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J Appl Physiol 102: 1123-1129, 2007. First published December 7, 2006; doi:10.1152/japplphysiol.00976.2006
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The effect of a myocardial infarction on the normalized time-varying elastance curve

¹Laboratory of Haemodynamics and Cardiovascular Technology, Ecole Polytechnique Fédérale de Lausanne, Lausanne; ²Department of Cardiovascular Surgery, Centre Hospitalier Universitaire Vaudois, Lausanne; ³Department of Cardiovascular Surgery, Inselspital, Bern; and ⁴Department of Cardiology, Centre Hospitalier Universitaire Vaudois, Lausanne, Switzerland

Submitted 4 September 2006 ; accepted in final form 4 December 2006

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 preejection 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 (E_minⁿ). MI provoked significant LV chamber dilatation, thus a 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 ± 0.31 mmHg/µl (CTRL) to 0.34 ± 0.11 mmHg/µl (MI) (P < 0.05). Normalized elastance was significantly reduced in the MI group during the preejection, ejection, and diastolic periods (P < 0.05). The slope of Eⁿ(tⁿ) during the _PEP and were significantly altered after MI (P < 0.05). Furthermore, and end-diastolic E_minⁿ 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.

compliance; ischemia; contractility; ventricular function; hemodynamics; conductance volumetry