By Dr. Geoffrey Modest
A Japanese study was just done of hypertensive patients, comparing clinic blood pressure readings to home-based monitoring, and finding that home-based monitoring was better overall, especially for coronary artery disease. (See Kario K. J Am Coll Cardiol 2016; 67: 1519).
- 21,591 treated hypertensive patients (mean age 64.9, 51% women, BMI 24, mean followup 2.02 years) were followed in the HONEST study.
- Patients were asked to measure their home BP (HBP) twice in the AM and twice in the PM on 2 different days in each measurement period and average the 2 measurements for each timeframe; done at 1, 4, 16 weeks, then at 6, 12, 18, and 24 months
- Clinic blood pressure CBP) was done by the “usual methods of each institution”, without further clarification
- 127 strokes (2.92/1000 patient-years) and 121 CAD events (2.78/1000 patient-years)
- For strokes:
- Higher incidence if morning home systolic BP (HSBP) ≥145 mmHg vs <125 mmHg [HR 6.01 (2.85-12.68)]. There was a graded increase in strokes as the morning HSBP increased, reaching significance at the 145-155 range (HR 3.97), then increasing in the ≥155 range to HR 12.57.
- Higher incidence if clinic systolic BP (CSBP) ≥150 mmHg vs <130 mmHg [HR 5.85 (3.17-10.67)]. There was a graded increase in strokes as the morning CSBP increased, reaching significance at the 150-160 range (HR 4.88), then increasing in the ≥160 range to HR 14.17.
- For CAD events (defined as MI and angina with coronary revascularization):
- Higher incidence if morning HSBP ≥145 mmHg vs <125 mmHg [HR 6.24(2.82-13.84)]. There was a graded increase in strokes as the morning HSBP increased, reaching significance at the 145-155 range (HR 4.15), then increasing in the ≥155 range to HR 12.61.
- Higher incidence if CSBP ≥150 mmHg vs <130 mmHg [HR 3.51 (1.71-7.20)]. There was a graded increase in strokes as the morning CSBP increased, reaching significance only at the ≥160 range to HR 8.82.
- In terms of diastolic BP, there were only significant increases in stroke in the ≥90 mmHg group by HBP, and ≥95 mmHg group by CBP. No difference in CAD events in any diastolic BP group.
- There did not appear to be a J-shaped curve in the relationship between HBP and stroke or CAD events (the numbers of events at the lower blood pressures was pretty small, so wide confidence intervals for these outcomes, but there was no apparent increase as the morning SBP decreased to 110 mmHg)
- A statistical analysis (goodness-to-fit) found that for stroke events, both HSBP and CSBP predicted events pretty equally. BUT for CAD events, the morning HSBP far outperformed the CSBP
So, a few points
- This study supports the importance of home-based blood pressure readings. There is much more data for ambulatory blood pressure monitoring (ABPM), with most but not all studies finding much better predictive value than clinic based measurements, leading to the NICE guidelines in the UK strongly recommending either ABPM or HBP in 2011, and the USPSTF following suit in 2015 [see https://blogs.bmj.com/bmjebmspotlight/2015/11/02/primary-care-corner-with-geoffrey-modest-md-uspstf-guidelines-on-blood-pressure-screening/which reviews the USPSTF screening recommendations for blood pressure and includes a Grade A recommendation to screen outside of the clinical setting, but also see a review (Hodgkinson J. BMJ 2011; 342:d3621).
- But this study adds the following useful insights:
- They focused on the AM blood pressures, since several studies have looked at blood pressure variability and found that blood pressure tends to be highest in the morning and the incidence of cardiovascular events and strokes is similarly higher then (presumably related to increased activation of the RAS system and increased platelet function/thrombotic tendency). So, from this study which generally found superior predictive value of home-based BP monitoring (especially for CAD), it makes sense for patients to focus just on the morning blood pressures as the decision point on therapy (it turns out in their data that the evening HSBP was also predictive of stroke events but not CAD events). Overall, looking at CSBP or evening HSBP underestimates CAD risk.
- It should be emphasized how important it is to check the home BP cuff (I ask patients to bring it in, and I simultaneously check one arm as they check the other, then vice versa)
- One other advantage of home based monitoring is that it empowers the patients around their medical care. In fact, a JAMA study showed that patients who take their BP at home have better blood pressure control (see https://blogs.bmj.com/bmjebmspotlight/2015/10/13/primary-care-corner-with-geoffrey-modest-md-bp-self-monitoringself-titrating-decreases-bp/ )
- So, my bottom line: I really do follow the HBP, which I have lots of patients do (some insurers cover the monitor, otherwise good monitors are about $50, should be appropriately sized upper arm cuffs, and many of my patients have had their kids get one for them). If the patient cannot do HBP monitoring, I ask them to go to a local pharmacy, sit quietly for a few minutes, then check their BP and record it. And I usually do not treat high blood pressure in the clinic if the home pressure is okay (and is done correctly by the patient and with a BP cuff which I find is accurate).