A Multicentre Randomised Study on Percutaneous Stellate Ganglion Block as First Line Treatment in Patients With Electrical Storm: the STAR 2 Study.

Electrical storm (ES) is a critical manifestation of electrical instability of the heart, characterized by clustered episodes of ventricular tachycardia (VT) or ventricular fibrillation (VF) that trigger repeated interventions by implantable cardioverter-defibrillators or require external defibrillation. Beyond the immediate risk of hemodynamic collapse and cardiac arrest, ES is associated with repeated myocardial injury from shocks, psychological distress, prolonged intensive care stays, and increased short- and medium-term mortality. Contemporary cohorts indicate that ES occurs in approximately 5% of patients with an ICD implanted for primary prevention and in up to 25% of those implanted for secondary prevention, underscoring its clinical relevance.

The pathophysiology of ES involves a dynamic interaction between an arrhythmogenic substrate, often related to structural heart disease or channelopathies, and transient triggers that promote initiation and maintenance of ventricular arrhythmias. Among these triggers, heightened sympathetic activity plays a central role. Experimental work beginning in the late 1960s demonstrated that acute myocardial ischemia activates sympathetic afferents before electrocardiographic changes become evident, and that direct stimulation of the left stellate ganglion can induce delayed afterdepolarizations and lower the threshold for VF. Conversely, left cardiac sympathetic denervation raises the fibrillation threshold and reduces arrhythmic vulnerability. These observations established the conceptual foundation for targeting the sympathetic nervous system in the management of malignant ventricular arrhythmias.

Despite this well-characterized pathophysiology, current guideline-directed management of ES remains anchored in pharmacological antiarrhythmic therapy, with intravenous amiodarone as the most widely adopted first-line agent. Amiodarone is recommended by European and American guidelines for recurrent VT/VF and advanced life support scenarios. However, its onset of action is not immediate, efficacy in refractory ES is variable, and its administration is not devoid of acute adverse effects, including hypotension, bradycardia, and potential proarrhythmia. In patients with recurrent shocks despite pharmacological therapy, additional options such as deep sedation, general anaesthesia, catheter ablation, or surgical sympathetic denervation may be considered, but these approaches are not universally available, may require significant resources, and are not always feasible in unstable patients.

In this context, percutaneous stellate ganglion block (PSGB) has emerged as a rapid, minimally invasive neuromodulatory intervention that can be performed at the bedside with equipment commonly available in cardiology and critical care settings. PSGB involves percutaneous injection of local anaesthetics near the left stellate ganglion, resulting in temporary blockade of sympathetic efferent fibres innervating the heart. Two main techniques have been described: an anterior anatomical approach based on palpation of the Chassaignac tubercle at the C6 level, and a lateral ultrasound-guided approach targeting the prevertebral space over the longus colli muscle. Both techniques have been employed in observational studies with comparable efficacy and safety profiles.

Clinical evidence supporting PSGB in ES has accumulated over the past two decades. Early case reports described successful termination of drug-resistant VT and VF following left PSGB in patients with prolonged QT interval and structural heart disease. Subsequent monocentric retrospective series consistently reported marked reductions in arrhythmic burden and ICD shocks after PSGB, often with complete suppression of treated arrhythmias in a substantial proportion of patients. More recently, two multicentre observational studies have provided more robust evidence. The STAR study, promoted by our group and involving 19 Italian centres, enrolled 131 patients who underwent 184 PSGB procedures. In that study, 92% of patients achieved a reduction of at least 50% in treated ventricular arrhythmias in the 12 hours following the last procedure, with a median reduction of 100%. A significant decrease in arrhythmic episodes was observed both in per-procedure analysis comparing the hour before and after each block, and in per-patient analysis comparing the 12 hours before and after the intervention. Importantly, only one major complication occurred, supporting an excellent safety profile even in a population frequently receiving antiplatelet and anticoagulant therapy. A second multicentre study from the United States and Czech Republic confirmed these findings, demonstrating significant reductions in VT/VF episodes and defibrillation events in the 24 hours following PSGB.