Heart & Cardiology/Significance of Interam Systolic BP Difference
Hello Dr Ahmed,
Last Saturday morning the BP on my right arm was 146/83 (avr of 3 readings) whereas my left arm, taken just before, registered 174/96 (average of 3 again.)
The difference in systolic BP between my arms is 28mmHg. This difference decreased during the day, and fluctuated a lot.
Not knowing the significance of this I looked at the academic literature on the inter-arm BP difference. I couldn't understand what I read, especially as the experts were, to some extent, in disagreement on the significance.
I suspect this is an early warning sign.
I am not on any BP meds except 50mg rauwolfia serpentine.
Thanks for any help.
Its an interesting question.
When it comes to inter-arm differences in blood pressure the most important thing is to ensure correct technique and conditions. The measurement should be taken after sitting for 5 minutes, and a similar technique and instrument used. I would ask someone else to measure it for you also to ensure the same is found. If this is confirmed then the next question is why is there a difference.
There is a significant inter-arm difference in BP for a sizable proportion of the population, usually between 5-20mmHg. If there is a high difference, for example >15 (no set number) then a pathologic cause needs to be ruled out, which can often be determined from a history and physical, and sometimes the use of imaging or blood tests. Examples would include atherosclerosis, vasculitis, connective tissue disorders, thoracic outlet compression, aortic dissection and congenital abnormalities among others.
In the absence of these causes, the exact cause is not known, and felt to be some intrinsic property of the vascular system. Some have speculated that this is due to changes in arterial stiffness. Which in itself has been associated with cardiovascular morbidity. The reason this has gained interested is that there has been a steady accumulation of evidence that the presence of inter-arm difference in blood pressure is associated with worse cardiovascular outcomes. The best thing to do is to use it as a potential marker for cardiovascular disease and like you are at the moment, paying attention to making sure you are minimizing risk factors such as treatment of blood pressure, healthy lifestyle etc.
Hope that was helpful.