–Hypertension experts disagree about how to apply SPRINT results in the real world.
Once again blood pressure experts are disagreeing about how to interpret SPRINT and how its results should be applied in the real world.
A new study claims that applying the SPRINT results to US patients who meet SPRINT criteria would prevent more than 100,000 deaths each year. But several leading experts say that conclusion is entirely unwarranted and is based on important misconceptions about how SPRINT can and should be used.
In a poster presented at the American Heart Association’s Council on Hypertension 2016 Scientific Sessions in Orlando, Holly Kramer, MD, MPH of Loyola Medical Center in Illinois and colleagues applied the SPRINT eligibility criteria to the National Health and Nutrition Examination Survey (NHANES) database. They calculated that about 18 million Americans would have been eligible for SPRINT (50 years of age or older, systolic blood pressure between 130-180 depending on the number of antihypertensive drugs already being taken, and high risk for cardiovascular disease). This group had an expected annual mortality rate of 2.2%.
Using the SPRINT results they then estimated that intensive blood pressure reduction as in SPRINT would prevent approximately 107,000 deaths each year (CI 93,300-121,000). This benefit would arrive at a cost of 55,000 episodes of hypotension, 33,000 episodes of syncope, 44,000 serious electrolyte disorders, and 88,000 cases of acute kidney injury each year.
“The SPRINT clinical trial clearly showed that intensive systolic blood pressure lowering lowers risk of death from all causes and will save lives among adults aged 50 years and older,” Kramer said in an AHA press release.
Dispute Over Blood Pressure Measurements
But several hypertension experts point out that it is difficult to apply SPRINT to NHANES, because the two studies measured blood pressure using completely different methods. In NHANES, Wanpen Vongpatanasin, MD of UT Southwestern in Dallas points out, blood pressure “was measured by physicians trained in the method using mercury sphygmomanometry and appropriately sized arm cuffs after volunteers rested 5 minutes seated. The second BP was used if two readings were taken; second and third values were averaged when available.”
In SPRINT, by contrast, blood pressure was obtained using an automated device, though as I have previously reported (here and here) there is some question about whether these measurements were obtained in the presence or absence of a healthcare professional. The SPRINT method may prove to be more reliable and reproducible than other methods but there is a broad consensus that it results in readings that are significantly lower than the more traditional method used in NHANES.
“I suspect that a NHANES blood pressure measurement of 140 mm Hg may be only 125-130 mm Hg if measured using the SPRINT method,” said Vongpatanasin.
“I think telling clinicians and patients they need to be below 120 mm Hg without educating them to difference in BP measurement techniques used in the trial versus in the routine office is a major mistake,” said George Bakris, MD, of the University of Chicago. “We will have to go back and clean up the epidemiological data that has been translated into the clinical setting without accounting for difference in measurement methodology.”
“Lower treatment target like in the recent SPRINT Study should only be considered if unattended automated office BP is used for measuring BP in the clinic,” said Sverre Kjeldsen MD, of Oslo, Norway.
Speaking on behalf of the American Heart Association, Mark Creager MD, of Dartmouth-Hitchcock said that “in SPRINT more aggressive treatment led to better outcomes than less aggressive treatment.” He acknowledged that 120 mm Hg may not be the goal for every patients since “one size doesn’t fit all.” He also pointed out that most patients are still not receiving any treatment. “SPRINT really reinforces the message that we need to be more aggressive in treating blood pressure to save lives. We need to intensify our efforts,” he said.
Suzanne Oparil, MD, of the University of Alabama Birmingham also defended SPRINT, though she agreed that a simple-minded adoption of 120 mm Hg as a target is not feasible. “The results of SPRINT are generalizable,” she said, “but there has to be common sense.”
Oparil acknowledged that there may be significant differences between blood pressure measurements obtained in SPRINT and NHANES but said she did not entirely “buy the difference between attended and unattended” blood pressure measurements. The important thing, she said, is for blood pressure to be measured in a quiet setting after 5 minutes of rest. Oparil also disclosed that NHANES will abandon the traditional measurement of blood pressure with a sphygmomanometer and will instead adopt a method similar to that used in SPRINT using an automatic measuring device.
Oparil said that “the extrapolation to office practices” of the SPRINT results “is difficult.” She said “that offices should change the way they measure blood pressure to make it more standardized.”