On the New American guideline on HPT issued by the American College of Cardiology/American Heart Association
Many may be taken by surprise by the new Amerian Guideline on Blood Pressure Management. This new guideline was issued by a joint taskforce of American College of Cardiology (ACC) and American Heart Association (AHA) which coincided with the AHA Annual Scientific Meeting at Anaheim California. For yet another time, the American shocked the world with their all low, new definition of high blood pressure, bringing the definition of hypertension to 130/80mmHg compared to the existing level of 140/90mmHg. Now they have made this bold statement that blood pressure should be classified to one of four: normal (below 120/80mmHg), elevated (120-129/<80mmHg), Stage 1 hypertension (>130/80mmHg), Stage 2 hypertension (>140/90mmHg).
For those who have been reading Cardiology literature and guidelines, may recall how the Americans stirred the world in 2013 when they ‘removed’ the target level for treating hyperlipidaemia (LDL cholesterol) in their new guideline – which later was ‘repositioned’ and added a new target as well as new non-statin agent which initially was not mentioned.
Then the Joint National Committee (JNC 8) released the new blood pressure guideline, to yet again stirred controversies on the opposite way when they suggested in older people above 60, the ‘normal’ blood pressure cut of was 150/90mmHg. As for younger people and target BP, it was all the same 140/90 mmHg. Of course, they are different and separate taskforce – but coming from the same continent, why there is so much difference of a 30mmHg in hypertension threshold, within a mere period of 3 years? Let’s not debate that since there had been numerous criticism on this JNC 8 (as much as the American new 2013 lipid guideline!) and a later publication suggesting an all new low BP target (refer to SPRINT – A Randomized Trial of Intensive versus Standard Blood-Pressure Control, NEJM Nov 2015).
So, was this new guideline on blood pressure driven by the surprise finding of SPRINT? Let’s examine briefly what this study was about. Prior to SPRINT, there had been a number of clinical trials such as HOT, ACCORD looking at lower BP target which did suggest lowering to a level of 130/80 may be beneficial. However the result of SPRINT seemed to be more impactful since it did also affect mortality, and the trial was stopped early due to the much lower event in the group assigned to lower BP target. The study recruited more than 9000 patients at high risk of cardiovascular events (note, they were not any ordinary person on the street with a slightly high blood pressure!) and randomised to two target BP groups: Standard – target BP <140/90 or Intensive arm – target BP <120/80 mmHg. Primary endpoint was myocardial infarction or other cardiac events and cardiovascular mortality.
What was the findings? In summary, the intensive BP group reached a level of systolic BP of 121.4mmHg while the standard group 136.2mmHg. The Intensive arm had a 25% lower primary endpoint (less overall incident of MI, other cardiac events and CV mortality 1.65 vs 2.19%) – individually it translated into reduction of CV death (by 43% – 0.25 vs 0.43%) as well as all cause death, and reduced Heart Failure by 38% (0.41 vs 0.67%). (All figures were annual incident by %) with median follow up of 3.2 years. Of note, incident of MI was reduced but not statistically significant. Therefore, what we can learn, in those patients with high risk of cardiovascular disease (or already having one), reducing their blood pressure to a target below 120mmHg will improve their overall outcome of death and heart failure, and overall cardiac events. This was a fairly short duration of study (median follow up 3.2 years), imagine the magnitude of benefit you are affording patients by treating their blood pressure to this low target over 10 or 20 years?
What’s the catch, you may ask. What would happen if you lower blood pressure to that low level? As anyone might guess, there were more incident of hypotension (low blood pressure), syncope (fainting) and decreased glomerular filtration rate (GFR) which is a index of deterioration of your kidney. There is another thing which the main article in the journal did not cover. How was the blood pressure measured? In contrast to all other trials of BP lowering, which used standard “office”blood pressure measurement (BP measured by doctor or trained staff according to standard measurement protocol), SPRINT was the only trial that used ‘unattended’ blood pressure measurement. Patients in the trial were left in a quite room, BP measurement started after 5 minutes of rest and repeated automatically 3 times, an average reading was taken. So this is not a normal way of BP measurement, may be closer to a home BP (patients measure their own BP at home which usually gives lower reading than clinic BP).
OK, you are right, those clever Americans did not just rely on one isolated study to support their work, of course. It is to now one surprise that even earlier study like Framingham cohort and MRFIT population data suggested that a linear increase in future cardiovascular event started when your BP climbs to more than 120mmHg (systolic). Lewington et al in 2002 (Lancet) plotted a graph depicting a ‘normal’ BP level whereby there would be no increase in future CV event, was 115/75mmHg! This was the basis, and now further enhanced by a number of studies and meta analysis of observational data suggesting that BP level of 120-129mmHg systolic was associated with increased CVD event by 1.1 to 1.5 times, while BP above 130mmHg (130-130mmHg systolic) by 1.5-2.0 times.
Indeed, if we have a closer look at the ‘older’ guidelines, and consistently be it Americans, Europeans, Canadians or Australians, they have asserted that there is this so-called ‘pre-hypertension’ level of BP between 130-139mmHg, in fact some of them have made recommendation to treat this BP level in high risk populations. Therefore, re-classifying the hypertension BP cut off does make sense, perhaps to put more emphasis to the treating physicians to go all the way in optimising their patient’s care.
It is no secret that any clinical trial that observed an increase in BP even as low as 2mmHg will be associated with a rise in CV events, in contrast those that showed BP reduction as little as 2 mmHg will be accompanied by lowering in CV events. To quote an example, there was an excellent HDL (high density lipoprotein) raising agent torcetrapib (CETP inhibitor) that showed impressive rise in HDL by 76%, however resulted in increase CV events, one of the reason which, was a rise in BP in the treatment arm (by 5mmHg)! (NEJM Nov 22, 2007). In the LIFE study comparing losartan (ARB) vs atenolol which proved an ARB to be superior in reducing CV outcomes among hypertensive, there was still a slight difference in BP of 1mmHg. Its miniscule, but remember what Lewington (Lancet 2002) et al had concluded in their meta analysis, of BP reduction as little as 2mmHg in clinical trials reduced CV events by up to 10%! Thefore any BP reduction does make a difference, implying the importance of lowering BP in patients at high risk or already having CV events.
So back to the new American guidelines, are you ready to accept being diagnosed as hypertensive by your doctor, if your BP is 130/80mmHg or more? Or even being told that your BP is on the high side, by having a measurement reading of 125/75mmHg? What is more important, perhaps is how do you treat the ‘new’ hypertension that matters. In this regard what being recommended is not a very new thing, since they are still dividing the hypertensive people to 2 categories (see the table). Which means, if you are a ‘normal’ person, not having diabetis or any cardiovascular risk factors, do not smoke, never being diagnosed with heart problem, having a blood pressure reading of 130/80mmHg, does make you a hypertensive person – though, you do not yet need any medication. However, if you already have a heart disease (angina/heart attack (MI)/stroke), or deemed at high risk by having one or more of those risk factors (and calculated ASCVD – atherosclerotic CV disease of 10% or more) then you should take blood pressure medication. This is no surprise, in fact, even before this guideline published, many doctors (cardiologists) would have recommended additional medications for similar situtation, despite you not being diagnosed hypertensive as yet. Basically, the guideline is recommending treating you as a whole person, rather than a blood pressure alone.
So what can you do if your blood pressure is 130/80 mmHg and you are now a new person with hypertension? Provided you have no other risk factors or heart disease, the recommendation is non-pharmacological intervention and regular check up of 6 monthly at least.
Non pharmacological intervention to prevent/delay HPT or reduce BP namely reduce weight, take the DASH (dietary approaches to stop hypertension) diet (high in fruit/vegetables), cut down sodium (salt), Potassium supplement – KCl, or fruit/veg & low fat dairy, regular exercise and cut down alcohol.
However, before you get diagnosed or confirmed hypertensive, ensure that at least two separate measurements (different times), first one preferrably on both arms have been carried out. There is a special condition called White Coat Hypertension – when your office blood pressure is high and home measurement is normal (below 120/80). If you are being diagnosed and medication being contemplated, it is worth to get a set of blood pressure machine (well validated one) to do your own measurement. Just make sure you do the measurement while at rest, not following a vigorous exercise or intake of any stimulant – preferably while seated after 5 minutes. If repeated measurement of home blood pressure is normal, while clinic reading always high, it is likely that you are having a WCH which do not require to be treated with medicines, though it’s still worth instituting all those healthy lifestyle measures.
Another important aspect is to have a thorough assessment of all cardiovascular risk factors which should include BMI, blood glucose and lipid, renal function, full blood count and ECG. A scoring system that predicts future risk of CVD such as the one recommended by the Americans (ASCVD calculator though may be at variance among Asians, may be helpful to gauge how intensive the treatment of blood pressure and other associated risk factors should be). One often forgotten risk factors but seen fairly common is family history of heart disease at young age (below 55 for men, <65 for women), or family member who died sudden death – which the likely cause is more often cardiac. So now you understand it is not just about the number, it is one’s overall cardiovascular profile that matters. Existence of high blood pressure (the higher, the more risk) along with other risks such as diabetes, kidney disease, obesity, high cholesterol and family history will increase the risk of a person having future CVD.