White coat hypertension in treated hypertensives: a three year follow-up study.

Patients who participated in an initial study in a hypertension outpatient clinic in a tertiary care hospital in Western Canada were approached three years later to participate in a follow-up study. The aim of this study was to describe changes, over three years, in office (OBP) and ambulatory blood pressure and blood pressure load (BPL) in a group of treated hypertensives, with and without white coat hypertension (WCH). In the initial study, 103 consecutive patients with OBP over 140/90 (either/both), despite being prescribed two or more antihypertensive drugs, were divided into groups based on average daytime ambulatory blood pressures (DABP). Sustained hypertension was defined as DABP > 140/90 (both) and WCH as DABP < 135/85 (both). All others were defined as borderline hypertension. In 1998, we repeated office and DABP readings in 79 of the original 103 patients. Daytime BPL decreased significantly over the three years of the study for those originally categorized as sustained hypertension [78 + 21 to 50 + 34 for systolic BPL (p = < 0.001) and 75 + 21 to 41 + 29 for diastolic BPL (p = < 0.001)]. Similarly, BPL fell in borderline hypertensives while BPL remained low, but increased somewhat, for WCH. OBP declined in all groups; thus, from a medical standpoint, this supports the argument that all those diagnosed with hypertension based on the OBP should remain on antihypertensive treatment. For nurses counselling patients with WCH, it provides a cautionary note that these patients, if already on antihypertensive medication, should probably continue treatment as WCH does not appear to be stable over time.