obesity and left ventricular mass in kids

A new long-term analysis of the Bogalusa Heart Study (in Bogalusa, LA) in kids has confirmed a longitudinal relationship between obesity and hypertension in the development of left ventricular remodeling/hypertrophy, with obesity being the most significant driver (see obesity kids and LV remodeling bogalusa JACC 2014 in dropbox, or doi.org/10.1016/j.jacc.2014.05.072) . there are a slew of studies finding that obesity and hypertension are associated with LVH (left ventricular hypertrophy). prior pediatric epidemiologic studies from several different countries have pretty consistently found that there is an association between cardiovasc risk factors in kids and increased left ventricular mass, and that early risk factors predict adult LVH as well as LV geometry. the current analysis looked at the long-term burden and trends of cardiovasc risk factors in kids and the development of LVH and LV geometry. The Bogalusa Heart Study is a biracial community-based study (65% white, 35% black) assessing the natural history of cardiovascular disease in kids, starting in 1973. there have been 9 cross-sectional surveys done in kids aged 4-18, then 10 more in 19-52 year olds who were analyzed initially as kids. in the current study, 1061 adults aged 24-46 who had been examined at least 4 times for BMI and BP starting in childhood were assessed for the total and incremental AUC (area under the curve) of BMI and BP and their relationship with different LV geometric shapes (normal, concentric remodeling or CR, eccentric hypertrophy or EH, and concentric hypertrophy or CH), with a mean followup of 28 years (see discussion below for significance of these terms). findings:

--baseline: for kids, the only significant racial difference was that DBP (diastolic blood pressure) was higher in black males. 

-- for adults at the end of the study, there were BMI differences (BMI higher in black vs white, mostly because of being much higher in black women); blood pressures higher in black than white, male than female.

--LV mass: higher in black than white for both sexes, and higher in males than females. LV geometry: black patients had higher EH than whites.

--higher BMI and both systolic and diastolic blood pressures in childhood and adulthood were associated with higher LV mass and LVH (adjusted for race, sex, and age) as well as with EH and CH but not with CR.

--this association was also with AUC and incremental AUC.  for AUC, both SBP and BMI were associated with increased risk of both EH (41% and 73% increase, respectively) and CH (123% and 140% increase). for incremental AUC, both SBP and BMI were associated with increased risk of both EH (28% and 93% increase, respectively) and CH (104% and 99% increase)​.

--BMI had a consistently and significantly greater effect than did the BP measurements.​

so, the adverse effects of​ BMI and blood pressure begins in childhood, as evidenced in their increased LV mass. the AUC calculation was reflects the group averages of the sum of the heights of the risk factor multiplied by the time the risk factor was high, over sequential measurements, thereby reflecting the total cumulative burden of this risk factor. the incremental AUC was the individual's variation from their own baseline, and therefore represented the trend of the risk factor over time for the individual patient. the AUC and incremental AUC were both strongly related to the adverse effect on LV mass and geometry, with most studies finding that CH, or concentric hypertrophy, is more strongly related to cardiac events, though EH, or eccentric hypertrophy, is also associated with risk. Since both of the AUC measurements were related to ventricular hypertrophy, this suggests that people who have less time with the risk factors or a lesser trend to an increase (eg, they lose weight, or lower their blood pressure), have less LV mass increases -- though remember that this is still just an observational, not intervention study. but other studies do suggest that decreasing blood pressure can lead to relatively rapid changes in LV mass (eg, a metaanalysis found that of the five categories of antihypertensives studied, specifically b-blockers, diuretics, calcium channel blockers, ACE-I's and ARBs, that b-blockers were unequivocally the worst and it seemed that ARBs were the best, with ACE-I pretty close behind in decreasing LV mass  -- see htn LVH regression metaanal Hypertension2009 in dropbox, or doi: 10.1161/HYPERTENSIONAHA.109.136655​) and other studies have found that decreasing LV mass decreases cardiac events (eg the LIFE study found that cardiac events were decreased by lowering EKG-LVH by either losartan or atenolol, but that losartan overall was much better than atenolol in decreasing LVH -- see htn LIFE study lancet 2002 in dropbox, or Lancet 2002; 359: 995–1003). and, small studies of patients with bariatric surgery have found decreasing LV mass within months of surgery.  so, bottom line, putting all of this together is: cardiac risk factors in kids tend to track into adulthood, the intensity and trend of the risk factor correlates with the effect on LV mass including concentric hypertrophy which is a pretty strong predictor of clinical events, that changes in these risk factors in kids does have an effect on adult LVH, that obesity is more of a risk factor than hypertension (at least for LVH), and (likely) if we as clinicians can help kids lose weight, this will have a positive effect on their risk of heart disease/strokes as an adult (and the earlier they lose weight, the better).