This news release describes an analysis of data from the Multi-Ethnic Study of Atherosclerosis (MESA) study showing a link between a buildup of calcium in coronary arteries and heart attacks in patients with borderline high blood pressure, referred to here as “prehypertension.” The study asserts that coronary artery calcification (CAC) can be used to guide treatment decisions for these “gray zone” patients. Aside from an overreaching headline and sub-headline, the news release delivers essential information including costs, harms, availability, and study limitations.
Nearly 30 percent of U.S. adults have prehypertension, defined as blood pressure between 120 and 139 for the first number (systolic) and/or 80 to 89 for the second number (diastolic). Preypertension is associated with a higher risk of heart attack as well as a heightened risk of developing high blood pressure, which increases the risk of stroke.
But the concept of “prehypertension” is somewhat controversial. The most recent hypertension guidelines (JNC 8) do not include this classification. It’s still a leap of faith to imply that identifying this risk group and more aggressively treating their blood pressure would significantly reduce their cardiovascular risk.
Patients generally are advised to make lifestyle changes such as exercise and weight loss, but medication is sometimes prescribed. A tool to better determine which patients would benefit from aggressive treatment — as coronary artery calcification scans might prove to be — could help clinicians make better recommendations, improving outcomes and reducing costs.
The news release says that coronary artery calcium scans “aren’t usually covered by insurance and can range in cost from $100 to $400.”
The news release does a good job of explaining the findings with numbers. It says the study shows “heart CT scans can help personalize treatment in patients whose blood pressure falls in the gray zone of just above normal or mild high blood pressure.” It says the study suggests “people with the highest calcium levels would benefit most from aggressive blood pressure treatment, whereas those with little or no calcium may not need to be treated as intensively, depending on their other heart disease risk factors.”
It gives some detailed numbers to show the risk differential between people with no calcium buildup and those with a lot of calcium. To paraphrase the release, among participants with borderline blood pressure readings, those with calcium scores of zero and high predicted risk of heart disease had a low actual event rate, of 12.7 events per 1,000 person-years. Those with calcium scores over 100 but a low predicted risk of heart disease ended up with a higher rate of actual cardiac events, 19.7.
“Thus,” the release says, “even though their calculated heart disease risk is relatively low and their blood pressure is below traditional cutoffs for treatment, the researchers say people in this category with calcium over 100 are high risk and may benefit from more aggressive blood pressure treatment.
Given that the difference in cardiac event rates between people with low calcium scores and those with high calcium scores isn’t extreme, this might amount to a marginal benefit; we would have liked some discussion of how many patients might fall into this “gray zone” and thus benefit from this approach.
Basically, the benefits, including the number needed to treat (NNT), cost-effectiveness, as well as harms and costs of obtaining these calcium scores are unknown. All we know is the magnitude of the increased potential risk associated with higher calcium scores, not whether this risk can be reduced.
The news release states: “The scans use radiation, so there is a very small cancer risk for susceptible individuals.” While the mention of cancer risk is laudable, we aren’t clear what’s meant by “susceptible individuals.” Also, it does not mention that CT scans are not recommended for pregnant women due to possible risk to the fetus. In addition, harms can also arise from medications prescribed to treat these calcium scores.
The news release is forthcoming about study limitations. It states: “The researchers caution that results are from an observational study, and a randomized trial would be needed to confirm the recommendations.” While other limitations are mentioned in the study, these are key ones readers should know about.
The news release is accurate when it states that nearly one in three adults in the US. has the range of blood pressure it describes as prehypertension. But we wonder why it mentions that 70 million adults in the U.S. have high blood pressure, since the study results do not directly apply to that population.
The news release mentions who funded the study, but it omits one potential conflict of interest that was reported in the study: one of the authors serves on a speakers’ bureau for GE Healthcare, which makes imaging equipment and software designed to detect coronary artery calcification. It’s not a a major concern, but the lack of disclosure means the release doesn’t quite meet our standard here.
The news release offers this comparison: “Previously, the appropriate blood pressure treatment for these patients used risk calculations and some guesswork, potentially leaving many vulnerable to heart disease or taking drugs they don’t need.”
Previous treatment guidelines (JNC 7) recommended only lifestyle changes for the average-risk prehypertensive patient. (And as noted above, the current guidelines do not include a prehypertensive category.) We would like to see some mention of these recommended lifestyle changes such as exercise, weight loss, dietary changes, and limiting alcohol, which can reduce blood pressure along with providing other health benefits.
Though CT scans are widely available, the news release mentions that coronary artery calcium scans aren’t usually covered by insurance. This seems to be an important stumbling block to widespread adoption. Could insurers be persuaded to pay for scans if the cost is outweighed by better targeting of treatments? Addressing this point would have added value to the news release.
The news release offers perspective via this quote from a researcher: “Our study, along with others, such as SPRINT and HOPE, positions cardiac risk and coronary artery calcium as helpful ways to determine if a given patient would either benefit from more intensive blood pressure control or do just fine with a more traditional blood pressure target.”
According to the study itself, it’s the “first to incorporate information on individual coronary artery calcium (CAC) burden to personalize the risk-based treatment of hypertension.”
It should be noted that the release is comparing an observational study with the HOPE and SPRINT trials which were randomized treatment trials. The former examines an association while the latter provides experimental evidence.
This is a close call. Overall the tone of this news release is measured. However, the sub-headline jumps the gun when it states the CAC score “gives risk assessment to prevent over- or undertreatment of blood pressure.” The score may be able to help guide treatment decisions when the path is unclear, but as the body of the news release mentions, a randomized trial is needed to find out whether there’s a clinical benefit.
Also, we’re wondering whether the term “personalized treatment” is overused. In the past it’s typically referred to treatment approaches directed by genetic variables. But in this case, the term has been expanded to cover variables in calcium buildup, with no known genetic component.
The release also states: “the researchers say these calcium scores allow physicians to go beyond the traditionally calculated risk factors to determine which blood pressure treatment strategy may be most appropriate for a particular patient.” At best, this provides the rationale for conducing a study to determine whether blood pressure treatment is appropriate–it cannot address the issue of which strategy.