Antitachycardia pacing for ventricular tachycardia in cardiac sarcoidosis

Cardiac sarcoidosis can create a difficult combination of myocardial inflammation, patchy fibrosis, conduction disease and ventricular arrhythmia. Ventricular tachycardia (VT) may arise from active inflammatory lesions, established scar, or both. For patients with an implantable cardioverter-defibrillator (ICD), antitachycardia pacing (ATP) offers a way to terminate many organised VT episodes without delivering a painful shock.

ATP is useful, but it is not a stand-alone treatment for the underlying disease. The best outcomes come from integrating device programming with immunosuppression when inflammation is active, guideline-directed heart failure therapy, catheter ablation, careful imaging and long-term rhythm surveillance. In Australia, that care often involves coordination between a local cardiologist, an electrophysiology service in a capital city and nuclear medicine or cardiac imaging teams with experience in sarcoidosis.

Why cardiac sarcoidosis produces ventricular tachycardia

Granulomatous inflammation may involve the atrioventricular node, His–Purkinje system and ventricular myocardium. As inflammation heals, replacement fibrosis creates areas of slow conduction and conduction block. These regions can form a re-entry circuit, particularly around the basal septum, lateral wall or ventricular aneurysm. The resulting VT is frequently monomorphic, making it a potential target for ATP.

The rhythm substrate can change over time. A patient may have active fluorodeoxyglucose uptake on positron emission tomography (PET) during one period and a predominantly fibrotic substrate later. A flare of inflammation can increase ventricular ectopy and destabilise a previously tolerated rhythm. Conversely, scar-related VT may continue after inflammation has settled. Cardiac magnetic resonance with late gadolinium enhancement, FDG-PET, echocardiography and clinical findings must therefore be interpreted together rather than treated as isolated results.

Device therapy is considered according to the patient’s arrhythmic risk, ventricular function, documented VT and broader clinical picture. An ICD can provide bradycardia pacing, ATP and defibrillation, but the indication and device type require individual assessment. A history of unexplained syncope, sustained VT, significant left ventricular dysfunction or extensive myocardial scar can change the risk calculation even when the ejection fraction is not severely reduced.

How ATP terminates organised VT

ATP delivers a short sequence of paced impulses faster than the tachycardia. If the impulses enter the re-entry circuit and reach excitable tissue at the right moment, they can interrupt the circuit and restore sinus rhythm. The patient may feel little or nothing, which is a major advantage over an ICD shock. Avoiding shocks can reduce distress, improve quality of life and limit repeated emergency presentations.

The response depends on the VT cycle length, the location of the circuit, the pacing site and the timing of each stimulus. Burst pacing uses pulses at a fixed interval, while ramp pacing progressively shortens the interval. A common strategy is to begin with a less aggressive sequence, then provide a second attempt before shock therapy. Programming must preserve a safety margin: overly rapid or poorly timed pacing can accelerate VT or, rarely, produce a faster ventricular rhythm.

ATP is most effective for stable monomorphic VT that is sufficiently organised for the device to recognise and pace. It is less reliable for polymorphic VT, ventricular fibrillation or very rapid rhythms. Detection duration and rate zones should be chosen to reduce inappropriate treatment while avoiding prolonged exposure to an unstable arrhythmia. Contemporary programming frequently uses longer detection intervals and evidence-based therapy zones, adjusted to the individual’s clinical history.

Programming decisions and device selection

The electrophysiology team needs a clear record of the patient’s clinical VT. Stored electrograms, twelve-lead ECGs and previous device episodes can show whether the rhythm is monomorphic, how quickly it begins and whether ATP has worked. Programming should then reflect the known VT cycle length, haemodynamic tolerance and the possibility of more than one circuit. A device clinic can review episode logs and adjust therapy after each appropriate or inappropriate treatment.

Patients should understand that a successful ATP episode may be recorded as a therapy even when no shock is felt. Recurrent episodes, presyncope, chest pain or breathlessness warrant urgent clinical review. A cluster of VT episodes may represent electrical storm, active inflammation, worsening ventricular function or a new trigger such as electrolyte disturbance. Management can include reprogramming, antiarrhythmic medication, sedation in an acute setting, sympathetic blockade, ablation and assessment for immunosuppression.

Device selection also matters. A transvenous ICD can deliver ATP because it has an intracardiac lead. A subcutaneous ICD avoids an intravascular lead and may be attractive when pacing is not required, but it cannot provide conventional ATP or ongoing bradycardia pacing. The practical differences are outlined in discussions of subcutaneous ICD programming, particularly when balancing lead-related complications against the need for ventricular tachycardia therapy.

Combining ATP with inflammation control and ablation

ATP treats the rhythm episode, not the granulomatous process or the scar that supports re-entry. When cardiac sarcoidosis is clinically active, a multidisciplinary team may consider corticosteroids and steroid-sparing therapy, guided by imaging, extracardiac involvement and the risks of immunosuppression. Arrhythmia recurrence does not automatically prove that inflammation is active, so treatment decisions should be based on the whole picture rather than device episodes alone.

Antiarrhythmic drugs may reduce VT recurrence and ICD interventions, although renal function, lung disease, thyroid status and drug interactions influence selection. Amiodarone can be effective but requires surveillance for pulmonary, hepatic, thyroid and ocular toxicity. Sotalol and other agents may be limited by QT prolongation or ventricular function. Electrolytes, especially potassium and magnesium, should be corrected during acute care and reviewed during follow-up.

Catheter ablation is considered when VT recurs despite medication and immunosuppression, when ATP or shocks are frequent, or when drug toxicity is unacceptable. Sarcoid VT may require endocardial and epicardial mapping because scar can involve multiple ventricular surfaces. Ablation can reduce arrhythmia burden, but it does not remove the need for an ICD in a patient who remains at risk of sudden cardiac death. Procedural planning should account for inflammation, anticoagulation, anaesthetic risk and the possibility of changing substrate.

Follow-up in Australian practice

Australian patients may receive specialist care through major electrophysiology centres in Sydney, Melbourne, Brisbane, Perth or Adelaide, while living several hours away in regional New South Wales, Queensland, Victoria or Western Australia. Remote device monitoring can reduce unnecessary travel, but it does not replace in-person assessment after a shock, syncope or a series of ATP episodes. Clear escalation pathways between the device clinic, emergency department and treating cardiologist are essential.

Access to cardiac PET and advanced MRI is variable, particularly outside metropolitan areas. Medicare arrangements, referral requirements and local availability can affect how quickly inflammation is assessed. A patient in regional Queensland or the Northern Territory may need to travel to a tertiary centre for imaging, biopsy, ablation or device revision. Care planning should include medication supply, transport, accommodation and communication with local clinicians rather than assuming every review can occur in a capital city.

The Australian rhythm community also works within a practical framework shaped by the Cardiac Society of Australia and New Zealand, state-based hospital systems and private electrophysiology services. Aboriginal and Torres Strait Islander patients may face additional distance, access and cultural safety barriers, so shared decision-making should include family, community-controlled health services and interpreters where appropriate. These considerations are clinically relevant when deciding between repeated hospital visits, remote monitoring, ablation and referral for advanced heart failure care.

The differential diagnosis deserves equal attention. Not every wide-complex tachycardia in a patient with suspected sarcoidosis is caused by cardiac sarcoid, and an apparent ventricular arrhythmia may occasionally reflect supraventricular tachycardia with aberrancy or an accessory pathway. In patients without structural disease, a structured idiopathic VF work-up illustrates why inherited arrhythmia syndromes, concealed cardiomyopathy and reversible causes should be considered before assigning a single diagnosis.

Atrial tachycardia and atrial fibrillation can also complicate device interpretation, increase inappropriate therapies and worsen ventricular function. Stored electrograms, atrial sensing and careful zone programming help distinguish these rhythms from VT. When an atrial rhythm remains uncertain or becomes a treatment target, broader electrophysiological techniques are relevant; experience with focal atrial tachycardia mapping demonstrates how detailed activation mapping can clarify complex tachycardia mechanisms.

For clinicians, the central task is to treat ATP as part of a continuing risk-management strategy. Review the substrate, confirm the rhythm, check for inflammation, examine the device record and ask whether the patient’s treatment remains appropriate as the disease evolves. For patients and families, knowing what ATP feels like, when to contact the device clinic and when to call emergency services can make device therapy safer and less frightening.

Researchers, trainees and practising clinicians can use the Journal of Arrhythmia’s peer-reviewed resources to follow developments in cardiac sarcoidosis, ventricular arrhythmia, ICD programming and catheter ablation. Careful reporting of device settings, imaging findings, treatment response and long-term outcomes will help refine ATP-based strategies for patients across Australia and the wider Asia-Pacific region.