Interventional cardiovascular procedures: overview and veterinary applications

Interventional cardiovascular procedures are nowadays readily available for the correction or palliation of congenital and acquired cardiovascular defects. This involves the passing of catheters via peripheral vessels, such as the femoral artery or the jugular vein, under general anesthesia. Access to the vessels involves a direct surgical dissection for arteries, although in some circumstances venous access using a Seldinger technique can also be used. Vascular access sheaths with a hemostatic valve are used to enter the vessels, allowing repeated and easy passage of various guide wires and catheters, with minimal blood loss.

Manipulation and directional control of the catheters and guide wires is observed under fluoroscopy with image intensification. The image on the monitor is typically magnified, thus accurate scaling is necessary. Scaling is achieved by measurement markings on a catheter placed within the esophagus, the heart or great vessels and the exact magnification measured at the commencement of the intervention. An angiographic pressure injector is required for rapid delivery of radiographic contrast and a blood pressure monitor for direct manometry.

The common conditions which nowadays are commonly managed by interventional techniques are (in the lecture I will use a case-based approach to discuss these indications) :

• Patent ductus arteriosus (PDA): Commonly closed using an Amplatz canine duct occluder (ACDO) in patients over 4 kg, or with a coil in cats and smaller dogs (catheterization of the femoral artery in a tiny puppy is not possible because the catheter needed to deliver the ACDO device typically exceeds the diameter of the lumen of the artery)
• Severe valvular pulmonic stenosis (PS): Using balloon dilation catheters the valvular stenosis can be reduced in severity in the majority of dogs with pure valvular stenosis
• Cor triatriatum dexter: This rare congenital heart diseases causes right-sided heart failure (ascites) due to a persistent membrane in the right atrium. Using balloon dilatation catheters (sometimes using a combination of cutting balloon and high-pressure) the obstruction can be relieved.
• Pacemaker implantation is now a well-recognized procedure for the management of various bradyarrhythmias causing symptoms, such as syncope, or for the risk of death such as third-degree AV block, advanced/symptomatic second-degree heart block (intermittent heart block), sinus arrest (often part of sick sinus syndrome), vasovagal syncope when the bradycardia portion is profound. Modern pacemakers are typically rate responsive, allowing an increase in the heart rate with exercise.
• Electrophysiological studies and ablation of tachyarrhythmias caused by congenital electrical bypass tracts is now available with increasing success rates
• Intra-hepatic portosystemic shunts (PSS): Numerous surgical techniques have been described for intrahepatic PSS attenuation, ranging from careful liver dissection around the shunting vessel to more technically demanding and complicated procedures involving temporary vascular hepatic inflow occlusion for intravascular repair, all with an unacceptable high mortality rate. Nowadays interventional techniques for intrahepatic PSS are available, using stenting of the caudal vena cava and placement of thrombogenic coils; these procedures are safe, successful, and improve the clinical situation of most affected dogs.  […]