Washington, DC - An implantable stent designed to narrow the coronary sinus to redistribute blood from nonischemic to ischemic parts of the heart may prove to be a useful therapy in people with chronic refractory angina who cannot undergo coronary revascularization. Results from a pilot study suggest that implantation of a "coronary sinus reducer stent" is safe and feasible and may improve angina score and ischemia [1].

Dr Shmuel Banai (Tel Aviv Medical Center, Israel) et al report the results of their first-in-human study in the May 1, 2007 issue of the Journal of the American College of Cardiology.

The device used in Banai et al's study is the Coronary Sinus Reducer (Neovasc Medical, Or Yehuda, Israel), and it was developed on the basis of observations that increased pressure in the coronary sinus can help enhance perfusion of ischemic portions of the heart. The stent itself, introduced via the right internal jugular vein, is an hour-glass-shaped, stainless-steel, balloon-expandable stent, 3 mm in diameter at its mid portion but inflatable to a diameter of 7 to 13 mm at both ends. If necessary, the narrowed waist of the reducer can be expanded, making the stent tubular in dimension.

For their study, Banai and colleagues implanted the reducer in 15 patients with Canadian Cardiovascular Society (CCS) class 2 to 4 angina, despite optimal medical therapy, and reversible ischemia who were deemed unsuitable candidates for CABG or PCI. In all patients, implantation was successful, and no procedure-related adverse events occurred during or following the procedure, out to roughly 11 months; CT angiography showed all devices to be patent and in position. At six months, angina score as measured by questionnaire improved in 12 of 14 patients, while exercise stress test in patients showed improvements in ST-segment depression in six of nine patients. Exercise duration and peak heart rate also increased in nine of 11 patients. Imaging studies showed reduced extent and severity of myocardial ischemia.

"The present study has shown that the use of this new technique to establish a narrowing of the coronary sinus is feasible and safe," the authors write. "Whether or not the reduction in coronary sinus diameter and the increased coronary sinus pressure will subsequently improve collateral blood flow into ischemic territories of the myocardium, reduce ischemia, and improve symptoms of angina is still to be proven in a larger clinical study designed and powered to prove efficacy."

Commenting on the study for heartwire, Dr C Richard Conti (University of Florida, Gainesville) called the reducer stent "an interesting idea."

"Intuitively it makes some good physiologic sense," he said. "I don't know if they noticed this at all, but one of the things I would be concerned about is when you increase pressure in the coronary sinus, you're increasing back pressure into the heart muscle itself, and you'd wonder about whether some fluid was leaking out into the myocardium. . . . Edema is not a good thing in the myocardium or anyplace else."

Whether an invasive strategy might prove better than other existing therapies for refractory-angina patients, including enhanced external counterpulsation or spinal cord stimulation, remains to be seen, Conti pointed out, suggesting that randomized controlled trials of the device on top of optimal medical therapy are just the first step. Such trials could possibly involve having all patients undergoing coronary sinus stent implantation, but with the stent fully expanded in half the patients. Conti also pointed out that "best medical therapy " has also evolved, possibly setting the bar higher for new strategies to treat angina.

"Now we have a new kid on the block, ranolazine, and that's made some people feel pretty good who have so-called refractory angina," Conti said.