According to the World Health Organization, there are 1.28 billion people worldwide with high blood pressure. However, as many as 80% of those people are unaware or improperly treating that pressure, and having readings in both arms can help ensure they receive proper treatment.
While blood pressure is recognized as one of the most important medical measurements, it is also one of the most poorly performed measurements in most medical settings. Known as the "silent killer," high blood pressure is often unfelt and unknown by patients until damage has been done. Regular monitoring is essential for overall health and wellness.
In addition, research has suggested the importance of measuring blood pressure in both arms. Different pressures between arms have been shown to indicate an increased risk for some potential health issues, including peripheral artery disease, heart attack, and stroke.
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Understanding Blood Pressure Differences Between Arms
Like water pressure in a home, blood pressure measures the amount of pressure the flow of blood places on a patient’s system. The first number, systolic pressure, is the pressure on the system when the heart beats. The second number, diastolic pressure, is the pressure on the system when the heart relaxes.
Patients might wonder why the blood pressure is different in each arm. For example, in a home, water pressure might vary slightly from place to place, but if the upstairs sink has high pressure and the downstairs shower has no pressure, it might be time to call a plumber.
It is normal for blood pressure to differ in each arm. However, anything above a 10-point systolic range could signal a problem in the heart or vasculature. Pressure should fall within the American Heart Association's standard range regardless of the arm.
A 13-year study showed people with arm-to-arm differences of 10 points or more were 38% more likely to have had a heart attack, stroke, or a related problem than those with arm-to-arm differences of less than 10 points.
Significance of 10, 15, 20, and 40-Point Differences in Blood Pressure Between Arms
While it is perfectly normal to have differences in blood pressure between arms, those pressures should stay within 10 points of the systolic pressure. Clinically, differences of 10, 15, 20, and 40 points systolic between each side indicate increased cardiovascular issues. In young, healthy adults, an arm difference of 10-15 points can be caused by musculature contracting an artery. However, the change should still be investigated to rule out potential cardiac issues.
According to the American Heart Association, a small difference, about 10-20 points between arms, can indicate:
- Blocked arteries in the arms, known as peripheral artery disease
- Diabetes
- Kidney disease
- Heart problem
According to an NIH study, a 20-point systolic difference is likely a sign of underlying vascular disease, and medical intervention is likely needed.
- A 30-40 point difference in blood pressure between arms is significant and a likely sign of cardiovascular disease. At this point, a physician will likely refer the patient to a cardiologist.
Causes and Risk Factors
Not all causes of blood pressure differences between arms are a cause for alarm. Still, any changes should be investigated to ensure they are benign.
- Anatomical variations, such as benign vascular abnormalities or muscular constrictions, especially in youth and adults with hypertrophic muscles, can cause slight changes between arms
- Cardiovascular conditions, such as peripheral artery disease, can also cause minor changes in each arm.
Risk Factors Associated with Significant Blood Pressure Differences
- Peripheral artery disease (PAD)
- Aortic dissection is a serious, potentially fatal condition that should be treated as an emergency. It can be the result of significant blood pressure differences between arms.
- In severe cases, 40 points or more of high blood pressure differences between the arms, such differences could indicate a potentially fatal issue known as an aortic dissection.
- There is a severe difference in arms before an aortic dissection occurs because the pressure buildup in the aorta changes the left-side pressure.
- Aortic dissections are three times more common among men and are more common among people of African ancestry (specifically African-American people) and less common among people with Asian ancestry. About three-fourths of aortic dissections occur in people aged 40 to 70 years.
Diagnostic and Measurement Techniques
In 1998, Norman Kaplan wrote in an American Journal of Hypertension editorial: “The measurement of blood pressure is likely the clinical procedure of greatest importance that is performed in the sloppiest manner.” This is still true today, and it is essential to realize how rarely proper blood pressure measuring techniques are used. It is even more imperative when measuring changes in each arm.
Proper methods for blood pressure (BP) measurements:
- The patient should be seated and relaxed, not talking, with legs uncrossed
- Any clothing tight enough to restrict flow in the arms must be removed
- Correct cuff size must be used
- The patient's arm should be supported with a cuff horizontally with the heart
- Place the stethoscope gently over the brachial artery
- Inflate the cuff rapidly to 30 mmHg above the occlusion of the pulse
- Deflate very slowly, 2 mmHg per second
- Record the systolic and diastolic measures
- Repeat the measurements twice more and average the last two BP readings.
- Each reading must be separated by at least 1 minute.
- If the readings are not within 5mmHg of each other, take additional readings until they are.
- Avoid common pitfalls and errors such as using a too-small or too-large cuff, not supporting the arm being measured, or only taking one measurement.
Interpreting and Documenting Results
- Best practices for recording BP differences include indicating specific pressures in each arm and ensuring future measurements are recorded on the arm with the higher pressure. Regular bilateral measurements should also be documented depending on the level of differences.
Management and Treatment
Managing patients with blood pressure differences between arms is almost the same as managing those without differences. The primary difference is treating the higher-pressure arm as the standard for measuring and using those numbers to determine risk factors.
According to an American Heart Association study, using the pressure from the higher-measurement arm reclassified the heart risk levels of 12% of the study’s patients. This reclassification ensured they received the level of care needed for their hypertension.
In addition, people who have chronic kidney disease and those who are older are more likely to have obstructive arterial disease. Patients with obstructive arterial disease are more likely to have more reproducibility of between-arm blood pressure differences.
Treatment and Interventions
Treatment for high blood pressure includes dietary changes, lifestyle changes, and some medications.
- Beta-blockers are standard blood pressure-regulating medications. Most beta blocker medication names end in “lol,” making them easier to remember. Some common beta blockers are metoprolol, atenolol, and bisoprolol.
- Dietary changes, such as a low-salt diet and regular exercise, are highly effective in treating hypertension.
Patients with between-arm pressure differences of 20 points or more should be referred to a cardiologist for investigation of arterial blockages in the higher-pressure arm.
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Key Takeaways
- Blood pressure measurements are some of the most vital in all medicine and should be performed properly.
- It is the responsibility of both the health care professional and the patient to ensure that pressures are taken accurately.
- While pressure differences between arms can indicate other issues, the general practice of taking proper blood pressure readings is more critical.
- If there are differences of more than 10 points between arms:
- A physician should investigate possible causes for the difference
- Investigate arterial disease and clotting issues.
- If the pressure is more than 40 points:
- This is an emergency situation and should be treated accordingly.
- It is important that patients know the importance of blood pressure measurements in understanding their overall health. Too often it is measured poorly or not given the importance due to a simple, non-invasive measurement that is highly correlative with overall cardiac health.
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