The importance of achieving blood pressure goals to delaying the progression of chronic kidney disease (CKD) is well established. Still, only 34% of patients have their blood pressure under control, according to recent evidence.1
A simple but underutilized approach to reaching target blood pressure is home monitoring, as discussed recently in a couple excellent reviews.2,3
Numerous studies also have examined 24-hour ambulatory blood-pressure monitoring (ABPM) and found the technique superior to clinic measurements in predicting end-organ complications, but ABPM is neither practical nor universally covered by insurers.
Benefits of Home Monitoring
There are multiple benefits of home blood-pressure monitoring.
* Cost: The expense of measuring blood pressure at home in a proper, standardized way is low. The cost of many home devices is less than $50—significantly less expensive than office visits.
* Frequency: Many more blood pressure values can be obtained at various times during the day with home monitoring, allowing for interpretation in the context of medication timing and under more general circumstances. Night blood-pressure dipping can be determined to a limited extent.
* Patient satisfaction and compliance: Patients report a preference for home monitoring over clinic measurements. Compliance with blood-pressure monitoring will likely increase compliance with medications.
* Exclusion of masked hypertension and white-coat hypertension: Random and artificial circumstances of measuring blood pressure in the office may lead to the underestimation (masked hypertension) or overestimation (white-coat hypertension) of blood-pressure burden.
The implications of white-coat hypertension are a matter of debate, with some studies suggesting that the condition is benign and others reporting that it's associated with a higher incidence of sustained hypertension and end-organ damage.
Masked hypertension, defined by clinic blood pressure below 140 mmHg/90 mmHg against a backdrop of daytime or ambulatory blood pressure exceeding 135 mmHg/85 mmHg, is associated with end-organ damage, with effects similar to those seen with sustained hypertension, including the presence of microalbuminuria. The incidence of masked hypertension is estimated to range from 14% to 30%.
Another key benefit of home blood pressure monitoring lies in its prognostic power.
Home blood-pressure readings correlate better with ambulatory values than office measurements do, as demonstrated by a cross-sectional study.4
In the study, doctors’ readings and recent clinic readings ranked systolic pressure poorly compared with ambulatory pressure and other measurements (r = 0.46 for doctor readings, r = 0.47 for clinic readings, and r = 0.75 for home readings).
Home measurements have been shown to be more predictive of hypertensive end-organ damage, including left ventricular hypertrophy and atherosclerosis, than office blood pressures, and as predictive as ambulatory monitoring.
In addition, studies have demonstrated home blood pressures to be better indicators of future cardiovascular and all-cause mortality than office measurements.
One of these studies, a large cohort study of 4,939 patients, assessed office blood pressure, home blood pressure, and cardiac risk factors at baseline.5
For each 10-mmHg rise in systolic home blood pressure, the cardiovascular risk increased by 17.2%, and for every 5-mmHg increase in home diastolic blood pressure, the cardiovascular risk went up 11.7%.
In contrast, increases in office blood pressures of the same magnitude were not associated with a significantly higher cardiovascular risk.
In terms of renal risk, a prospective study of 217 patients with chronic kidney disease followed for a median of 3.5 years showed that home blood pressure was a strong predictor of end-stage renal disease or death compared with clinic blood pressure.6
Recommended blood pressure targets are lower for home measurements than for office measurements. The Seventh Report of the Joint National Committee on Prevention, Detection, Evaluation, and Treatment of High Blood Pressure (JNC 7) and hypertension societies suggest a cutoff of 135 mmHg/85 mmHg in a home blood-pressure reading as indicative of hypertension.1 That threshold drops below 130 mmHg/80 mmHg for patients with proteinuria and/or chronic kidney disease.
Given the benefits of home blood-pressure monitoring, we have encouraged its use in our CKD clinic of over 3,000 patients. All patients are instructed on the use of the monitor, and they are told to call in home readings to our staff if medication changes have been implemented and to bring the list of measurements to their follow-up visits.
A number of home devices have been validated by the Association for the Advancement of Medical Instrumentation and other societies. The standard home device is oscillometric, records blood pressure from the brachial artery, and is more accurate than wrist or finger devices.
All home equipment must be calibrated with office blood pressure equipment, and the difference between a home device and an auscultatory office device should be 5 mmHg or less.
If the difference is greater than 5 mmHg, it may be possible to make adjustments based on the manufacturer's instructions, or the device may still be used to monitor changes in blood pressure, with the readings adjusted according to the calibrated measurements. All measurements should be recorded with pulse, date, and time.
The suggested timing and frequency of monitoring depends upon clinical circumstances. For new-onset hypertension, twice-daily recordings for three to seven days are recommended, with one measurement done in the morning and one in the evening. For regular monitoring and for medication dose adjustments, a frequency of once to twice a day every two to three days for two to three weeks is recommended.
Patients should avoid exercise, cigarettes, and caffeine within the 30 minutes prior to measurement. For best results, the arm must be supported while blood pressure is taken, and both feet should be flat on the floor.
The artery marker should be placed directly over the brachial artery. Cuff size is important—the cuff should encircle 80% of the arm at mid level.
In patients with Stage IV or V chronic kidney disease, measurements should be taken in the dominant arm in order to protect the nondominant arm for vascular access.
Some, but not all, insurers will cover the cost of a home blood-pressure monitor. It is our opinion that home blood-pressure monitoring has an outstanding cost-benefit ratio and devices should be covered by all insurers.
Even if not covered by insurance, though, the savings to the patient in office co-payments will quickly recoup the cost of a home device.
We have found most patients willing to incur the expense if necessary, and we believe home monitoring has a favorable effect on blood-pressure control and, by extension, progression of chronic kidney disease.
1. Chobanian AV, Bakris GL, Black HR, et al, for the National Heart, Lung, and Blood Institute Joint National Committee on Prevention, Detection, Evaluation, and Treatment of High Blood Pressure, and the National High Blood Pressure Education Program Coordinating Committee. The Seventh Report of the Joint National Committee on Prevention, Detection, Evaluation, and Treatment of High Blood Pressure: the JNC 7 report. JAMA 2003;289:2560–2572.
2. Mallick S, Kanthety R, Rahman M. Home blood pressure monitoring in clinical practice: a review. Am J Med
3. McManus RJ, Mant J. Management of blood pressure in primary care. BMJ
4. Little P, Barnett J, Barnsley L, Marjoram J, Fitzgerald-Barron A, Mant D. Comparison of agreement between different measures of blood pressure in primary care and daytime ambulatory blood pressure. BMJ
5. Bobrie G, Chatellier G, Genes N, et al. Cardiovascular prognosis of “masked hypertension” detected by blood pressure self-measurement in elderly treated hypertensive patients. JAMA
6. Agarwal R, Andersen MJ. Prognostic importance of clinic and home blood pressure recordings in patients with chronic kidney disease. Kidney Int