Statement of Problem: Over the last several decades the prevalence of pediatric hypertension has increased fourfold, thought to be partially attributable to the concurrent rise in pediatric obesity. Hypertensive children are at increased cardiovascular disease risk as they often manifest other cardiovascular disease risk factors such as obesity, dyslipidemia, and insulin resistance. Further, up to 40% have target organ damage in the form of left ventricular hypertrophy at initial diagnosis. Left ventricular hypertrophy, a pathological remodeling of the heart thought to be secondary to increased left ventricular afterload as seen in hypertension, causes arrhythmias, heart failure and myocardial infarction in adults. Its striking prevalence at initial diagnosis suggests that elevated blood pressure detection and hypertension diagnosis in children may be delayed or because other factors, specifically obesity, play a more substantial role in its development among hypertensive children.
Methods: We conducted two studies: 1) a pre-post evaluation of a quality improvement initiative to improve elevated blood pressure recognition among children and adolescents seen for primary care. The intervention consisted of a one-time provider educational session and implementation of an ongoing real-time electronic medical record alert; and 2) a prospective, observational study of hypertensive children to investigate the association of obesity and obesity-related risk factors with the presence of left ventricular hypertrophy and with the change in left ventricular mass over a 12-month period of anti-hypertensive therapy.
Results: We found that recognition of elevated blood pressure among patients seen for pediatric primary care was poor overall but increased from 12.5% pre-intervention to 42% during the intervention period (p<0.001). Recognition was no different by educational session attendance status. During both pre-intervention and intervention periods, systolic BP ≥120mmHg was associated with greater recognition. However, the prevalence ratio (PR) was smaller in the intervention period: intervention PR 1.3, 95% confidence interval (CI) 1.2 – 1.5 (p<0.001) versus pre-intervention PR 2.4, 95% CI 1.4-3.9 (p=0.001). Similar relationships were observed for other cardiovascular disease risk factors. Acute care visit encounters were associated with decreased recognition in the intervention period (PR 0.6, 95% CI 0.5- 0.7; p<0.001).
We also found a high prevalence of cardiovascular disease risk factors among children with hypertension: 51% were overweight/obese and 41% had left ventricular hypertrophy. Children with LVH had greater BMI z-score and BMI percentile, higher serum uric acid level, a lower serum lipoprotein (a) level and a greater pro-B natriuretic peptide level than those without LVH. There was no difference in multiple measures of blood pressure between those children with and without LVH. Children who were obese at both study visits experienced the greatest increase in LVMI over time: mean change in LVMI was 6.4 g/m2.7 (95% CI 2.4, 10.5) among those overweight or obese at each visit, vs. 0.95 g/m2.7 (95%CI -3.2, 5.1) among children who were of healthy weight at each visit (p=0.056). Overweight/obese children with and without LVH at baseline demonstrated a larger increase in LVMI compared to healthy weight children. Healthy weight children with LVH were the only ones with decreased LVMI over time. BMI z-score at baseline was positively associated with change in LVMI over time (β 4.08, 95% confidence interval 1.54, 6.61, p=0.002) during multivariable regression analyses adjusting for age, sex, race, and LVMI at baseline. The association remained essentially unchanged after sequential adjustment for postulated mediating pathways between BMI z-score and LVMI with the exception of pulse pressure and serum aldosterone. When added to the model, those two risk factors decreased the point estimate and p-value.
Conclusion/Implications: Elevated blood pressure in children is largely unrecognized, and those with minimal to no additional cardiovascular disease risk factors are least likely to be recognized in a primary care setting. Real time electronic medical record alerts substantially increase provider recognition of elevated BP in children and hold considerable promise as a means to improve adherence to practice guidelines. These alerts particularly aid in the recognition of elevated blood pressure among those not at obvious cardiovascular disease risk. However, the persistence of under-recognition of elevated BP in children highlights the need for additional strategies to further improve provider recognition.
Hypertensive children referred for subspecialty care demonstrate not only a high prevalence of co-morbid cardiovascular risk factors at baseline, but an increase in both their prevalence and severity over time. Most striking of these cardiovascular risk factors is the presence and substantial degree of overweight and obesity. In fact, adiposity as determined by body mass index z-score was the greatest risk factor for left ventricular hypertrophy and change in LVMI over time. None of the many measures of blood pressure assessed during this study were associated with the presence of LVH or with the change in LVMI over time. And, two risk factors potentially modified by diet - pulse pressure, a marker of intravascular volume, and serum aldosterone, a hormonal regulator of blood pressure – appeared to be the most important partial mediators of the relationship between adiposity and change in LVMI. These findings support the overwhelming public health concern regarding the obesity epidemic and suggest that greater emphasis on overweight and obesity prevention and treatment should be made among hypertensive children.
Future Directions: Our work emphasizes the substantial prevalence of cardiovascular disease risk factors among children and adolescents. It also suggests that current population estimates of the burden of pediatric hypertension may underestimate the true prevalence as a substantial number of children with elevated blood pressure are unrecognized in a primary care setting. A common underlying theme to this increased CVD risk is overweight and obesity. Despite providing standard of care guidance on weight loss and adherence to a heart healthy diet, the children in our study became more overweight/obese and demonstrated an increase in number and severity of CVD risk factors over a year of observation. Enhanced preventive and therapeutic strategies targeting overweight and obesity in children holds significant promise as we work towards primordial and primary prevention of adult cardiovascular disease. Further research should test innovative interventions designed to assist youth with adherence to a heart healthy lifestyle and determine the effect of these interventions on cardiovascular disease risk factors
