Epicardial Ablation for Ventricular Tachycardia: Techniques and Complications

Epicardial ablation has become an important option for patients with ventricular tachycardia (VT) whose arrhythmogenic substrate lies on, or extends to, the outer surface of the heart. Although most ventricular tachycardia procedures begin with an endocardial approach, scar-related VT in arrhythmogenic right ventricular cardiomyopathy, non-ischaemic cardiomyopathy, cardiac sarcoidosis, and selected post-infarction cases may require access to tissue that cannot be reached from inside the cardiac chambers.

The procedure can improve rhythm control when carefully selected, yet it introduces risks that are distinct from conventional catheter ablation. Pericardial bleeding, coronary artery injury, phrenic nerve damage, diaphragmatic dysfunction, and postoperative inflammation require detailed planning and experienced multidisciplinary care. For Australian electrophysiology services, the balance between clinical benefit, referral pathways, equipment access, and follow-up capacity is central to safe practice.

Clinical Role And Patient Selection

Epicardial mapping is most useful when imaging, electrocardiography, and previous ablation findings suggest a predominantly epicardial or intramural VT substrate. Clues include a non-ischaemic pattern of scar on cardiac magnetic resonance imaging, a delayed intrinsicoid deflection on the surface ECG, inferior or lateral Q waves without a matching coronary distribution, and failure of an adequate endocardial procedure. In arrhythmogenic right ventricular cardiomyopathy, the so-called “triangle of dysplasia” may extend from the right ventricular epicardium into the outflow tract and inferior wall.

The decision should be based on the clinical burden of VT, implantable cardioverter-defibrillator therapies, ventricular function, comorbidities, and procedural risk. A patient with recurrent electrical storm despite antiarrhythmic medication may justify an aggressive strategy, while a person with limited life expectancy or severe systemic illness may require a different goal of care. Anticoagulation, thrombocytopenia, prior cardiac surgery, and adhesions can materially change the risk profile.

Pre-procedure imaging is particularly valuable. Contrast-enhanced CT can define the relationship between the coronary arteries and intended ablation targets, while cardiac MRI helps identify scar distribution and viable myocardium. In Australia, complex cases are commonly referred to high-volume tertiary centres in Sydney, Melbourne, Brisbane, Perth, or Adelaide, especially when the referring hospital lacks cardiac surgery and advanced three-dimensional mapping support.

Mapping And Access Strategy

Percutaneous subxiphoid access is the most widely used technique. After imaging and sterile preparation, a needle is advanced beneath the xiphoid process into the pericardial space, usually with fluoroscopic, pressure, or echocardiographic guidance. A guidewire and sheath then permit introduction of an ablation catheter. The operator must control the trajectory carefully because the liver, diaphragm, internal mammary vessels, and right ventricular surface may be close to the access path.

A posterior or lateral approach may be needed when the target cannot be reached from a standard subxiphoid puncture. Prior sternotomy, coronary bypass surgery, or inflammatory pericardial disease may produce adhesions that limit catheter movement or prevent safe fluid distribution. In such patients, surgical subxiphoid or thoracoscopic access can be considered, often with a cardiac surgeon present or immediately available.

Epicardial mapping begins with identification of low-voltage regions, late potentials, fractionated electrograms, and local activation patterns during VT or sinus rhythm. High-density mapping catheters can distinguish dense scar from border-zone tissue and help define channels that sustain re-entry. A combined endocardial–epicardial map is often more informative than either surface alone, particularly in non-ischaemic cardiomyopathy where scar can be patchy and layered.

Energy Delivery And Substrate Modification

Radiofrequency energy remains the standard modality for most epicardial VT ablation. Irrigated-tip catheters allow deeper, more consistent lesions, but excessive power can injure adjacent coronary arteries, the phrenic nerve, or the oesophagus. Contact force, impedance, temperature, catheter stability, and lesion duration must be interpreted together rather than used as isolated targets.

Before delivering energy, the operator should assess the course of the major coronary vessels using angiography or integrated imaging. A conservative safety margin is required because thermal injury can cause acute occlusion or delayed stenosis. The phrenic nerve can be identified with high-output pacing; mechanical displacement using pericardial fluid, air, or a balloon may be considered when the nerve overlies the intended lesion set. These methods require careful monitoring because displacement is not always complete.

Ablation may target abnormal electrograms during sinus rhythm, the clinical VT circuit, or a broader scar region when VT is unstable or cannot be induced. Substrate modification can reduce recurrent arrhythmia, but it should be proportionate to the likely mechanism. Overly extensive lesions increase procedural exposure without guaranteeing durable control. Cryoablation has a limited but potentially useful role in selected locations, although availability, lesion characteristics, and operator experience vary across the local market.

Major Complications And Their Mechanisms

The most immediate concern is bleeding into the pericardial space. A needle or sheath can lacerate the right ventricle, coronary artery, internal mammary artery, or another vascular structure, resulting in haemopericardium and tamponade. Sudden hypotension, rising pericardial pressure, reduced chamber filling, or changes on intracardiac electrograms should prompt rapid assessment. Echocardiography, blood products, pericardiocentesis equipment, and surgical backup must be available.

Coronary artery injury is a distinctive hazard of epicardial ablation. Thermal damage may produce spasm, dissection, thrombosis, or delayed narrowing. Coronary angiography before and, when indicated, after energy delivery helps define risk. The circumflex artery is particularly important near the mitral annulus and lateral left ventricle, while the right coronary artery may be vulnerable along the inferior right ventricular and diaphragmatic surfaces.

Phrenic nerve injury can cause diaphragmatic paresis, breathlessness, or persistent elevation of a hemidiaphragm. Injury to the oesophagus, stomach, liver, or pericardial vessels is less common but potentially serious. Pericarditis and inflammatory chest pain are frequent enough to anticipate, while constrictive pericarditis is rare. Adhesions can increase both access difficulty and the chance of organ injury.

Risk Reduction And Periprocedural Care

Safety begins with a coordinated plan involving electrophysiology, cardiac anaesthesia, imaging, nursing, and cardiothoracic surgery. General anaesthesia may improve catheter stability and control in patients with recurrent VT, but it can also alter haemodynamics and suppress arrhythmia inducibility. Defibrillation capability, arterial pressure monitoring, vascular access, and rapid blood product availability should be established before puncture.

Anticoagulant management requires individualisation. The team must balance thromboembolic risk from the endocardial component against bleeding risk from the pericardial access. Intraprocedural heparinisation is commonly delayed until epicardial access is secured, with subsequent reversal or adjustment according to the procedural stage and institutional protocol. Baseline haemoglobin, platelet count, renal function, and cross-sectional imaging can reveal correctable risks.

At the end of the case, the pericardial space should be inspected for ongoing bleeding, and a drain may be left when clinically appropriate. Serial echocardiography, haemoglobin measurement, ECG review, and observation for hypotension or chest pain are essential. Pain control and anti-inflammatory treatment can improve recovery, but unexplained tachycardia, dyspnoea, or hypotension should never be attributed to routine post-ablation inflammation without assessment.

Recovery And Long-Term Rhythm Control

Successful substrate ablation does not remove the underlying cardiomyopathy. Patients usually continue to require guideline-directed heart failure therapy and, where indicated, an implantable cardioverter-defibrillator. Antiarrhythmic medication may be reduced in selected patients, but changes should reflect ventricular function, arrhythmia burden, renal and hepatic status, and the result of follow-up monitoring.

Early recurrence can result from transient inflammation, incomplete lesion formation, or an untreated endocardial component. Device interrogation is therefore central to follow-up. Stored electrograms can distinguish sustained VT from supraventricular tachycardia, oversensing, or inappropriate therapy. Broader rhythm surveillance principles are also relevant in device populations, as illustrated by the discussion of screening after cryptogenic stroke, although atrial arrhythmia detection and VT surveillance involve different clinical questions.

Patients should receive clear instructions about fever, worsening chest pain, syncope, palpitations, breathlessness, and wound problems. Rehabilitation and return to driving or physically demanding work must follow Australian state or territory regulations and the patient’s arrhythmia history. People travelling long distances from regional Western Australia, the Northern Territory, or remote Queensland may need coordinated local follow-up before returning home.

Evidence, Team Expertise And Australian Practice

Outcomes depend heavily on substrate, disease stage, previous procedures, and centre experience. Epicardial access can produce meaningful reductions in VT recurrence in carefully selected patients, but it is not a universal replacement for endocardial ablation. Randomised evidence remains limited in several disease groups, and published series often come from highly specialised institutions. Registry data and prospective collaboration are therefore important for refining patient selection and reporting complications consistently.

Australian practice also reflects a mixed public and private health system. Access to advanced mapping platforms, hybrid operating facilities, cardiac surgery, and cardiac MRI may differ between metropolitan and regional hospitals. Medicare-funded pathways can involve substantial referral coordination, while privately insured patients may encounter different scheduling and coverage arrangements. Device generators, mapping catheters, epicardial equipment, and imaging support are also influenced by Therapeutic Goods Administration approval, procurement contracts, and hospital budgets.

Training should include simulation of subxiphoid access, recognition of tamponade, coronary protection, phrenic nerve testing, and management of unstable VT. Centres can improve quality by maintaining a prospective database covering access attempts, conversion to surgery, bleeding, coronary injury, neurological events, recurrence, and survival. The Journal of Arrhythmia provides a useful setting for clinicians and researchers to follow developments in ventricular arrhythmia, electrophysiology, ablation, and implantable device care.

Epicardial VT ablation is safest when it is treated as a complex cardiac intervention rather than an isolated catheter procedure. Careful imaging, a clear anatomical hypothesis, experienced operators, surgical readiness, and structured follow-up should be established before the first puncture. Australian electrophysiology teams can strengthen patient care by concentrating complex cases in appropriately equipped centres, sharing outcomes across referral networks, and contributing high-quality local data to the international evidence base.