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NDT Advance Access published online on March 6, 2008
Nephrology Dialysis Transplantation, doi:10.1093/ndt/gfn094
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© The Author [2008]. Published by Oxford University Press on behalf of ERA-EDTA. All rights reserved. For Permissions, please e-mail: journals.permissions@oxfordjournals.org


Is it time to celebrate a century of blood pressure management?

Kenrick Berend and Marcel Levi

Department of Internal Medicine, St. Elisabeth Hospital, Willemstad, Curacao, Netherlands Antilles; Academic Medical Center, University of Amsterdam, Amsterdam, The Netherlands 58 St. Elisabeth Hospital, Department of Internal Medicine, Willemstad, Curacao Netherlands Antilles

Correspondence and offprint requests to: Kenrick Berend, St. Elisabeth Hospital, Department of Internal Medicine, Willemstad, Curacao, Netherlands Antilles. E-mail: kenber{at}scarlet.an



   Abstract
Top
 Abstract
Introduction
 Are physicians capable of...
 Conclusion
 References
 
Background. Even after a century of hypertension management, several trivial issues have remained unsolved and still result in inadequate control of blood pressure in many patients.

Methods. We have performed a critical literature review on topics pertaining the assessment and management of hypertension, focusing on the gaps in knowledge and pitfalls of hypertension management in clinical practice.

Results. Physicians are often not capable of adequately measuring blood pressure themselves; the office blood pressure recordings are not sufficiently reliable and the timing of the start of the treatment is often not satisfactory. However, much progress has been made in the past century. Research in this field not only expanded the potential of blood pressure measurements for risk stratification and risk management but also identified many erroneous assumptions and technical mistakes. An important step forward may be the development of affordable ‘high tech’ blood pressure measuring devices that continuously monitor the intra-arterial pressure in a noninvasive way to eliminate human factors and equipment errors. Technological advances will also provide adequate data storage and software allowing management on an international scale.

Conclusions. Hypertension management can almost be celebrated; however, the pressure is still on!

Keywords: blood pressure; hypertension



   Introduction
Top
 Abstract
 Introduction
Are physicians capable of...
 Conclusion
 References
 
In 1827, Bright suggested that kidney disease and cardiovascular abnormalities could be the result of an increased intravascular pressure [1]. He had to wait for evidence supporting this hypothesis until the end of the 19th century when routine blood pressure measurements were made possible. Scipione Riva-Rocci invented the inflatable cuff to measure the brachial systolic pressure in 1896 [2] and Nikolai Korotkoff developed a technique for the ausculatory measurement of the diastolic pressure in 1904 [3]. When we reflect on what we have accomplished managing hypertension over the last 100 years, we should ask ourselves some questions.



   Are physicians capable of properly measuring the blood pressure?
Top
 Abstract
 Introduction
 Are physicians capable of...
Conclusion
 References
 
The quality and the duration of life of more than one billion adults with hypertension [4] depend on the correct assessment of blood pressure. However, there are a large number of alarming papers on inadequate blood pressure measurement methods [5–16], and there has not been much improvement in recent years. The consequences of these inaccuracies may be substantial. If we underestimate or overestimate the diastolic blood pressure by 5 mmHg, >50% of hypertensives are missed or overdiagnosed, respectively [8]. Especially in the elderly, there may be an important discrepancy between Korotkoff sounds and intra-arterial readings, which can lead to pseudohypertension and potentially harmful therapy [5].

Numerous guidelines have been developed describing the correct determination of blood pressure, but it seems difficult, if not impossible, for physicians to comply with them [5,7]. In a survey of 114 doctors, not a single physician completely followed the recommended blood pressure-measuring techniques of the American Heart Association [8]. The most common mistakes included use of an inappropriately sized cuff, too short of a resting period before measurement, deflating the cuff too quickly, failure to palpate maximal systolic pressure before auscultation and not measuring the blood pressure in both arms. In addition, the ‘white coat’ hypertensive response during an office visit can be significant. Blood pressure taken with a sphygmomanometer by an unfamiliar doctor may raise the systolic pressure >20 mmHg within the first few minutes, an effect that attenuates within 5–10 min and that is less pronounced when a nurse measures the pressure. A similar pattern can be seen with the diastolic pressure [9]. Inappropriate timing of the measurement to monitor the effect of antihypertensive treatment can also lead to errors. Blood pressure should be measured just before antihypertensive medication is taken to estimate the trough or nadir effect. Instead, if the blood pressure is measured too soon after drug ingestion, it may be normal or even below normal and will then gradually increase to potentially hypertensive levels until the next dose is taken.

Both in clinical practice and medical research, blood pressure is still largely measured by auscultation using a mercury sphygmomanometer. At a large London teaching hospital, ~500 mercury sphygmomanometers and their associated cuffs were examined. More than half had serious problems that would have rendered them unsuitable for accurately measuring blood pressure. At the same time, the assessment of the technical knowledge needed to measure blood pressure by the ausculatory technique carried out amongst medical and nursing staff showed a considerable level of ignorance [10]. In another study, the working order of all sphygmomanometers (manual and automated) in a teaching hospital was evaluated. Of 543 manual sphygmomanometers, only 14% were in perfect working order. Interestingly, all 135 automated portable devices were in perfect working order although service requirements were seldom met. The average time since last service was 18 months [17]. Most practices often neglect to have their sphygmomanometers checked and serviced because only a minority of physicians calibrate devices at least once a year [7,12].

As mercury sphygmomanometers are being removed from clinical practice with a tendency to replace them with aneroid devices, inaccuracy of recordings will be even worse [10,12]. Everyday use of these devices affects accuracy over time, usually leading to false low readings, with the consequent underestimation of the blood pressure [7,12]. In one study, 58% of aneroid sphygmomanometers have been shown to have errors of > 4 mmHg, with ~33% of these having errors of >7 mmHg [13]. Moreover, aneroid sphygmomanometry is prone to all the problems of the auscultatory technique, namely observer bias and terminal digit preference. Surprisingly, even large international trials are not devoid of such problems as end-digit preference, with a clear bias towards reporting the blood pressure values just below the goal blood pressure level [14]. This all will inevitably lead to inaccurate measurement of blood pressure with serious consequences.

On top of all these shortcomings, even with proper equipment and proper technique, the indirect measurement of blood pressure by auscultation of Kortokoff sounds still underestimates intra-arterial systolic levels by 5–8 mmHg and overestimates diastolic levels by 3–7 mmHg [15]. Based on these inaccuracies, up to 21% of patients are misdiagnosed with uncontrolled hypertension [16]. The predictive value of the average of two diastolic blood pressure readings above 90 for the presence of ‘true’ diastolic blood pressure above 90 is only 52% [5]. If we also consider the fact that errors can be made in at least 23 guidelines for the measurement of blood pressure and more than 50 factors can affect the immediate accuracy of office blood pressure measurement [7,12], then office blood pressure measurement is highly unreliable. An obvious conclusion may be that physicians should stop measuring the blood pressure in their office.

Should we use only out of office blood pressure recordings?
As it seems better to monitor the blood pressure out of doctors’ offices, patients themselves may be doing a better job. Certainly, there will be no physician-related errors and multiple recordings would be made in a normal daily life situation. Unfortunately, however, there is also a great potential for errors in these recordings. Simply the muscular activity to inflate the cuff can, in itself, raise the blood pressure as much as 12/9 mmHg [9]. Recordings may also be unreliable due to inadequate equipment or poor calibration of the sphygmomanometers. Devices for home blood pressure measurement are produced worldwide at a rate of more than 10 million a year [17]. Only a small percentage of those devices are sufficiently validated on a frequent basis, if ever [10–14].

Even the ‘gold standard’, the 24-h ambulatory blood pressure monitoring, has its problems. The usual 24-h recording can produce misleading data as the mean blood pressure may differ by 7 mmHg or more from day to day [18]. Usually the blood pressure drops ~10–20% during the night (dipping). Although most essential hypertensive patients are ‘dippers’, continuous monitoring identifies a subgroup as ‘non-dippers,’ who seem to have more target organ damage and higher cardiovascular morbidity and mortality rates than dippers [5,19,20]. However, the ‘dipping status’ cannot be easily reproduced as 30% of patients cannot be classified as dippers or non-dippers when followed on consecutive days [21,22].

Interestingly, ambulatory blood pressure monitoring taught us that the reverse situation, a normotensive office blood pressure but an elevated ambulatory level, also exists. This so-called masked hypertension, isolated ambulatory hypertension or white coat normotension may be a significant predictor of target organ damage and cardiovascular disease. This problem may occur in as much as 10% of hypertensive patients [20,21]. The incidence and impact of masked hypertension in normotensive type 2 diabetic patients on microvascular complications and echocardiographic parameters is even worse [23].

In any case, the relatively high cost of 24-h ambulatory blood pressure measurement is an important factor that still does not allow this approach to be used for routine application. This penny-wise approach, however, may unfortunately lead to years of unnecessary and expensive (pound foolish) drug treatment. In fact, as many as 25% of people are erroneously diagnosed as hypertensive patients with conventional measurement [7]. In a study in Switzerland, it was estimated that, over a 10-year period, two million Swiss francs could be saved if therapeutic decisions were based on ambulatory blood pressure monitoring rather than conventional blood pressure monitoring [24].

It remains remarkable that for the measurement of blood pressure in patients outside intensive care units, we do not measure the blood pressure directly. We resort to various imperfect measures of the brachial artery—a large artery whose structure is never overtly affected by hypertension. The most common cause of death in hypertension is a consequence of vessel wall disease of the large arteries; we therefore need useful determinants for risk stratification of hypertensives such as pulse wave velocity and the augmentation index that can be used as arterial stiffness indices [25].

Do we initiate treatment at the right time?
We usually wait to treat patients until their blood pressure is high, but this may not be the optimal timing. Vascular wall damage mediated by blood pressure possibly begins early. This subtle damage is potentially preventable or reversible, but soon progresses to more important and advanced markers of damage, and along the way, vascular wall damage leads to stiffening of conduit arteries and a progressive rise in the systolic blood pressure, which renders hypertension more resistant to treatment. It is often at this late stage that we decide to treat blood pressure [26]. Studies indicate that short-term treatment of so-called pre-hypertension might prevent or delay the onset of hypertension and result in a sustained delayed onset of hypertension after discontinuation of therapy. However, treatment of prehypertension with antihypertensive medication will have serious consequences. In the United States alone, there are ~25 million pre-hypertensive patients who may require treatment. In addition, important questions remain to be addressed, including who should be treated and for how many years? Also, the most optimal treatment and dosing strategy is still unclear as well as the safety of this approach [27].

Do we need new management strategies for undertreated groups?
Hypertension and diabetes mellitus are both common conditions associated with high morbidity and mortality. When the two conditions occur together, as they do in 50% of diabetic individuals, the result is a 7.2-fold increase in mortality. If hypertension occurs in association with diabetes mellitus and diabetic nephropathy, mortality rises to 37-fold above that of a healthy population [28]. Almost 100% of individuals with diabetes who progress to end-stage renal disease have hypertension. One reason for the high prevalence of diabetic renal disease is an insufficient control of blood pressure. Although the awareness of the blood pressure problem has increased slightly over the last few years, the percentage of patients whose blood pressure is controlled has remained unchanged [29].

Hypertension is largely uncontrolled across ethnic groups. The high prevalence of hypertension in minority communities is a major contributor to the disproportionate degree of premature cardiovascular mortality observed in Asian/Pacific islanders, blacks, Hispanics, and native Americans [30,31]. Less than 30% of those with hypertension are taking medication that controls their condition and this percentage is even declining recently [32]. Rising concern over the poor level of blood pressure control among hypertensive patients has prompted searches for novel ways of managing hypertension. Black patients suffer earlier onset, greater severity and more end-organ damage as a result of hypertension. This is manifested, in comparison to whites, by a threefold increase in overall cardiovascular mortality, a six- to sevenfold increase in mortality under the age of 50, the earlier development of hypertensive nephrosclerosis, and a 5- to 18-fold rise in the incidence of end-stage renal disease. This is thought to be, in part, due to their higher night-time blood pressure with a smaller degree of nocturnal blood pressure dip [30,31]. As a result, effective evaluation and antihypertensive therapy are particularly important in these patients, and apparently we have to find new ways of managing hypertension. An interesting recent study evaluated barbershops for this purpose. Six black-owned barbershops were used for hypertension detection, referral and follow-up. They recorded 8953 blood pressure checks during 10,066 haircuts, resulting in an increasing intervention exposure and progressively improved treatment and control [33].



   Conclusion
Top
 Abstract
 Introduction
 Are physicians capable of...
 Conclusion
References
 
Thanks to the efforts of Riva-Rocci and Kortakov, and many others to follow, important lessons have been learned from the past. Research in this field not only expanded the potential of blood pressure measurements for risk stratification and risk management but also identified many erroneous assumptions and technical mistakes. Because we do not want to go back in time when barbers worked as physicians, hypertension management has to level with the help of modern technology. The quality of blood pressure assessment had been taken too much for granted with serious, though often invisible, consequences. Although physicians are still not capable of measuring the blood pressure themselves and several issues still complicate the treatment of hypertension, we are increasingly aware of the current limitations. Studies on the existence of white coat hypertension, masked hypertension, pseudohypertension, undertreatment, overtreatment and the high percentage of patients with uncontrolled hypertension have led us to a new era of hypertension management. The process of abandoning all inaccurate blood pressure-measuring techniques, including the outdated Riva-Rocci/Korotkoff method and replacing them with reliable non-invasive devices that allow continuous measurement of blood pressure in everyday life, is already in place. Traditional office blood pressure measurement will be soon eliminated. Technological advances will provide adequate data storage and software allowing management [34–37] on an international scale.

For decades, systolic and diastolic blood pressures were the exclusive mechanical factors predicting cardiovascular risk in populations of normotensive and hypertensive individuals. The high prevalence of systolic hypertension in patients older than 50 years and the development of non-invasive Doppler and echotracking techniques have made it possible to determine large-artery stiffness with a high degree of reproducibility [25,38,39]. If hypertension acts as a mechanical factor with deleterious consequences on the arterial wall, the focus on vascular resistance and small arteries may shift to management focused on the larger arteries tailored for the individual patient. Pulse wave analysis will assist in a better understanding of hypertension as well as in establishing the extent of cardiovascular disease and of monitoring therapy. Traditionally, arterial stiffness has been assessed by pulse wave velocity, a non-invasive parameter that has been shown to predict cardiovascular mortality. Pulse wave analysis has been increasingly used to determine the augmentation index, a parameter that describes the effect of pulse wave reflection on the central aortic pressure configuration [25,38,39]

Rising concern over the poor level of blood pressure control among hypertensive patients has prompted searches for novel ways of managing hypertension. With the use of modern technology, systems are developed that actively engage patients in the process of care. This will ultimately lead to improved drug adherence if we use devices like home blood pressure tele-management systems that involve a mobile phone and a Bluetooth-enabled home blood pressure monitor [34–37]. These devices may be also used for other physiologic parameters (e.g. blood glucose, oxygen saturation and body weight) and opens up a new approach to chronic disease management [37]. Conversely, health plans may save money by avoiding unnecessary treatment, reducing the number of office visits and lowering morbidity and mortality rates.

Hypertension management can almost be celebrated; however, the pressure is still on!

Conflict of interest statement. None declared.



   References
Top
 Abstract
 Introduction
 Are physicians capable of...
 Conclusion
 References
 

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Received for publication: 7.12.07
Accepted in revised form: 30. 1.08


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