The effect of a myocardial infarction on the normalized time-varying elastance curve

Abstract

Jegger D, Mallik AS, Nasratullah M, Jeanrenaud X, da Silva R, Tevaearai H, von Segesser LK, Stergiopulos N. The effect of a myocardial infarction on the normalized time-varying elastance curve. J Appl Physiol 102: [1123][1124][1125][1126][1127][1128][1129] 2007. First published December 7, 2006; doi:10.1152/japplphysiol.00976.2006.-It has been suggested that the shape of the normalized time-varying elastance curve [E n (t n )] is conserved in different cardiac pathologies. We hypothesize, however, that the E n (t n ) differs quantitatively after myocardial infarction (MI). Sprague-Dawley rats (n ϭ 9) were anesthetized, and the left anterior descending coronary artery was ligated to provoke the MI. A sham-operated control group (CTRL) (n ϭ 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 E n (t n ) derived. Slopes of E n (t n ) during the preejection period (␣PEP), ejection period (␣EP), and their ratio (␤ ϭ ␣EP/␣PEP) were calculated, together with the characteristic decay time during isovolumic relaxation () and the normalized elastance at end diastole (E min n ). MI provoked significant LV chamber dilatation, thus a loss in cardiac output (Ϫ33%), ejection fraction (Ϫ40%), and stroke volume (Ϫ30%) (P Ͻ 0.05). Also, it caused significant calcium increase (17-fold), fibrosis (2-fold), and LV hypertrophy. End-systolic elastance dropped from 0.66 Ϯ 0.31 mmHg/l (CTRL) to 0.34 Ϯ 0.11 mmHg/l (MI) (P Ͻ 0.05). Normalized elastance was significantly reduced in the MI group during the preejection, ejection, and diastolic periods (P Ͻ 0.05). The slope of E n (t n ) during the ␣PEP and ␤ were significantly altered after MI (P Ͻ 0.05). Furthermore, and end-diastolic E min n were both significantly augmented in the MI group. We conclude that the E n (t n ) 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 THE END-SYSTOLIC PRESSURE-VOLUME RELATION (ESPVR) provides a useful measure of contractile function of the heart in health and disease (23,30). At the basis of the ESPVR stands the time-varying elastance [E(t)] concept, whereby the E(t) gives a time-domain description of the heart pump function (30). The shape of the normalized time-varying elastance curve [E n (t n )] has been shown to be similar in different animal species (10). It has been reported that, when E(t) is normalized with respect to peak value and peak time, the shape (wave form) of the E n (t n ) is independent of different cardiac pathologies, afterload, preload, and contractility (28). The single-beat estimation method of ESPVR was proposed, based on the assumption that human E n (t n ) were indeed identical under various physiopathological conditions (28). However, to date, detailed quantification of the difference in E n (t n ) between healthy ...

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