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Cardiac Interventional Therapy in Companion Animals

Amara H. Estrada, DVM, DACVIM (Cardiology), University of Florida

James Curtis Fudge Jr., MD, MHS, University of Florida

Simon Swift, MRCVS, DECVIM-CA (Cardiology), University of Florida

Himesh Vyas, MD, University of Florida

Cardiology

|January 2016|Peer Reviewed

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Cardiac Interventional Therapy in Companion Animals

Cardiac interventional therapy is the treatment of cardiac disease using minimally invasive percutaneous techniques. Cardiac catheterization has historically been considered the gold standard for diagnosis of congenital and acquired heart disease.

With the evolution of noninvasive imaging modalities (eg, echocardiography), the need for diagnostic catheterization has decreased substantially. The focus of cardiac catheterization has shifted to the development of interventional treatment strategies. Advancements in technique and equipment have allowed interventionalists to provide a less invasive approach to the definitive treatment of many types of heart disease while complementing the surgical treatment of others.


Overview

Indications and Advantages

As the field of cardiac interventional therapy continues to evolve, more of its applications will likely be used in veterinary medicine. Many diseases once thought untreatable may soon have more palliative or corrective treatment options available. The use of interventional techniques in veterinary patients offers a number of advantages compared with more traditional therapies. These procedures are minimally invasive and may lead to reduced perioperative morbidity and mortality, shorter anesthesia times, and shorter hospital stays. Some less equipment-intensive procedures can result in reduced costs as well. In addition, some techniques offer alternative treatment options for patients with conditions that may not be amenable to standard therapies such as congestive heart failure that is not clinically responsive to medical management, medically refractory arrhythmias, or an owner who cannot afford such therapies.

Over the past decade, tremendous improvement has been made in techniques now considered common in veterinary cardiology, such as transvenous pacemaker therapy for bradyarrhythmias,1-10 balloon valvuloplasty for pulmonic stenosis,11-14 and canine-specific occlusive devices for patent ductus arteriosus.15-18

Growth has likewise developed in catheter-based procedures for the more uncommon interventions such as: use of cutting balloons for subaortic stenosis19 and cor triatriatum dexter20 and sinister21; high-pressure balloons for pulmonic11,22-24 and subaortic19 stenosis; atrial or ventricular septal defect closure devices25-27; percutaneous valve repair and replacement techniques28-33; stenting of dysplastic valves34 and other occlusive intracardiac and peripheral arterial lesions35,36; targeted cardiac stem cell37 or gene therapy38; as well as more advanced electrophysiological applications of intracardiac defibrillation devices39 and ablation techniques.40-42

Potential advantages of interventional therapies include reduced morbidity and mortality owing to the minimally invasive nature of the procedures. These therapies also offer alternative treatments for conditions in which standard treatments do not exist (eg, subaortic stenosis, extremely dysplastic pulmonary valves) or involve unacceptable risks (eg, open heart surgical repair necessitating cardiopulmonary bypass in small patients) or when palliation is the goal (eg, stenting peripheral pulmonary arteries compressed by heart base masses). Although some of these therapies have been performed in veterinary patients with success, there is even greater potential to expand their application in veterinary medicine.

Challenges and Disadvantages

Because most of these procedures are minimally invasive (performed through catheters or small holes in the skin), traditional sterile operating rooms are recommended but not required. Most of these procedures are performed in clean angiography suites. The entry sites receive a traditional sterile scrub, and operators wear full lead gowns, lead thyroid shields, caps, gowns, masks, and gloves. The radiation exposure during conventional or C-arm fluoroscopy can be substantial. The operator should review radiation safety guidelines, minimize exposure time and beam size, and maximize shielding and distance from the beam.

Vascular access is arguably the most important part of any cardiac or vascular interventional procedure. Several access sites are commonly used in veterinary medicine. For venous access, the jugular, femoral, or saphenous vein is typically used. For arterial access, the femoral, carotid, or brachial artery is typically used. These vessels can be accessed using either a percutaneous approach or a small cutdown incision. For the former, the vessel is initially entered with a blind needle stick; for the latter, the vessel is bluntly dissected and entered with a needle using direct visualization. With either approach, a series of over-the-wire exchanges are then made to place an introducer with a hemostasis valve into the vessel through which various catheters can be passed without concern of blood loss. For many of the more commonly performed procedures, a traditional fluoroscopy unit is sufficient. A C-arm fluoroscopy unit has the advantage of mobility of the image intensifier, permitting multiple tangential views without moving the patient.

The primary challenges or disadvantages of interventional therapy include the required technical expertise, specialized equipment (fluoroscopy with or without digital subtraction capabilities), and the requisite large initial capital investment to amass a suitable inventory of catheters, guidewires, balloons, stents, and coils.

Potential advantages of interventional therapies include reduced morbidity and mortality owing to the minimally invasive nature of the procedures.

Clinical Impact

Interventional catheterization, better termed therapeutic catheterization, is commonly used in adult, pediatric, and veterinary cardiology. Techniques are constantly improving thanks to smaller introducers and sheaths, low-profile balloons, novel devices, and innovative uses of equipment. These advancements have allowed cardiologists to provide a less invasive approach to the definitive treatment of many types of heart disease while complementing the surgical treatment of others. Hybrid approaches, in which interventional cardiologists and surgeons work together to allow delivery of devices or access to locations in the heart in very small patients, are continuously being developed.25

References and Author Information

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