Published 10 July 2009, doi:10.1136/bmj.b2669
Cite this as: BMJ 2009;339:b2669

Head to Head

Is systolic blood pressure all that matters? No

¹ Conway Institute of Biomolecular and Biomedical Research, University College Dublin, Dublin 4, Ireland

Peter Sever (doi:10.1136/bmj.b2665) argues that abandoning diastolic measurements will improve control of blood pressure, but Eoin O’Brien thinks that we should change the method of measurement instead

Since Riva-Rocci and Korotkoff gave us the technique for measuring blood pressure over a century ago, we have landed men on the moon, encircled Mars, invented the automobile and aeroplane, and most importantly revolutionised the technology of science with the microchip. Why, we might ask, has medicine ignored scientific evidence for so long and perpetuated a grossly inaccurate measurement technique in both clinical practice and hypertension research?¹ And now we have a call from eminent clinical scientists to modify the technique by abandoning measurement of diastolic blood pressure in people over 50 years old.

In fairness there would be an attraction to the argument if we were dependent solely on conventional measurement of blood pressure since the technique is grossly misleading. Firstly, it creates the phenomenon of white coat hypertension, which affects as many as 20% of patients with hypertension diagnosed by conventional measurement.² Secondly, it fails to detect hypertension in some 10–20% of the population, which if even conservatively estimated at 5% translates into as many as 10 million people in the US.³ Thus the diagnosis of hypertension with conventional blood pressure measurement may be incorrect in as many as a third of all patients. Conventional blood pressure measurement also gives no indication of nocturnal hypertension, which is one of the most sensitive predictors of cardiovascular events.⁴

Advantages of ambulatory techniques

We need to embrace technological advances, especially ambulatory blood pressure measurement, to improve the deplorable level of blood pressure control in our societies. The technique not only gives us an insight into blood pressure behaviour over 24 hours, but also shows the appalling inaccuracy of conventional blood pressure measurement, whether systolic or diastolic, automated, or auscultatory. Measurement of nocturnal blood pressure is important because recent outcome studies show that control of both daytime and night-time systolic and diastolic blood pressure is crucial to prevent stroke.^{1 5}

Ambulatory measurement also provides indices of measurement dependent on both systolic and diastolic pressure, such as pulse pressure and the ambulatory arterial stiffness index, which may provide valuable information on arterial stiffness well in advance of the onset of stroke and heart attack.⁶ However, the greatest advantage of ambulatory measurement has been made possible by advances in telecommunication that allow us to transmit and store data centrally. This facilitates an assessment of the prevalence of differing forms of hypertension, the incidence of resistant hypertension, and the status of blood pressure control in the community.¹

Blood pressure control

Treatment of hypertension is largely wasted unless blood pressure is controlled. Treated patients with uncontrolled blood pressure have a cardiovascular risk only modestly less than that of untreated individuals.⁷ Yet scarcely a third of patients with hypertension in the United States achieve control⁸ and in the UK the figure is only just over 20%.⁹ These figures may not be quite as bad as they seem, however, because they are based on inaccurate conventional measurements rather than automated measurement over 24 hours. In Spain, for example, the establishment of a national network of ambulatory measurement in primary care has shown that conventional measurements were about 16/9 mm Hg higher than ambulatory measurements in low to moderate risk patients, with a greater difference in high risk patients. Blood pressure control based on ambulatory measurement was more than twice as good as control based on conventional measurement.¹⁰

Need for action

It is estimated that the proportion of the population aged 65 and over in Europe will increase from 20% in 2000 to 35% in 2050.¹¹ The prevalence of hypertension increases with advancing age to the point where more than half of people aged 60 to 69 years old and about three quarters of those aged 70 years and older have hypertension.¹² If we are to avert the burden of stroke and heart failure in an increasingly ageing population we need to change our practice. We have adequate drugs to control blood pressure; in the light of evidence on the daunting consequences of uncontrolled hypertension we must no longer quibble about simplifying measurement but rather marry the technologies of automation and telecommunication to ensure that we achieve blood pressure control without delay.

The cost of ambulatory monitoring is higher, but software enabling computer generated reports has reduced costs and the overall cost has to be balanced against the savings from preventing stoke and other cardiovascular complications of hypertension. Cooperation of patients also does not seem to be a problem. In Spain over 100 000 patients have been enrolled from hundreds of practices, and we are doing likewise in Ireland.

Rather than abandon diastolic pressure, I would advocate that every patient with suspected hypertension should have both systolic and diastolic pressure measured over 24 hours to confirm or refute the diagnosis of sustained hypertension. And every patient with uncontrolled hypertension, whether systolic, diastolic, or both, should have ambulatory blood pressure measurement repeated until 24 hour control of blood pressure is achieved.

Cite this as: BMJ 2009;339:b2669

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Competing interests: EO’B has contributed financially to the development of the dabl ABPM software program for ambulatory blood pressure measurement and is a member of the board of dabl Limited.

References

1. O’Brien E. Ambulatory blood pressure measurement: the case for implementation in primary care. Hypertension 2008;51;1435-41.
2. Pickering TG, James GD, Boddie C, Harshfield GA, Blank S, Laragh JH. How common is white-coat hypertension? JAMA 1988;259:225–8.[Abstract/Free Full Text]
3. Pickering TG, Davidson D, Gerin W, Schwartz JE. Masked hypertension. Hypertension 2002;40:795-6.[Free Full Text]
4. Dolan E, Stanton A, Thijs L, Hinedi K, Atkins N, McClory S, et al. Superiority of ambulatory over clinic blood pressure measurement in predicting mortality: the Dublin outcome study. Hypertension 2005;46:156-61.[Abstract/Free Full Text]
5. Salles GF, Cardoso CRL, Muxfeldt ES. Prognostic influence of office and ambulatory blood pressures in resistant hypertension. Arch Intern Med 2008;168:2340-6.[Abstract/Free Full Text]
6. Dolan E, Thijs L, Li Y, Atkins N, McCormack P, McClory S, et al. Ambulatory arterial stiffness index as a predictor of cardiovascular mortality in the Dublin outcome study. Hypertension 2006;47:365-70.[Abstract/Free Full Text]
7. Mancia G. Effective ambulatory blood pressure control in medical practice. Good news to be taken with caution. Hypertension 2007;49;17-8.
8. Jones DW, Hall JE. Hypertension pathways to success. Hypertension 2008;51:1249-51.[Free Full Text]
9. Primatesta P, Poulter NR. Improvement in hypertension management in England: results from the health survey for England 2003. J Hypertens 2006;24:1187-92.[Web of Science][Medline]
10. Banegas JR, Segura J, Sobrino J, Rodrguez-Artalejo F, de la Sierra A, de la Cruz JJ, et al. Effectiveness of blood pressure control outside the medical setting. Hypertension 2007;49:62-8.[Abstract/Free Full Text]
11. Truelsen T, Piechowski-Jozwiak B, Bonita R, Mathers C, Bogousslavsky J, Boysen G. Stroke incidence and prevalence in Europe: a review of available data. Eur J Neurol 2006;13:581–98.[CrossRef][Web of Science][Medline]
12. Chobanian AV, Bakris GL, Black HR, Cushman WC, Green LA, Izzo JL Jr, et al. Seventh report of the joint national committee on prevention, detection, evaluation, and treatment of high blood pressure. Hypertension 2003;42:1206-52.[Abstract/Free Full Text]

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