A coronary sinus reducer (CSR) may lead to a significant reduction in the number of angina episodes in patients with chronic chest pain, but it was not superior to a placebo device for improving myocardial blood flow, according to the results of the ORBITA-COSMIC study, presented during a Late-Breaking Clinical Trial session at ACC.24 and published simultaneously in The Lancet.

The investigator-initiated double-blind trial, conducted between May 2021 and June 2023 at six hospitals in the U.K., randomly assigned 51 patients (median age 67, 86% men, 49% White, 35% Asian) with symptomatic angina, ischemia and coronary artery disease with no further medical or interventional options to either a CSR implant or a placebo procedure. A total of 44 patients (86%) had a previous CABG and 28 (55%) a previous PCI. Their median left ventricular ejection fraction was 62%.

Participants used the Orbita app to record their angina symptoms for the next six months and they underwent exercise testing and a cardiac MRI immediately before the procedure and again at six months.

Results showed that the CSR did not improve the primary endpoint of stress myocardial blood flow in ischemic segments, with a between-group difference of 0.06 mL/min per g (95% credible interval –0.09-0.20; probability of benefit=78.8%). For the primary symptom endpoint of the number of daily angina episodes, patients who received the CSR device were 40% more likely to report a reduction (odds ratio, 1.4; probability of benefit=99.4%), with results first seen at 10 weeks and sustained to six months.

Angina frequency, a secondary endpoint, was also lower in the intervention group. Most of the patients who received the device did not experience complete elimination of angina symptoms but reported reductions in the number of daily pain episodes and the number of days on which they experienced pain. There was no difference in treadmill exercise time at follow-up. Patients who received the CSR implant had an improvement in the subendocardial to subepicardial ratio of stress myocardial blood flow and there was a detectable difference in this effect between ischemic and nonischemic segments.

The CSR device was found to be generally safe. Two patients in the CSR group experienced blood clots, but no myocardial infarctions or deaths occurred.

"For a patient, what they want to know is whether the device will help them to feel better. With the results of this placebo-controlled trial, we can tell them that their symptoms are more likely to improve with the reducer," said Rasha Al-Lamee, MBBS, PhD, lead author of the study. "However, we still need to work out why."

The study authors plan on further investigating the mechanisms of action involved and determine whether CSR implants may be more beneficial to certain subgroups. The CSR device is approved for use in Europe and the U.K., but it is not approved by the U.S. Food and Drug Administration and a trial is underway.

"Due to the small sample size, this result should be viewed as preliminary," commented ACC.org Editor-in-Chief Kim A. Eagle, MD, MACC. "A much larger trial would be needed to verify benefit."