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Diagnosing Hypertension

Next to things like immunizations, clean water, and adequate sanitation, treating hypertension is one of the most significant things that has helped improve quality and quantity of life. Hypertension does its damage quietly and silently. If you ever feel anything prior to your stroke or heart attack, it means you have had elevated blood pressure for a long time. Sudden or new vision changes or headaches can be symptoms of prolonged untreated hypertension.

Diagnosing and treating hypertension decreases the long-term health risks associated with high blood pressure (HBP), such as stroke, heart disease, and kidney damage. The diagnosis is made based on elevated blood pressure on at least two separate doctor’s office visits or by wearing an ambulatory blood pressure monitor. The US Preventive Services Task Force (USPSTF) recommends obtaining blood pressure measurements outside of the doctor’s office to confirm diagnosis before starting treatment. This can be done with either ambulatory or home blood pressure monitoring with a validated and accurate device.

Ambulatory blood pressure monitoring (ABPM) involves wearing a small, portable machine that automatically records blood pressure noninvasively, usually at 20- to 30-minute intervals over 12 to 24 hours while you go about your normal activities including sleeping. Home blood pressure monitoring involves measuring your own blood pressure at home with a fully automated home blood pressure device that you activate.

Measurements are taken much less frequently than with ABPM (e.g., 2-3 times a day, but usually over a longer period of time, e.g., weeks).

The studies upon which HBP data and results are based measure blood pressure in a specific way. This means office-based blood pressure and home blood pressure should be taken properly to avoid getting inaccurate readings (usually falsely high).

This is the proper way to take one’s blood pressure:

  1. Avoid caffeine, exercise, and smoking for at least 30 minutes before measurement.

  2. Empty your bladder/make sure you do not have to urinate.

  3. Relax, sit in a chair with feet flat on floor and back supported for at least 5 minutes.

  4. No talking during the rest period or during the measurement—this includes cell phones.

  5. The BP cuff should be directly on your skin in the middle of your upper arm with no clothes between it and your skin.

  6. Your arm should be resting, supported (e.g. resting on a desk), at heart level.

  7. Use calibrated and validated equipment.

  8. Use the correct cuff size; cuffs that are too small or too large can lead to false results.

  9. Take two or three measurements 1-2 minutes apart from each other and average the results.

These steps improve the chances your blood pressure measurement is accurate, which can determine if you have HBP or if it is uncontrolled, which may mean your medications need to be adjusted.

When your properly measured systolic blood pressure is greater than or equal to 140 or the diastolic blood pressure is greater than or equal to 90, you have HBP. Family physicians and other primary care doctors diagnose and treat most HBP. Both the American Academy of Family Physicians and the American College of Physicians endorse 140/90 as the cutoff for most average people. There are people with certain medical conditions (e.g., heart failure, kidney transplant, known ischemic heart disease, chronic kidney disease stages 3, 4, or 5 especially if there is protein in the urine) for whom 130/80 is a better target. The American Heart Association and American College of Cardiology prefer a cutoff or 130/80 for nearly all people. This controversy stems from the types of patients included and excluded in key studies used to set thresholds as well as tolerance level for side effects that can occur with overly aggressive HBP treatment.

It is important for you to speak with your doctor to get a personalized application of the guidelines. Some may even suggest using different thresholds to diagnose HBP based on whether the BP is measured in the office, at home, or via ABPM. However, the key is to make sure you or your doctor’s office accurately measure your blood pressure. Next quarter we will discuss approaches to treating high blood pressure.

Dr. Stephen A. Wilson, MD, MPH, FAAFP, is Chair of Family Medicine at Boston University Chobanian and Avedisian School of Medicine and Chief of Family Medicine for Boston Medical Center.

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