Etude échocardiographique de la fonction ventriculaire gauche dans l'insuffisance aortique de l'enfant avant et après l'opération de Ross
(1996)
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- This study evaluates the history of left ventricular function in children with aortic valve dysfunction. The growth related modification of left ventricle (LV) dimensions, the abnormal left ventricular loading conditions due to aortic valve disease and the need of repeated measurements are making this evaluation a complex task in infants and children. Combined echocardiographic measurements of LV shorts axis velocity of shortening, shortening fraction and end-systolic wall stress allow a non invasive and easily repeatable evaluation of LV function and of its components: preload, afterload and contractility. <BR> In the first part of this study, the potential of myocardial impairment in relation to aortic valve disease and the difficult choice of the timing of aortic valve replacement in children are considered. The benefits of autograft transplantation of the pulmonary valve in aortic position (Ross operation) in comparison with aortic valve replacement with a mechanical valve or an homograft are discussed. <BR> In the second part, some concepts in relation with LV function are discussed to avoid the confusion which still persists between LV function and myocardial contractility in the literature are presented. Modification of LV geometry in relation with LV loading condition are explained. <BR> The controls and patients subjects, as well as the methods used are presented in the third part of this thesis. <BR> In the 4th part, LV dimensions, indices of LV function and LV geometry are compared in 11 age matched normal subjects and in 37 patients with various forms of aortic valve dysfunction before aortic valve replacement. This observation illustrates the left ventricular adaptation to the abnormal loading conditions by LV remodelling with LV dilatation and hypertrophy. Such LV changes allow to maintain normal global indices of LV function, while in some patients the myocardial health is impaired as indicated by a depressed contractility. <BR> In the 5th part, we analyse the benefits of the Ross operation on LV function. From January 94 to June 95, a Ross procedure was performed in 15 patients (median age 10 years, range 3 to 21 years). Echocardiography was obtained preoperatively and serially up to one year after surgery to study LV function. All patients remained asymptomatic (NYHA class 1) and were free of complications and received no medication; neither gradient nor significant aortic incompetence could be demonstrated. End-diastolic LV dimension (EDD) diminished drastically from 3.31 ± 2 SD above normal to 0.63 ± 2 SD at one week postoperatively (day 10). LV mass remained abnormal at d10 (from 5.2 ± 3 SD to 5.3 ± 3.8 SD) and diminished more progressively to reach normal values at 1 month. <BR> This resulted in a significant decrease of end-systolic wall stress (-3.6 ± 2 SD) and in a hyperdynamic function in the immediate postoperative days, except in 2 patients. LV fractional shortening remained low (<25%) at long term follow-up in those 2 patients. Before surgery, those 2 patients had normal shortening fraction, a more dilated LV (EDD 5.3 ± 2 SD vs 1.6 ± 2 SD), decreased end-diastolic LV wall thickness/dimension ratio (0.14 vs 0.22), a more spherical LV, a decreased velocity of shortening (VDFc : 0.83 vs 1.19 circ/sec). They were the only 2 patients with decreased contractility as indicated by abnormal (< -2 SD) LV end-systolic circumferential stress (ESSc) – VCFc relation. <VR> The Ross procedure suppresses completely the abnormal LV myocardial mechanics associated with volume load in aortic incompetence in most patients. Surgery should be performed before deterioration of LV contractility indicated by an abnormal ESSc-VCFc relation
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Shango-Lody, L. N. P. (1996). Etude échocardiographique de la fonction ventriculaire gauche dans l’insuffisance aortique de l’enfant avant et après l’opération de Ross. https://hdl.handle.net/2078.5/111499