“We know too little about blood pressure in atrial fibrillation”
Joakim Olbers is a cardiologist and has recently presented a thesis on blood pressure in atrial fibrillation, in which the rhythm of the heart becomes irregular.
Text: Annika Lund, first published in Swedish in the magazine Medicinsk Vetenskap no 1/2021.
What’s special about high blood pressure in atrial fibrillation?
“High blood pressure is the most common risk factor for developing atrial fibrillation. But we also believe that the atrial fibrillation, which makes the rhythm irregular, itself affects blood pressure. What that means for patients – how it affects their risk of other, serious cardiovascular disease – hasn’t been studied. The truth is we don’t really know.”
What's your dissertation about?
“We’ve looked at how atrial fibrillation affects blood pressure. We’ve quantified how much blood pressure varies from beat to beat in people with atrial fibrillation compared to people who have what is called a sinus rhythm, that is to say, a heart rate without rhythm disturbances. We saw that there was much greater blood pressure variation in people with atrial fibrillation. The overpressure had about twice the variability, and the underpressure had six times the variation from beat to beat, compared to the usual sinus rhythm.
What does that mean?
“We don’t know. One can speculate that it could be harmful for the vessels to endure such varying pressures, but we don’t know if that’s true. However, it is already clinically known that it’s more difficult to obtain a correct blood pressure measurement in people with atrial fibrillation. To reduce the measurement error, it is recommended to measure blood pressure three times in succession and calculate an average.
You say blood pressure seems to work differently in atrial fibrillation. What do you mean by that?
“You can restore the heart rhythm in people with atrial fibrillation through electrical cardioversion. We found that when normal heart rhythm is restored in people with atrial fibrillation, the over- and underpressures go in different directions. The overpressure becomes higher, but the underpressure becomes lower. The difference between over- and underpressure is called pulse pressure. So when people with atrial fibrillation regain regular heart rhythms, their pulse pressure – the gap between their upper and lower pressure – increases. Normally it’s considered good to have a lower pulse pressure. But when a person with atrial fibrillation returns to normal heart rhythm, their pulse pressure increases. This raises questions – what’s the cause, what does it mean for the patient’s risk of cardiovascular disease? We don’t currently know. But we know that pulse pressure is normally affected by things that develop very slowly, like stiffness in the vessels. The fact that the pulse pressure changes this quickly during electrical cardioversion thus suggests that the atrial fibrillation itself affects blood pressure. That’s one of the things I’m thinking about when I say that blood pressure seems to work differently in atrial fibrillation.”
How do you think research should move forward?
“Hypertension is very common, but atrial fibrillation is also common. At least 100,000 Swedes have both conditions. It’s a major shortcoming in our knowledge that we don’t know more about how blood pressure works in people with atrial fibrillation. Nor do we know how people with both conditions should best be treated. We need knowledge about whether we should aim for the same blood pressure target for people who have atrial fibrillation or whether they should have other goals than people with regular heart rhythms.
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