Calcium that builds and blocks the arteries of the heart is the sworn enemy of interventional cardiologists (doctors specialized in the treatment of cardiovascular disease through catheter-based procedures). In fact, the level of calcification has a direct influence on the success rate, length and risk of complications of the nonsurgical procedure to clear completely blocked arteries, better known as a chronic total occlusion (CTO) angioplasty.
However, a guide wire being tested for the first time at the McGill University Health Centre (MUHC) could help practitioners overcome the technical challenges of this procedure, making it not only faster and easier, but also safer for the patient. The new device could lower the risk of complications and the need for open heart surgery (bypass surgery).
“This wire could mean the difference between the success and failure of a CTO angioplasty because it will be able to break through areas where other guides fail to penetrate. It will clear the way and allow us to treat the diseased artery,” says Dr. Stéphane Rinfret, chief of Interventional Cardiology at the MUHC and a physician specialized in complex angioplasties.
Shock waves to break the calcium wall
Between 10 and 50 per cent of all CTO angioplasties — depending on the level of expertise of the practitioner — are unsuccessful, primarily because ordinary wires can’t break through the wall of calcium. The new technology could allow operators to overcome this problem.
Developed by the Quebec-based company SoundBite, the SoundBite™ Active Wire is a guide wire that is connected to a shockwave generator. Working like a jackhammer, the device can break through the arterial blockage in a controlled way while leaving the walls of healthy vessels unharmed. Another version of the guide wire was used for the first time in December 2016 during a procedure performed by colleagues at the Centre hospitalier universitaire de Sherbrooke (CHUS) to clear the arteries of the leg.
A potentially indispensable tool
According to Dr. Rinfret, who is also an associate professor of medicine at McGill, the new guide wire could become an indispensable tool for interventional cardiology because it usage is within the capabilities of less experienced practitioners.
“Only five per cent of the angioplasties performed in Canada are for a CTO because many practitioners aren’t trained in the most advanced and complex techniques. This new technology could help make more effective and skilful.”
The SoundBite Active Wire will be tested as part of a two-year study that will recruit 150 patients in Canada and the United States.
CTO and CTO angioplasty
- CTO is a chronic total obstruction of a coronary artery that has been present for more than three months. It affects about 20 per cent of patients suffering from coronary atherosclerosis.
- CTO angioplasty consists of opening the completely blocked artery to insert a catheter with a small balloon at the tip which widens the artery. This procedure improves patient quality of life, reducing shortness of breath and chest pain. Only 36 per cent of CTOs are revascularized (26 per cent by bypass open-heart surgery and 10 per cent by angioplasty).
- At the MUHC, which is a centre of high expertise and high volume in the percutaneous treatment of the CTO, more than 50 per cent of the patients treated in order to clear a CTO have already undergone bypass operations. Since the leg veins used in this type of surgery can also become diseased or clogged, a second treatment may be necessary. For these patients, another bypass surgery wouldn’t be the best option.
- 300,000 patients in North America could benefit from this technology.