- Email: [email protected]
New approach to measurement of blood pressure in the office
Hipertens Riesgo Vasc. 2012;29(3):63---68
www.elsevier.es/hipertension
ORIGINAL ARTICLE
New approach to measurement of blood pressure in the office M.G. Myers a,∗ , L. Ruilope b a
Division of Cardiology, Schulich Heart Centre & Department of Medicine, Sunnybrook Health Sciences Centre and University of Toronto, Toronto, Ontario, Canada b Hypertension Unit, Hospital 12 de Octubre & Department of Public Health and Preventitive Medicine, University Autónoma, Madrid, Spain Received 20 March 2012; accepted 12 April 2012 Available online 12 July 2012
KEYWORDS Blood pressure measurement; Automated sphygmomanometers; Hypertension diagnosis
PALABRAS CLAVE Medición de la presión sanguínea; Esfigmomanómetro automático; Diagnóstico de la hipertensión
∗
Abstract Automated office blood pressure (AOBP) measurement has important advantages over conventional manual office blood pressure (MOBP) readings. AOBP requires the use of a fully automated sphygmomanometer which takes multiple readings with the patient resting alone. By following these three principles of AOBP, it is possible to obtain office readings which are similar to home BP and to the awake ambulatory BP recorded with 24-h BP monitoring. All three methods of automated BP measurement define hypertension as a BP ≥ 135/85 mm Hg. The correlation between the awake ambulatory BP (a recognized gold standard for predicting future cardiac events in relation to BP status) and AOBP is significantly stronger than it is for routine MOBP. AOBP eliminates office-induced hypertension (white coat hypertension) and correlates with target organ damage significantly stronger than does routine MOBP. After 100 years of manual BP measurement with the mercury sphygmomanometer, it is now time to adopt AOBP for use in routine clinical practice in order to achieve a more accurate assessment of a patient’s BP status and future cardiovascular risk. © 2012 SEHLELHA. Published by Elsevier España, S.L. All rights reserved.
Nuevas consideraciones sobre la medida de la presión arterial en consulta Resumen La medición automática de la presión sanguínea en consulta (MAPSC) presenta importantes ventajas sobre la medición manual de la presión arterial en consulta (MMPAC). La MAPSC requiere el uso de un esfigmomanómetro totalmente automático que registra múltiples lecturas con el paciente en reposo y sin la presencia del clínico. Al seguir estos tres principios de la MAPSC, es posible obtener lecturas en consulta similares a las obtenidas en domicilio y con monitorización ambulatoria de la PA de 24 horas con el paciente despierto. Los tres métodos de medición automática de la PA definen la hipertensión como una presión arterial ≥ 135/85 mmHg.
Corresponding author. E-mail address: [email protected] (M.G. Myers).
1889-1837/$ – see front matter © 2012 SEHLELHA. Published by Elsevier España, S.L. All rights reserved. http://dx.doi.org/10.1016/j.hipert.2012.04.002
64
M.G. Myers, L. Ruilope La correlación entre la PA ambulatoria con el paciente despierto (un estándar de oro reconocido para la predicción de futuros eventos cardíacos en relación con el estado de la PA) y la MAPSC es mucho mayor que para la MMPAC rutinaria. La MAPSC elimina la hipertensión de bata blanca y se correlaciona con el da˜ no al órgano diana de forma significativamente superior que la MMPAC rutinaria. Después de 100 a˜ nos de medición manual de la PA con el esfigmomanómetro de mercurio, es hora de adoptar el uso de la MAPSC de forma rutinaria en la práctica clínica a fin de lograr una evaluación más precisa de la PA del paciente y su riesgo cardiovascular futuro. © 2012 SEHLELHA. Publicado por Elsevier España, S.L. Todos los derechos reservados.
The standard approach to recording a patient’s blood pressure (BP) in the doctor’s office has remained virtually unchanged for almost a century. Typically, a physician or nurse asks the patient to be seated and then records BP once or twice using a mercury sphygmomanometer. More recently, aneroid or automated devices have been used but BP is still taken by the health professional. The patient may or may not rest for several minutes before the first reading and conversation may also occur. Although almost every national and international organization has guidelines for proper BP measurement, adherence to recommendations is often lacking. Only recently has the reality of poor quality office BP readings and its consequences come to be fully appreciated.1 Data from the Spanish Hypertension Registry2 clearly demonstrate the impact that the current approach to routine office BP measurement has on the diagnosis of hypertension. In 4729 patients, office BP in clinical practice (152/82 mm Hg) was significantly higher than the awake ambulatory BP (135/75 mm Hg), a recognized gold standard for determining future cardiovascular risk in relation to an individual’s BP status. This difference is substantially greater than the 5/5 mm Hg which separates the awake ambulatory BP cut-point of 135/85 mm Hg from the conventional office BP cut-point of 140/90 mm Hg used to define hypertension.3 These findings are far from unique. Other studies which have recorded manual BP in routine clinical practice have reported similar differences (Table 1). Of equal interest is the finding1 that routine office BP is, on average, 10/7 mm Hg higher than a comparable research quality BP, the reading upon which the cut point for defining hypertension in the office (140/90 mm Hg) is based. Not only is routine office BP higher but these readings also correlate poorly with left ventricular mass whereas both research quality manual BP and awake ambulatory BP exhibit a significantly higher correlation.4 The main concern regarding the apparent office-induced hypertension, which is also called ‘‘white coat effect’’,5 is that the poor quality of routine clinic BP leads to an over-diagnosis of hypertension. As a consequence, there has been a trend away from relying on office BP to diagnosis hypertension to the point where the recently updated NICE guidelines6 now recommend that 24-h ambulatory BP monitoring (ABPM) be performed, whenever possible, before making a diagnosis of hypertension. Not surprising, this recommendation has generated considerable controversy, especially given the limited availability of ABPM and its cost.
Automated office blood pressure One response to concerns about the quality of office BP has been the application of advances in automated BP measurement to the primary care setting. The key to eliminating the white coat response which is a major contributor to the comparatively high office BP readings was the development of a fully automated sphygmomanometer, the BpTRU (BpTRU Medical Devices Inc., Coquitlam, BC, Canada), designed especially for professional use in the office setting.7 With the BpTRU it became possible to record multiple BP readings in the office automatically with the patient resting alone. By following these three basic principles of automated office blood pressure (AOBP), it is possible to improve the quality and accuracy of BP measurement. There are now three fully automated, oscillometric sphygmomanometers which have been used for AOBP measurement, the BpTRU, Omron HEM 907 (Omron Healthcare Inc., Bannockburn, IL, USA8 ) and Microlife WatchBP Office (Microlife Corp., Heerbrugg, Switzerland9 ). Unlike conventional manual BP measurement, AOBP does not require a prolonged period of rest prior to the first reading. Research studies in AOBP have used these three devices to record between three and five AOBP readings at 1---2 min intervals without an observer being present. An important difference among the individual devices which could explain the need for three versus five readings is that the five BpTRU readings are timed from the start of one reading to the start of the next one whereas the three readings taken with the other two devices are timed from the end of one reading to the start of the next one. Comparative studies setting the interval between readings at 1 min have shown that the three or five readings taken over a similar 5 min period are comparable either to each other or to the awake ambulatory BP.10,11 To date, almost all clinical studies involving AOBP have used the BpTRU device, although there is now more interest in using the other devices. Clinical studies in primary care practice12 and with patients referred for 24-h ABPM13 have reported AOBP to be 11/3 and 20/12 mm Hg, respectively, lower than routine manual office BP readings with mean AOBP being similar to the awake ambulatory BP. Furthermore, routine manual BP readings correlated poorly with the awake ambulatory BP whereas the correlation between AOBP and awake ambulatory BP was significantly stronger (Table 2). Several other aspects of AOBP are worth noting. Most of the decrease in BP occurs within 1---2 min of the patient being left alone.14 Readings taken at 1 or 2 min intervals
Measurement of BP in the office
65
Table 1 Mean BP readings taken manually in routine clinical practice by the patient’s own physician, readings taken as part of a research study using a mercury sphygmomanometer and the mean awake ambulatory BP. First author, study
4
Myers Myers13 Brown29 Graves30 Gustavsen31 Head32
N
147 309 611 104 420 6817
Type of blood pressure measurement (mm Hg) Routine clinical practice
Research quality office
Mean awake ambulatory
146/87 152/87 161/95 152/84 165/104 150/89
140/83 140/80 152/85 138/74 156/100 142/82
132/78 134/77 139/82 --147/96 ---
are similar,15 with more recent studies using the 1 min interval setting. Unlike manual BP, AOBP does not change when recorded within or outside of the treatment setting.16 Readings taken during sequential visits to the office also show excellent agreement.16 AOBP requires the use of a fully automated sphygmomanometer. If a patient-activated automatic sphygmomanometer is used to simulate AOBP, readings are increased by about 5/5 mm Hg.17 AOBP does not increase the prevalence of ‘masked hypertension’ (normal office BP and high awake ambulatory BP or home BP18 ).
Use of AOBP in routine clinical practice The impact of introducing AOBP into routine clinical practice has recently been evaluated20 in the Conventional versus Automated Measurement of Blood Pressure in the Office (CAMBO) Trial. Patients with predominantly treated systolic hypertension were allocated to management by AOBP (N = 303) or conventional manual BP (N = 252) by cluster randomization of 67 physician practices. The last routine manual BP reading taken prior to the patient being enrolled into the study was obtained from the patient’s medical records. Practices randomized to managing their patients using AOBP were instructed on the use of the BpTRU device which was programmed to take readings at 2 min intervals which was the method in use in 2006 when the study began. Physicians in the control group were told to continue to record BP manually, the same as before enrollment into the study. A target BP of <140/90 mm Hg was set for the control group and <135/85 mm Hg for the AOBP group, taking into account the relationship of each type of BP reading with the awake ambulatory BP. Nothing further was said about how the patients were to be managed or which drugs should be used to treat hypertension. All patients in the
study underwent 24-h ABPM at baseline and again after two years. During follow-up, office BP readings and other data were collected by research staff from the patients’ medical records. The principal findings in the CAMBO Trial were already evident at the first office visit after enrollment.19 AOBP recorded using the BPTRU device was 14/4 mm Hg lower than the last routine manual BP reading taken during the last office visit prior to the patient’s enrollment into the study. Only the AOBP was similar to the awake ambulatory BP. Patients randomized to the manual BP control group also exhibited a fall in BP (9/2 mm Hg) which was attributed to regression to the mean and to participation in a research study on the part of both the patient and the physician, a phenomenon known as the Hawthorne Effect.20 The awake ambulatory BP also showed a stronger correlation for systolic/diastolic BP with the AOBP readings (r = 0.34/r = 0.56) compared to manual BP readings (r = 0.10/r = 0.40). Digit preference with readings rounded off to the nearest zero value was seen in about 50% of manual BP readings but was eliminated by AOBP, occurring in only 13% of readings. Follow-up of the patients for two years21 generally confirmed these findings although BP readings in the control manual BP group gradually decreased further despite few signs of any improvement in the quality of the readings, once again suggesting that the Hawthorne Effect20 was present despite efforts taken to minimize any impact participation in the study might have on the manual BP readings. The findings in the CAMBO Trial are consistent with the results of previous studies (Table 3) reporting that AOBP eliminates the white coat effect associated with manual BP measurement in routine clinical practice while producing readings which are highly correlated with the awake ambulatory BP.12,22 Moreover, these results should be applicable to most patients in clinical practice in the community since the CAMBO Trial and
Table 2 Compares coefficients of correlation for systolic/diastolic awake ambulatory blood pressure (BP) versus either routine manual BP or automated office BP in different patient populations. First author, study
Beckett Myers13 Myers19
12
N
481 309 303
Patient population
Community family practice Ambulatory BP unit Community family practice
Correlation of coefficient (r) office BP versus awake ambulatory BP Automated office BP
Manual office BP
0.57/0.61 0.62/0.72 0.34/0.56
0.15/0.32 0.32/0.48 0.10/0.40
66
M.G. Myers, L. Ruilope
Table 3
Studies comparing automated office BP with awake ambulatory BP.
First author, study Beckett Myers13 Myers15
12
Myers16 Myers27 Godwin22 Myers17 Myers19 Andreadis25
#Subjects
Population
Automated office BP (mm Hg)
Awake ambulatory BP (mm Hg)
481 309 200 200 62 254 654 139 303 90
Family practice ABPM unit ABPM unit ABPM unit Hypertension clinic ABPM unit Family practice ABPM unit Family practice Research unit
140/80 132/75 133/72 132/76 140/77 133/80 139/80 141/82 135/77 140/88
142/80 134/77 135/76 134/77 141/77 135/81 141/80 142/81 133/74 136/87
ABPM (ambulatory blood pressure measurement).
other AOBP study populations were conducted in primary care practice.
Introduction of AOBP into routine clinical practice The advantages of AOBP over manual BP measurement were recognized by the Canadian Hypertension Education Program in 201023 with the recommendation that AOBP be included in the Canadian guidelines for diagnosing hypertension as an alternative to manual BP readings. Based upon comparative BP data (Table 3), the cut point for diagnosing hypertension using AOBP was set at 135/85 mm Hg which is similar to the cut points for both awake ambulatory BP and home BP.1 To date, there have not been any long-term clinical outcome studies reported using AOBP readings. However, there are preliminary outcome data involving intermediate measures of target organ damage. Campbell et al.24 correlated AOBP and manual BP readings with the intima media thickness of the carotid artery in a predominantly normotensive population. Despite the presence of relatively few hypertensive patients, they found that AOBP still predicted intima media thickness after multiple regression analysis which included manual BP as a variable. In a recent study using the Microlife WatchBP Office to record AOBP, Andreadis et al.25
24-h ABPM (if available)
Awake BP < 135/85 24-hour BP < 130/80
Continue to follow-up
Figure 1 BP).
Awake BP ≥ 135 SBP ≥ 85 DBP 24-hour BP ≥ 130 SBP ≥ 80 DBP Diagnosis of Hypertension
have reported that another intermediate measure of target organ damage, left ventricular mass, correlates significantly (p = 0.37) with both AOBP and the awake ambulatory BP whereas the correlation with BP taken by a research assistant was relatively weak (r = 0.12). Clinical outcome data for AOBP should soon become available. The precise role of the three different automated methods for recording BP, AOBP, ABPM and home BP, has yet to be clearly defined. In 2005, the Canadian guidelines26 added an algorithm for diagnosing hypertension which included both ABPM and home BP. The recent NICE report6 has recommended a similar approach, proposing ABPM as the ideal technique for evaluating an individual’s BP status. As with the Canadian guidelines, NICE stated that home BP could be used as an alternative to ABPM for making a diagnosis of hypertension if the latter was not available. AOBP has also recently been proposed for inclusion into the algorithm for diagnosing hypertension.27 The advantages of AOBP over routine manual BP using this algorithm (Fig. 1) have been reported in two studies. In 254 untreated patients27 referred for 24-h ABPM, only 7% with a systolic AOBP of 140 mm Hg or greater had an optimum awake ambulatory BP, as defined by American Heart Association criteria,28 of <130 mm Hg. This low prevalence of misdiagnosis of hypertension was achieved by the substantial reduction in the white coat effect, which predominantly affects the systolic BP. Similar results were reported by
Home BP Automated office BP
< 130/80
≥ 140/90
Borderline normal/high BP 130-139/80-89 Continue to follow-up
Diagnosis of Hypertension
Interpretation of automated office BP (mm Hg) readings in routine clinical practice (SBP = systolic BP; DBP = diastolic
Measurement of BP in the office Godwin et al.22 in 654 treated hypertensive patients studied in primary care practice in the community. Only 5% of patients with a systolic AOBP ≥ 140 mm Hg had an optimum BP < 130 mm Hg. In both studies, the proportion of patients with misdiagnosis of hypertension due to white coat effect was significantly greater when manual BP readings were used in the algorithm instead of AOBP. Diastolic BP showed similar findings to systolic BP. The addition of AOBP to the pre-existing algorithm in the Canadian hypertension guidelines26 can be achieved by simply adding AOBP to the same box as home BP.27 ABPM remains the ideal method for diagnosing hypertension with home BP and AOBP being complementary. If ABPM is not available, hypertension can be diagnosed and patients followed using a combination of AOBP and home BP. These techniques are particularly useful for the long-term follow-up of these patients since repeated ABPM is impractical. Thus, BP measurement in the office setting does not have to be abandoned because of the recognized deficiencies of routine manual BP recordings but can continue to play an important role in the diagnosis and management of hypertension if manual BP is replaced by AOBP. By following the three basic principles of AOBP, multiple BP readings taken with a fully automated sphygmomanometer with the patient resting alone, it is possible to obtain readings in the office which are comparable to the awake ambulatory BP and home BP. The use of AOBP is almost certain to increase as its advantages become more apparent to physicians in clinical practice. Moreover, greater recognition that a manual BP recorded in routine clinical practice is not equivalent to a research quality manual BP should lead to greater reliance on automated BP measurement, including AOBP.
Ethical disclosures Protection of human and animal subjects. The authors declare that no experiments were performed on humans or animals for this investigation. Confidentiality of Data. The authors declare that no patient data appears in this article. Right to privacy and informed consent. The authors declare that no patient data appears in this article.
Conflict of interest The authors have no conflict of interest to declare.
References 1. Myers MG, Godwin M, Dawes M, Kiss A, Tobe SW, Kaczorowski J. Measurement of blood pressure in the office----recognizing the problem and proposing the solution. Hypertension. 2010;55:195---200. 2. Banegas JR, Messerli FH, Waeber B, Rodríguez-Artalejo F, de la Sierra A, Segura J, et al. Discrepancies between office and ambulatory blood pressure: clinical implications. Am J Med. 2009;122:1136---41. 3. The Task Force for the Management of Arterial Hypertension of the European Society of Hypertension (ESH), of the European Society of Cardiology (ESC). 2007 Guidelines for the management of arterial hypertension. J Hypertens. 2007;25:1105---87.
67 4. Myers MG, Oh P, Reeves RA, Joyner CD. Prevalence of white coat effect in treated hypertensive patients in the community. Am J Hypertens. 1995;8:591---7. 5. Myers MG. Pseudoresistant hypertension attributed white-coat effect. Hypertension. 2012;59, to http://dx.doi.org/10.1161/hypertensionaha.111.189472. 6. National Institute for Health and Clinical Excellence. Hypertension NICE clinical guidelines 127. London, UK: National Clinical Guidelines Centre; 2011 August. 7. Wright JM, Mattu GS, Perry Jr TL, Gelfer ME, Strange KD, Zorn A, et al. Validation of new algorithm for the BPM-100 electronic oscillometric office blood pressure monitor. Blood Press Monit. 2001;6:161---5. 8. White WG, Anway YA. Evaluation of the overall efficacy of the Omron office digital blood pressure HEM-907 monitor in adults. Blood Press Monit. 2001;6:107---10. 9. Stergiou GS, Tzamouranis D, Protogerou A, Nasothimiou E, Kapralos C. Validation of the Microlife Watch BP Office professional device for office blood pressure measurement according to the International Protocol. Blood Press Monit. 2008;13:299---303. 10. Myers MG, Valdivieso M, Kiss A, Tobe SW. Comparison of two automated sphygmomanometers for use in the office setting. Blood Press Monit. 2009;14:45---7. 11. Valdivieso M, Myers MG. Comparison of automated office blood pressure using the Microlife WatchBP office recorder with the awake ambulatory blood pressure. J Hypertens (abstract); in press. 12. Beckett L, Godwin M. The BpTRU automatic blood pressure monitor compared to 24-h ambulatory blood pressure monitoring in the assessment of blood pressure in patients with hypertension. BMC Cardiovasc Disord. 2005;5:18. 13. Myers MG, Valdivieso M, Kiss A. Use of automated office blood pressure measurement to reduce the white coat response. J Hypertens. 2009;27:280---6. 14. Myers MG. Automated blood pressure measurement in routine clinical practice. Blood Press Monit. 2006;11:59---62. 15. Myers MG, Valdivieso M, Kiss A. Optimum frequency of automated blood pressure measurements using an automated sphygmomanometer. Blood Press Monit. 2008;13:333---8. 16. Myers MG, Valdivieso M, Kiss A. Consistent relationship between automated office blood pressure recorded in different settings. Blood Press Monit. 2009;14:108---11. 17. Myers MG, Valdivieso M, Chessman M, Kiss A. Can sphygmomanometers designed for self-measurement of blood pressure in the home be used in office practice? Blood Press Monit. 2010;15:300---4. 18. Myers MG. Prevalence of masked hypertension in routine clinical practice [abstract]. J Hypertens. 2009;27 Suppl. 4: S328. 19. Myers MG, Godwin M, Dawes, Kiss A, Tobe SW, Grant FC, et al. Conventional versus automated measurement of blood pressure in primary care patients with systolic hypertension: randomized parallel design controlled trial. BMJ. 2011;342:d286, http://dx.doi.org/10.1136/bmj.d286. 20. The Hawthorne Effect. BMJ. 2011;344:d8262, http://dx.doi.org/10.1136/bmj.d8262. 21. Myers MG, Godwin M, Dawes M, Kiss A, Tobe SW, Kaczorowski J. Conventional versus automated measurement of blood pressure in the office (CAMBO) trial. Fam Pract. 2011, http://dx.doi.org/10.1093/fampra/cmr113. 22. Godwin M, Birtwhistle R, Delva D, Lam M, Casson I, MacDonald S, et al. Manual and automated office measurements in relation to awake ambulatory blood pressure monitoring. Fam Pract. 2011;28:110---7. 23. Quinn RR, Hemmelgarn BR, Padwal RS, Myers MG, Cloutier L, Bolli P, et al. The 2010 Canadian Hypertension Education Program recommendations for the management of hypertension:
68
24.
25.
26.
27.
28.
M.G. Myers, L. Ruilope Part 1----blood pressure measurement, diagnosis and assessment of risk. Can J Cardiol. 2010;26:241---8. Campbell NRC, McKay DW, Conradson H, Lonn E, Title LM, Anderson T. Automated oscillometric blood pressure versus auscultatory blood pressure as a predictor of carotid intimamedial thickness in male fire-fighters. J Hum Hypertens. 2007;21:588---90. Andreadis Ea, Agaliotis GD, Angelopoulos ET, Tsakanikas AP, Chaveles IA, Mousoulis GP. Automated office blood pressure and 24-h ambulatory measurements are equally associated with left ventricular mass index. Am J Hypertens. 2011;24:661---6. Myers MG, Tobe SW, McKay DW, Bolli P, Hemmelgarn BR, McAlister FA, on behalf of the Canadian Hypertension Education Program. New algorithm for the diagnosis of hypertension. Canadian Hypertension Education Program recommendations (2005). Am J Hypertens. 2005;18:1369---74. Myers MG. A proposed algorithm for diagnosing hypertension using automated office blood pressure measurement. J Hypertens. 2010;28:703---8. Pickering TG, Hall JE, Appel LJ, Falkner BE, Graves J, Hill MN, et al. Recommendations for blood pressure measurement in
29. 30.
31.
32.
humans and experimental animals. Part 1: blood pressure measurement in humans a statement for professionals from the subcommittee of Professional and Public Education of the AM Heart Association Council on High Blood Pressure Research. Hypertension. 2005;45:142---61. Brown MA, Buddle ML, Martin A. Is resistant hypertension really resistant? Am J Hypertens. 2001;14:1263---9. Graves JW, Nash C, Burger K, Bailey K, Sheps SG. Clinical decision-making in hypertension using an automated (BpTRU) measurement device. J Hum Hypertens. 2003;17: 823---7. Gustavsen PH, Hoegholm A, Bang LE, Kristensen KS. White coat hypertension is a cardiovascular risk factor: a 10-year follow-up study. J Hum Hypertens. 2003;17:811---7. Head GA, Mihailidou AS, Duggan KA, Beilin LJ, Berry N, Brown MA, et al., Ambulatory Blood Pressure Working Group of the High Blood Pressure Research Council of Australia. Definition of ambulatory blood pressure targets for diagnosis and treatment of hypertension in relation to clinic blood pressure: prospective cohort study. BMJ. 2010;340:c1104, http://dx.doi.org/10.1136/bmj.c1104.
www.elsevier.es/hipertension
ORIGINAL ARTICLE
New approach to measurement of blood pressure in the office M.G. Myers a,∗ , L. Ruilope b a
Division of Cardiology, Schulich Heart Centre & Department of Medicine, Sunnybrook Health Sciences Centre and University of Toronto, Toronto, Ontario, Canada b Hypertension Unit, Hospital 12 de Octubre & Department of Public Health and Preventitive Medicine, University Autónoma, Madrid, Spain Received 20 March 2012; accepted 12 April 2012 Available online 12 July 2012
KEYWORDS Blood pressure measurement; Automated sphygmomanometers; Hypertension diagnosis
PALABRAS CLAVE Medición de la presión sanguínea; Esfigmomanómetro automático; Diagnóstico de la hipertensión
∗
Abstract Automated office blood pressure (AOBP) measurement has important advantages over conventional manual office blood pressure (MOBP) readings. AOBP requires the use of a fully automated sphygmomanometer which takes multiple readings with the patient resting alone. By following these three principles of AOBP, it is possible to obtain office readings which are similar to home BP and to the awake ambulatory BP recorded with 24-h BP monitoring. All three methods of automated BP measurement define hypertension as a BP ≥ 135/85 mm Hg. The correlation between the awake ambulatory BP (a recognized gold standard for predicting future cardiac events in relation to BP status) and AOBP is significantly stronger than it is for routine MOBP. AOBP eliminates office-induced hypertension (white coat hypertension) and correlates with target organ damage significantly stronger than does routine MOBP. After 100 years of manual BP measurement with the mercury sphygmomanometer, it is now time to adopt AOBP for use in routine clinical practice in order to achieve a more accurate assessment of a patient’s BP status and future cardiovascular risk. © 2012 SEHLELHA. Published by Elsevier España, S.L. All rights reserved.
Nuevas consideraciones sobre la medida de la presión arterial en consulta Resumen La medición automática de la presión sanguínea en consulta (MAPSC) presenta importantes ventajas sobre la medición manual de la presión arterial en consulta (MMPAC). La MAPSC requiere el uso de un esfigmomanómetro totalmente automático que registra múltiples lecturas con el paciente en reposo y sin la presencia del clínico. Al seguir estos tres principios de la MAPSC, es posible obtener lecturas en consulta similares a las obtenidas en domicilio y con monitorización ambulatoria de la PA de 24 horas con el paciente despierto. Los tres métodos de medición automática de la PA definen la hipertensión como una presión arterial ≥ 135/85 mmHg.
Corresponding author. E-mail address: [email protected] (M.G. Myers).
1889-1837/$ – see front matter © 2012 SEHLELHA. Published by Elsevier España, S.L. All rights reserved. http://dx.doi.org/10.1016/j.hipert.2012.04.002
64
M.G. Myers, L. Ruilope La correlación entre la PA ambulatoria con el paciente despierto (un estándar de oro reconocido para la predicción de futuros eventos cardíacos en relación con el estado de la PA) y la MAPSC es mucho mayor que para la MMPAC rutinaria. La MAPSC elimina la hipertensión de bata blanca y se correlaciona con el da˜ no al órgano diana de forma significativamente superior que la MMPAC rutinaria. Después de 100 a˜ nos de medición manual de la PA con el esfigmomanómetro de mercurio, es hora de adoptar el uso de la MAPSC de forma rutinaria en la práctica clínica a fin de lograr una evaluación más precisa de la PA del paciente y su riesgo cardiovascular futuro. © 2012 SEHLELHA. Publicado por Elsevier España, S.L. Todos los derechos reservados.
The standard approach to recording a patient’s blood pressure (BP) in the doctor’s office has remained virtually unchanged for almost a century. Typically, a physician or nurse asks the patient to be seated and then records BP once or twice using a mercury sphygmomanometer. More recently, aneroid or automated devices have been used but BP is still taken by the health professional. The patient may or may not rest for several minutes before the first reading and conversation may also occur. Although almost every national and international organization has guidelines for proper BP measurement, adherence to recommendations is often lacking. Only recently has the reality of poor quality office BP readings and its consequences come to be fully appreciated.1 Data from the Spanish Hypertension Registry2 clearly demonstrate the impact that the current approach to routine office BP measurement has on the diagnosis of hypertension. In 4729 patients, office BP in clinical practice (152/82 mm Hg) was significantly higher than the awake ambulatory BP (135/75 mm Hg), a recognized gold standard for determining future cardiovascular risk in relation to an individual’s BP status. This difference is substantially greater than the 5/5 mm Hg which separates the awake ambulatory BP cut-point of 135/85 mm Hg from the conventional office BP cut-point of 140/90 mm Hg used to define hypertension.3 These findings are far from unique. Other studies which have recorded manual BP in routine clinical practice have reported similar differences (Table 1). Of equal interest is the finding1 that routine office BP is, on average, 10/7 mm Hg higher than a comparable research quality BP, the reading upon which the cut point for defining hypertension in the office (140/90 mm Hg) is based. Not only is routine office BP higher but these readings also correlate poorly with left ventricular mass whereas both research quality manual BP and awake ambulatory BP exhibit a significantly higher correlation.4 The main concern regarding the apparent office-induced hypertension, which is also called ‘‘white coat effect’’,5 is that the poor quality of routine clinic BP leads to an over-diagnosis of hypertension. As a consequence, there has been a trend away from relying on office BP to diagnosis hypertension to the point where the recently updated NICE guidelines6 now recommend that 24-h ambulatory BP monitoring (ABPM) be performed, whenever possible, before making a diagnosis of hypertension. Not surprising, this recommendation has generated considerable controversy, especially given the limited availability of ABPM and its cost.
Automated office blood pressure One response to concerns about the quality of office BP has been the application of advances in automated BP measurement to the primary care setting. The key to eliminating the white coat response which is a major contributor to the comparatively high office BP readings was the development of a fully automated sphygmomanometer, the BpTRU (BpTRU Medical Devices Inc., Coquitlam, BC, Canada), designed especially for professional use in the office setting.7 With the BpTRU it became possible to record multiple BP readings in the office automatically with the patient resting alone. By following these three basic principles of automated office blood pressure (AOBP), it is possible to improve the quality and accuracy of BP measurement. There are now three fully automated, oscillometric sphygmomanometers which have been used for AOBP measurement, the BpTRU, Omron HEM 907 (Omron Healthcare Inc., Bannockburn, IL, USA8 ) and Microlife WatchBP Office (Microlife Corp., Heerbrugg, Switzerland9 ). Unlike conventional manual BP measurement, AOBP does not require a prolonged period of rest prior to the first reading. Research studies in AOBP have used these three devices to record between three and five AOBP readings at 1---2 min intervals without an observer being present. An important difference among the individual devices which could explain the need for three versus five readings is that the five BpTRU readings are timed from the start of one reading to the start of the next one whereas the three readings taken with the other two devices are timed from the end of one reading to the start of the next one. Comparative studies setting the interval between readings at 1 min have shown that the three or five readings taken over a similar 5 min period are comparable either to each other or to the awake ambulatory BP.10,11 To date, almost all clinical studies involving AOBP have used the BpTRU device, although there is now more interest in using the other devices. Clinical studies in primary care practice12 and with patients referred for 24-h ABPM13 have reported AOBP to be 11/3 and 20/12 mm Hg, respectively, lower than routine manual office BP readings with mean AOBP being similar to the awake ambulatory BP. Furthermore, routine manual BP readings correlated poorly with the awake ambulatory BP whereas the correlation between AOBP and awake ambulatory BP was significantly stronger (Table 2). Several other aspects of AOBP are worth noting. Most of the decrease in BP occurs within 1---2 min of the patient being left alone.14 Readings taken at 1 or 2 min intervals
Measurement of BP in the office
65
Table 1 Mean BP readings taken manually in routine clinical practice by the patient’s own physician, readings taken as part of a research study using a mercury sphygmomanometer and the mean awake ambulatory BP. First author, study
4
Myers Myers13 Brown29 Graves30 Gustavsen31 Head32
N
147 309 611 104 420 6817
Type of blood pressure measurement (mm Hg) Routine clinical practice
Research quality office
Mean awake ambulatory
146/87 152/87 161/95 152/84 165/104 150/89
140/83 140/80 152/85 138/74 156/100 142/82
132/78 134/77 139/82 --147/96 ---
are similar,15 with more recent studies using the 1 min interval setting. Unlike manual BP, AOBP does not change when recorded within or outside of the treatment setting.16 Readings taken during sequential visits to the office also show excellent agreement.16 AOBP requires the use of a fully automated sphygmomanometer. If a patient-activated automatic sphygmomanometer is used to simulate AOBP, readings are increased by about 5/5 mm Hg.17 AOBP does not increase the prevalence of ‘masked hypertension’ (normal office BP and high awake ambulatory BP or home BP18 ).
Use of AOBP in routine clinical practice The impact of introducing AOBP into routine clinical practice has recently been evaluated20 in the Conventional versus Automated Measurement of Blood Pressure in the Office (CAMBO) Trial. Patients with predominantly treated systolic hypertension were allocated to management by AOBP (N = 303) or conventional manual BP (N = 252) by cluster randomization of 67 physician practices. The last routine manual BP reading taken prior to the patient being enrolled into the study was obtained from the patient’s medical records. Practices randomized to managing their patients using AOBP were instructed on the use of the BpTRU device which was programmed to take readings at 2 min intervals which was the method in use in 2006 when the study began. Physicians in the control group were told to continue to record BP manually, the same as before enrollment into the study. A target BP of <140/90 mm Hg was set for the control group and <135/85 mm Hg for the AOBP group, taking into account the relationship of each type of BP reading with the awake ambulatory BP. Nothing further was said about how the patients were to be managed or which drugs should be used to treat hypertension. All patients in the
study underwent 24-h ABPM at baseline and again after two years. During follow-up, office BP readings and other data were collected by research staff from the patients’ medical records. The principal findings in the CAMBO Trial were already evident at the first office visit after enrollment.19 AOBP recorded using the BPTRU device was 14/4 mm Hg lower than the last routine manual BP reading taken during the last office visit prior to the patient’s enrollment into the study. Only the AOBP was similar to the awake ambulatory BP. Patients randomized to the manual BP control group also exhibited a fall in BP (9/2 mm Hg) which was attributed to regression to the mean and to participation in a research study on the part of both the patient and the physician, a phenomenon known as the Hawthorne Effect.20 The awake ambulatory BP also showed a stronger correlation for systolic/diastolic BP with the AOBP readings (r = 0.34/r = 0.56) compared to manual BP readings (r = 0.10/r = 0.40). Digit preference with readings rounded off to the nearest zero value was seen in about 50% of manual BP readings but was eliminated by AOBP, occurring in only 13% of readings. Follow-up of the patients for two years21 generally confirmed these findings although BP readings in the control manual BP group gradually decreased further despite few signs of any improvement in the quality of the readings, once again suggesting that the Hawthorne Effect20 was present despite efforts taken to minimize any impact participation in the study might have on the manual BP readings. The findings in the CAMBO Trial are consistent with the results of previous studies (Table 3) reporting that AOBP eliminates the white coat effect associated with manual BP measurement in routine clinical practice while producing readings which are highly correlated with the awake ambulatory BP.12,22 Moreover, these results should be applicable to most patients in clinical practice in the community since the CAMBO Trial and
Table 2 Compares coefficients of correlation for systolic/diastolic awake ambulatory blood pressure (BP) versus either routine manual BP or automated office BP in different patient populations. First author, study
Beckett Myers13 Myers19
12
N
481 309 303
Patient population
Community family practice Ambulatory BP unit Community family practice
Correlation of coefficient (r) office BP versus awake ambulatory BP Automated office BP
Manual office BP
0.57/0.61 0.62/0.72 0.34/0.56
0.15/0.32 0.32/0.48 0.10/0.40
66
M.G. Myers, L. Ruilope
Table 3
Studies comparing automated office BP with awake ambulatory BP.
First author, study Beckett Myers13 Myers15
12
Myers16 Myers27 Godwin22 Myers17 Myers19 Andreadis25
#Subjects
Population
Automated office BP (mm Hg)
Awake ambulatory BP (mm Hg)
481 309 200 200 62 254 654 139 303 90
Family practice ABPM unit ABPM unit ABPM unit Hypertension clinic ABPM unit Family practice ABPM unit Family practice Research unit
140/80 132/75 133/72 132/76 140/77 133/80 139/80 141/82 135/77 140/88
142/80 134/77 135/76 134/77 141/77 135/81 141/80 142/81 133/74 136/87
ABPM (ambulatory blood pressure measurement).
other AOBP study populations were conducted in primary care practice.
Introduction of AOBP into routine clinical practice The advantages of AOBP over manual BP measurement were recognized by the Canadian Hypertension Education Program in 201023 with the recommendation that AOBP be included in the Canadian guidelines for diagnosing hypertension as an alternative to manual BP readings. Based upon comparative BP data (Table 3), the cut point for diagnosing hypertension using AOBP was set at 135/85 mm Hg which is similar to the cut points for both awake ambulatory BP and home BP.1 To date, there have not been any long-term clinical outcome studies reported using AOBP readings. However, there are preliminary outcome data involving intermediate measures of target organ damage. Campbell et al.24 correlated AOBP and manual BP readings with the intima media thickness of the carotid artery in a predominantly normotensive population. Despite the presence of relatively few hypertensive patients, they found that AOBP still predicted intima media thickness after multiple regression analysis which included manual BP as a variable. In a recent study using the Microlife WatchBP Office to record AOBP, Andreadis et al.25
24-h ABPM (if available)
Awake BP < 135/85 24-hour BP < 130/80
Continue to follow-up
Figure 1 BP).
Awake BP ≥ 135 SBP ≥ 85 DBP 24-hour BP ≥ 130 SBP ≥ 80 DBP Diagnosis of Hypertension
have reported that another intermediate measure of target organ damage, left ventricular mass, correlates significantly (p = 0.37) with both AOBP and the awake ambulatory BP whereas the correlation with BP taken by a research assistant was relatively weak (r = 0.12). Clinical outcome data for AOBP should soon become available. The precise role of the three different automated methods for recording BP, AOBP, ABPM and home BP, has yet to be clearly defined. In 2005, the Canadian guidelines26 added an algorithm for diagnosing hypertension which included both ABPM and home BP. The recent NICE report6 has recommended a similar approach, proposing ABPM as the ideal technique for evaluating an individual’s BP status. As with the Canadian guidelines, NICE stated that home BP could be used as an alternative to ABPM for making a diagnosis of hypertension if the latter was not available. AOBP has also recently been proposed for inclusion into the algorithm for diagnosing hypertension.27 The advantages of AOBP over routine manual BP using this algorithm (Fig. 1) have been reported in two studies. In 254 untreated patients27 referred for 24-h ABPM, only 7% with a systolic AOBP of 140 mm Hg or greater had an optimum awake ambulatory BP, as defined by American Heart Association criteria,28 of <130 mm Hg. This low prevalence of misdiagnosis of hypertension was achieved by the substantial reduction in the white coat effect, which predominantly affects the systolic BP. Similar results were reported by
Home BP Automated office BP
< 130/80
≥ 140/90
Borderline normal/high BP 130-139/80-89 Continue to follow-up
Diagnosis of Hypertension
Interpretation of automated office BP (mm Hg) readings in routine clinical practice (SBP = systolic BP; DBP = diastolic
Measurement of BP in the office Godwin et al.22 in 654 treated hypertensive patients studied in primary care practice in the community. Only 5% of patients with a systolic AOBP ≥ 140 mm Hg had an optimum BP < 130 mm Hg. In both studies, the proportion of patients with misdiagnosis of hypertension due to white coat effect was significantly greater when manual BP readings were used in the algorithm instead of AOBP. Diastolic BP showed similar findings to systolic BP. The addition of AOBP to the pre-existing algorithm in the Canadian hypertension guidelines26 can be achieved by simply adding AOBP to the same box as home BP.27 ABPM remains the ideal method for diagnosing hypertension with home BP and AOBP being complementary. If ABPM is not available, hypertension can be diagnosed and patients followed using a combination of AOBP and home BP. These techniques are particularly useful for the long-term follow-up of these patients since repeated ABPM is impractical. Thus, BP measurement in the office setting does not have to be abandoned because of the recognized deficiencies of routine manual BP recordings but can continue to play an important role in the diagnosis and management of hypertension if manual BP is replaced by AOBP. By following the three basic principles of AOBP, multiple BP readings taken with a fully automated sphygmomanometer with the patient resting alone, it is possible to obtain readings in the office which are comparable to the awake ambulatory BP and home BP. The use of AOBP is almost certain to increase as its advantages become more apparent to physicians in clinical practice. Moreover, greater recognition that a manual BP recorded in routine clinical practice is not equivalent to a research quality manual BP should lead to greater reliance on automated BP measurement, including AOBP.
Ethical disclosures Protection of human and animal subjects. The authors declare that no experiments were performed on humans or animals for this investigation. Confidentiality of Data. The authors declare that no patient data appears in this article. Right to privacy and informed consent. The authors declare that no patient data appears in this article.
Conflict of interest The authors have no conflict of interest to declare.
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