Home BP = Better BP?

Your patient is taken back to the exam room and his blood pressure checked – 155/98. He sits in the exam room for a few minutes, and you check the BP – now 146/92. He says “But doc – whenever my RN wife checks my BP, it’s always 124/80!” All of us have seen this before… but which is the RIGHT blood pressure to use in deciding to initiate or to adjust antihypertensive treatment? Office BP measurement is plagued by poor technique (did the medical assistant allow the patient to sit for five minutes, then take the pressure slowly and carefully?), and by ‘white-coat’ effect.

JNC-7 (2003) doesn’t help much, suggesting use of home BP monitoring when there is a conflict between office measurement and home measurement, and there is no end-organ disease. However, there is a growing database of studies and recommendations that favor home monitoring as probably more accurate than office BP measurement. A number of large, prospective studies find that home BP measurements predict cardiovascular risk better than office BP. Also, home BP correlates well with ambulatory 24-hour measurements, and can help to confirm suspected white-coat hypertension. Interestingly, just having patients measure their BP lowers BP by an average of 2.5mm Hg systolic.

The AHA does recommend home monitoring as a part of routine care for hypertensive patients, but defines normal home BP as SBP<135 and DBP <85.  Although outcome studies have yet to prove that home-monitoring decreases hypertension-related morbidity and mortality, it appears the evidence is solid enough.

Here’s how to do it. Have patients get a recommended automatic arm or wrist cuff (a recent Consumer Reports review found monitors from Omron and Rite Aid were just as accurate as the best arm models and more comfortable), generally $50-$70. Then….

• Have patients check their BP 1^st thing in the AM, repeating a measurement one minute later. Obtain one more paired measurement again in the evening.
• Do this for an entire week. Consider discarding one high and one low reading, then average the rest.
• Use this procedure before starting medication, a month after adjusting medication to assess effectiveness, and about every three months for controlled patients.
• Have patients bring in their log and the machine to appointments.
• Periodically check patient technique with their machines to make sure they are correctly using the machine, and that the machine is accurate.

Home monitoring encourages patients to be more active participants in their care, and can also reduce their need for office visits if they correspond with their physicians (I ask them to e-mail me their results). Satisfied patients, satisfied doctors!

-Jeremy Golding, MD