Coronary Artery Disease
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Coronary artery disease (CAD), or heart disease, is the leading cause of death in Canada and the U.S. The heart is a muscle that requires a constant supply of blood and oxygen in order for it to pump blood into the lungs and the rest of the body. It pumps blood to itself through blood vessels that go directly to the heart muscle. These are known as coronary arteries.
A gradual buildup of fat and cholesterol accumulate in the coronary arteries, forming a plaque that narrows the artery and reduces blood flow to the heart. This buildup can cause angina (chest pain) or a heart attack (blockage of an artery). Heart attacks, also known as myocardial infarctions, cause a part of the heart muscle to die leaving a weakness in the pumping function of the heart. If severe enough, it can lead to death.
There have been three major types of treatment developed over the past few decades when medication, diet and exercise fail. In bypass surgery, (A) the surgeon uses a vein (typically from the leg) and connects the vein above and below the blockage site. This bypasses the obstruction, improving blood flow to the heart and preventing more serious heart problems. Although this procedure is still commonly performed today, its expense and invasive nature present considerable drawbacks. In balloon angioplasty (B), developed two decades ago, a balloon-tipped catheter is inserted into an artery, and the balloon at the tip of the catheter is inflated, pushing the plaque back against the vessel wall. This widens or unblocks the artery to restore blood flow. Compared to bypass surgery, this treatment is relatively low risk, lower cost and much less invasive. However, angioplasty still carries a high rate of re-intervention due to restenosis. Forty percent of arteries reclose after the initial procedure. More recently, bare metal stents, (C) wire cages designed to prop open arteries after expansion by balloon angioplasty, were developed to improve this procedure. Unfortunately, bare metal stents still have significant room for improvement, with a failure rate between 25 to 40 percent due to restenosis.
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