Asthma treatment, blood pressure, cancer reporting, and learning difficulties

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What are the new concerns about diastolic blood pressure in the SPRINT trial?

Dr. Norman Swan 0:00

Hello and welcome to this week's Health Report with me, Norman Swann. Today, good news for parents of children with asthma, dyslexia in a digital world, the media and cancer reporting, and a caution for people with high blood pressure. Don't ignore the bottom number of your pressure, what's called your diastolic. Last November on the Health Report, we covered a study called the SPRINT trial, which found that for people at high risk of a heart attack or stroke. Going on to high blood pressure treatment, which aimed for a top number, or systolic blood pressure, of one hundred and twenty or less, was lower was associated with significant benefits compared to the usual target of one hundred and forty.

Dr. Norman Swan 0:38

This has made many countries wonder whether they should tell doctors to lower blood pressure targets in their patients at high risk of heart disease. But you'll notice I've only talked about the top number, the systolic pressure, which is the pressure generated by the heart beating and pumping blood through your arteries. The bottom number, the diastolic pressure, is the background pressure between heartbeats and has a critical role in keeping blood going to organs like the brain and heart. A group led by researchers at Johns Hopkins University in Baltimore was concerned that there might be a risk in people whose diastolic pressure falls too far with more aggressive blood pressure treatment. It's a story consumers need to know about.

Bill McAvoy 1:25

Which is the pressure, as you said, between heartbeats tends to be lower. And that means that there can be less profusion of the organ Drawing diastole, which is for all intents and purposes approximately half of the heartbeat.

Dr. Norman Swan 1:38

And just to capture what you said there, essentially is a low diastolic blood pressure could be a reflection of very stiff arteries in somebody who's already considerably at risk.

Bill McAvoy 1:46

Yes. And to add to that, those patients with stiff arteries tend to have higher systolic blood pressures. And that means that the pulse pressure, which is the difference between the two, systolic minus phastolic, is larger. So those patients with a higher pulse pressure, which is a higher systolic and a lower diastolic, likely due to stiff arteries. If they're gonna be treated to this target of one twenty, they may end up with a non treatment diastolic blood pressure that's lower than we would like and that has theoretical reasons for concern specifically with respect to the coronary blood flow. The coronary arteries, as you know, are the arteries that supply the heart muscles itself. And those coronary arteries, because they go through the heart muscle, when the heart squeezes in systole, which is the time when the heart's pumping blood out

Bill McAvoy 2:37

Those vessels are constricted and there's no flow. So the only time that there's actually flow to the heart muscle through those horne rearies is during diastole. And for that particular reason, it could be that in the Astley When the diastolic blood pressure is too low that you're getting actually reduced blood flow to the heart muscle, which can cause damage.

Dr. Norman Swan 2:58

So you studied eleven and a half thousand people, average age fifty seven, both men and women, to look at the relationship between whether or not you could measure heart damage by a chemical called troponin related to their diastolic blood pressure. Were those people being treated for their blood pressure, or th this was their natural diastolic blood pressure?

Bill McAvoy 3:16

It was a mix. This is a fairly healthy population in their fifties and specifically did not have a prior history of coronary artery disease. So most of the patients were not on treatments. We found that even when we stratified the analysis based on hypertension treatment status, that is, we looked both at the group of patients or adults in the study who were getting treatment for blood pressure. And we looked at the group who were not on any treatment. we saw that the results were the same. That is that the diastolic blood pressure, the lower that blood pressure was, the more likely that we saw an association with heart damage like this troponin.