What is Coronary Arterial Disease (CAD)?

What is Coronary Arterial Disease (PAD)?

Coronary artery disease (CAD) is defined as an obstruction of blood flow in the arteries that supply the heart muscle, the coronary arteries. This clinical condition is characterized by plaque accumulation and gradual narrowing of the coronary arteries, which is known as stenosis. Advanced CAD and progression of plaque accumulation may result in the formation of complete blockage of a coronary artery. Once complete this lesion is referred to as a total occlusion. When a total occlusion extends for of duration greater than 3 months it may be considered “chronic”, and is then referred to as a Chronic Total Occlusion (CTO).

Risk factors for CAD are similar to the risk factors associated with peripheral arterial disease (PAD) and include smoking, diabetes, hypertension, hyperlipidemia and a family history of vascular disease.

Predominant symptoms of coronary artery disease include stable angina pectoris (chest pain or discomfort), unstable angina pectoris, and myocardial infarction. CAD can also contribute to heart failure due to weakening of the heart muscle. Symptomatic CAD is a common clinical condition and is a major cause of death and disability in developed countries, counted for about one-third of all deaths in individuals over age 35.

What are Chronic Total Occlusions (CTO)?

CTOs, defined as arterial obstructions lasting more than 30 days, are frequently found in patients with advanced coronary and/or peripheral arterial disease. These arterial occlusions are mainly composed of smooth muscle cells, connective tissue, calcium, thrombus, lipids and inflammatory cells.

Chronic total occlusions in the coronary arteries may be more in excess of 5cm, whereas the length of peripheral occlusions may exceed 20cm. CTOs are often heavily calcified or extremely fibrotic, therefore the treatment of such lesions is considered highly challenging.

In the coronary vasculature, the most commonly occluded arteries are the left anterior descending artery (LAD,) the right coronary artery (RCA) and the circumflex artery (LCX). The superficial femoral artery (SFA) is the most commonly diseased artery in the peripheral vasculature, partially because it is the longest artery in the human body, running the length of the thigh toward the knee. CTOs of the SFA present in up to 50% of the patients treated for peripheral PAD.

Why open a CTO?

CTO crossing and blood flow restoration are essential for improved blood supply and perfusion in the effected tissue. All CTO revascularization techniques aim at reducing or eliminating the clinical symptoms associated with the disease, thereby improving patient quality of life and reducing the need for more aggressive treatment.

In coronary cases, opening of the CTO is associated with reduced angina, improved left ventricular function and prolonged survival, while in peripheral patients the CTO opening is associated with reduction in claudication, cramping and pain and can prevent amputation of the effected limb. 

What are the treatment options for CTO?

Treatment strategies include medication, lifestyle modification, endovascular techniques and/or bypass surgery. Lifestyle modification and medication are advised for moderate PAD, however they have limited efficacy in treating a CTO. Endovascular therapy is the treatment of choice for many stenotic or occlusive lesions; however by-pass surgery is still the recommended treatment option for extremely long and/or calcified lesions. 

What is endovascular therapy?

Endovascular therapy is a minimally invasive technique where a physician gains access to the arterial vasculature via a single puncture site, usually the femoral artery. The equipment used during the revascularization procedure is advanced by the physician from the access site via the arteries toward the occluded artery. Endovascular techniques for CTO crossing typically require the use of guidewires – long metal wires less than 1mm in diameter. Crossing the occlusion with a guidewire is a prerequisite for opening the occluded artery. Following successful guidewire crossing, adjunctive therapies such as balloon dilatation or atherectomy are often used to expand the vessel lumen. Guidewire positioning distal to the occlusion may also be achieved by sub-intimal crossing. Sub-intimal crossing is a technique in which the vessel wall is deliberately dissected to allow guidewire advancement. The main challenge of this technique is the ability to re-enter into the vessels true lumen after tangential passing of the occlusion. Sub-intimal crossing will often result in uncontrolled guidewire advancement well beyond the target lesion, thus requiring sub-intimal angioplasty or stenting beyond the occluded segment.

Why is there a need for a crossing device?

Success rates of endovascular CTO procedures are highly variable and largely dependent upon lesion morphology and operator experience. Recanalization of CTOs in the peripheral vasculature has a failure rate of up to 30% when using traditional guidewire and balloon technology, whereas the failure rate of coronary CTO procedures can be as high as 50%. The main reason for failure is the inability to cross the occlusion with a guidewire or inability to re-enter the true lumen following sub-intimal crossing (xi,xii). Crossing devices are intended to improve the safety and effectiveness of endovascular therapy for CTOs, potentially reducing the need for by-pass surgery.

What is the ENABLER-P Balloon Catheter System?

The ENABLER-P Balloon Catheter System is designed to facilitate the intraluminal advancement of standard guidewires beyond chronic total occlusions in the peripheral vasculature.

See Technology page for detailed description and animation.

References

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