Should Those Whose Main Symptom is Chest Pains Get Stent or Bypass Surgery?
The Monday November 18, 2019 Wall Street Journal was one of many news outlets to report on the preliminary results of the ISCHEMIA study of whether individuals with chest pains, but mild test results, should have surgery to put in a stent or a bypass—as well as pursuing lifestyle changes, statins and blood thinners such as aspirin—or whether they should only pursue lifestyle changes and drug treatment. These results were reported an American Heart Association conference presentation. There doesn’t seem to be a full-scale paper. The website for that presentation is shown above.
One thing to note is how big the confidence intervals are given the rarity of big medical events over even over 3.3 years in this population. Betsy McKay assumes in writing her Wall Street Journal article “Study Finds Limited Benefits of Stent Use for Millions With Heart Disease” assumes its readers cannot understand p-values or confidence intervals. Here is what the presentation website says:
The primary outcome of cardiovascular death, myocardial infarction, resuscitated cardiac arrest, or hospitalization for unstable angina or heart failure at 3.3 years occurred in 13.3% of the routine invasive group compared with 15.5% of the medical therapy group (p = 0.34). The findings were the same in multiple subgroups.
The p-value for a 2.2 percentage point difference implies that for a difference to be significant at the 5% level would have required a 4.5 percentage point difference in probability of a bad medical event.
The statistical imprecision of the result is also indicated by the opposite-direction results for the two most severe of the four bad medical events:
Cardiovascular death or myocardial infarction: 11.7% of the routine invasive group compared with 13.9% of the medical therapy group (p = 0.21)
No statistical test is reported on the presentation website for this result:
Quality of life outcomes: Improvement in symptoms was observed among those with daily/weekly/monthly angina, but not in those without angina.
I suspect the following is also statistically quite unclear. From the head of the ISCHEMIA study, as quoted in Betsy McKay’s Wall Street Journal article:
Six months into their treatment, the group with invasive procedures suffered a heart attack or other event at a higher rate—5.3%—than the group receiving medical therapy only, at 3.4%, suggesting complications from the procedures, Dr. Hochman said.
Given the statistical imprecision, it was easy to various scientists to interpret the results differently. The following two quotations from Betsy McKay’s Wall Street Journal article argue for a change in medical practice (bullets added to indicate separate passages):
“You won’t prolong life,” said Judith Hochman, chair of the study and senior associate dean for clinical sciences at the New York University Grossman School of Medicine.
“This shows the safety of not panicking when you see a positive stress test,” said Jay Giri, a practicing interventional cardiologist and associate director of the Penn Cardiovascular Outcomes, Quality, and Evaluative Research Center at the University of Pennsylvania Perelman School of Medicine.
The results show “there is no compelling benefit to proceeding with these invasive procedures in people with stable symptoms as opposed to people with a heart attack,” [Steven Nissen, chief academic officer of the Heart and Vascular Institute at the Cleveland Clinic] said.
But this quotation interprets the study as support for the status quo:
Kirk Garratt, chief of cardiology at health system ChristianaCare in Wilmington, Del., and a past president of the Society for Cardiovascular Angiography & Interventions, said the study reinforces current practices for stable patients, and shows the benefits of procedures for people who are bothered by frequent chest pain. “People don’t want to be limited by their heart problems,” he said.
The two interpretive statements Betsy McKay quotes that seem most on target to me are these:
“Statins and aspirin are critically important,” [Judith Hochman] said. “We need to understand better how to get people to modify their risk factors.” Lifestyle changes can be hard to make and sustain, she said.
… large blockages, while frightening, don’t generally cause heart attacks, some research shows. They are caused instead more by ruptures in smaller, softer pieces of plaque that aren’t always visible on a scan.
Medicines have improved over the past several years and shrink those dangerous small plaques, said Steven Nissen.… “The reason medical therapy is triumphing is that it’s treating the entire artery,” he said. “This is a systemic disease, not a local disease.”
According to Betsy McKay, the drug and lifestyle changes urged in both arms of the study are “cholesterol- and blood-pressure-lowering drugs, smoking cessation and changes in diet.” She does not mention aspirin.
It is not considered a good idea to use statins, blood pressure drugs or aspirin if one has no risk factors. (If you want to try a little blood thinning, cinnamon or turmeric might be safer than aspirin.) But improvements in diet are safe enough to try before you have any symptoms. Of course, there is a great deal of debate about which direction is an “improvement in diet.” For my current views, see all of the other posts I have lined up links for here:
I hope to learn much more about the determinants of heart disease as I read more.