VOL: 98, ISSUE: 08, PAGE NO: 34
ANDREW JACKSON, BSc, RGN, RNT, is cardiology nurse specialist at Pontefract General Infirmary, West YorkshireAtrial fibrillation (AF) is the most common sustained disorder of cardiac rhythm and is associated with an increased risk of thromboembolic events. Its incidence increases with age, from less than 2% in people aged under 65 to over 11% in those aged 80 and over (Lake et al, 1989). It has been estimated that, depending on the underlying pathology, up to 75% of these cases may result in cerebrovascular accidents (Cabin et al, 1990).
Atrial fibrillation (AF) is the most common sustained disorder of cardiac rhythm and is associated with an increased risk of thromboembolic events. Its incidence increases with age, from less than 2% in people aged under 65 to over 11% in those aged 80 and over (Lake et al, 1989). It has been estimated that, depending on the underlying pathology, up to 75% of these cases may result in cerebrovascular accidents (Cabin et al, 1990).
Electrical direct current (DC) cardioversion can restore and maintain sinus rhythm in suitable patients. Although this treatment was provided in our district general hospital, this was on an ad hoc basis and pressure on coronary care unit (CCU) beds meant that the procedure was often cancelled on the day it was due. To address this problem and provide a total care package, a nurse-led AF service was developed. It is run by a cardiology nurse specialist.
What is atrial fibrillation?
In AF there is a complete absence of coordinated atrial systole. This is characterised on an electrocardiogram (ECG) by no discernible P waves, narrow QRS complexes and an irregular rhythm (Levy et al, 1998). This irregular irregularity results in a lack of atrial and ventricular synchrony and a consequent fall in cardiac output of up to 10% in most cases (Broch and Muller, 1957). In diseased hearts this percentage may be higher (Samet et al, 1966).
The increased risk of thromboembolism in patients with AF begins with Virchow's Triad conditions: stasis, endothelial dysfunction and hypercoagulability. The haemodynamic and haemostatic mechanisms responsible for clinical thromboembolism in AF have been detected through serial imaging and coagulation studies. The processes involved are complex and would be impossible to cover in this article. More specific information may be obtained in the relevant section on thromboembolism in the recently published guidelines for the management of patients with AF (Task Force Report, 2001).
Cardioversion from AF to sinus rhythm should be considered for all suitable patients, that is those with the greatest probability of restoring and maintaining sinus rhythm (Lip et al, 1996). This includes patients who have an underlying cause that is treatable, those who have been in AF for less than a year and those who do not have grossly dilated atria or valvular disease on echocardiography.
The potential benefits of restoring sinus rhythm include an improvement in well-being and exercise capacity, the avoidance of potentially dangerous long-term anticoagulant therapy and a potential reduction in thromboembolic events.
DC cardioversion involves the delivery of an electric current synchronised to the activity of the heart. A measured amount of electricity is administered during the ventricular contraction of the heart, which is represented on the ECG by the R wave. This technique ensures that electrical stimulation does not occur during the vulnerable period of the cardiac cycle - ventricular repolarisation, which is represented on an ECG by the T wave (Task Force Report, 2001).
Before the nurse-led service was developed, patients found to be in AF may have been considered for elective DC cardioversion when fully anticoagulated and haemodynamically stable. They were admitted to the CCU when a bed was available and had to fast from midnight before the day of admission. They then telephoned the unit at 9am to see if a bed was still available, and if so they were admitted.
A 12-lead ECG was taken to confirm AF and their blood was tested to ensure that biochemical and haematological markers were within the ranges agreed in the local protocol.
The anaesthetists covering the intensive care unit would fit the procedure into their schedules.
This was not ideal as many procedures were cancelled because a CCU bed or anaesthetist was not available. Also, if the cardioversion took place after 2pm the patient would not have eaten for at least 14 hours.
An attempt was made to reduce the number of cancellations and the increasing waiting list for cardioversion by reserving beds on the medical admissions unit. This should have enabled three patients a week to be admitted on a Tuesday morning for the elective procedure, which took place in a CCU bed. A designated consultant anaesthetist was also assigned, ensuring a degree of continuity.
Unfortunately, acute medical assessment beds could not be guaranteed, so although more cardioversions took place there were still cancellations when beds were not available on the CCU or medical admissions unit.
A nurse-led service
To improve the service, it was decided to develop a nurse-led service. Interested parties, such as the cardiology consultants, anaesthetists, nurses on the day surgical unit, theatre staff, laboratory staff and the day case coordinators, were consulted and the revised process was put in place.
A designated list was drawn up so that four patients are admitted directly to the day surgical ward, where beds are guaranteed. The necessary administration procedures are completed by a member of the cardiology medical team, although consent must be obtained by a doctor. The anaesthetist also has an opportunity to review patients before the procedure, which takes place in the day surgery theatres.
Patients see the phlebotomist at 11am on the day of admission to have their blood tested for routine biochemical and haematological markers - urea and electrolytes, random blood glucose and the international normalised ratio (INR).
The most important values are a normal potassium level, because hypo/hyperkalaemia may potentiate dysrhythmias, and an appropriate level of anticoagulation denoted by the INR, which is an internationally recognised ratio of a patient's ability to clot. If a patient is not adequately anticoagulated with warfarin there is an increased risk of embolisation and an elective cardioversion is not recommended until a safe and stable level of anticoagulation has been achieved.
After the blood test, patients have a baseline 12-lead ECG to ensure they still need the cardioversion. They are then transferred to the day surgical unit to await medical review.
The cardiology nurse specialist carries out the cardioversion following a predetermined protocol, which is reviewed annually to reflect any changes in practice. The main change over the past year has been from monophasic to biphasic technology, which allows a lower range of electricity to be administered. It is also becoming increasingly common to combine electrical and chemical therapy to restore and/or maintain sinus rhythm.
The theatre list begins at 2pm. All patients are taken to theatre recovery before returning to the day surgical ward. All are back by 3.30pm. They remain on bedrest for a further two hours, are given oxygen as directed by the anaesthetist and have a repeat 12-lead ECG.
Patients are informed whether or not the procedure has restored their sinus rhythm and are discharged at 7pm, providing someone is available to be with them. If not, overnight admission is arranged as supervision is required after any general anaesthetic.
All patients in AF who could benefit from cardioversion can book the procedure during their outpatient appointment. Appointments may also be made for the anticoagulation clinic and a precardioversion review by the cardiology nurse specialist.
To maintain continuity, the outpatient appointment with the cardiology nurse specialist is booked for two to three weeks before the cardioversion so that the procedure can be explained and any questions answered before admission. If a patient is taking anti-arrhythmic therapy, chemical cardioversion may have occurred. This can be identified at the preprocedural appointment, freeing up another elective slot.
Postcardioversion follow-up with the cardiology nurse specialist takes place at six weeks and three months. If sinus rhythm is maintained, anticoagulation may be discontinued and aspirin introduced. The patient is then referred back to the consultant who requested the treatment.
The patient's journey is overseen entirely by the cardiology nurse specialist. If the cardioversion is not successful, a repeat procedure may be booked and anti-arrhythmic therapy altered after consultation with the appropriate medical team.
With proper consultation and planning, nurse-led AF can provide a seamless service for most patients presenting with the condition. A nurse specialising in cardiology may assess, treat and evaluate these patients, resources are used appropriately and patients can be given dates and times for the procedure, along with any support they may require.
Atrial fibrillation is a common arrhythmia that requires prompt and appropriate treatment if sinus rhythm is to be restored and the patient's quality of life improved.
- A number of older references have been chosen for this article to show that AF is not a recently recognised problem, but has been studied over many decades. The first reference to the use of electricity to terminate cardiac arrhythmias using a synchronised capacitor was published in The Journal of the American Medical Association in 1962, and the most up to date and comprehensive is The Task Force Report (2001).
- A copy of the protocol approved by Pontefract and Pinderfields NHS Trust is available from Mr Jackson on request