Chocolate® angioplasty balloon for the treatment of atherosclerotic lesions of the lower limbs

The most common symptom of peripheral arterial disease (PAD) is intermittent claudication, but noninvasive measures, such as the ankle-brachial index, show that asymptomatic PAD is several times more common in the population than intermittent claudication.

PAD prevalence and incidence are both sharply age-related, rising >10% among patients in their 60s and 70s. With aging of the global population, it seems likely that PAD will be increasingly common in the future. Prevalence seems to be higher among men than women for more severe or symptomatic disease.

The major risk factors for PAD are similar to those for coronary and cerebrovascular disease, with some differences in the relative importance of factors. Smoking is a particularly strong risk factor for PAD, as is diabetes mellitus, and several newer risk markers have shown independent associations with PAD. PAD is strongly associated with concomitant coronary and cerebrovascular diseases.

After adjustment for known cardiovascular disease risk factors, PAD is associated with an increased risk of incident coronary and cerebrovascular disease morbidity and mortality. 1 Angioplasty is the mechanical alteration of a narrowed or occluded vessel lumen.

The word derives from the roots “angio” or vessel and “plastics” or fit for molding. Nowadays it is used to describe a variety of percutaneous vascular interventions. Percutaneous transluminal angioplasty (PTA) is used to describe angioplasty of vessels other than the coronary arteries. Charles Dotter introduced transluminal angioplasty in 1964.

By using progressively increasing sizes of catheter he was able to dilate stenosed leg arteries. Andreas Gruentzig performed the first balloon angioplasty of a human peripheral artery in 1974. PTA has been most commonly used to treat iliac and leg arteries with atherosclerotic disease.

The progression of expertise and equipment has expanded the use of PTA to all vascular beds, both venous and arterial. In many situations stenting has become the treatment of choice for completing percutaneous procedures; however, there remain clinical situations where PTA alone is acceptable if not preferred.

The application of peripheral balloon angioplasty exerts a centrifugal force from within the vessel lumen. This force is delivered via a balloon that is inserted percutaneously and inflated adjacent to the treatment area. The outward radial force, called hoop stress, stretches or separates the components of the vessel wall.

This radial force is a product of the pressure applied and the area against which it is applied. In treating peripheral arterial diseases (PAD), stent placement to restore and maintain the patency is a viable treatment option and its results are superior compared to plain balloon angioplasty (BA) in terms of long-term patency and target-vessel revascularization (TVR). 2,3 However, patency rate using stent for the femoropopliteal (FP) arterial disease was still disappointing despite the continuous remarkable improvement of stent technology.

Stent fatigue and fracture problem of implanted stents for the younger patients and longer requirement of antiplatelet therapy for elderly patients might be the important problems which could not be ignored.

Consequently, there was a need for novel treatment option with better treatment outcome compared to stent angioplasty. Recently, drug coated balloon (DCB) have been introduced with very promising results that work without vascular irritation with additional anti-proliferative effect directly towards the vessels. However, bailout stenting rates were reported as high as approximately 60%,  and most of them required stenting because of dissection.

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Recently, favorable outcome data was shown with several studies using Chocolate® balloon with reduction in bailout stenting rate. Chocolate® balloon catheter (Medtronic©, Santa Rosa, USA) is a novel concept of angioplasty device characterized by a mounted nitinolconstraining structure, allowing uniform inflation and rapid deflation (Fig.1).

The attributes of the nitinol-constrained balloon are designed for modulated dilatation and creation of small balloon segments (so called ‘‘pillows’’), intended to minimize balloon elongation during angioplasty and radial stress on arterial walls, reducing vessel damage. 6 The Chocolate PTA Balloon Catheter is an over-thewire balloon dilatation catheter that is compatible with 0.014- and 0.018-inch guidewires.

It is available in sizes to treat both above (ATK) and below-the-knee (BTK) lesions with balloon diameters of 2.5–6 mm, balloon lengths of 40–120 mm, and catheter lengths that range from 120 to 150 cm.

The design of the Chocolate® balloon catheter includes a braided catheter shaft designed to provide robust push to reach and cross lesions, grooves to allow for plaque release, minimizing traumatic angioplasty effect, pillows to provide predictable vessel dilation without cutting or scoring, the tapered tip to enable lower entry profile for optimal lesion access and a nylon, semi-compliant balloon to allow for optimal balloon pillow formation. Nitinol-constraining structure shields vessel wall from shear (torsional) stress caused by balloon unfolding, enables the even distribution of radial and longitudinal forces during balloon inflation, and allows for rapid deflation and uniform rewrap.

From a speculative point of view, the use of a nitinol-constrained balloon, with its force fraction proprieties, can allow for a better vessels expansion, and a homogeneous drug distribution with (DCB dilatation).

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