Left ventricular mass is underestimated in overweight children because of incorrect body size variable chosen for normalization

BackgroundLeft ventricular mass normalization for body size is recommended, but a question remains: what is the best body size variable for this normalization—body surface area, height or lean body mass computed based on a predictive equation? Since body surface area and computed lean body mass are derivatives of body mass, normalizing for them may result in underestimation of left ventricular mass in overweight children. The aim of this study is to indicate which of the body size variables normalize left ventricular mass without underestimating it in overweight children.MethodsLeft ventricular mass assessed by echocardiography, height and body mass were collected for 464 healthy boys, 5–18 years old. Lean body mass and body surface area were calculated. Left ventricular mass z-scores computed based on reference data, developed for height, body surface area and lean body mass, were compared between overweight and non-overweight children. The next step was a comparison of paired samples of expected left ventricular mass, estimated for each normalizing variable based on two allometric equations—the first developed for overweight children, the second for children of normal body mass.ResultsThe mean of left ventricular mass z-scores is higher in overweight children compared to non-overweight children for normative data based on height (0.36 vs. 0.00) and lower for normative data based on body surface area (-0.64 vs. 0.00). Left ventricular mass estimated normalizing for height, based on the equation for overweight children, is higher in overweight children (128.12 vs. 118.40); however, masses estimated normalizing for body surface area and lean body mass, based on equations for overweight children, are lower in overweight children (109.71 vs. 122.08 and 118.46 vs. 120.56, respectively).ConclusionNormalization for body surface area and for computed lean body mass, but not for height, underestimates left ventricular mass in overweight children.背景：临床推荐基于体尺寸对左心室质量（Left Ventricular Mass）进行校正，但仍存在争议：用于该校正的最佳体尺寸变量为何——是体表面积（Body Surface Area）、身高，还是基于预测公式计算得到的去脂体重（Lean Body Mass）？由于体表面积与计算所得去脂体重均为体质量的衍生指标，以其作为校正变量可能会低估超重儿童的左心室质量。本研究旨在明确，在超重儿童中，哪种体尺寸变量可实现左心室质量的校正且不会出现低估情况。方法：本研究纳入464名5~18岁的健康男性儿童，收集其经超声心动图（Echocardiography）评估的左心室质量、身高与体质量数据，并计算去脂体重与体表面积。基于分别针对身高、体表面积及去脂体重建立的参考数据，计算左心室质量Z评分（z-score），并比较超重与非超重儿童间的该评分差异。随后，针对每一种校正变量，基于两种异速生长公式（allometric equations）——其一针对超重儿童建立，其二针对体质量正常儿童建立——估算预期左心室质量，对配对样本的估算结果进行比较。结果：基于身高的参考数据计算所得左心室质量Z评分，超重儿童的平均评分（0.36）高于非超重儿童（0.00）；而基于体表面积的参考数据计算所得评分则相反，超重儿童平均评分（-0.64）低于非超重儿童（0.00）。基于超重儿童的公式、以身高作为校正变量估算的左心室质量，超重儿童的估算值（128.12）高于非超重儿童（118.40）；但以体表面积与去脂体重作为校正变量、基于超重儿童的公式估算的左心室质量，超重儿童的估算值（分别为109.71与118.46）均低于非超重儿童（分别为122.08与120.56）。结论：在超重儿童中，以体表面积与计算所得去脂体重作为校正变量会低估左心室质量，而以身高作为校正变量则无此问题。