Grape pomace (GP), the residue left after grape pressing in winemaking, is rich in polyphenols, including flavonoids, tannins, and phenolic acids, which have antioxidant and anti-inflammatory properties. The present study aimed to evaluate the cardioprotective effects of white grape pomace (WGP) extract in two concentrations rich in polyphenols (795 mg polyphenols from WGP/kg body weight (bw) and 397.5 mg polyphenols from WGP/kg bw)), on isoproterenol (ISO)-induced myocardial infarction (MI), focusing on its anti-inflammatory and antioxidant effects. White grape pomace administration for 14 days offered a cardio-protective effect and prevented prolongation of the QT and QTc intervals on the electrocardiogram. Both concentrations of WGP prevented the elevation of nitric oxide (NO) and malondialdehyde (MDA) in the serum, with the best results being observed for the highest concentration (