In anesthetized pigs, we investigated whether asynchrony (T) and nonuniformity (regional differences) in contractility (E) could describe the interaction between normal and stunned myocardium. Mechanical interaction was evaluated by regional postsystolic work (PSW) before and after production of stunning by a 5-min occlusion of the left circumflex coronary artery [LCX (LCX stunning)] and a subsequent 10-min occlusion of the left anterior descending coronary artery [LAD (LAD stunning)]. T and E were intensified by intracoronary (LAD) infusions of dobutamine. From regional end-systolic pressure-segment length relationships, systolic segment shortening (SS), end-systolic elastance (E), external work (EW), and PSW were determined. LCX stunning decreased SS_LCX from 14 ± 2 (mean ± SE, n = 9) to 10 ± 2% and E_LCX from 103 ± 25 to 52 ± 7 mmHg/mm, whereas the LAD region was unaffected. EW_LCX decreased from 165 ± 16 to 138 ± 20 mmHg · mm, whereas PSW_LCX increased from 4 ± 6 to 8 ± 3 mmHg · mm. Additional LAD stunning reduced SS_LAD from 16 ± 2 to 9 ± 3% and E_LAD from 79 ± 10 to 31 ± 6 mmHg/mm, without affecting SS_LCX and E_LCX. In the normal myocardium, PSW_LAD increased and PSW_LCX decreased, but, during local LAD dobutamine infusions after stunning, both PSW_LCX and PSW_LAD increased. In normal myocardium, the changes in PSW_LCX could be described by T (65 ± 11%) and E (37 ± 15%). After stunning of the LAD area, the contribution of E increased to 55 ± 14% at the expense of T (37 ± 15%). Similar contributions of E (54 ± 13%) and T (57 ± 13%) were found when both the LCX and LAD distribution areas were stunned. In normal myocardium, both T and E modulate mechanical interaction, with the contribution of T exceeding that of E. In stunned myocardium, both factors contribute, but the contribution shifts in favor of E.