[Arterial hypertension difficult to control in the elderly patient. The significance of the "white coat effect"].

OBJECTIVE: Previous studies have revealed a high prevalence of white coat effect among treated hypertensive patients. The difference between clinic and ambulatory blood pressure seems to be more pronounced in older patients. This abnormal rise in blood pressure BP in treated hypertensive patients can lead to a misdiagnosis of refractory hypertension. Clinicians may increase the dosage of antihypertensive drugs or add further medication, increasing costs and producing harmful secondary effects. Our aim was to evaluate the discrepancy between clinic and ambulatory blood pressure in hypertensive patients on adequate antihypertensive treatment and to analyse the magnitude of the white coat effect and its relationship with age, gender, clinic blood pressure and cardiovascular or cerebrovascular events.

POPULATION AND METHODS: We included 50 consecutive moderate/severe hypertensive patients, 58% female, mean age 68 +/- 10 years (48-88), clinic blood pressure (3 visits) > 160/90 mm Hg, on antihypertensive adequate treatment > 2 months with good compliance and without pseudohypertension. The patients were submitted to clinical evaluation (risk score), clinic blood pressure and heart rate, electrocardiogram and ambulatory blood pressure monitoring (Spacelabs 90,207). Systolic and diastolic 24 hour, daytime, night-time blood pressure and heart rate were recorded. We considered elderly patients above 60 years of age (80%). We defined white coat effect as the difference between systolic clinic blood pressure and daytime systolic blood pressure BP > 20 mm Hg or the difference between diastolic clinic blood pressure and daytime diastolic blood pressure > 10 mm Hg and severe white coat effect as systolic clinic blood pressure--daytime systolic blood pressure > 40 mm Hg or diastolic clinic blood pressure--daytime diastolic blood pressure > 20 mm Hg. The patients were asked to take blood pressure measurements out of hospital (at home or by a nurse). The majority of them performed an echocardiogram examination.

RESULTS: Clinic blood pressure was significantly different from daytime ambulatory blood pressure (189 +/- 19/96 +/- 13 vs 139 +/- 18/78 +/- 10 mm Hg, p < 0.005). The magnitude of white coat effect was 50 +/- 17 (8-84) mm Hg for systolic blood pressure and 18 +/- 11 (-9 +/- 41) mm Hg for diastolic blood pressure. A marked white coat effect (> 40 mm Hg) was observed in 78% of our hypertensive patients. In elderly people (> 60 years), this difference was greater (50 +/- 15 vs 45 +/- 21 mm Hg) though not significantly. We did not find significant differences between sexes (males 54 +/- 16 mm Hg vs 48 +/- 17 mm Hg). In 66% of these patients, ambulatory blood pressure monitoring showed daytime blood pressure values < 140/90 mm Hg, therefore refractory hypertension was excluded. In 8 patients (18%) there was a previous history of ischemic cardiovascular or cerebrovascular disease and all of them had a marked difference between systolic clinic and daytime blood pressure (> 40 mm Hg). Blood pressure measurements performed out of hospital did not help clinicians to identify this phenomena as only 16% were similar (+/- 5 mm Hg) to ambulatory daytime values.

CONCLUSIONS: Some hypertensive patients, on adequate antihypertensive treatment, have a significant difference between clinic blood pressure and ambulatory blood pressure measurements. This difference (White Coat Effect) is greater in elderly patients and in men (NS). Although clinic blood pressure values were significantly increased, the majority of these patients have controlled blood pressure on ambulatory monitoring. In this population, ambulatory blood pressure monitoring was of great value to identify a misdiagnosis of refractory hypertension, which could lead to improper decisions in the therapeutic management of elderly patients (increasing treatment) and compromise cerebrovascular or coronary circulation.