Abstract P140: Linear Versus Volumetric Measures Of Left Ventricular Sphericity: Concordance And Normal Reference Values

Abstract

Introduction: Greater left ventricular (LV) sphericity, a more globular shape, is associated with poor outcomes. Two measures of sphericity are commonly used: Linear sphericity (LinS) is the ratio of LV end-diastolic diameter (EDD) to 4-chamber length (4cL); volumetric sphericity (VolS) is the ratio of end-diastolic volume (EDV) to the volume of a sphere with diameter=4cL. We sought to compare LinS to VolS and to determine: 1) whether LinS and VolS differ with sex and age group; 2) normal values for LinS and VolS, 3) whether LinS and VolS are concordant in how they stratify individuals. Methods: 1794 adults (age 65±9y, 47.1% men) in the Framingham Offspring cohort underwent CMR imaging; LV EDD, EDV and 4cL were measured. A referent group (340M, 512W) free of clinical cardiovascular disease, hypertension, diabetes and smoking was identified. Among these, we compared LinS and VolS between sexes and across age groups (<55, 55-64, ≥65y). Referent-group upper 90 th percentile (P90) cutpoints for LinS and VolS were determined and applied to the entire cohort (N=1794) to stratify each individual as having or not having high sphericity. Concordance between LinS and VolS was assessed using kappa coefficient and McNemar’s test. Methods: LinS was greater than VolS for each sex, but there was robust, positive linear (Pearson) correlation between LinS and VolS for men (r=0.864) and women (r=0.855), p<0.0001 both. The Table shows women had minimally greater sphericity than men. Sphericity did not vary with age group in either sex. LinS and VolS were concordant in classifying individuals as having high (≥P90) sphericity with kappa=0.63 (men) and 0.62 (women), p<0.0001 for both. McNemar’s test for difference was not significant (p>0.27) for either sex. Conclusion: Linear and volumetric measures of LV sphericity are concordant in how they rank and stratify adults in a community dwelling cohort, but the measures are not directly comparable, as mean LinS is markedly greater than VolS. Neither measure of sphericity varies with age among healthy adults.