The following is the abstract of the article discussed in the subsequent letter: Gentles TL and Colan SD. Wall stress misrepresents afterload in children and young adults with abnormal left ventricular geometry. .-Wall stress, although commonly used as an index of afterload, fails to take into account forces generated within the wall of the left ventricle (LV) that oppose systolic fiber shortening. Wall stress may, therefore, misrepresent fiber stress, the force resisting fiber shortening,

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... cularly in the presence of an abnormal LV thickness-to-dimension ratio (h/D). M-mode LV echocardiograms were obtained from 207 patients with a wide range of values for LV mass and/or h/D. Diagnoses were valvar aortic stenosis, coarctation repair, anthracycline treated, and severe aortic and/or mitral regurgitation. Endsystolic wall stress (WS es) and fiber stress (FSes) were expressed as age-corrected Z scores relative to a normal population. The difference between WS es and FSes was extreme when h/D was elevated or reduced [WSes Z score Ϫ FSes Z score ϭ 0.14 ϫ (h/D) Ϫ1.47 Ϫ 2.13; r ϭ 0.78, P Ͻ 0.001], with WSes underestimating FSes when h/D was increased and overestimating FSes when h/D was decreased. Analyses of myocardial mechanics based on wall stress have limited validity in patients with abnormal ventricular geometry.