Introduction
Ventricular tachycardia (VT) is a type of arrhythmia (abnormal heart rhythm) that occurs when the heart’s lower chamber beats very fast (more than 100 to 120 beats per minute) with three or more consecutive irregular heartbeats. It may be a potentially life-threatening condition if it lasts for more than a few seconds. Ischemic heart disease (reduced blood flow to the heart) is one of the most common causes of ventricular tachycardia. The other causes of ventricular tachycardia include non-ischemic dilated cardiomyopathy (abnormally stretching of the left ventricle), congenital heart disease, electrolyte imbalances, and illicit drugs such as Cocaine or Methamphetamine. Idiopathic ventricular tachycardia is a rare type of ventricular tachycardia and is mostly found in young people with no evidence of structural heart defects.
Catheter ablation is an effective treatment option for patients with ventricular tachycardia. However, the prognosis depends on the underlying cause or structural abnormalities in the heart.
What Is Percutaneous Epicardial Ablation?
Ventricular tachycardia, or VT ablation, employs cold or heat energy to create small scars in the heart tissues. These scars block the irregular signals that cause erratic or rapid heartbeats, thus restoring regular cardiac rhythm. This procedure is usually recommended when medications and other methods are ineffective for the patient. Ventricular ablation can be done inside and outside the heart, sometimes in both areas. If the ablation is performed from outside the heart using a minimally invasive approach, it is called epicardial ablation. It has become an adjunctive tool for electrophysiologists to treat cardiac arrhythmias, including atrial and ventricular tachycardia. Epicardial mapping (a technique to identify the epicardial site using a contrast medium) and ablation have been safely conducted for over a decade at many healthcare centers worldwide.
What Are the Indications for Epicardial Mapping and Ablation?
Epicardial ablation is a commonly employed technique after a failed endocardial ablation (a catheter is used to create deep lesions). It may also be used if the patient has a subepicardial or mid-myocardial scar, commonly seen in patients with right ventricular cardiomyopathy, dilated cardiomyopathy (DCM), and hypertrophic cardiomyopathy (HCM) (thickening of the heart muscles). Studies have shown that when epicardial ablation was performed with endocardial ablation, patients with ischemic cardiomyopathy experienced freedom from VT recurrence compared to other limited endocardial strategies. Selecting an epicardial approach in ventricular tachycardia ablation needs several factors to be considered, such as
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Previous history of unsuccessful endocardial ablation.
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Electrocardiographic criteria.
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Scar localization by imaging studies.
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Likelihood of epicardial ventricular tachycardia in the underlying condition.
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Intra-procedural mapping.
How Is Epicardial Ablation Performed?
Percutaneous epicardial mapping and ablation is a catheter-based procedure to treat ventricular tachycardia caused by subepicardial or intramural substrates in patients with nonischemic cardiomyopathy. The epicardial ablation technique is used when critical parts of the VT circuits are mainly epicardial. The procedure is performed in a hospital and takes three to six hours. Before the procedure, anesthesia is administered to help the patient relax and numb the area during the surgery. Regional anesthesia or general anesthesia is used; the amount of sedation depends on the severity of the condition and the patient's overall health.
Percutaneous epicardial ablation involves threading a long flexible tube called a catheter through a small needle puncture into a blood vessel, usually in the groin region. It is gently guided towards the heart to access the outside of the heart muscle. Sensors are placed on the catheter's tip, sending electrical signals and recording heart activity. The surgical doctors use this data to determine the suitable site for the VT ablation treatment. Radiofrequency (heat energy) or cryoablation (cold energy) creates tiny scars in the heart tissues that block irregular heart rhythms. The surgeon places a needle through the skin on the chest wall and into the fluid-filled sack lining around the heart. A sheath is then inserted, and catheters go through the sheath and access the outside area of the heart. After the procedure, the patient is shifted to a recovery area for an overnight stay for close monitoring by the healthcare team.
What Are the Complications of Percutaneous Epicardial Ablation?
Percutaneous epicardial access and ablation may cause collateral injury to the thoracic and abdominal structures, including the lungs, phrenic nerve, pleura, diaphragm, liver, and epicardial vessels. A detailed medical and surgical history is required to assess the possibility of pericardial adhesions.
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Complications related to percutaneous epicardial ablation can be further subdivided into vascular injury and right ventricular (RV) puncture. It can occur in about 17 percent of cases where percutaneous access is attempted, and approximately 50 percent of these cases may result in pericardial bleeding. Most of the cases are self-limiting; however, in rare instances, large right ventricular perforations may need surgical repair due to persistent bleeding.
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Pericarditis (inflammation of the pericardium) is also one of the common complications of epicardial ablation; approximately 30 percent of patients undergoing this procedure may experience this condition. However, most cases can be managed conservatively by anti-inflammatory agents. Regular use of systemic, non-steroidal, and intrapericardial corticosteroids can also prevent procedure-related pericarditis.
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Although rare, phrenic nerve injury has been reported in some patients if the ablation site is near it. Therefore, phrenic nerve mapping must be done to prevent this complication.
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Some of the unusual complications include pseudoaneurysm (swelling of the blood vessel) and fistulas (an abnormal connection between the blood vessels) involving the right ventricle, hepatic injury (liver injury), and coronary vasospasm (sudden constriction of cardiac arteries).
Conclusion
Ventricular tachycardia is one of the challenging medical conditions encountered by both cardiac patients and healthcare professionals treating them. Percutaneous epicardial ablation is a technique in which a catheter is inserted through a small needle puncture in the chest wall. It allows access to the outside of the heart muscle, where irregular heart rhythms occur. This approach is utilized during ablation procedures and the traditional approach by cardiac electrophysiologists for ventricular and supraventricular tachycardias. Most patients feel less tired and experience an improved quality of life after the VT ablation procedure. However, there may be a relapse of irregular heart rhythm in some rare cases. Therefore, there is still scope for improving the safety of epicardial access and the efficacy of sources to minimize complications and successfully deliver the treatment.
