It has been suggested that the shape of the normalized time-varying elastance curve, Eⁿ(tⁿ), is conserved in different cardiac pathologies. We hypothesize, however, that the Eⁿ(tⁿ) differs quantitatively after myocardial infarction (MI). Sprague-Dawley rats (n=9) were anesthetized and the left anterior descending coronary artery was ligated to provoke the MI. A sham operated control group (CTRL) (n=10) was treated without the MI. Two months later, a conductance catheter was inserted into the left ventricle (LV). The LV pressure and volume were measured and the En(tn) derived. Slopes of Eⁿ(tⁿ) during the pre-ejection period (_PEP), ejection period (_EP) and their ratio (=_EP/_PEP ) were calculated, together with the characteristic decay time during isovolumic relaxation () and the normalized elastance at end diastole (Eⁿ_min). MI provoked significant LV chamber dilatation thus loss in cardiac output (-33%), ejection fraction (-40%) and stroke volume (-30%)(p<0.05). Also, it caused significant calcium increase (17 fold), fibrosis (2 fold) and LV hypertrophy. End-systolic elastance dropped from 0.66±0.31mmHg/µl (CTRL) to 0.34±0.11mmHg/µl (MI)(p<0.05). Normalized elastance was significantly reduced in the MI group during the pre-ejection, ejection and diastolic period (p<0.05). The slope of Eⁿ(tⁿ) during the PEP, and were significantly altered after MI (p<0.05). Further, and end-diastolic Eⁿ_min were both significantly augmented in the MI group. We conclude that the Eⁿ(tⁿ) differs quantitatively, in all phases of the heart cycle, between normal and hearts post MI. This should be considered when utilizing the single-beat concept.