By Isaac Levine, Shivam Kaushik, and Deepak Iyer

Historical:

Long before Dr. Seldinger and Dr. Dotter went to work, the first iterations of the catheter began to find their way into clinical care. In fact, the concept of catheters have existed for centuries.

The ancient Greeks would create thin tubes made of materials they could find (gold, silver, brass, etc) to try and treat urinary difficulty and discomfort. They would modify the wire until they were able to make it work. Centuries later in America, Benjamin Franklin began to tinker with the invention to treat his brother’s kidney stone. At this point in time, catheters served a very niche purpose of treating urological conditions. It wasn’t until the 1800s when catheters became sized upon realization that poorly sized catheters can cause abrasions that promote bacterial infections as well as advancements in available technology. In the early 20th century, the indwelling Foley Catheter was invented and has since become a standard form of treatment, subsequently disrupting the biomedical device industry. Since then, the indications for catheters have increased dramatically. In 1923, the first angiography was performed on a human body, and the technology associated with this historic concept has improved dramatically ever since1-3.

Within the past few decades, the catheter has undergone a variety of improvement due to increased research and technological advancements within the industry. In 1964, Dr. Charles Dotter pioneered the field of IR by performing percutaneous angioplasty4. Since then, there have been a variety of iterations of the technology such as soft double-lumen catheters. Further applications of the catheter have also been created allowing for innovative solutions to major medical problems. For example, transjugular intrahepatic portosystemic shunts have been a mainstay for the field of IR to treat portal hypertension since 19674,5. Catheters are now used in the field of IR to treat non-vascular indications such as diseases of the pancreas, kidney, and spinal cord. In this highlight of catheter innovations, we hope to explore some of the current advancements in catheter innovation.

Current:

What are commonly used catheter options these days?
  • Selective vs. Non-selective (Flush)
  • End hole vs. Side hole
  • Hydrophilic vs. Non-hydrophilic

In a broad sense, catheters can be divided into two groups — selective catheters and non- selective (flush) catheters. Flush catheters are used for high-flow injections into large vessels. They therefore are designed to have high wall strength, and often have multiple side holes to prevent catheter or vascular damage during power injections due to the end-hole jet effect1.

Commonly-used flush catheters include Angiodynamics’ Omniflush and Pigtail6.To this end, they are designed with increased rotational stiffness in order to transmit any manipulation of the trailing end reliably to the leading end. In addition, selective catheters come in many different shapes to accommodate specific anatomy in an effort to increase selectivity and stability. The angle of a catheter’s primary curve is designed to approximate the takeoff angle of the target vessel to enhance selectivity. Secondary curves may also be employed, to enhance stability. For example, the Angiodynamics Mikaelsson catheter ( ) is designed to maintain position of the catheter while working in an aortic branch vessel, as the posterior bulge opposes the wall of the aorta, maintaining the catheter in the vessel ostium.

Cobra’s (Cordis) shape ( ) has similar uses, although its decreased curve allows for easier advancement over a guidewire6.

Microcatheters, typically 3F or smaller, make up a subset of selective catheters. These are often used when sub-selection of small vessels is critical, such as vascular embolization for hemorrhage or chemo- or radioembolization1.

Catheters can also be broken down into categories based on hydrophilicity. Hydrophilic catheters (e.g. Terumo’s Glidecath), commonly made with Teflon (polytetrafluoroethylene [PTFE]-62) glide smoothly through vessels, an important point in highly tortuous and smaller vessels. However, this very property means that hydrophilic catheters have limited positional stability. In addition, due to the lower rotational stiffness of materials used in their production, these catheters are more difficult to manipulate accurately1.

More specialized catheter designs are also in use today, including dual- and even triple-lumen catheters. One of the more well known of these catheters is the Hickman catheter, a central venous catheter commonly used as an alternative to arteriovenous fistula for the administration of chemotherapy or parenteral nutrition introduced in the 1970s. There have been many innovations since then, including kink resistant catheters and others.

Impact of Catheter Innovation:

From its humble origins in Dr. Seldinger’s work of vascular access to Dr. Dotter’s groundbreaking angioplasty, the catheter has been a cornerstone in interventional radiology. Initial designs were used primarily for angiography but as the field of interventional radiology took, advances were made in the technology used. Dr. Dotter and Bill Cook created the stiff coaxial Teflon catheter which then led to Dr. Judkins using a modified catheter “bullet nose” model which led to pre-shaped catheters. Present day catheters offer a pre-shaped curve to aid in tracking off a vessel1.

Initially clots were treated with drug therapy to activate the process of fibrinolysis but mechanical thrombectomy gave rise to an improved approach. Since 2009 guidelines were released by SIR

for endovascular stroke several studies have shown intra-arterial catheter-directed treatment offers improved outcomes. Microcatheters helped to revolutionize the process of clot removal in stroke patients. The procedure requires placing a microcatheter through the guiding catheter and once the microcatheter is distal to the clot a snare is deployed. Using this procedure a clot can be retrieved leading to regeneration of blood flow to poorly perfused areas. Treatment of ischemic stroke due to thrombus formation can be managed via innovative catheter technology in the field of IR.

Material and composition leads to an interesting review of catheter versatility. With the advancement of research, the field went from Dotter’s Teflon catheter to devices of various shapes and sizes. The wide selection offers interventional radiologists to perform vast procedures ranging from PAD interventions to even managing neurological procedures.

Hydrophilic catheters allow easier glide in the lumen of a vessel and reduced friction thus lowering the risk of injury. Moreover, the coating allows for successful tracking of more tortuous anatomy that is typically seen in the cerebral vasculature7.

Another interesting innovation of key interest is lithotripsy. A catheter partnered with a balloon and electrical emission unit is passed through a calcification. Once delivered across, electrical discharge disrupts a calcified lesion leading to its removal from vessels. Reports in literature show that this technology can be beneficial in treating highly stenotic lesions in patients and lead to improved procedures due to catheter selection1.

Atherectomy catheters are used in CLI (critical limb ischemia) interventions with great success. Removal of atherosclerosis in arterial walls helps to restore blood flow to the lower limb via the use of aspiration, rotational motion, or laser based approaches leading to removal. The usage of these catheter devices offers an alternative to stent implantation due to biomechanical stress1,7.

In conclusion, the advancement of the catheter ushered in interventional radiology’s diversity. The innovative spirit at the core of the field inspired improvements on existing devices and only time can tell what the next steps will be. Interventional radiologists provide a unique perspective to endovascular minimally invasive procedures as we are well trained in imaging, technical skills, and clinical experts in disease management. We all look forward to the next frontier!

References:

1. Taslakian B, Ingber R, Aaltonen E, Horn J, Hickey R. Interventional Radiology Suite: A Primer for Trainees. J Clin Med. 2019;8(9).

2. Abele JE. Society of Interventional Radiology History: John E. Abele’s Perspective. J Vasc Interv Radiol. 2018;29(5):729-730.

3. Steinberger JD. Innovation in Interventional Radiology. Tech Vasc Interv  2017;20(2):83.

4. Tang Z, Jia A, Li L, Li C. [Brief history of interventional radiology]. Zhonghua Yi Shi Za Zhi. 2014;44(3):158-165.

5. Strunk H, Marinova M. Transjugular Intrahepatic Portosystemic Shunt (TIPS): Pathophysiologic Basics, Actual Indications and Results with Review of the Literature. 2018;190(8):701-711.

6. Northcutt BG, Shah AA, Sheu YR, Carmi L. Wires, Catheters, and More: A Primer for Residents and Fellows Entering Interventional Radiology: Resident and Fellow Education Feature. 2015;35(5):1621-1622.

7. Murphy TP, Soares GM. The evolution of interventional radiology. Semin Intervent Radiol. 2005;22(1):6-9.