For children, even mild untreated high blood pressure can lead to a potentially dangerous enlargement of the heart, according to results of a study by researchers at the Johns Hopkins Children’s Center and the Children’s Hospital at Montefiore in Bronx, New York. (The findings were reported at the 2006 annual meeting of the American Society of Nephrology Nov. 14-19 in San Diego, CA.)

“It’s apparently not true for children, at least, that the higher the blood pressure the worse the strain on the heart, and that surprised us,” says kidney specialist Tammy Brady, M.D., a fellow at the Johns Hopkins Children’s Center. “In this study, children with minimally high, very high and severely high blood pressure had evidence of heart enlargement.”

Persistently elevated blood pressure, or hypertension, is a well-known risk factor for left-ventricular hypertrophy (LVH), a thickening or enlarging of the lower left chamber of the heart, and the conventional wisdom has been that the degree of hypertension predicted the degree of  LVH. Pediatric guidelines say that any elevation in pressure measured in children on three consecutive office visits is by definition evidence of hypertension.

In the Hopkins study, researchers examined 141 children seen at three medical centers from 1997 to 2005. All of the subjects, between the ages of 3 and 21, had primary hypertension, or high blood pressure not resulting from another underlying condition. Of the 141 children, 41 percent had LVH.

 “Not only were our findings a surprise, but they are of concern given the growing numbers of children with high blood pressure, most likely due to spiraling rates of overweight and obesity,” Brady says.

Brady recommends ultrasound imaging of the heart for all children with hypertension. Untreated LVH in adults can lead to heart failure and increase the risk of sudden cardiac death.