Role of Anthropometric Indexes and Blood Pressure as Determinants of Left Ventricular Mass and Geometry in Adolescents

Methods

Results

Age and sex were not different among the groups, which allowed us to study each group as a whole. Weight, BSA, and BMI were significantly higher in group 1 compared with the other two groups (Table 1⇓).

LVM and the LVM index were greater in group 1 (P<.004 and P<.05, respectively), as shown in Table 1⇑. Abnormalities in ventricular pattern did not differ among the groups (6 subjects [22.2%] from group 1, 1 [2.7%] from group 2, and 6 [13.6%] from group 3 [χ²=5.7964, P>.05]). However, statistical significance was found when group 1 was compared with group 2 (χ²=6.1054, P<.02). The observed alterations in left ventricular geometry were 1 subject with concentric hypertrophy, 3 with eccentric hypertrophy, and 2 with concentric remodeling in group 1; 1 subject with concentric remodeling in group 2; and 2 subjects with eccentric hypertrophy and 4 with concentric remodeling in group 3.

Table 2⇓ summarizes the correlations between LVM and age, age according to sex, anthropometric indexes, and systolic and diastolic BP. There was no significant relation between LVM and either age or age according to sex. All the correlations between LVM and anthropometric indexes were positive and significant. LVM was also significantly correlated with systolic and diastolic BP. The variables used for calculation of LVM were positively correlated with all the anthropometric indexes and BP (Table 3⇓).

In a multiple regression model LVM was used as the dependent variable and systolic BP and BSA as independent variables. The partial correlation coefficients were .6256 (P<.00001) for BSA and .4717 (P=.07) for systolic BP. The final model, however, was statistically significant (R²=.3993, P<.00001).

In similar models when BSA was controlled, systolic BP maintained a significant and positive correlation with VS and PW but not with LVDD. When VS was used as the dependent variable, the partial correlation coefficients were .4850 (P=.002) for BSA and .4642 (P=.007) for systolic BP, and the final model was significant (R²=.2735, P<.00001). When the dependent variable was PW, BSA had a partial correlation coefficient of .4245 (P<.02) and systolic BP one of .4202 (P<.02). The final model had a determination coefficient (R²) of .2122 (P<.00001). When LVDD was used as the dependent variable, the partial correlation coefficients were .5239 (P<.00001) for BSA and .2882 (P=.86) for systolic BP; however, the final model reached statistical significance (R²=.2608, P<.00001).

Discussion

Few studies evaluating LVM in children and adolescents have been conducted in the last decade.^{5 11 12 13 14 15} The aim of these previous studies was the early identification of subjects who are prone to developing LVH and its prognostic implications. In this context the authors focused their attention on the possible factors that could determine LVH. The present study was carried out in a healthy population, attenuating the selection biases inherent to hospital-based studies.

The group of children and adolescents who maintained BP at or above the 95th percentile in all phases showed weight, BSA, and BMI values higher than those in the other two groups. This finding reinforces the concept that body size is strongly related to BP levels in children and adolescents.^{22 23} The Bogalusa Heart Study²³ and Brandão et al,²² analyzing the correlation between different anthropometric indexes and BP, have emphasized that the strongest association was between systolic BP and weight.

Echocardiography provides good information about the structure of the left ventricle. The determination of VS and PW and the size of the left ventricular chamber by echocardiography have a good sensitivity for determination of LVM and the different ventricular geometric patterns.^{3 24} In adults, the Framingham Study defined the normal limits of LVM as 100 g/m² for women and 131 g/m² for men.¹⁹ Devereux et al,²⁵ studying a more heterogeneous population, found 110 g/m² for women and 134 g/m² for men as the normal limits for LVM. Recently, Koren et al³ defined 125 g/m² as a cutoff point for detection of LVH. This value corresponds to approximately the 95th percentile of LVM in two normal samples studied in their center. In young people the normal values of LVM should also derive from the LVM distribution curve. In our study the corresponding value to the 95th percentile for LVM index was 124.21 g/m², which is almost the same value found by Koren et al.³

LVM and LVM index were greater in group 1 than in the other groups. Our results are in agreement with other investigators who found higher values of LVM and LVM index in adolescents with BP persistently above the 95th^{11 12} or even above the 90th percentile.¹⁵ Higher values of LVM index have also been demonstrated in Japanese boys aged 9 to 12 years tracking in the highest systolic BP quintile over a 3-year period.¹¹ The Muscatine Study,¹⁴ evaluating students from 9 to 18 years of age, has shown greater values of LVM index in the group from the highest BP quintile. However, other investigators²⁶ have failed to demonstrate significant differences in LVM comparing children with BP above the 95th percentile with those from the lower part of the BP distribution curve.

Some authors have shown high values of LVM and LVM index in normotensive offspring of hypertensive parents.^{27 28} According to Koren et al³ the prognostic value of LVM for morbid events was striking, but it could still be improved by more detailed consideration of ventricular geometry. In our population the cutoff point of RWT was 0.45, corresponding to the 95th percentile. From the 108 adolescents studied, only 13 had abnormal left ventricular patterns: 6 (22.2%) from group 1, 1 (2.7%) from group 2, and 6 (13.6%) from group 3. The finding of these low prevalences is a consequence of the essentially healthy population analyzed. However, our results reinforce the concept that quantitative and qualitative alterations may occur early, without established hypertension. Moreover, we observed that concentric remodeling and eccentric hypertrophy were more prevalent than the classic concentric hypertrophy, in agreement with Ganau et al²⁹ and Verdecchia et al.³⁰ However, it is worth noting that the only case of concentric hypertrophy was found in the group of adolescents who maintained BP at or above the 95th percentile.

This study extends the current knowledge about the relationship of BP and anthropometric indexes to LVM and left ventricular geometry. We found strong correlations between LVM and BP as well as all the anthropometric indexes. The increase in left ventricular wall thickness with age has been demonstrated in some studies.^{1 7 9 31} However, recent data from the Framingham Study³¹ suggest that the positive correlation of left ventricular wall thickness with age depends on the increase in weight and BP during a lifetime. The correlation between LVM and age or age according to sex was not significant, which could be due to the narrow age range of the studied subjects.

The majority of the studies that correlated LVM index to anthropometric indexes concluded that BMI is one of the most important determinants of LVM in hypertensive adults³² and children⁵ as well as in healthy individuals,⁸ especially if obesity is present.^{1 7 33} In the present study the best correlation was found between LVM and BSA, similar to the findings of Devereux et al.²⁵ The usual way of correcting LVM by BSA (LVM index) could mask the possible effects of obesity on LVM. Moreover, the Framingham Study found a greater prevalence of LVH using the correction of LVM/height rather than LVM/BSA.¹⁹ Thus, if obesity is present the correction of LVM by BSA could lead to underrecognition of increasing LVM, with prognostic and therapeutic implications.

Our data concerning the association between LVM and BP, especially systolic levels, are consistent with this well-known association.^{1 6 14 34 35 36} The variables used in the LVM calculation also had good correlation to both BP and anthropometric indexes. On the basis of this finding we tested the correlations between systolic BP levels, controlled by BSA, and the variables that comprise the LVM formula. In this model, systolic BP maintained a positive correlation with VS and PW but not with LVDD.

These data suggest that increases in LVM related to BP elevations are due to ventricular wall thickening and those related to greater body size are due to enlargement of the ventricle cavity. The Bogalusa Heart Study¹³ showed that systolic BP was associated with left ventricular wall thickness but not with LVM. Verdecchia et al,³⁷ comparing hypertensive patients with normal LVM with a control group, found a greater prevalence of asymmetrical septal thickening in hypertensive subjects than in the healthy group, despite both groups having similar anthropometric indexes.

We conclude that quantitative and qualitative LVM alterations can occur early after initial abnormalities of BP. Considering that isolated or combined actions of BSA and systolic BP were the best predictors of left ventricular alterations in adolescents, the usual way of correcting LVM by BSA should be reviewed. These observations suggest that intervention programs of BP and weight control may provide important ways to prevent the development of LVH.

Selected Abbreviations and Acronyms