Does Size Matter?

Abstract

Abstract-Extensive evidence is available that cardiovascular structure and function, along with other biological properties that span the range of organism size and speciation, scale with body size. Although appreciation of such factors is commonplace in pediatrics, cardiovascular measurements in the adult population, with similarly wide variation in body size, are rarely corrected for body size. The patient is a very tall 23-yearold competitive rower with a height of 203 cm and weight of 100 kg referred to the clinic for preparticipation athletic screening. He has never experienced syncope, palpitations, or chest pain during exertion and has no significant past medical history, but he occasionally feels "light-headed" at the end of an exhaustive competitive workout. He has no family history of sudden cardiac death or of premature cardiovascular disease. He is actively training 5 to 6 hours per day, 6 days per week in preparation for the upcoming Olympic Games. The examination is remarkable only for a soft systolic ejection murmur, cardiomegaly, and a third heart sound. An ECG is ordered, which is remarkable for sinus bradycardia, a 15-mV R wave in lead aVL, and R-wave voltage in lead V 5 plus S-wave voltage in lead V 1 totaling 46 mV. On a follow-up echocardiogram, septal and posterior wall thicknesses of 14.5 mm are observed with a left ventricular (LV) internal dimension in diastole of 53 mm. No significant obstructive LV outflow pattern is present, and wall thickness appears symmetrical. On the basis of current echocardiographic criteria, this patient is in the "gray zone" between physiological and pathological hypertrophy. His nonspecific symptoms and lack of other contributing history add to the ambiguity in diagnosis. Clinical Vignette No. 2:The patient is a 66-year-old woman who has a height of 155 cm and a body mass of 49 kg.She has a history of hyperlipidemia and abdominal aortic aneurysm. She comes to the clinic for her yearly ultrasound follow-up, which shows a maximum aneurysm diameter of 50 mm. She is in a "gray zone" in which neither surgical correction nor watchful waiting is definitively indicated.Considerable evidence is available that biological processes from metabolic enzyme activity 1 to plant and animal metabolic rates 2-4 to cancer metastasis 5 scale with body size over the entire range of organism size and speciation. Cardiovascular structural and functional variables also scale with body size. Compare, for instance, the blue whale, which has a heart mass of 600 kg and a resting heart rate of 6 bpm, with the smallest mammal, the shrew, which has a heart mass of 12 mg and a resting heart rate of up to 1200 bpm. 6 Despite the clear relationship between body size and cardiovascular dimensions and functional parameters, the practice of scaling cardiovascular measurements is poorly applied in adult clinical cardiology. This contrasts with pediatric medicine, in which measurements are universally indexed to body size. The intuitive idea that body growth implies a greater need for scaling in pe...

Gender Differences in Ventricular Remodeling and Function in College Athletes, Insights from Lean Body Mass Scaling and Deformation Imaging

“…and Bella et al [16][17][18] We also verified that in our study population, the allometric coefficients used were body size independent (BSI); to be considered BSI, no relationship should be observed between the scaled parameter and the scaling parameter. For BSA or height, we used the allometric coefficients recommend by the ASE guidelines.…”

“…15 Scaling of cardiac dimensions, volumetric and mass data to LBM was performed using allometric coefficients. The choices of coefficients were based on the literature especially the studies of George et aland Bella et al [16][17][18] We also verified that in our study population, the allometric coefficients used were body size independent (BSI); to be considered BSI, no relationship should be observed between the scaled parameter and the scaling parameter. For BSA or height, we used the allometric coefficients recommend by the ASE guidelines.…”

Geographic variation in left ventricular mass and mass index: a systematic review

“…43 Indexing to a power of height is the most widely accepted method of indexation in older children, but it is less consistently applied in adults. Of people with hypertension, LVH may be underdiagnosed in those that are obese, where measured mass may be elevated; however, it is incorrectly compensated for by adjusting for BSA.…”

Indexation of left ventricular mass to body surface area and height to allometric power of 2.7: is the difference limited to obese hypertensives?

“…In particular, it has been shown that indexation to height 2.7 provides the highest prevalence of LVH, to some extent independently from the cut-off settled, since this normalization identifies both obesity-and BP-related LVH. 22 In the VITAE Study (Ventriculo Izquierdo Tension Arterial Espana) including 946 essential hypertensives (53.3% women, 45% obese) from primary care centres, LVH prevalence ranged from 59.2% by indexing to BSA (that is, LVMI X111/102 g m À2 ) to 70.7% by indexing to height (that is, LVMI X50/ 47 g m À2.7 ). 23 In the Gubbio Population Study, a clinical survey performed in a small Italian town, the prevalence of LVH among 250 hypertensive patients was nearly twofold higher (43.6 vs 24.0%) when LVM was indexed to height (that is, LVMI 49.2/46.7 g m À2.7 ) compared to BSA indexation (that is, 116/104 g m À2 ).…”