ELECTROPHYSIOLOGY STUDIES:
Invasive electrophysiology studies (EPS) involve the recording of
spontaneous and pacing-induced intracardiac electrical activation
patterns and their study in a controlled environment.
AIM:
To investigate the electrical aspects of abnormal heart function for
diagnostic, therapeutic and/or prognostic purposes.
EPS may be performed
* To establish the site of origin and the mechanism of a tachycardia or
bradycardia (e.g. the cause of a cardiac arrest, to assess a documented
arrhythmia in which the diagnosis may not be apparent from the surface ECG)
* To guide in the treatment of arrhythmias (e.g. drug therapy or other
interventions such as implantation of defibrillators, RF ablation, surgery).
* To assess the likelihood of future arrhythmic events.
More information for patients having EPS
The Electrophysiology Lab
THERAPEUTIC INTERVENTIONS
CATHETER ABLATION 
This is a new technique designed to cure certain types of tachycardia
(rapid heart beating). From your
electrocardiogram (ECG) tracings, your doctor has determined that you have
a heart rhythm disturbance which may be amenable to this technique.
There are 2 broad types of tachycardia that may be suitable for treatment
These are supraventricular tachycardias (SVT) and ventricular tachycardia (VT).
SVT comprises abnormal heart rhythms either originating in the
top chambers of the heart (atrium) which cause the heart to beat rapidly (may be regular or irregular beating),
and regular, rapid beating due to an abnormal extra wire connecting the atrium and bottom chamber (ventricle) leading to a short circuit in the heart.
SVT may be due to a bypass tract or to a double circuit in the central
electrical junction in the heart, the AV node.
Other types of SVT amenable to ablation include atrial fibrillation,
atrial tachycardia and flutter. Sites of ablation may be the extra wire
or the normal electrical system itself may be the target for ablation.
If the normal electrical system is the target a permanent pacemaker will
also have to be inserted.
VT is an abnormal rapid beating of the ventricles and it may result
from scarring in the heart from a heart attack or it may be seen in young people
with structurally normal hearts. A small area in the ventricle is the usual
target for ablation in these cases.
The ablation procedure is very similar to the EP study.
The EP study makes it possible to study heart rhythm disturbances
under controlled conditions. By using special insulated wires called catheters,
the doctor can identify the heart rhythm disturbance and determine whether
to go ahead with the ablation procedure.
Xray showing catheters in the heart
Preparation:
The patient is required to fast for at least 6 hours before
the study so that the stomach will be empty. A light sedative tablet will be
ordered just prior to the study.
PROCEDURE
The EP study and ablation are performed in a special laboratory.
The patient is awake during the procedure but lightly sedated to help him/her
relax. Once in the lab, the patient is attached to monitoring
equipment by way of sticky electrodes on the chest and arms, an
automatic blood pressure cuff on the arm and a finger cuff to monitor the
oxygen level in the blood.
Next, the groin or groins (and in many cases, the neck) are cleaned with an
antiseptic solution and sterile towels are placed over the body. Local
anaesthetic is then injected into these areas to numb
them for insertion of the catheters into the heart. The catheters are then
inserted into the heart. While this is happening, the patient may be aware of
some extra or missed heart beats, or the tachycardia may occur. This is due to
the catheters inside the heart and the doctor will be able to terminate this
with restoration of the normal heart beat, once the catheters are in place.
The doctor then stimulates various areas in the heart to obtain the information
necessary to determine the mechanism of the tachycardia and will then be able
to decide if ablation is feasible.
The ablation involves passage of a specialized catheter into either the artery
or vein in the groin into the heart. Certain types of tachycardia will require
passage of the catheter into the left ventricle or into the right atrium and
ventricle. Once the abnormal circuit is located. one or more applications of
cautery are made through this catheter. The patient will probably not feel any
pain but some patients have described a mild discomfort lasting only for a few
seconds.
After the cautery has been applied, the electrical system in the heart is retested
to ensure that the tachycardia circuit has been eliminated (ablated). If a
satisfactory result has been achieved the catheters will be removed and the patient
is returned to the ward. Pressure is then applied to the neck and groins for
several minutes. If an artery was used to insert the ablation catheter, pressure
may be applied for up to 30 minutes and a sand bag may be left on the groin for
the next few hours. The patient will need to stay in bed for 4 hours after the
procedure and will remain connected to the ECG monitor for the next 24 hours.
Is there is any risk of complications?
There is a small risk of complications associated with the procedure.
This ranges from minor discomfort and bruising associated with the sites of
catheter insertion to a risk of heart damage. There is a small risk of
damaging the "normal"
electrical system in the heart particularly if the area of ablation
(the abnormal circuit) is located close to the normal electrical system.
If this occurs, a permanent pacemaker may be required to restore the
normal heart action. In some situations, intentional ablation of the normal
electrical system is the goal to successful control of some tachycardias such
as atrial fibrillation. In addition, perforation of the heart by the catheter
and damage to the internal structures of the heart is always a potential risk
with catheter procedures. Such risk is estimated at less than 1 in every 100
cases based on the world experience. In cases where the ablation catheter is
inserted into the left ventricle via the arterial system, there is a small risk
of a clot forming on the catheter during the procedure and becoming dislodged
into the circulation. In order to minimise this risk, an anticoagulant drug
(blood thinner) is routinely given during the procedure and aspirin is continued
generally for 1 month after the procedure.
The decision to proceed with catheter ablation,
therefore, must be made after the risks and benefits of the procedure have
been considered and discussed with your doctor.
HIS BUNDLE ABLATION:
His bundle ablation (HBA) is a procedure used to stop A-V conduction in atrial fibrillation, flutter (when flutter ablation is not indicated) or tachycardia. A permanent pacemaker (PPM) must be inserted. A ventricular pacing catheter and an ablation catheter are inserted via the femoral vein . The ablation catheter is positioned on the His bundle
and the conductive tissue is destroyed by application of radiofrequency energy so the abnormal atrial rhythm is not conducted through to the ventricles.
PERMANENT PACEMAKER IMPLANTATION:
The presence of symptoms remains the most common indication for pacemaker treatment. Symptomatic bradycardia is the term used to identify clinical manifestations associated with a heart rate that does not allow cardiac output to meet physiologic demands.
The aim of the procedure is to ensure optimal heart rate in a heart with a conduction deficit. Duration of the implant is 1-2 hours dependant on the number of leads and
the difficulty of access. Local anaesthetic (usually Marcain 0.4%) is
administered at the site. It is a sterile procedure, in which the medical
practitioner scrubs, gowns and gloves. Cutdown cannulation of the cephalic
vein and/or percutaneous cannulation of the sub-clavian vein provides access
to the R atrium and ventricle. The pacing leads are then inserted into the
heart via this access and the lead parameters measured via the alligator leads
and the PSA. The pacing device is then connected to the lead(s), inserted
into a pre-pectoral pocket, and the wound closed. A drain may be required,
particularly if the pt has been anti-coagulated.
Antibiotic prophylaxis is given routinely - usually a cephalosporin, with
occasional gentamycin cover also. If allergic to penicillin, a skin test for drug reaction is performed with the cephalosporin.
Cardioversion may (rarely) be required to continue the procedure (e.g. in the event of VF and VT).
Information: Going home after pacemaker implantation.
INTERNAL CARDIOVERTER DEFIBRILLATOR (ICD) IMPLANTATION:
The ICD maybe used in pt's with prior cardiac arrest or ventricular tachycardia. It is used when medications
fail to control the arrhythmia or or the patient is at high risk for sudden death.
The antitachycardia pacemaker is an important adjunct to AICD therapy for pts with frequent episodes of
well-tolerated VT. Some devices have the facility to perform anti-tachycardia
pacing as well as delivering shocks, others are shock-only.
PROCEDURE:
Duration of the implant is 1-2 hours dependant on the difficulty of
access, positioning the leads to get satisfactory parameters, and testing
of the device. Local anaesthetic is administered at the site. It is a sterile
procedure, in which the medical practitioner scrubs, gowns and gloves. Cutdown
cannulation of the cephalic vein and/or percutaneous cannulation of the
subclavian vein provides access to the heart. The pacing/sensing lead also
delivers the shock. It is inserted into the R ventricular apex via the
cephalic or subclavian vein, and the lead parameters are measured via
the alligator leads and the PSA. An 'Active Can"is implanted - and the
device shocks against this, however, if defibrillation thresholds are
high, a second lead may be inserted via the subclavian vein into the
superior vena cava as well. Alternately, some new leads have a second
pole incorporated ino the "shocking" lead which is positioned in the
vena cava. The ICD is then connected to the leads and tested. It is inserted into a pre-pectoral pocket, and the wound is closed.
An anaesthetist delivers a general anaesthetic before any shocks are delivered.
Antibiotic prophylaxis is given routinely - usually a cephalosporin, with occasional gentamycin cover also. If allergic to penicillin, a skin test for drug reaction is performed with the cephalosporin.
Backup transthoracic cardioversion may be required.
Information: Going home after defibrillator implantation.
TILT TESTING:
A cardiovascular cause of syncope can be identified in most patients by the
use of electrophysiologic studies or the head-up tilt test. Tilt testing with
or without isoprenaline can provoke hypotension and bradycardia in patients
with
neurocardiogenic mechanisms of syncope, also known as vasovagal, vasodepressor,
or neurally mediated syncope. Vasovagal is the most common cause of syncope
in otherwise healthy young persons.
PROCEDURE:
No hospital admission is required for tilt tests - they may be done as an
outpatient. Bookings are made with the procedure room RN.
The pt is assessed in the flat position for 5 minutes before being tilted at
60 degrees for 45 minutes or the onset of syncope. If syncope occurs, stat BP
is recorded and the pt returned to the horizontal position. If no syncope
occurs after 45 minutes, commence isoprenaline infusion at 1ug/min and increase
until heart rate is 120% of baseline. Continue for 15 minutes or until syncopal.
Links to other arrhythmia sites:
Cardiac arrhythmias
Long QT syndrome
Mitral valve prolapse
Pacemakers and defibrillators
Arrhythmogenic RV dysplasia
Brugada syndrome
If you wish to contact us,
Phone: (02) 9361 7300 Fax: (02) 9361 7410
CONSULTATION:
Do you have any questions: opinions on patients, ECGs etc?
Feel free to e-mail us.
