ACC: Cardiac imaging & the elderly—expensive & a bad choice

SAN FRANCISCO—A controversy session focused on imaging senior patients reached the general consensus that not enough data exist to support MPI and cardiac CT in the elderly, according to a March 9 session at the American College of Cardiology (ACC) scientific session.

The demographic outlook shows a burgeoning geriatric population, said Michael A. Chen, MD, of the division of cardiology at University of Washington in Seattle. The population older than 65 years of age is expected to peak at 20 percent of the population in 2030. By that year, more than 19.5 million U.S. adults will be older than 80 years of age. Increasing age brings a dramatic increase in the prevalence of coronary artery disease, he continued.

Diagnosis of symptomatic coronary artery disease can guide therapy and lifestyle modifications, and myocardial perfusion imaging (MPI) can risk stratify patients into more conservative and aggressive therapy.

Chen fell into the pro-imaging camp and listed the benefits of MPI. Compared with exercise stress testing, MPI adds sensitivity and can localize ischemia, which can provide prognostic information, according to multiple trials. MPI also can inform risk stratification, Chen said.

The hitch, according to Chen as well as other presenters, is that most previous studies focused on middle-aged adults in their 50s and 60s rather than healthy elderly.

Chen referenced one study focused on approximately 1,000 people 80 years old and older. This population had higher event rates compared with younger patients. The researchers also demonstrated early cardiac catheterization and revascularization referral increased with increasing severity on MPI, which suggests physicians use MPI data to drive therapy, according to Chen.

Todd D. Miller, MD, of the department of cardiovascular diseases at Mayo Clinic in Rochester, Minn., disagreed with Chen and contended that MPI brings little proven value for risk assessment in the elderly. He acknowledged a review article focused on patients in their 70s and 80s suggested nuclear imaging could identify low-risk versus high-risk patients.

However, these data originated from retrospective registries. Numerous prospective studies in select groups have shown that MPI has no value in diabetics (DIAD), women (WOMEN) and general coronary artery disease patients (COURAGE). “When we go forward, the results aren’t so encouraging,” argued Miller.  

He reminded the audience of the conventional risk assessment pyramid that begins with clinical assessment and reserves stress testing for some patients and angiography for a subset of this group. In any clinical scoring system, age is the biggest driver for risk, Miller said. In addition, the paradigm is to look for severe disease and revascularize those with severe disease.

The key question, according to Miller, is if physicians can refer a high-risk patient for imaging and recategorize him or her as low risk. “We can’t reassure the elderly that they are low-risk based on a scan.”

He recommended cardiologists talk to older patients about what they want. Perhaps some are willing to undergo PCI, but most are not afraid to die and want to maintain quality of life, Miller said.

“Keep it simple and cheap,” he advised. If a patient shows signs of coronary artery disease, start with a trial of medical therapy. If the patient is refractory, send him or her to the cath lab, and consider PCI based on findings and the patient’s wishes. “Skip the stress test. It’s expensive and doesn’t help.”

Rita Redberg, MD, a cardiologist at University of California, San Francisco, expanded on Miller’s suggestion to include CT angiography and calcium scoring. “This kind of testing is a bad choice [for the elderly who present with chest pain],” she said. The imaging exams should not be performed to diagnose coronary artery disease and risk stratify the elderly.

Redberg agreed with Miller and acknowledged that the absence of data in the elderly is an issue. She also referred to basic principles of diagnostic imaging. These are:

  • Pre-test probability. Testing is most helpful in the intermediate pre-test probability group. Because age is a major risk factor in the elderly, once chest pain develops the patient can be considered high-risk and be treated accordingly.   
  • Diagnostic accuracy is lower in the elderly. The prevalence of coronary calcium in the elderly reaches 70 percent of patients in their 70s and 80 percent in the next decade of life. High pre-test probability translates in low diagnostic accuracy of CT angiography and calcium scoring in the elderly.
  • Post-test probability. The key question, according to Redberg, is how does the test refine the physician’s diagnosis and improve diagnostic confidence in either a negative or positive result. A negative result is less reliable in an elderly person, she said, suggesting most cardiologists would treat an elderly person with symptoms of angina and a negative scan.

“We are still looking for evidence to support calcium scoring and cardiac CT in the very elderly," Redberg said. "We want to know if it improves discrimination and adds to clinical assessment … and if it can be used to predict major events and guide therapy. Most importantly, is it associated with an outcomes benefit? The current answer is no.”