Differences in exercise duration for patients with stable angina who received either PCI or a placebo treatment were not statistically significant, according to research presented Nov. 2 at the annual Transcatheter Cardiovascular Therapeutics (TCT) scientific symposium and published simultaneously in The Lancet.
The ORBITA trial, a randomized, blinded, placebo-controlled study, analyzed 105 patients in the PCI arm and 91 in the placebo arm. All patients had coronary stenosis of at least 70 percent in a single vessel and were deemed suitable for PCI. Researchers assessed the patients via treadmill tests, dobutamine stress echocardiography and quality of life assessments both pre-randomization and six weeks after the procedure.
Exercise time increased from baseline to six weeks by a mean 28.4 seconds in the PCI group and 11.8 seconds in the placebo group. The trial was designed to detect a difference of 30 seconds between the groups.
“Despite PCI markedly improving hemodynamic and imaging indices, there was no significant difference between PCI and placebo in exercise time increment,” said co-investigator Rasha Al-Lamee, MD, from Imperial College London. “This first placebo-controlled trial of PCI for stable angina suggests that the common clinical observation of symptomatic improvement from PCI may well contain a placebo component.”
There were no significant differences for health-related quality of life measures, although improvement was noted in both arms. The PCI group showed a significant reduction in ischemia compared to the placebo group.
Although the results of the study make a provocative suggestion—that a placebo effect plays a role in post-PCI recovery—physicians not involved in the research questioned the validity of the findings.
“These patients had a very good baseline exercise capacity so to show an incremental difference would be difficult,” said Martin B. Leon, MD, with Columbia University Medical Center/New York Presbyterian Hospital.
Also, the small sample size, short duration of follow-up and intensive medical therapy received by both groups could have factored into the outcomes.
“I just think people need to understand the limitations,” Leon said. “If they understand the study, then it can lead to some interesting conversations.”
In a statement, Kirk N. Garratt, MD, MSc, president of the Society for Cardiovascular Angiography and Interventions, defended the use of PCI in these patients.
“The number of patients studied was very small, so the study is far from conclusive,” Garratt said. “The primary endpoint used, exercise tolerance, is imprecise and very subjective. Patient tolerance of exercise normally varies from week to week, so differences of a few seconds in exercise tolerance are hard to interpret. Despite this, the improvement in exercise time among PCI patients was almost 2.5 times greater than in sham patients, suggesting PCI led to incremental improvement.
“The most objective measure of ischemia relief in ORBITA was a secondary endpoint of heart performance called the DSE peak stress wall motion score index. This measure was significantly improved by PCI over sham treatment. Since PCI provides benefit by relieving ischemia, this test proved that PCI worked, and can provide added benefit even with optimal medical therapy.”
Al-Lamee, in part, agreed with the concerns raised by fellow doctors. She said the trial shouldn’t be interpreted as a knock against PCI, but as a way to spur patient-centered discussions about PCI or optimal medical therapy for people with stable angina.
“I think it would be very easy to take the results of this trial and over-extrapolate them,” she said. “To use this to downgrade angioplasty in the guidelines, and I say this as one of the investigators, would be an incredibly large overreach.”