Increasing pressures to 30 mmHg in right (RV) and left (LV) ventricles and surrounding heart (SH) in isolated, arrested, maximally vasodilated, blood-perfused dog hearts shifted pressure-flow (PF) curves rightward and increased zero flow pressure (P_zf) by an amount equal to the RV applied pressure, SH applied pressure, or two-thirds of the LV applied pressure. There were comparable increases in coronary venous pressures. Increasing LV or SH pressures decreased coronary blood flows, especially in the subendocardium. Decreases in driving pressure decreased flows in all layers, but even with driving pressure of 5 mmHg, a few subepicardial pieces had flow. We conclude with the following: 1) raising pressures inside or outside the heart shifts PF curves and raises P_zf by increasing coronary venous pressure; 2) the effects are most prominent in the subendocardial muscle layer; and 3) as driving pressures are decreased, there is a range of P_zf in the heart with the final P_zf recorded due to the last little piece of muscle to be perfused.