BARCELONA, Spain – Two out of 10 cases of percutaneous coronary stenting come to a fork in the road where the interventionalist needs to make a decision about how to treat a tricky situation.
This juncture, literally where a side artery branches off the main artery, challenges the limits of today's tubular stents with a demand for a Y-shaped geometry.
"There is not a standard for care for treating a bifurcation and physicians are doing their best with the tools that are out there," said H. Richard Davis, chief engineer of the Side Branch Stent for Tryton Medical (Durham, North Carolina), which proposes a novel solution to the problem.
Mark Paquin, MD, who leads physician training for the new Sideguard stent for Cappella Medical Devices (Galway, Ireland), said, "there are currently 11 companies vying in this space using what can be called provisional stenting of the main artery, and now there are two of us, Capella and Tryton, bringing a new approach to stenting the side branch."
In a global market estimated at 500,000 cases annually, the interventionalist places a traditional stent in the main artery crossing the junction with the side branch much like parking a semi-trailer truck in the center of an intersection.
The physician then employs a wait-and-see strategy, watching whether this action of placing the sieve-like stent provokes a change in the blood flow into the side artery.
If the condition seems improved, no further action is taken, and three times in four, this operation is good enough to improve the outcome.
The other 25% of patients are called back to the cath lab for a more serious procedure to address the problem.
Add to this population the 20% of cases that are too serious for a provisional solution and a clear unmet medical need emerges.
To this point the accepted practice for amore serious approach is to place two separate stents and join them together with equally provisional techniques such as crushing, culotting and cutting holes in the wire mesh.
Both Tryton and Capella have each engineered a more advanced approach to meet the challenge that while following the physicians' logic of joining two stents, proposes novel sequence of first anchoring a short segment in the side artery.
Both companies then allow the interventionalist to use any preferred bare metal or drug-eluting stent for the main artery.
Both companies recently received the CE mark.
Tryton: A paradigm shift
"For interventionalists, saving the main artery is the priority at a bifurcation, and on its face it seems to be the practical approach," said Davis, who is a patent holder on the Side Branch Stent from Tryton.
"What is unique with Side Branch is that we shift the paradigm by suggesting the physician treat the side branch first, focusing on the ostium," the opening to the side branch that forms the forked intersection.
A 17 mm to 18 mm cobalt chromium stent, the short leading end of Side Branch is a conventional stent-strut design that anchors this piece of the puzzle to the side branch vessel walls using a standard single-wire balloon-expandable stent delivery system.
The stent then features a mid section, or transition zone, with a more open strut architecture to continue lending radial strength before ending in a third zone that features the most minimal strut design to offer an open architecture as it enters the main artery so that a conventional stent can be tracked through and then expanded to join the two pieces together in a penultimate "kissing post-dialation bifurcation."
The company received a first CE mark in February, but following design enhancements for manufacturing of the full package of catheter and guide wires, received final CE approval in April, according to Davis.
The Side Branch concept and the company was founded in 2003 by Aaron Kaplan, MD, and the venture capital firm Spray Venture Partners (Newton, Massachusetts). The company remains privately held with additional investments from PTV Sciences (Austin, Texas), and RiverVest Ventures (St. Louis).
Introducing the product at the European Bifurcation Club in Prague (Medical Device Daily; Sept. 29, 2008), CEO Greg Davis said the stent will be available first in the Netherlands through TOP Medical, with additional European countries to follow.
The Side Branch has enjoyed the support of leading European interventionalists, with Patrick Serruys, MD, of Erasmus Medical Center in the Netherlands, presenting six-month clinical and angiographic results from the Tryton 1 First-In-Man study.
Serruys concluded that the core angiographic data demonstrated the hybrid approach of a bare metal Side Branch stent in conjunction with a standard drug-eluting stent, "provides the same type of restenosis reduction we have seen when drug eluting stents are used to treat standard lesions. This is the first time I have seen such promising results in the treatment of bifurcation disease."
Sequential T-stenting for bifurcations
With a rollout planned for June in Italy and a staged ramp up set for Germany followed by the UK, Cappella may be the first of the two side branch stenting competitors to score sales.
"We are registered for reimbursement in Italy as 'stent other,' which means we will get our price and are now working with reference hospitals and practitioners," said Paquin.
Cappella's Sideguard is a nitinol stent that anchors in the side branch as a conventional stent would, but is flared with a trumpet-shaped proximal end extending into the main artery.
A conventional, or "workhorse," stent is then placed in the main artery and expanded by balloon dialation.
Two guidewires are reintroduced, one into each stent and simultaneous inflation, or double kissing, creates an aperture in the main stent against which the flared proximal end of the Sideguard is secured.
The three-stage technique, called sequential T-stenting, assures a maximal ostial coverage according to Antonio Colombo, MD, a company co-founder who presented the procedure at a EuroPCR 2009 session chaired by Eberhard Grube, MD, a leading interventionalist who is head of the department of cardiology and angiology at Heart Center Siegburg in Germany.
"There is no crushing or distortion of the stents with this technique," Paquin said.