From Northwestern University Medical School, Chicago, Ill.
Correspondence to Samuel S. Gidding, MD, 2300 Children's Plaza/MC #21, Chicago, IL 60614. E-mail s-gidding{at}nwu.edu
The
ability to measure left ventricular mass (LVM) by
echocardiography has led to an important
understanding of the contribution of inappropriate LVM to the
pathogenesis of cardiovascular disease. In particular,
the identification by Levy et al,1 in the
Framingham Study, of increased LVM as a risk factor for
cardiovascular morbidity and mortality independent of
conventional risk factors, including obesity and hypertension,
initiated many studies by independent investigators to better
understand the clinical significance of this finding.
Because children and adolescents grow rapidly and their blood
pressure increases with age, pediatric studies have been important in
understanding the evolution of LVM in generally healthy individuals.
Cross-sectional studies have shown that the major determinants of left
ventricular growth are body size and sex, with a smaller
contribution made by blood pressure.2 3 Allometric
relationships between somatic and cardiac growth have been established,
and although these coefficients vary slightly from study to study, they
consistently explain a significant percentage of mass
variation.2 3 The importance of somatic growth as the major
determinant of left ventricular growth has been established
by repeat measurements of mass over a 5-year interval in the Bogalusa
Heart Study and by the recognition that lean body mass contributes
somewhat more to cardiac growth than fat mass.4 5
In this issue of Circulation, Schieken et
al6 complete the epidemiological work necessary to
understand the characteristics of LVM in children. LVM tracks from
early to late adolescence in black and white boys and girls to about
the same degree as other important risk factors, such as
cholesterol and blood pressure, with a correlation
coefficient of
However, epidemiological studies do not help establish the difference
between appropriate and excessive increases in LVM. The notion that
such pathological increases exist is supported by the increased risk
for cardiovascular mortality associated with LVM
independent of body size and blood pressure.1 7 To define
excessive LVM, investigators have taken two approaches: indexing LVM
for body size and defining patterns for left ventricular
hypertrophy that may confer increased
risk.8
In this issue of Circulation, Daniels et al9
apply an allometric definition of excessive mass (>51
g/m2.7) and definitions of patterns of
hypertrophy (concentric, eccentric, and concentric
remodeling) to a cohort of children with essential hypertension
followed up in a pediatric hypertension clinic. They have shown that
these children have a distribution of LVM shifted toward excessive
hypertrophy, that a small but significant percentage have
pathological levels of LVM, and that a significant percentage also have
the concentric pattern associated with increased mortality in adults.
These finding have clinical significance. They establish the concept
that cardiac end-organ damage from hypertension exists in children,
that LVM assessment is important in the management of childhood
hypertension, and that clinical trials to determine the effect of
medical therapy of pediatric hypertension on LVM should be
performed.
When interpreted collectively, the studies by Schieken et
al6 and Daniels et al9 resolve an apparent
controversy in the pediatric literature: how important is blood
pressure in the acquisition of LVM in children?10
Cross-sectional and longitudinal studies of generally healthy children
have shown predominantly positive effects of body size and very small
positive effects of blood pressure on LVM, whereas comparisons of
hypertensive children with normotensive children have shown large,
significant differences in mass.4 11 In the study by
Daniels et al,9 patients' average blood pressure was
25 mm Hg higher than in the study by Schieken et al,6
and study entry was contingent on elevated blood pressure being
sustained over a period of time. This is in contrast to children and
adolescents in population-based studies in which blood pressure may
have significant variability. Thus, for healthy children, the primary
prevention of obesity is the most important approach to
maintenance of normal LVM; for hypertensive children with
established left ventricular hypertrophy, more
aggressive treatment approaches are required.
What is the current status of LVM assessment in children? For the
clinician, measurement of LVM should be performed in those with
elevated blood pressure and perhaps in those with significant obesity.
The presence of increased LVM or concentric remodeling may suggest the
need for more aggressive therapy. For epidemiologists and researchers,
the challenge will be to further refine the assessment of LVM. At any
given level of blood pressure or body mass index, a significant range
of LVM remains, from normal adaptation to pathological
hypertrophy. What are the determinants of this variation?
And is all "excess" mass pathological? Are there
physiological markers that distinguish appropriate
increases in mass associated with exercise from an excessive response
to hypertension or obesity?
Over the past 25 years, the concept of identifying
cardiovascular risk factors in youth has become firmly
established, as has the concept of beginning primary prevention efforts
at earlier ages through diet, physical activity, maintenance of
normal weight for height, and the avoidance of tobacco. Studies of
end-organ damage, such as that by Daniels et al,9 suggest
that a new dimension should be considered in preventive
cardiology for youths. If a child or adolescent has an
identified risk factor, such as hypertension, and an identified adverse
sequela, such as left ventricular hypertrophy,
why should pharmacological therapy be withheld because of the
patient's age? The time for better definitions of candidates for
secondary prevention in youth has arrived.
Footnotes
The opinions expressed in this editorial are not necessarily those of the editors or of the American Heart Association.
References
© 1998 American Heart Association, Inc.
Editorials
Clinical and Epidemiological Significance of Left Ventricular Mass Assessed in Children and Adolescents
Key Words: Editorials • pediatrics • ventricles • hypertension • risk factors • left ventricular mass
0.4. Furthermore, race, sex, body size, heart rate,
and blood pressure have small but important interactive effects with
change in LVM. Although studies that link tracking of LVM from
adolescence into adulthood remain to be performed, the concept that at
least some factors associated with cardiac growth are in place early in
life is firmly established.
This article has been cited by other articles:
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  J. M. Gardin, D. Brunner, P. J. Schreiner, X. Xie, C. L. Reid, K. Ruth, D. E. Bild, and S. S. Gidding Demographics and correlates of five-year change in echocardiographic left ventricular mass in young black and white adult men and women: the Coronary Artery Risk Development in Young Adults (CARDIA) Study J. Am. Coll. Cardiol., August 7, 2002; 40(3): 529 - 535. [Abstract] [Full Text] [PDF]
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