The most important test used for the diagnosis of rhythm disorders is the electrophysiological study (EPS). It is a procedure used to identify the cause of palpitations if a diagnosis cannot be established through 24-hour Holter monitors or event recorders. EPS is a diagnostic test performed to determine the cause of an abnormal heart rhythm. Similar to cardiac catheterization and angiography, EPS is performed under local anesthesia applied to the groin and/or neck region, and in some special cases, under general anesthesia. Ablation therapy is the procedure of eliminating the region identified as the source of the rhythm disorder during the EPS procedure, typically by delivering radiofrequency energy. In other words, it is a permanently curative procedure for arrhythmia.
Who Should Undergo Cardiac Electrophysiological Study (EPS) and Ablation Treatments, and What Are They Used to Treat?
Did you know that your heart has a system similar to a city's electrical grid? In reality, impulses originating from the main center located in the right atrium (sinus node) pass through an intermediate station located between the atria and ventricles (atrioventricular node) with a short delay, and then spread to the ventricles via specialized conduction pathways. Thus, the electrical impulse generated in the main center is transmitted to all heart muscle cells, enabling the heart to contract. Due to various reasons, disruptions can occur in this normal impulse and conduction system of the heart. Sometimes, congenital accessory pathways can lead to "short circuits" in conduction, causing rapid heartbeats known as tachycardia.
Furthermore, sometimes an impulse can be generated from any part of the heart outside the control of the aforementioned main impulse center, causing rapid heartbeats. Not all rhythm disorders are life-threatening. In most patients, they only cause a feeling of discomfort. However, some rare rhythm disorders carry the risk of fainting and death. With this diagnostic method called electrophysiological study, thin wires called electrode catheters are inserted into the vessels through the groin and/or neck and guided to the heart. Electrical signals taken directly from inside the heart are evaluated via an advanced computer to investigate deviations from the normal. In this way, it is understood whether the heart's main center impulse system is working well and whether the system transmitting the impulses is functioning reliably.
In most cases, in patients with complaints of palpitations in the form of rapid heartbeats, the cause of the patient's complaint is investigated by creating these rapid heartbeats using special methods with impulses delivered from these wires (2-4 wires, depending on the purpose of the study and the type of rhythm disorder) placed inside the heart. Thus, if the presence of short circuits is detected, the palpitations are completely treated by delivering point-specific energy via radio waves, or if a focus causing the palpitations is identified, it is eliminated by delivering radio wave energy again. This is called catheter ablation therapy. Today, improvements have been made in the equipment used in electrophysiological studies, and new techniques have been introduced. In addition to traditional EPS, treatments using 3D methods and treatments by cooling/freezing (cryoablation) in addition to heating have become possible.
In such procedures, the patient may need to receive general/superficial anesthesia, undergo transesophageal echocardiography (TEE), and use additional materials to pass from the right atrium to the left atrium of the heart via a needle. Although these techniques offer a chance of treatment for some previously untreatable rhythm disorders, they carry risks for the patient such as bleeding, embolism (blood clots traveling to the body), and perforation of heart chambers that may require surgery. Today, permanent treatments for most palpitations in the form of rapid heartbeats (tachycardia) have become possible with electrophysiological studies.
How Do 3D Mapping Systems Work?
3D electroanatomical navigation mapping systems can visualize the position of catheters in real-time on a computer screen and reconstruct a detailed 3D surface anatomy of a specific heart chamber. At the same time, they label this reconstructed endocardial or epicardial surface geometry (which appears like a shell in a virtual 3D space) with local electrophysiological information such as activation time (i.e., the timing of local activation), unipolar or bipolar voltage amplitude (i.e., the presence of normal healthy tissues or scar tissue), and the presence of fractional complex electrograms or late potentials in cases of atrial fibrillation or ventricular tachycardia.
Currently, only three major systems are on the market for complex mapping and are widely used by the medical community: CARTO®, EnSite, and RHYTHMIA.
The CARTO System
In this system, first proposed in 1996, artificial magnetic fields are used for electroanatomical navigation and geometry reconstruction. This system requires specially produced catheters with magnetic sensors (in the form of three miniature coils) at their tips to create maps. As with other systems, the 3D geometry of the entire heart chamber is reconstructed by dragging the catheter along the endocardial/epicardial surface, collecting electrical information at each point. Activation times at each recorded point on the map are compared with a reference time (intracardiac or surface electrocardiogram on a reference catheter) and then color-coded (from red to purple, yellow to green, and blue) from the beginning to the end of a predefined "window of interest," thereby revealing re-entry circuits or focal sources of activation.
With the map created by the mapping system, it is possible to merge computed tomography scans or magnetic resonance imaging reconstructions of the heart chamber of interest, develop detailed anatomical points for a more comprehensive map, and correct geometry errors to a certain degree. The precision of these merging techniques is around 2-3 mm. The system also provides the operator with information about distance and the effectiveness of the applied treatment on the tissue in a 3D environment with artificial intelligence support. In this form, the CARTO system continues to be the world's most advanced technology in this field.
The system provides the doctor with a real-time map providing anatomical geometry, an activation map showing the course of the electrical wave over the muscle, and a voltage map providing information about the viability of the tissue. Additionally, a pace mapping feature, which allows the comparison of the signal generated by the stimulation of the muscle with the signal generated by spontaneous muscle stimulation, is also very useful for the doctor in planning effective treatments.
Does Communication Between the Patient and the Doctor Continue During the Procedure?
During an electrophysiological study, you may feel palpitations when test impulses are delivered from inside the heart, or you may feel a similar sensation when the palpitations that are your main complaint are triggered by the impulses delivered to the heart. Sometimes, after a rapid heartbeat arrhythmia is triggered, it may be necessary to deliver an electric shock to correct it from the outside. You will not feel pain as you will often be given medication to put you to sleep before the shock delivery.
Electrophysiological examinations performed for diagnostic purposes last about 30-60 minutes. If a therapeutic intervention is required, these are procedures that can take up to 1-4 hours. During this procedure, the medical team and the patient are exposed to a certain amount of X-rays. If pregnancy is a possibility, the doctor must be informed before the procedure. These procedures are fundamentally low-risk applications. However, as with any procedure, they can bring some problems. The probability of death is very low. Rarely, blood may leak into the pericardium due to perforation of the heart muscle during the procedure. Again, rarely, during therapeutic procedures (ablation), blocks may occur in the heart's conduction system during the delivery of radio wave energy because the short circuit causing the palpitations is very close to the heart's normal conduction system. In such cases, a permanent pacemaker may need to be implanted. In 2-3% of cases, bleeding, subcutaneous hematomas, and associated swelling and pain may occur at the vascular access sites. However, these usually do not cause significant problems and resolve spontaneously. Although rare, due to the invasive nature of the procedure, air and blood may leak into the pleural space, and pulmonary or systemic embolism may occur. These complications are quite rare and will be managed appropriately by the operator.
Data obtained through electrophysiological study cannot be provided by any other diagnostic method. It is often applied when other diagnostic methods are insufficient. Rhythm disorder treatment performed by delivering radio waves via the catheter ablation method is applied in rhythm disorders that cannot be controlled with medication or if patients do not wish to take medication for life. In some cases, the rhythm disorder can be life-threatening. In such cases, direct catheter ablation may be required. The success rate of catheter ablation for rapid heartbeat rhythm disorders varies between 70-95%, depending on the type of palpitation targeted for treatment and the location of the short circuit. Success is defined as the permanent elimination of palpitations. After a successful application, the probability of recurrence of palpitations varies according to the type of rhythm disorder. For example, in palpitations due to short circuits in the heart, this probability is between 5-8%.
The procedure is basically performed under local anesthesia by numbing the needle entry sites, and in some cases under general anesthesia; sedative medication may be administered to help you feel comfortable during the procedure. After the procedures, you may need to lie down without moving your legs to prevent bleeding.
With the Carto 3 system, many arrhythmias with complex mechanisms have become treatable in a shorter time and with higher success rates compared to traditional EPS. This has ensured that this technology meets skill and that the best treatments are offered to our patients with courage.
Prof. Dr. Sinan Altan KOCAMAN
Specialist in Cardiovascular Diseases and Rhythm Disorders
Interventional Cardiologist and Electrophysiologist
