Physicians should be on the lookout for signs of increased risk for high blood pressure (hypertension) in patients referred for moderate hypertension, but who have normal or high-normal blood readings on repeated testing, Italian researchers advise.

In particular, these patients may have isolated ambulatory hypertension (IAH), which increases the risk of progression to continuous hypertension, Dr. Paolo Palatini of the University of Padova and colleagues report.

They set out to investigate the clinical significance of IAH, or “masked hypertension.” The opposite of white-coat hypertension, IAH means a person has normal blood pressure in the doctor’s office but high blood pressure outside of the office.

Little is known about the consequences of IAH, the researchers note in the August issue of Hypertension. It is also unclear how to identify these patients because blood pressure monitoring would normally not be performed on a person who does not have high blood pressure in the clinic.

The researchers followed a group of 871 people diagnosed with stage 1 hypertension who had not received treatment. Stage 1 hypertension is systolic pressure (the top reading) between 140 and 159 mmHg and diastolic (the bottom reading) between 20 and 99 mmHg.

The researchers used progression to severe hypertension and need for antihypertensive medication as the study’s endpoint. In 244 of the patients, or 28 percent, clinic blood pressure fell below 140/90 mm Hg during three months of observation. Among these patients, 120 had elevated ambulatory blood pressure along with low clinic blood pressure, meaning they had IAH.

Over a six-year period, the researchers found, individuals with IAH were at a 2.2 times greater risk of eventually needing hypertensive medication than those in the group whose blood pressure remained normal in both ambulatory and clinical settings.

The findings suggest that physicians should look for this condition in subjects who are referred for stage 1 hypertension and are found to have normal or high-normal blood pressure readings on repeat clinic blood pressure testing, the researchers conclude.

In fact, 50 percent of these subjects actually have high blood pressure outside of the doctor’s office and a large proportion of them develop continuous hypertension over the next six years, the researchers add.

SOURCE: Hypertension August 2004.