The expansion of interventional cardiology, and centres that can perform these procedures, has meant that nurses have a greater opportunity than ever to be involved with exciting and more advanced techniques and the nursing care that goes with them. A number of potentially serious cardiovascular conditions can be treated by minimally invasive interventional techniques, such as transarterial occlusion of patent ductus arteriosus and balloon valvuloplasty for pulmonic stenosis. Transvenous pacemaker placement for the management of bradyarrhythmias, such as third-degree atrioventricular block, also use minimally invasive techniques. Nurses have a large role to play in patient preparation and anaesthesia for patients undergoing these procedures.

One of the major benefits of interventional cardiology is that it uses minimally invasive techniques to approach the heart. Catheters or guidewires are passed into veins or arteries and manoeuvred into position using fluoroscopic guidance. The small incisions that are required to access the vessels mean that recovery time is reduced compared to thoracotomy, as is hospitalisation time and the potential risk of hospital-acquired infections.

The conditions that can benefit from interventional procedures are:

 Patent ductus arteriosus (PDA)

 Pulmonic stenosis (PS)

 Bradyarrhythmias requiring pacemaker therapy

Another procedure performed by cardiology centres is electrical cardioversion, which can treat some atrial tachyarrhythmias. This procedure does not involve access to blood vessels, but is more of an 'electric shock' to the thorax.

Patent Ductus Arteriosus

PDA is one of the most common congenital cardiac diseases in the dog, but it is rarely seen in the cat. The nature of this defect is that the fetal blood vessel (ductus arteriosus) that connects the descending aorta with the main pulmonary artery has failed to close following birth. As a consequence of the ductus arteriosus failing to close, blood shunts from the higher-pressure aorta to the lower-pressure pulmonary artery. This can lead to left-sided congestive heart failure. Prognosis is generally poor if the PDA is not closed. Surgical ligation used to be the only option for occlusion, but other methods have become more common. These include coils and vascular plugs or occlusion devices. The Amplatz^TM Canine Duct Occluder (ACDO) is a device specifically designed for closure of canine PDAs. Prognosis is good if closure is successful, and most patients lead a normal life.

Nursing Considerations for Ductal Occlusion Patients

On recovery from anaesthesia, and for the next 12–24 hours, the patient should be kept calm to minimise the risk of haemorrhage from the wound site. Femoral artery access is used for the ACDO technique, using a cut-down method, so regular checks are needed to ensure that there is no postoperative swelling or haemorrhage at the incision site. If there are no complications, most patients are able to go home the next day. Owners should be advised that exercise should be restricted until the femoral sutures have been removed.

Pulmonic Stenosis

PS is also a common defect seen in the dog, but again, is uncommon in the cat. Deoxygenated blood leaves the right ventricle via the pulmonary artery to the lungs. Stenosis of the pulmonary valve impedes the flow of blood and so can cause high pressure on the right side of the heart. The right ventricle has to work harder to maintain adequate lung perfusion and this can cause right ventricular hypertrophy. This can lead to compromised cardiac output and/or right-sided congestive heart failure. Patients that have severe valvular stenosis are recommended to undergo balloon valvuloplasty.

Nursing Considerations for Patients Undergoing Balloon Valvuloplasty

The patient should be slowly woken from general anaesthesia and kept as calm as possible for the next 12–24 hours. Jugular access for balloon valvuloplasty is percutaneous, so monitoring should record any haemorrhage from the jugular vein. If there are no complications, most patients are able to go home the next day. Owners are advised that neck leads should not be used for 2–3 days after the procedure.

Pacemaker Implantation

Pacemaker therapy is considered when patients have a slow heart rate or rhythm that causes haemodynamic compromise. Examples of these rhythms would be a high second- or third-degree atrioventricular block, sick sinus syndrome, or normokalaemic atrial standstill. Bradyarrhythymias can occur for many different reasons, but those requiring pacemaker therapy are usually idiopathic in origin.

Nursing Considerations for Patients with Pacemakers Implanted

Management of patients should focus on minimising the risk of dislodging the lead, damaging the lead or generator which are located in the neck area and also the risk of infection. A transvenous technique is generally used, from the right jugular through the right atrium, and into the right ventricle.

Short term:

 Cleaning the surgical sites must be done very gently, wearing sterile gloves.

 Neck leads should never be used on a patient with a pacemaker.

 If the femoral vein method was used for temporary pacing, then this should be monitored for postoperative haemorrhage and swelling.

Long term:

 Patient should only be exercised using a harness.

 Jugular venepuncture should not be performed because the needle may cause the pacing lead to fracture.

 Once a patient has had a pacemaker implanted, magnetic resonance imaging (MRI) is contraindicated.

 When the patient dies, the pacemaker must be removed before cremation, because the battery will explode.

Electrical Cardioversion

Synchronous electrical cardioversion is occasionally used in the termination of tachycardias such as atrial fibrillation. It does this by giving a low-energy shock at a specific point in the cardiac cycle. It is hoped that this will 'reset' the heart rhythm and allow restoration of normal sinus rhythm.

Nursing Considerations of the Patient That Has Undergone Electrical Cardioversion

If the procedure has been successful, the patient should be allowed to recover from the general anaesthetic slowly and gently, as any sympathetic surge could allow the tachyarrhythmia to resume. Due to the effect of the shock on the skin, an anti-inflammatory cream can be used on burnt areas of the thorax.

Conclusions

Interventional cardiology has many practical advantages over previous treatment options, and is now being practised more commonly. The preparation, both for the procedure and the patient, the anaesthetic monitoring, and then patient care, both short and long term, can be challenging but extremely rewarding for the veterinary nurse.

References

1.  Eyster GE, Eyster JT, et al. Patent ductus arteriosus in the dog: characteristics of occurrence and results of surgery in 100 consecutive cases. Journal of American Veterinary Medicine Association 1976;168:435–438.

2.  Luis Fuentes V, Johnson LR, et al. BSAVA Manual of Canine and Feline Cardiorespiratory Medicine. 2nd ed. Quedgeley: British Small Animal Veterinary Association, 2010.

3.  Oyama M, Sisson D, et al. Practices and outcome of artificial cardiac pacing in 154 dogs. Journal of Veterinary Internal Medicine 2001;15:229–239.

4.  Stafford Johnson M, Martin M. Results of balloon valvuloplasty in 40 dogs with pulmonic stenosis. Journal of Small Animal Practice 2004;45:148–153.

5.  Ware W. Cardiovascular Disease in Small Animal Medicine. London: Manson Publishing Ltd, 2007.