Can’t Exercise for a Cardiac Stress Test? That’s a Bad Sign

One of the strongest predictors of long-term mortality among patients undergoing a cardiac stress test is the need for a pharmacologic versus treadmill test, new data show.

Moreover, although the risk of dying over a follow-up period of about 7 years increased along with the number of CAD risk factors and comorbidities present at the time of a pharmacologic stress test, a similar trend was not seen in patients who did a treadmill test, in whom the annual mortality risk remained below 1% throughout the study.

“Traditionally, we haven’t looked at long-term risk so much with people after stress testing, but over recent years, that has become more of a concern: how do people fare in the long term after stress testing as opposed to just the short term?” lead investigator Alan Rozanski, MD (Mount Sinai Morningside Hospital, New York, NY), told TCTMD.

This study, published recently online in Mayo Clinic Proceedings, adds to data supporting the benefits of exercise over the long term, he said. But also, he added, “it tells you that when people come in for stress testing, the mere ability to get on a treadmill and exercise versus needing pharmacological stress testing is one of the most important vital signs we have in terms of predicting patients’ risk.”

A More Comprehensive Look at Risk

Although prior studies have demonstrated a greater mortality risk in patients who can’t perform an exercise stress test, “to date, there is no knowledge as to how the mortality risk of stress testing patients is synergistically influenced by the comprehensive assessment of all the relevant potential modifiers of clinical risk,” the investigators say.

To help address this, they looked at data on 11,256 patients (mean age 61.3 years; 43% women) who underwent stress SPECT myocardial perfusion imaging between 2008 and 2017 and provided information on CAD risk factors (ie, diabetes, high blood pressure, and smoking) and comorbidity burden. Slightly under half (48.1%) required pharmacologic testing, with or without a walk, versus exercise testing according to the Bruce protocol.

Patients who underwent pharmacologic stress testing had more CAD risk factors and comorbidities and were more likely to have myocardial ischemia compared with those who were able to get on the treadmill.

In addition, over a mean follow-up of 6.7 years, those who could not perform treadmill testing were markedly more likely to die from any cause (19.2% vs 2.6%; P < 0.001).

We know that exercise is that magic pill. Alan Rozanski

After risk adjustment, the factors most strongly associated with mortality were age (HR per 5 years of 1.27; 95% CI 1.24-1.31) and pharmacologic testing (HR 2.35 with a walk and 4.61 without a walk).

Mortality risk increased along with a greater number of CAD risk factors and comorbidities, but only among the patients who underwent pharmacologic stress testing. In that group, the annualized mortality rate ranged from 1.4% for those with no risk factors or comorbidities to 7.7% for those at least two risk factors and two comorbidities. Among the patients who were able to perform a treadmill test, that range was much smaller—0.2% for those with no risk factors or comorbidities to 0.9% for those with multiples of each; the findings were similar when confined to patients 65 and older.

Asked how the ability to exercise during a stress test might influence mortality risk several years in the future, Rozanski said, “We know that exercise is that magic pill. When you are being physically active, you are [affecting] all of the physiological systems that benefit you. You decrease insulin resistance. You will improve the endothelium. You decrease your risk for atherosclerosis. You’re improving muscle conditioning and decreasing your risk for frailty.”

He and his colleagues acknowledge that these observational data cannot be used to conclude that the ability to exercise directly resulted in the low mortality risk in that group. “However,” they say, “the stark difference in the mortality risk of our exercise versus pharmacologic patients strongly suggests that maintained exercise ability provides a strong protective role in reducing mortality risk of patients with multimorbidity.”

Time to Tweak the Test Reports?

Rozanski said it’s time to adjust reports of stress test results to put a greater emphasis on what it means when a patient can or cannot exercise, noting that, currently, there is “a very reductionist approach” focused on whether a patient has ischemia.

A more holistic approach that encompasses information on both ischemia and overall clinical risk—including whether a patient was able to get on the treadmill and how much exercise they could perform—is needed, he indicated.

“What this would then lead to, if we improve reporting, is better shared discussions between doctors and patients,” Rozanski said, adding that getting patients to be more active improves not only their health, but also their health behaviors.

Just them not being able to exercise, it’s expected that it’d be a sicker population. Renee Bullock-Palmer

Commenting for TCTMD, Renee Bullock-Palmer, MD (Deborah Heart and Lung Center, Browns Mills, NJ), said she wasn’t surprised to see a strong relationship between a patient’s inability to exercise and a higher mortality risk. “Just them not being able to exercise, it’s expected that it’d be a sicker population,” she said, although she acknowledged that it was a bit surprising to see the association last for so many years. “The length of it just shows the strength of that marker of inability to exercise.”

She noted that when patients require a pharmacologic stress test, it’s appropriate to use PET imaging over SPECT whenever possible. “It has greater accuracy and can also look for triple-vessel disease, so you’re digging deeper in terms of the information that you’re able to get,” Bullock-Palmer said.

If PET isn’t available, she suggested, physicians might want to also look at coronary calcification. “Let’s say someone did a pharmacologic stress test, the perfusion is normal, but then their calcium score comes back as being 1,000. That’s someone that you really have to watch carefully,” said Bullock-Palmer. “And if they continue to have symptoms, you might even often send them to the cath lab, more so than someone who has no calcium in their arteries.”

As for whether the reports of stress test results should change, Bullock-Palmer pointed out that they already include information on whether patients were able to exercise. “But what you could add is that . . . in light of the fact that they are unable to exercise, that might be a more high-risk marker [and] these patients should be observed more carefully,” she said.

Bullock-Palmer added that there are some unanswered questions from this study, including whether there were any sex differences and whether performing calcium scoring after the stress tests might have changed the results.