Development of a Novel Angioplasty Catheter for Treatment of Calcified Arteries

Coronary artery disease is very common, has significant associated morbidity and mortality, and is frequently treated by balloon angioplasty. Coronary artery calcification is highly prevalent in coronary artery disease and poses a significant challenge to angioplasty procedures. In 2012, 1.1 million angioplasty procedures were performed in the US; 38% of which involved moderate to severe calcification. Coronary artery calcification can prevent effective coronary artery dilation during balloon angioplasty leading to incomplete expansion of coronary stents; a well-established risk factor for major adverse cardiovascular events, including stent thrombosis and restenosis. Use of higher balloon pressures to crack the calcification increases the risk of complications and damage to the artery. Extensive coronary artery calcification frequently precludes angioplasty leading to coronary artery bypass grafting; a costlier alternative. Coronary artery calcification increases in prevalence with age and in older patients in which the risks of coronary artery bypass grafting may be prohibitive. We seek to address this unmet need. We have prototyped a novel device capable of delivering impacts of variable frequency and energy to sites of calcification. Such impacts lead to micro-fractures in vascular mural calcification and subsequently enable traditional angioplasty balloon dilation and stenting techniques to proceed unhindered. The proposed solution would enable the interventional cardiologist to render angioplasty in calcified coronary arteries much more predictable and therefore safe. As a standard over-the-wire technology, little additional training would be needed and minimal procedural time required to site, deploy, activate and retreive the device. Induction of micro-fractures within the vascular mural calcium would then allow safe, predictable low-pressure vessel expansion during standard balloon dilation and subsequent stenting. This approach will also potentially allow extension of the indications for angioplasty procedures into populations where calcification is currently deemed too extensive for angioplasty, particularly in the older population where calcific disease has a high prevalence but co-morbidities preclude open heart surgery.

Coronary calcification is an inherent element of atherosclerotic coronary disease which poses significant challenges to percutaneous coronary intervention (PCI) procedures. Vascular mural calcification can prevent effective coronary dilation or lead to incomplete expansion of coronary stents. Extensive coronary calcification at present may preclude a PCI approach necessitating either open heart surgery or a palliative medical strategy. The number of procedures with coronary calcification is increasing as coronary intervention moves into an older population. We seek to address this need with a novel PCI compatible device.
Currently two technologies are in use both having either limited efficacy or require training in a unique complex skillset not familiar to the majority of operators. Scored or 'cutting' balloons are bulky and delivery into calcific lesions is frequently impossible. Rotational atherectomy or rotablation is a technology where a rotating diamond coated burr is introduced to disrupt coronary calcification. Rotablation is effective but requires specific training distinct from traditional PCI techniques. It is notable that although this technology has been available for many years, the proportion of trained operators remains low. Both methods are associated with increased complication rates due to vessel injury, dissection and perforation.
It is known from elementary mechanics that impulses can produce a great amount of force over a short time interval. This is the functional principle that instruments like impact hammer or impact wrench work very well. It is also well know from fluid mechanics that incompressible fluids can be used as a medium for rapid and efficient power transmission. Such fluids have been used in familiar hydraulic jacks. We propose to adapt these technologies to develop a catheterised device enabling localised endovascular therapy at a controlled depth and energy for disrupting the vascular calcium to facilitate subsequent PCI

Our impact strategy is based around three primary beneficiaries: patients/doctors; health service providers and UK academic and industrial medical devices developers. Through transformation of the current treatment paradigm for the management of patients with calcific vascular disease, we will work during and beyond the duration of this grant to deliver this impact through the successful development, commercialisation and dissemination into clinical practice of our novel device solution.
Beneficiaries:
Patients and doctors will benefit due to the development of a more effective treatment strategy for the percutaneous treatment of calcific vascular disease. This is particularly pertinent as the combination of an aging population in Western healthcare markets coupled with the effect of preventative treatments for atherosclerotic disease, means percutaneous vascular procedures such as percutaneous coronary intervention (PCI) are moving into an increasingly elderly and multimorbid population where calcific vascular disease is highly prevalent. This is also the population where co-morbidities often preclude coronary artery bypass grafting (CABG). PCI in calcific vessels is challenging with an increased risk of complications, prolonged procedure times (and costs) and frequent procedure failure. Also of relevance is the added importance of adequate lesion dilation with the increasing trend toward bioabsorbable vascular scaffolds (which have less radial strength compared to traditional metal stents). Current device solutions are either of limited efficacy and predictability (e.g. cutting or non-compliant balloons) or require specialist equipment and operator training preventing broad adoption (e.g. rotablation and laser). Our device solution will make PCI in calcified vessels safer and simpler leading to a more successful and predictable outcome.
Patients will benefit from shorter and simpler procedures with a lower risk of complications. Effective treatment (not previously possible in many patients) will lead to reduced symptoms, less drug related side-effects and improved exercise capacity (e.g. due to reduced angina), leading to enhanced quality of life and reduced care needs. There is also potential for societal benefits (through reduced disability and increased potential for employment). Furthermore, as experience of using the device in clinical practice progresses, some patients currently referred for high risk CABG due to the current challenges of PCI in extensive calcific disease will become amenable to device assisted PCI. This will likely reduce operative risk.
Clinicians will benefit from simplification and shortening of the PCI procedure in these patients and a reduction in the procedural complications inherent to existing approaches. By basing the device on existing over-the-wire catheter technologies, it will be easy to use for operators familiar with intravascular procedures without the need for additional training.
Health service providers will benefit through cost savings. These will arise because of more effective percutaneous management of calcific vascular disease. This will improve patient symptoms therefore reducing medication requirements (and consequential side effects) and clinical care requirements, including clinic assessment and admissions to hospital for inadequately controlled angina. There may be additional PCI costs savings due to shorter more predictable device-assisted PCI procedures with fewer complications, less equipment utilisation and a reduced post procedural length-of-stay. Also there will be cost savings from patients whose previous management would have been with high risk CABG (where prolonged ITU and hospital stay is likely) but whose disease will be amenable to device-assisted PCI. UK academic and industrial medical device developers will benefit through market advantage and provision of a developmental model for other academic, SMEs or industrial partners .