Electrophysiology study
Encyclopedia
An electrophysiology
study (EP test or EP study) is a minimally invasive procedure
which tests the electrical conduction system of the heart
to assess the electrical activity and conduction pathways of the heart
. The study is indicated to investigate the cause, location of origin, and best treatment for various abnormal heart rhythms. This type of study is performed by a specialist (an electrophysiologist
) and is performed using a single or multiple catheter
s situated within the heart through a vein
or artery
.
machine and large magnets (2-3 tesla
, 2 ft. diameter) for manipulating the electrodes, in addition to other necessary equipment.
An IV
tube is generally inserted to keep the patient hydrated and to allow for the administration of sedative
s, anesthesia
, or drugs.
In order to reach the heart with a catheter, a site will be prepared that will allow access to the heart via an artery or vein, usually in the wrist or groin. This site is then described as the insertion point.
A metal plate is placed underneath the patient between the shoulder blades, directly under the heart. An automated blood pressure cuff is placed on the arm which periodically measures the patient's blood pressure. A pulse oximeter
is placed on one of the patient's fingers which steadily monitors the patient's pulse and oxygen saturation of the blood.
The insertion point is cleanly shaved and sterilized. A local anesthetic is injected into the skin to numb the insertion point. A small puncture is then made with a needle in either the femoral vein in the groin or the radial vein in the wrist, before a guide wire is inserted into the venous puncture. A plastic sheath (with a stiffer plastic introducer inside) is then threaded over the wire and pushed into the vein (the Seldinger technique
). The wire is then removed and the side-port of the sheath is aspirated to ensure venous blood flows back. It is then flushed with saline. Catheters are inserted using a long guide wire and moved towards the heart. Once in position the guide wire is then removed.
The next step is pacing the heart, this means he/she will speed up or slow down the heart by placing the electrode at certain points along the conductive pathways of the heart and literally controlling the depolarization rate of the heart. The doctor will pace each chamber of the heart one by one, looking for any abnormalities. Then the electrophysiologist tries to provoke arrhythmias and reproduce any conditions that have resulted in the patient's placement in the study. This is done by injecting electric current into the conductive pathways and into the endocardium
at various places. Lastly, the electrophysioligst may administer various drugs (proarrhythmic agents) to induce arrhythmia. If the arrhythmia is reproduced by the drugs, the electrophysiologist will search out the source of the abnormal electrical activity. The entire procedure can take several hours.
(similar to microwave
s) to effectively "cook" the abnormal cells.
. Trying to sit up or even lift the head is strongly discouraged until an adequate clot has formed. The patient will be moved to a recovery area where he/she will be monitored.
For patients who had a catheterization at the femoral artery or vein (and even some of those with a radial insertion site), generally recovery is fairly quick as the only damage is at the insertion site. The patient will probably feel fine within 8 to 12 hours after the procedure, but may feel a small pinch at the insertion site. After a short period of general rest, the patient may resume some minor activity such as gentle, short, slow walks after the first 24 hours. If stairs must be climbed, they should be taken one step at a time and very slowly. All vigorous activity must be postponed until approved by an physician.
It is also important to note that unless directed by a doctor, some patients should avoid taking blood thinners and foods that contain salicylates, such as cranberry containing products until the clot has healed. (1–2 weeks)
More severe but relatively rare complications include: damage or trauma to a blood vessel, which could require repair; infection from the skin puncture or from the catheter itself; cardiac perforation, causing blood to leak into the sac around the heart and compromising the heart's pumping action, requiring removal using a needle under the breast bone (pericardiocentesis); hematoma at the site(s) of the puncture(s); induction of a dangerous cardiac rhythm requiring an external shock(s); a clot may be dislodged, which may travel to a distant organ and impede blood flow or cause a stroke; myocardial infarction; unanticipated reactions to the medications used during the procedure; damage to the conduction system, requiring a permanent pacemaker; death.
Cardiac electrophysiology
Cardiac electrophysiology is the science of elucidating, diagnosing, and treating the electrical activities of the heart. The term is usually used to describe studies of such phenomena by invasive catheter recording of spontaneous activity as well as of cardiac responses to programmed electrical...
study (EP test or EP study) is a minimally invasive procedure
Invasiveness of surgical procedures
There are three main categories which describe the invasiveness of surgical procedures. These are: non-invasive procedures, minimally invasive procedures, and invasive procedures ....
which tests the electrical conduction system of the heart
Electrical conduction system of the heart
The normal intrinsic electrical conduction of the heart allows electrical propagation to be transmitted from the Sinoatrial Node through both atria and forward to the Atrioventricular Node. Normal/baseline physiology allows further propagation from the AV node to the ventricle or Purkinje Fibers...
to assess the electrical activity and conduction pathways of the heart
Heart
The heart is a myogenic muscular organ found in all animals with a circulatory system , that is responsible for pumping blood throughout the blood vessels by repeated, rhythmic contractions...
. The study is indicated to investigate the cause, location of origin, and best treatment for various abnormal heart rhythms. This type of study is performed by a specialist (an electrophysiologist
Cardiac electrophysiology
Cardiac electrophysiology is the science of elucidating, diagnosing, and treating the electrical activities of the heart. The term is usually used to describe studies of such phenomena by invasive catheter recording of spontaneous activity as well as of cardiac responses to programmed electrical...
) and is performed using a single or multiple catheter
Catheter
In medicine, a catheter is a tube that can be inserted into a body cavity, duct, or vessel. Catheters thereby allow drainage, administration of fluids or gases, or access by surgical instruments. The process of inserting a catheter is catheterization...
s situated within the heart through a vein
Vein
In the circulatory system, veins are blood vessels that carry blood towards the heart. Most veins carry deoxygenated blood from the tissues back to the heart; exceptions are the pulmonary and umbilical veins, both of which carry oxygenated blood to the heart...
or artery
Artery
Arteries are blood vessels that carry blood away from the heart. This blood is normally oxygenated, exceptions made for the pulmonary and umbilical arteries....
.
Preparation
It is important for patients not to eat or drink for up to 12 hours before the procedure. This is to prevent vomiting, which can result in aspiration, and even cause severe bleed from the insertion site of the catheter. Failure to follow this simple preparation may result in dangerous consequences. Generally small amounts of water can be consumed up to 2 hours before the exam. Patients should try to schedule the exam at a time when they will be having symptoms and will not need to drive for 2 to 3 days.Procedure
This procedure is performed in a cath lab which is a specially equipped operating room. More modern cath labs contain a video X-rayX-ray
X-radiation is a form of electromagnetic radiation. X-rays have a wavelength in the range of 0.01 to 10 nanometers, corresponding to frequencies in the range 30 petahertz to 30 exahertz and energies in the range 120 eV to 120 keV. They are shorter in wavelength than UV rays and longer than gamma...
machine and large magnets (2-3 tesla
Tesla (unit)
The tesla is the SI derived unit of magnetic field B . One tesla is equal to one weber per square meter, and it was defined in 1960 in honour of the inventor, physicist, and electrical engineer Nikola Tesla...
, 2 ft. diameter) for manipulating the electrodes, in addition to other necessary equipment.
An IV
Intravenous therapy
Intravenous therapy or IV therapy is the infusion of liquid substances directly into a vein. The word intravenous simply means "within a vein". Therapies administered intravenously are often called specialty pharmaceuticals...
tube is generally inserted to keep the patient hydrated and to allow for the administration of sedative
Sedative
A sedative or tranquilizer is a substance that induces sedation by reducing irritability or excitement....
s, anesthesia
Anesthesia
Anesthesia, or anaesthesia , traditionally meant the condition of having sensation blocked or temporarily taken away...
, or drugs.
In order to reach the heart with a catheter, a site will be prepared that will allow access to the heart via an artery or vein, usually in the wrist or groin. This site is then described as the insertion point.
A metal plate is placed underneath the patient between the shoulder blades, directly under the heart. An automated blood pressure cuff is placed on the arm which periodically measures the patient's blood pressure. A pulse oximeter
Pulse oximeter
A pulse oximeter is a medical device that indirectly monitors the oxygen saturation of a patient's blood and changes in blood volume in the skin, producing a photoplethysmograph. It is often attached to a medical monitor so staff can see a patient's oxygenation at all times...
is placed on one of the patient's fingers which steadily monitors the patient's pulse and oxygen saturation of the blood.
The insertion point is cleanly shaved and sterilized. A local anesthetic is injected into the skin to numb the insertion point. A small puncture is then made with a needle in either the femoral vein in the groin or the radial vein in the wrist, before a guide wire is inserted into the venous puncture. A plastic sheath (with a stiffer plastic introducer inside) is then threaded over the wire and pushed into the vein (the Seldinger technique
Seldinger technique
The Seldinger technique is a medical procedure to obtain safe access to blood vessels and other hollow organs. It is named after Dr. Sven-Ivar Seldinger , a Swedish radiologist from Mora, Dalarna County, who introduced the procedure in 1953....
). The wire is then removed and the side-port of the sheath is aspirated to ensure venous blood flows back. It is then flushed with saline. Catheters are inserted using a long guide wire and moved towards the heart. Once in position the guide wire is then removed.
- NOTE It is standard procedure to use the venous system, and place the catheter's tip in the right atrium at the beginning of the procedure. The advantage of this that the SA nodeSinoatrial nodeThe sinoatrial node is the impulse-generating tissue located in the right atrium of the heart, and thus the generator of normal sinus rhythm. It is a group of cells positioned on the wall of the right atrium, near the entrance of the superior vena cava...
is in the right atrium, which is the place where the procedure will start testing the pacing system of the heart.
EP Study
Once the catheter is in and all preparations are complete elsewhere in the lab, the EP study begins. The two large magnets are brought in on either side of the patient. They are large and looming and will sandwich the patient, but are able to precisely control the position of the electrodes that are on the end of the catheters. The X-ray machine will give the doctor a view of the heart and the position of the electrodes, and the magnets will allow the doctor to guide the electrodes through the heart. The magnets are controlled with either a joystick or game controller. The electrophysiologist begins by moving the electrodes along the conduction pathways and along the inner walls of the heart, measuring the electrical activity along the way.The next step is pacing the heart, this means he/she will speed up or slow down the heart by placing the electrode at certain points along the conductive pathways of the heart and literally controlling the depolarization rate of the heart. The doctor will pace each chamber of the heart one by one, looking for any abnormalities. Then the electrophysiologist tries to provoke arrhythmias and reproduce any conditions that have resulted in the patient's placement in the study. This is done by injecting electric current into the conductive pathways and into the endocardium
Endocardium
The endocardium is the innermost layer of tissue that lines the chambers of the heart. Its cells are embryologically and biologically similar to the endothelial cells that line blood vessels....
at various places. Lastly, the electrophysioligst may administer various drugs (proarrhythmic agents) to induce arrhythmia. If the arrhythmia is reproduced by the drugs, the electrophysiologist will search out the source of the abnormal electrical activity. The entire procedure can take several hours.
Ablation
If at any step during the EP study the electrophysiologist finds the source of the abnormal electrical activity, he/she may try to ablate the cells that are misfiring. This is done using high energy radio frequenciesRadio frequency
Radio frequency is a rate of oscillation in the range of about 3 kHz to 300 GHz, which corresponds to the frequency of radio waves, and the alternating currents which carry radio signals...
(similar to microwave
Microwave
Microwaves, a subset of radio waves, have wavelengths ranging from as long as one meter to as short as one millimeter, or equivalently, with frequencies between 300 MHz and 300 GHz. This broad definition includes both UHF and EHF , and various sources use different boundaries...
s) to effectively "cook" the abnormal cells.
Recovery
When the necessary procedures are complete, the catheter is removed. Firm pressure is applied to the site to prevent bleeding. This may be done by hand or with a mechanical device. Other closure techniques include an internal suture and plug. If the femoral artery was used, the patient will probably be asked to lie flat for several hours (3 to 6) to prevent bleeding or the development of a hematomaHematoma
A hematoma, or haematoma, is a localized collection of blood outside the blood vessels, usually in liquid form within the tissue. This distinguishes it from an ecchymosis, which is the spread of blood under the skin in a thin layer, commonly called a bruise...
. Trying to sit up or even lift the head is strongly discouraged until an adequate clot has formed. The patient will be moved to a recovery area where he/she will be monitored.
For patients who had a catheterization at the femoral artery or vein (and even some of those with a radial insertion site), generally recovery is fairly quick as the only damage is at the insertion site. The patient will probably feel fine within 8 to 12 hours after the procedure, but may feel a small pinch at the insertion site. After a short period of general rest, the patient may resume some minor activity such as gentle, short, slow walks after the first 24 hours. If stairs must be climbed, they should be taken one step at a time and very slowly. All vigorous activity must be postponed until approved by an physician.
It is also important to note that unless directed by a doctor, some patients should avoid taking blood thinners and foods that contain salicylates, such as cranberry containing products until the clot has healed. (1–2 weeks)
Complications
As with any surgical procedure, cardiac catheterizations come with a generic list of possible complications. One of the complications that is sometimes reported involves some temporary nerve involvement. Some times a small amount of swelling occurs that can put pressure on nerves in the area of the incision. There have been reports of patients feeling like they have hot fluid like blood or urine running down their leg for up to a month or two after the incision has healed. This usually passes with time, but patients should tell their doctor if they have these symptoms and if they last.More severe but relatively rare complications include: damage or trauma to a blood vessel, which could require repair; infection from the skin puncture or from the catheter itself; cardiac perforation, causing blood to leak into the sac around the heart and compromising the heart's pumping action, requiring removal using a needle under the breast bone (pericardiocentesis); hematoma at the site(s) of the puncture(s); induction of a dangerous cardiac rhythm requiring an external shock(s); a clot may be dislodged, which may travel to a distant organ and impede blood flow or cause a stroke; myocardial infarction; unanticipated reactions to the medications used during the procedure; damage to the conduction system, requiring a permanent pacemaker; death.
See also
- ElectrocardiogramElectrocardiogramElectrocardiography is a transthoracic interpretation of the electrical activity of the heart over a period of time, as detected by electrodes attached to the outer surface of the skin and recorded by a device external to the body...
(ECG or EKG) - Electrical conduction system of the heartElectrical conduction system of the heartThe normal intrinsic electrical conduction of the heart allows electrical propagation to be transmitted from the Sinoatrial Node through both atria and forward to the Atrioventricular Node. Normal/baseline physiology allows further propagation from the AV node to the ventricle or Purkinje Fibers...
- Ventricular tachycardiaVentricular tachycardiaVentricular tachycardia is a tachycardia, or fast heart rhythm, that originates in one of the ventricles of the heart...
- Arrhythmia
- Antiarrhythmic agents