Is the case for ABPM as a routine investigation in clinical practice not overwhelming?

One sometimes has to ponder what it takes to make a technique so indispensable to practice that it must, needs be, become the rule rather than the exception. And yet nothing is new under the sun; it seems to me that ambulatory blood pressure measurement (ABPM) is in much the same historic position at the start of the 21st century as conventional measurement with the mercury sphygmomanometer and stethoscope was at the end of the 19th when one skeptic, while acknowledging that “the middle-aged and successful physician may slowly and imperceptibly lose the exquisite sensitiveness of his finger tips through repeated attacks of gouty neuritis,” went on to express his sincere doubts that the sphygmomanometer would ever be welcomed by “the overworked and underpaid general practitioner, already loaded with thermometer, stethoscope, etc., etc.,.”1 ABPM is not exactly new to medicine; in fact it has been with us in one form or another for nearly half a century. In 1964 Sir George Pickering showed for the first time the profound fall in blood pressure recorded during sleep and the fluctuations in pressure during the course of 24 hours. Pickering’s group went on to develop an ambulatory technique whereby pressure could be measured directly from the brachial artery with a small plastic catheter, and the first intraarterial ambulatory blood pressure measurement in unrestricted man was performed in 1966. In 1962, Hinman and his colleagues described the first truly portable ambulatory system for the noninvasive measurement of blood pressure, which was subsequently developed commercially by the Remler Company in California. So began noninvasive measurement of ambulatory blood pressure.2 We first used ABPM in 1979 when we anticipated that “development of a cheap and accurate means of ambulatory recording would have a considerable impact on the diagnosis of borderline hypertension and the assessment of the efficacy of treatment.”3 This forecast has been slow to materialize but the evidence that ABPM is indispensable to good clinical practice has been growing steadily, and during the last decade the information that can be derived from ABPM has surprised even the most ardent supporters of the technique.4,5 In clinical practice the most common use of ABPM and the only one for which reimbursement is approved by the Centers for Medicare & Medicaid Services (CMS) in the US is to identify patients with suspected white coat hypertension; this is defined as “office blood pressure 140/90 mm Hg on at least 3 separate clinic/office visits with 2 separate measurements made at each visit.” In addition “there should be at least 2 blood pressure measurements taken outside the office, which are 140/ 90 mm Hg and “there should be no evidence of end-organ damage.”6 Are these stipulations for reimbursement too restrictive and are they, in fact, mitigating against the wider use of ABPM? The CMS decision to permit ABPM in suspected white coat hypertension ignores the fact that there are no clinical characteristics that permit the practicing physician to “suspect” the condition. A number of studies suggest that in untreated subjects with essential hypertension, the probability of white coat hypertension increases in nonsmoking female subjects with mild hypertension of recent origin, who have had a limited number of office blood pressure measurements and who have small left ventricular masses.6 But one must ask of what use are these vague and nebulous characteristics to the practicing physician? Another important stipulation in the CMS directive is that potential patients for ABPM should have no evidence of target organ damage. However, the means whereby a practicing physician is to determine the target organ status of a patient is not stipulated. Should all patients being considered for ABPM undergo an echocardiograph or some other measure of target-organ involvement? Indeed 4 years on from the CMS directive, it is difficult not to reiterate with greater conviction (because of stronger evidence) the conclusion from the European Society of Hypertension statement on “When to suspect white coat hypertension”: “In truth, it must be admitted that it is difficult to escape the conclusion that all patients in whom a diagnosis of hypertension is being contemplated based on office/clinic blood pressure, should have ABPM to exclude white coat hypertension. . . ”6 Let us leave aside white coat hypertension aside for the moment and turn to other potential uses of ABPM that may benefit patients with hypertension. Continuing on the diagnostic front, ABPM can identify patients with masked hypertension (estimated to be present in as many as 10 million people in the US) in whom conventionally measured blood pressure in the clinic setting is normal but ABPM is increased.7 Clearly ABPM cannot be performed The opinions expressed in this editorial are not necessarily those of the editors or of the American Heart Association. From the Conway Institute of Biomolecular and Biomedical Research, University College Dublin, Ireland. Correspondence to Eoin O’Brien, Professor of Molecular Pharmacology, The Conway Institute of Biomolecular and Biomedical Research, University College Dublin, Belfield, Dublin 4, Ireland. E-mail [email protected] (Hypertension. 2007;50:284-286.) © 2007 American Heart Association, Inc.