Borderline Hypertension: Hypertension Seminars at östra Hospital, Göteborg, Sweden

Borderline hypertension was the topic of one of the “Hypertension seminars” arranged by the Hypertension Section at the Ostra Hospital, Goteborg, Sweden. On that occasion Professor Stevo Julius, Ann Arbor, Michigan, USA, was an invited guest. During the seminar, various aspects of borderline hypertension were discussed, e.g. the natural history, hemodynamics and management of this condition. The present review is based on these discussions. Key iivrds: borderline hypertension, hemodynamics, epidemiology. Acta Med Scand 208: 481. 1980. It has been shown beyond doubt , and there is general agreement today, that arterial pressure in any population is distributed as a continuous variable, the curves being Gaussian in shape when converted t o the logarithmic scale. In other words, arterial pressure is a quantity, not a quality. With this in mind, it is not logical t o treat arterial pressure as a quality and set up a dichotomy: normotension and hypertension, a fact repeatedly pointed ou t by Sir George Pickering (75, 76) . The fact that most physicians and scientists still use the terms hypertension and normotension, and also the term borderline hypertension, the topic of this seminar, does not mean that they d o not recognize that blood pressure (BP) is a quantitative variable. T h e use of these terms reflects the realization that individuals with a certain level of B P have several common physiologic and epidemiologic characteristics which often mandate specific investigative and practical approaches. As will become evident during this seminar, the term borderline hypertension signifies not just a certain range of B P between “normotension” and “hypertension”, but rather a clinical condition with recognizable and reproducible characteristics. D E F I N I T I O N S The WHO has defined hypertension as systolic BP (SBP) 2 160 and/or diastolic BP (DBPp95 mmHg and normotension as s 140/90 mmHg, leaving the range between these two delineations to be called borderline hypertension (101). The Ann Arbor group has previously defined patients with borderline hypertension as those having, out of five indirect casual BPs within the last year, at least one with a diastolic value a90 mmHg and at least one ~ 9 0 mmHg (45). Others have defined borderline hypertension as BP intermittently above 150 mmHg systolic or 90 mmHg diastolic (94). Since arterial pressure tends to increase with age in the Western world, all the above definitions have inherent problems, simply because they do not consider the age of the subject. However, the Ann Arbor group has recently taken age into consideration and defines borderline hypertension in the following manner: age 17-40: >140/90, 150/90. 60: > 160/90, < 175/100 (40). Obviously the intent of all these classifications is to delineate the mildest possible form of hypertension. Consequently, the term borderline hypertension excludes the existence of BP-related target organ damage such as hypertensive retinopathy and left ventricular hypertrophy (with conventional methods) or impaired renal function. A number of synonyms to borderline hypertension have been proposed. The term labile hypertension is not logical as it implies increased BP variability. Some of the early studies indicating a higher degree of BP variability in subjects with systolic blood pressure above 120 mmHg as compared to those with BPs below this level, are open to serious criticism, e.g. that in the lower BP group the upward variability of the BP was limited by definition (it could reach a maximum of 120 mmHg) whereas no such restrictions existed in the high BP group (78). Furthermore, several studies have demonstrated that there is no correlation between the level of BP and its variability when repeated measurements are made during 1-3 weeks (10, 26). In addition, BP fluctuates markedly Requests for reprints to: L. Hansson, M.D., Dept. of Medicine, Ostra Hospital, S-416 85 Goteborg, Sweden. 3 1-802986 Acta Med S w n d 208 even in normotensive individuals (4) . I t is therefore not surprising to find that an excessive variability of BP has never been established as a characteristic feature of borderline hypertension. Even if the BP variability were increased, the importance of this finding would be questionable. The extreme ranges of BPdo not seem to predict the risk of cardiovascular disease. Thus, Sokolow et al. (85) found that the five highest and five lowest BPs during a 24-hour recording did not relate to cardiovascular morbidity, whereas the average BP during that period carried an important predictive power. The term "labile" should be reserved for individuals with extremely variable BPs, irrespective of whether these occur in the normotensive, borderline or hypertensive range. The term prehypertension indicates a condition which almost invariably leads to established hypertension. Since this is not the case, which will be shown later, the term is not logical. Latent hypertension points to a condition which may develop into hypertension or which may remain latent, and this term is accordingly a useful synonym. Marginal hypertension is also acceptable. whereas early essential hypertension should be avoided for the same reasons as prehypertension. However, borderline hypertension is such an accepted and commonly used expression that any attempt to use synonyms for this condition is likely to cause confusion. For this reason we would recommend that the use of synonyms be restricted.