May 20, 1998 DALLAS, May 19 -- Teenagers, especially boys, with high blood pressure may be harboring a serious, but silent, heart condition, according to two new studies and an editorial in today's Circulation: Journal of the American Heart Association.
As a result, researchers are urging more frequent blood pressure testing and weight assessment and, in some cases, an echocardiogram in teenagers. Both studies found that thickening of the heart walls -- called left ventricular hypertrophy -- is common in teens who have high blood pressure and obesity.
One study found that left ventricular hypertrophy tracks during a person's lifetime. Thus, a child with severe left ventricular hypertrophy will be at higher risk for having the heart problem as an adult. The second study found that about 10 percent of children with severe high blood pressure had left ventricular hypertrophy. The heart condition was more common in boys than girls and in overweight children of both sexes.
The Task Force on Blood Pressure Control in Children of the National Heart, Lung, and Blood Institute recommends children's blood pressure is measured at least annually after age three.
According to one of the study's authors, Stephen R. Daniels, M.D., Ph.D., of Children's Hospital Medical Center in Cincinnati, children in the higher percentiles of blood pressure should receive echocardiograms -- an ultrasound of the heart -- periodically to determine whether the child is developing increased thickening of the heart and should be treated with drugs to lower blood pressure.
Left ventricular hypertrophy, a complication of high blood pressure, is an ominous sign that elevated blood pressure is affecting the heart. In adults, this condition is a risk factor for a heart attack, heart failure and stroke. However, researchers don't know if the condition in children also increases the risk of dying early from heart disease. Keeping blood pressure normal treats the disease.
For healthy children with normal blood pressure, prevention of obesity is thought to be the most important approach to maintain normal left ventricular mass. However, for children with established left ventricular hypertrophy, Daniels urges more aggressive treatment approaches to control high blood pressure.
He also notes that many children are not tested yearly. In addition, many pediatricians "are unaware of which blood pressure numbers to use as a guide to indicate blood pressure elevation.
"Since our study shows that severe left ventricular hypertrophy is relatively prevalent in young patients with high blood pressure, measurement of high blood pressure should happen more often in the pediatrician's office," says Daniels.
In an accompanying editorial, Samuel S. Gidding, M.D., of Northwestern University Medical Center, Chicago says, "The concept that at least some factors associated with heart growth are in place early in life is firmly established, and children with sustained high blood pressure have early evidence of heart problems.
"Over the last 25 years," he adds, "the concept of identifying heart disease 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 and the avoidance of tobacco.
"Studies as this one by Daniels and colleagues suggest a new dimension should be considered in preventive cardiology in youth. If a child has an identifiable risk factor such as high blood pressure or obesity and the identified adverse effect such as left ventricular hypertrophy, why should medical therapy be withheld because of the person's age? The time for better definition of candidates for prevention in youth has arrived," says Gidding, associate professor of pediatrics and preventive medicine at Northwestern.
Daniels and co-researchers at Children's Hospital Medical Center in Cincinnati found that 14 percent of 130 adolescents with high blood pressure had severe left ventricular hypertrophy. In 11 of the children, the changes already exceeded the adult at-risk "cutpoint."
In a significant number of adolescents, the researchers also found a "concentric" pattern of hypertrophy, which is associated with increased heart disease death in adults.
Percentiles were used to categorize the degree of ventricular mass. About half of the children had a left ventricular mass above the 90th percentile for their age; and six percent were in between the 99th percentile and the adult cutpoint. Eight percent were above this risk level.
"Our study indicates that over half of young people with high blood pressure fall into the intermediate- to high-risk group," says Daniels. "It's fairly clear that kids with blood pressure at the upper end of the spectrum are already showing adverse changes in the heart."
Richard M. Schieken, M.D., and researchers from the Medical College of Virginia, Richmond, division of pediatric cardiology, examined changes in blood pressure, heart rate and left ventricular mass in a group of children participating in the college's MCV Twin Study. Children were examined during five visits at 18-month intervals from ages 11 through 17. The number of children in the study decreased with each successive visit: 231 were examined on at least three visits; 203 at least two times; and 87 children completed all five visits.
For the entire group, as weight increased so did ventricular mass. Peer rank order, or "tracking," persisted for ventricular mass throughout the entire study period, says Schieken.
Throughout the child's adolescence, left ventricular mass was consistently larger for boys than girls.
Gidding comments that when "examined together, the studies resolve an apparent controversy in pediatrics -- how important is blood pressure in the acquisition of left ventricular mass in children?"
While during adolescence left ventricular mass tracks significantly in both black and white children, the importance of tracking in predicting premature heart disease remains unknown and needs further study, says Schieken.
"Though we have demonstrated significant tracking during puberty, the degree of tracking between adolescence and adulthood is largely unknown," concludes Schieken. "At our state of knowledge, we do not know whether or not the degree of left ventricular mass in adolescence predicts premature atherosclerosis in the adult."
Because of this, Schieken says he sees no reason for adolescents falling below the 95th percentile for blood pressure and obesity to be examined by echocardiogram.
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