Professor Kazem Rahimi from The George Institute of Global Health, University of Oxford, UK, speaks to Cardio Debate & Radcliffe Cardiology about blood pressure lowering for the prevention of cardiovascular disease and death during the ESC2016 Congress held in Rome, Italy.
You have recently had a paper published in the Lancet. Could you describe the rationale behind your research ?
We are interested in finding out in more detail the impact of blood pressure lowering with antihypertensives on a range of cardiovascular outcomes and in a range of patients.
The rationale behind this is that we know quite a lot about what blood pressure lowering does, its benefit. But there have been a number of key remaining questions.
What has been uncertain, for instance, is who we should treat? Does the effect of blood pressure lowering depend on the baseline blood pressure of the individuals, for instance?
Or does it depend on what background conditions those people have? And to what extent is this modified by the type of drug that people take.
And that was the key motivation for us, to look at those questions in more detail, be able to clarify who should be treated and when we should start treatment.
What were the conclusions from your research and how do you think they should impact clinical practice?
What we found in the first was to confirm what previous studies had shown.
We conducted a major meta-analysis identifying randomised patients, over 500,000 of those patients. And what we found was that obviously blood pressure lowering reduces substantially the risk of cardiovascular outcomes.
The important finding of this study was that the study showed that there was no evidence, and that those proportional risk reductions, those proportional effects on outcomes differed by the baseline blood pressure of patients.
In other words, everything else being equal, if a patient’s starting blood pressure was 140 and another patient’s blood pressure to start off with was 160, and in both patients the blood pressure was reduced by 10mm Mercury, the relative benefit that they gained was the same – or there was no evidence that the benefit was different.
And there is quite important implications for clinical practice, suggesting that we should not put so much emphasis on randomly selected targets of blood pressure value when we start treatment and how far we go.
So the focus should be on the risk of the individuals, and trying to reduce that risk. And one way of reducing that risk would be antihypertensive medication – obviously bearing in mind potential side effects or inconvenience of taking those drugs for individuals.
So that was one key aspect of the study findings that has implications.
The other one was, does it matter whether the patient has a history of ischaemic heart disease or stroke, or diabetes or kidney disease? In other words, it this all about primary prevention, or is the effect similar if you do secondary prevention. And what we found again was there was no statistical evidence that the observed effects differed based on the condition that you had.
And that simplifies again the clinical practice guidelines as to who should be treated.
There were some differences, particularly among diabetes and people with kidney disease, but overall there was no suggestion that there is a significant difference.
And the third key finding of the study was to look at the different drugs. Do different classes of drugs have different effects on different outcomes? And what we found was yes, they do, depending on what outcome you want to look at.
For instance drugs such as calcium channel blockers were shown to have greater relative risk reduction on stroke, whereas diuretics reduce the risk of heart failure more strongly, and beta-blockers were the weakest drugs comparing for those outcomes.
So those differences came out as well, which could help to fine-tune the recommendations for antihypertensive therapy. But the key messages was the baseline blood pressure of individuals is not a key determinant of the benefit that they gain, assuming that they are at substantial risk of benefiting from blood pressure lowing treatment.