n=15), a series of functional measurements was performed prior and 15 days after intra-myocardial GFs/V injection. BrdU was continuously infused by osmotic pump to detect cell proliferation. Excised hearts were subjected to anatomical, morphometric and immuno-histochemical studies or immunoblot and quantitative RT-PCR analyses. In MI+GF rats compared with MI+V, stress-induced telemetrically recorded ventricular arrhythmias were less (-58%*). Effective refractory period by multiple lead epicardial recording was longer (+29%*) while QTc and ventricular mRNA levels for K-channel a-subunits K_v1.4, K_v4.2 and K_v4.3 were similar in both groups. Lower mRNA levels for b-subunit KChIP2 (-22%*) and structural changes indicative of positive remodelling (+27/-52%*) were found in remote myocardium. By echocardiograpy and invasive hemodynamics, the correlation of infarct size with deterioration of mechanical function observed in MI+V was abolished. Larger amounts of new myocardium and properly connected developing myocytes were documented by BrdU incorporation and distribution of connexin 43 and N-cadherin. In conclusion, GF delivery in chronic MI increases the liminal length for impulse formation by better intercellular coupling and reduces unfavourable ventricular remodelling, ameliorating cardiac electrical stability. *=p<.05.