New BP target not necessarily good for all, say experts
While intensive treatment of hypertension may benefit patients with a higher risk for cardiovascular disease (CVD), it may do more harm than good for those with a lower CVD risk, reveals a stratified analysis of the SPRINT* study.
“Classifying patients by degree of future risk might be the best way to identify who could benefit most from intensive treatment,” said lead author Professor Robert Phillips from the Houston Methodist Institute for Academic Medicine in Houston, Texas, US.
Among 9,323 SPRINT participants who were stratified by quartiles of baseline CVD risk, participants with a 10-year CVD risk of ≥18.2 percent experienced more benefit than harm from intensive treatment to a target systolic blood pressure (SBP) of <130 mm Hg, as indicated by a benefit-to-harm ratio of >1 in the higher-risk quartiles (ratios, 2.13 and 4.80 in the 3rd and 4th quartiles**, respectively). [J Am Coll Cardiol 2018;71:1601-1610]
Conversely, those with a 10-year CVD risk of <18.2 percent had more harm than benefit from intensive treatment, as indicated by a <1 benefit-to-harm ratio (0.50 and 0.78 in the 1st and 2nd quartiles***, respectively).
The higher the risk for CVD, the greater the benefit derived relative to harm ─ as shown by a significant trend of increasing benefit-to-harm ratios from the lowest- to the highest-risk quartiles (p<0.001). Benefit refers to prevention of primary outcome events, while risk relates to serious adverse events.
“The results of the present analysis of SPRINT suggest a SBP target of <130 mm Hg would be appropriate for hypertensive individuals with 10-year CVD risk ≥18.2 percent … while for those whose risk is <18.2 percent, <140 mm Hg is an appropriate target,” said Phillips and co-authors, who noted that the numbers are in contrast to the 2017 ACC/AHA# BP guidelines which recommend treating patients whose 10-year CVD risk is >10 percent.
One size does not fit all
“Applying a flat 130/80 cut-off to all adults is probably not the best way forward,” said Dr Paul Chiam, senior consultant cardiologist at The Heart & Vascular Centre, Mount Elizabeth Hospital, Singapore, who was unaffiliated with the study.
“To treat the entire population to a BP below 130/80 will entail increased costs, significant increase in drug side effects, and very marginal health benefits in many patients.”
He explained that while a 75-year-old male with a BP of 135/85 mm Hg would not be considered as having hypertension by most physicians, a young man aged 40 years with a BP of 135/85 mm Hg would most likely be considered to have hypertension ─ since we expect the BP to rise further with age. Also, a reduction in BP would have significant long-term health consequences for the young man.
“[Whether an intensive BP target applies to a patient] depends on the patient's age and concomitant diseases. Younger patients with multiple risk factors (eg, diabetes, high cholesterol, kidney disease) should have the lower cut-off of 130/80 mm Hg applied,” Chiam added.
Potential risks with stricter threshold
The findings that the net benefits and harms of BP lowering depend on the baseline CVD risk resonated with three experts who were unrelated to the SPRINT study.
Writing in a separate opinion paper, the authors said people could be put at risk in at least three ways with the stricter diagnostic and treatment thresholds for hypertension in the new BP guideline. [JAMA Intern Med 2018;doi:10.1001/jamainternmed.2018.0310]
“First, wider disease definitions mean more people are labelled as unwell, even if they have low risk of a disease … Labelling a person as having hypertension increases their risk of anxiety and depression,” said lead author Dr Katy Bell of the University of Sydney, Australia.
“SBP has poor reproducibility, with a 10 mm Hg standard deviation for repeat measurements between clinics,” added report co-author Professor Paul Glasziou from Bond University in Gold Coast, Australia. “Since a large proportion of all adults have a ‘true’ SBP near the threshold of 130 mm Hg, the inherent variability of BP increases the potential that hypertension will be diagnosed.”
Secondly, more people may experience potential incremental harms from serious adverse drug effects as a result, according to Bell.
“Third, in countries without universal health coverage, such as the US, people newly diagnosed with hypertension may face difficulties gaining insurance coverage for a ‘pre-existing’ condition,” said Bell.
Where do we stand now?
“Many of us feel that [the new BP target] should be more of a ‘marker’ to increase our vigilance for BP monitoring,” said Chiam.
Seeing that Singapore and most of South-East Asian nations have yet to adopt the new BP guideline, Chiam believed that “it is reasonable to maintain the old guideline of 140/90 mm Hg”, since there is also strong evidence of significant health benefits with a BP threshold of 140/90 mm Hg.
“The newer guideline does, however, increase our awareness that BP is really a continuum and not a one level (artificial) cut-off value. This may motivate doctors and patients to be more proactive in controlling or preventing hypertension.”
When asked on whether the new guideline will be adapted to the local setting in the future, Chiam said more robust scientific evidence which compares BP lowering to <130/80 mm Hg vs <140/90 mm Hg in terms of health benefits vs increased costs and side effects will be needed.
Although more people will be labelled as hypertensive under the new ACC/AHA guideline, this does not mean they should start drug treatment, said Chiam.
“For the vast majority of patients [with BP] between 130/80–140/90, lifestyle changes may be enough to control and lower their BP. Exercise, weight loss, and reducing sodium (salt) intake are effective ways to help reduce BP,” he suggested.
“[Before starting BP medication,] we have to assess the patient’s age, risk profile, and long-term benefits from the medications,” advised Chiam. “We should always give a period of 2–3 months to try lifestyle modifications and then review the BP control. Medications should only be started if the BP is still between 130–140 after good attempt at lifestyle changes.”
“When there is a question of starting BP medication, the risk of CVD should be estimated using a reliable risk calculator and the potential benefits and harms discussed with the patient,” said JAMA report co-author Professor Jenny Doust from Bond University.