Diagnostic Electrophysiological Studies
Electrophysiological studies are invasive diagnostic procedures for the investigation of possible arrhythmias and the assessment of the risk for life-threatening conditions in patients who present with episodes of tachyarrhythmia or syncope. This invasive diagnostic procedure, performed percutaneously under local anesthesia, allows access to the function of the electrical system of the heart and identification of the mechanism potentially responsible for the arrhythmia. It is most of the time used to investigate and determine the appropriate therapeutic approach of tachyarrhythmias, while patients with bradyarrhythmias are subjected less frequently to this diagnostic procedure. Moreover, it enables risk stratification of potentially dangerous future events in patients with arrhythmias and determination of the need for pharmacological or more invasive treatment.
Ablation Therapy for Arrhythmias
Ablation enables eradication of the cause of the arrhythmia—such as an ectopic arrhythmogenic focus or a reentrant circuit—and its efficacy depends on the type of arrhythmia. The procedure is performed via puncture of the femoral vein or artery under local anesthesia. Once the arrhythmogenic substrate is located, catheters bearing electrodes at their tips are percutaneously introduced into the heart under fluoroscopic guidance to record electrical signals from the relevant cardiac structures. These steps are typically already completed if a prior electrophysiological study has been performed. After the catheters are placed and tachycardia is induced, a specialized ablation catheter is positioned so that its electrodes contact the myocardial regions responsible for the arrhythmia. The catheter may need to be moved from site to site until the optimal target area is found. Subsequently, localized high-frequency current is delivered through radiofrequency waves via the ablation catheter, producing thermal destruction of small areas of myocardium responsible for the arrhythmia. Ablation may also be performed using cryoballoon technology (cryoablation) or the newer pulse field ablation method.
If diagnostic electrophysiological studies reveal the need for interventional ablation therapy, this may be performed during the same session. Once the mapping of the arrhythmia’s origin and characteristics has been completed, therapeutic intervention with ablation may follow, if appropriate and after discussion with the patient. The two procedures are often combined in the same session to minimize patient discomfort, as vascular access has already been established for advancing the specialized catheters used during ablation.
Depending on the location and mechanism of the arrhythmia, interventional therapeutic procedures include:
| Tachycardia Type | Success rate of ablation |
|---|
| Atrial fibrillation | 70–80% |
| Atrial flutter | 95% |
| Atrial tachycardia | 85% |
| Atrioventricular nodal reentrant tachycardia | 97% |
| AV nodal ablation | >97% |
| Accessory pathway ablation | 92% |
| Ventricular tachycardia ablation | 50–80% |
Pacemaker Implantation
A pacemaker is a medical device that uses electrical impulses delivered through electrodes to stimulate the heart muscles and regulate the heartbeat. The primary purpose of the device is to maintain an adequate heart rate, either because the intrinsic rate is too slow or because there is a block in the electrical conduction system of the heart. Normally, the heart has its own natural pacemaker located in the right atrium, known as the sinoatrial node, which generates electrical impulses that initiate myocardial contraction. These impulses are then transmitted to the atrioventricular node, located near the center of the heart, and subsequently to the ventricular myocardium, resulting in ventricular contraction and blood circulation.
Pacemaker implantation is indicated in cases of dysfunction of the sinoatrial node or conduction abnormalities involving the atrioventricular node. The procedure is performed under local anesthesia, sometimes with mild sedation, in a dedicated hemodynamic or electrophysiology laboratory. A small incision is typically made below the clavicle to gain vascular access by puncturing the cephalic or, if not feasible, the subclavian vein. Through this vein, the leads are advanced and positioned in the myocardium under fluoroscopic guidance after appropriate electrical measurements have been performed using an external device.
In recent years, leadless pacemakers have been introduced, which are implanted directly within the heart via catheters through the femoral vein, eliminating the need for incisions or transvenous leads.
Implantable Cardioverter-Defibrillator (ICD) Implantation
An implantable cardioverter-defibrillator (ICD) is a device that detects life-threatening arrhythmias—such as ventricular tachycardia or ventricular fibrillation—and delivers an electrical shock to the heart when necessary to restore normal rhythm. ICDs significantly reduce the risk of sudden cardiac death in patients who have experienced an episode of severe, life-threatening tachyarrhythmia or are at high risk of such an event. Patients with underlying cardiac conditions such as myocardial infarction, dilated cardiomyopathy, other cardiomyopathies, or conduction system diseases who are at high risk for sudden cardiac death should be evaluated for ICD implantation.
The implantation procedure is similar to that of conventional pacemakers. Recently, new models have been developed that can be implanted subcutaneously with a single lead, avoiding the need to place electrodes within the cardiac chambers.
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