Abnormal Matching Between the Left Ventricle and the Arterial System in Patients With Acute Myocardial Infarction After Thrombolysis Plus Adjuvant Angioplasty

Abstract

The purpose of this study was to investigate the relationship between the left ventriculo-arterial coupling and the left ventricular (LV) mechanical efficiency in human hearts with acute myocardial infarction (AMI) after thrombolytic therapy combined with subsequent percutaneous coronary intervention. Twenty-six patients with post-AMI at cardiac catheterization were divided into two groups according to their resting ejection fraction (EF). The first group included 18 patients with EF greater than or equal to 50%, and the second group consisted of 8 patients with EF less than 50%. LV pressure-volume relations were measured by the conductance catheter method with preload altered by inferior vena cava obstruction in the 26 patients who received the thrombolytic therapy in 6 h and the percutaneous coronary intervention at first week after the AMI event. The ventriculo-arterial coupling relationship was determined by the ratio of the ventricular chamber elastance Ees (the slope of the LV end-systolic pressure relation) and the effective arterial elastance Ea (the slope of the arterial end-systolic pressure-stroke volume relation). The results showed no significant difference in the ratio of Ees/Ea between Group 1 (0.78 ± 0.34) and Group 2 (0.72 ± 0.22). Significant difference (p < 0.05) in the stroke work was found between Group 1 (7188 ± 1923 mmHg × ml) and Group 2 (5677 ± 670 mmHg × ml), although the potential energy in Group 1 was not significantly different from that in Group 2. We also found in the two patient groups that Ees but not Ea was linearly increased with the Ees/Ea ratio (Group 1: r = 0.84, p < 0.001 and Group 2: r = 0.76, p < 0.05). In addition, the ventricular mechanical efficiency in the infracted hearts with EF more than 50% (r = 0.71) was shown to be linearly increased with the Ees/Ea ratio, but not in those with EF of less than 50%. We concluded that in spite of no significant difference in the values of Ees/Ea between the infarct hearts with larger EF and those with smaller EF, all infarcted LV elastance but not their afterload depends linearly on Ees/Ea. Also, in myocardial infarcted patients with higher EF, their † Biomed. Eng. Appl. Basis Commun. 2008.20:223-230. Downloaded from www.worldscientific.com by NANYANG TECHNOLOGICAL UNIVERSITY on 08/25/15. For personal use only.LV mechanical efficiency may tend to correlate linearly with the ventriculo-arterial coupling index, although the abnormal coupling between the left ventricle and arterial system still exists.