Peripheral Artery Disease

Peripheral Artery Disease (PAD) is the narrowing or blockage of vessels that carry blood from the heart to the extremities. Caused by the buildup of plaque within the walls of arteries, PAD occurs primarily in the legs, but can be found in vessels throughout the body.1 Common PAD symptoms include pain, aching or cramping while walking (claudication) and non-healing ulcers or sores (critical limb ischemia). PAD is also a marker for significant cardiovascular morbidities and patients generally present with many co-morbidities.1

Initial treatment for PAD is through medication and lifestyle adjustments. More advanced cases are treated using invasive surgical bypass or minimally invasive interventional procedures. Patients with Critical Limb Ischemia (CLI), the most advanced patients, may have a combination of surgery (amputation) and interventional therapy.

Although angioplasty is often considered to be the leading interventional treatment for PAD, recent studies have revealed that angioplasty 12 month patency rates are estimated to be 30-50%.2 When angioplasty fails, stent implantation can help improve patency, but the underlying issues relating to the presence of calcification remain and stent placement reduces future treatment options. More recently, Drug Coated Balloons have been introduced to the market. Designed to target the inflammatory response caused by angioplasty, these have shown an improvement in the patency of standard lesions but are known to be significantly less effective in the presence of calcification.3

Peripheral Artery Disease and Calcium

As patients with PAD live longer thanks to improved therapeutic options and lifestyle changes, the plaque in their arteries mineralizes and becomes calcified. Over the last few decades, the prevalence of calcified lesions has risen along with life expectancy, with severe calcium being present in as many as 60% of patients with PAD.3 The incremental nature of improvements to devices available to treat these lesions has resulted in calcium becoming a significant obstacle to achieving successful outcomes.

The most common device used to treat calcified lesions is a standard balloon dilatation catheter, often deployed at very high constant pressure. Unfortunately, the physics of constant high pressures in the presence of calcium preferentially targets, or damages, soft tissue leading to elastic recoil, dissections and frequently requires a bailout stent. This has been known to occur in up to 60% of standard lesions, and may occur even more often in calcified lesions.4

Over the last 20 years several technologies have been developed in an attempt to overcome these shortcomings, some incremental such as scoring and cutting balloons, and others more dramatic and severe such as atherectomy. Each of these fails to address the fundamental need: effective dilation of calcified lesions while limiting vascular injury and complications such as perforations, distal emboli, and the need for bailout stenting.

Lithoplasty Technology Solution for PAD

Shockwave Medical leveraged the power of Lithoplasty® Technology to develop devices for the treatment of calcified peripheral vascular lesions. Built on a semi-compliant balloon platform, each catheter incorporates multiple lithotripsy emitters activated (with the touch of a button) while the integrated balloon is inflated to low sub-nominal pressures. Once activated, these emitters produce pulsatile mechanical waves that are inherently tissue-selective, passing through the balloon and soft vascular tissue, preferentially disrupting the calcified plaque by creating a series of micro-fractures. Once the calcium has been disrupted, the vessel can be effectively dilated using low pressures thereby enabling even historically challenging PAD patients to be treated effectively and with minimal injury to the vessel.5

In an initial peripheral clinical study of 99% moderate and severely calcified lesions, Lithoplasty Technology demonstrated ease of use, minimal interruption to procedure flow and an excellent safety profile. Treatment with Lithoplasty Technology resulted in a low residual stenosis of 24% and with only 1 stent implanted. Click here for more information.

The technology is inherently familiar, easy to use, operates with just the push of a button, and works seamlessly with existing cardiovascular treatments. And because it is built on a traditional balloon catheter platform, it is compatible with clinicians’ existing workflow.

Product Details

Peripheral Lithoplasty Balloon Dilatation catheters are available in diameters ranging from 3.5mm to 7.0mm. Standard balloon techniques, integrated proximal and distal markers and predetermined Lithoplasty Technology settings ensure the catheters can be prepared, delivered, accurately placed and activated with minimal disruption to standard procedure flow.

Miniaturized lithotripsy emitters apply intermittent pulsatile pressure waves along the length and diameter of the balloon. Activated under low pressure (4 atmospheres), these pressure waves selectively disrupt calcified lesions, after which the balloon can be dilated to reference vessel diameter.

DIAMETER (mm) LENGTH (mm) GUIDEWIRE COMPATIBILITY (in) SHEATH COMPATIBILITY WORKING LENGTH (cm)
3.5 60 0.014 6F 110
4 60 0.014 6F 110
4.5 60 0.014 6F 110
5 60 0.014 6F 110
5.5 60 0.014 6F 110
6 60 0.014 6F 110
6.5 60 0.014 7F 110
7 60 0.014 7F 110
Summary of Treatment Options for PAD and Calcium
TREATMENT DESCRIPTION Impact on Calcium
Surgical Bypass
  • A graft connects above and below a blockage, creating a new path for blood to flow.
  • Can completely bypass calcified lesions but calcium in the artery may limit proximal starting and distal landing zones.
Angioplasty
  • A catheter with a balloon in its tip is advanced to reach the narrowed or blocked artery.
  • The balloon is inflated, widening the vessel by pushing the plaque against the artery wall.
  • Cutting or scoring balloons could be used in place of standard balloons to cut into soft tissue.
  • This could be supplemented with the use of a Drug Coated Balloon to reduce the inflammatory response of the vessel due to the injury caused by angioplasty.
  • Excessive force transfers to soft tissue leads to elastic recoil, poor lesion expansion and frequent dissections, requiring stent placement for efficacy or bailout reasons.
  • Scoring or cutting elements have limited effectiveness in calcified lesions.
  • DCB have not been shown to improve patency rates in calcified vessels.
Stenting
  • A stent is a tiny mesh tube that is placed inside an artery, often after angioplasty, to help keep the vessel open.
  • Stents are designed to remain in the blood vessel indefinitely.
  • Can be difficult to deliver in highly calcified lesions.
  • Insufficient radial strength may lead to suboptimal luminal gain.
  • Increased risk of stent fracture.
  • Permanent implant limits and adds complexity to future treatment options.
Atherectomy
  • Extracts atherosclerotic plaque through sanding or shaving of vessel tissue.
  • Can be acutely effective in superficial calcium, but neglects the deep calcium that impacts vessel expansion.
  • Extensive soft tissue removal creates significant vessel injury and increases the risk of vessel perforation and distal embolization.
  • Difficult to use, interrupts procedure flow. Complicated and lengthy procedures requiring specialized training and a change to normal procedure flow.
Lithoplasty Balloon Dilatation Catheters
  • Harness the power of Lithoplasty Technology to disrupt calcium.
  • Semi-compliant balloon catheters with multiple lithotripsy emitters along the length of the balloon.
  • Delivers pulsatile mechanical energy that disrupts both superficial and deep calcium.
  • Pulsing occurs at sub-nominal pressures followed by dilatation to reference vessel diameter.
  • Pulsatile mechanical energy is inherently tissue-selective, disrupting calcium while minimizing injury to soft tissue.
  • Low-pressure dilatations avoid injury to vessel walls while maximizing luminal gain.
  • Familiar balloon-based technology is compatible with clinician’s existing workflow.
  1. Centers for Disease Control and Prevention. Peripheral Arterial Disease in the legs, http://www.cdc.gov/DHDSP/data_statistics/fact_sheets/fs_PAD.htm.
  2. Rocha-Sinh KJ1, Jaff MR, Crabtree TR, Bloch DA, Ansel G; Viva Physicians, Inc. “Performance goals and endpoint assessments for clinical trials of femoropopliteal bare nitinol stents in patients with symptomatic peripheral arterial disease.” Catheter Cardiovasc Interv. 2007. May 1;69(6):910-9.
  3. F.Fanelli et al.: Calcium Assessment and Impact on DEB. Cardiovasc Intervent Radiol (2014) 37:898-907
  4. Tepe et al.; Drug-coated Balloons and SFA Lesions, Circulation 2015;131:495-502
  5. Levin S. “Shockwave Medical: Cracking the Calcium Code in Cardiology.” The MedTech Strategist, 2015 Aug 12; 12(2):30-37.