Critical Care Alert: Electrical Storm Treatment by Percutaneous Stellate Ganglion Block: The STAR Study

ARTICLE: Savastano S, Baldi E, Compagnoni S, et al., for the STAR study group. Electrical Storm Treatment by Percutaneous Stellate Ganglion Block: The STAR Study. Eur Heart J. 2024;45(10):823-833.

OBJECTIVE: To evaluate the effectiveness and safety of percutaneous stellate ganglion block (PSGB) on refractory electrical storm

BACKGROUND

Electrical storm (ES) is defined as the occurrence of 3 or more episodes of ventricular tachycardia (VT) or ventricular fibrillation (VF) within 24 hours.¹ ES is relatively common in patients with implantable cardioverter defibrillators (ICD), occurring in approximately 5% of patients with ICD for primary prevention and in 25% of patients with ICD for secondary prevention. ES is most common in patients with a low ejection fraction, chronic kidney disease, and prior myocardial infarction.²

Treatment of ES has historically been difficult and can quickly lead to patient decompensation and cardiac arrest. Traditional treatment includes both antiarrhythmic drugs and anti-tachycardic pacing or direct current shocks, both of which can be difficult to obtain quickly in the setting of the decompensated patient.³ Patients experiencing ES have increased sympathetic tone at baseline, which can be further compounded by repeated shocks as well as the exogenous epinephrine that is given during ACLS. The surge in catecholamines and sympathetic overactivation makes the heart more susceptible to ischemia and further potentiates arrhythmias, putting the patient in a vicious cycle. As a result, ES is associated with significant morbidity and mortality.⁴ Therefore, further treatment options are needed to address ES appropriately.

PSGB first became available in the 1970s after the relationship between sympathetic activation and ventricular arrhythmias was discovered. Since then, several isolated case reports and small case studies have been published that illustrate the effectiveness of the PSGB for ES.⁵ However, several challenges have led to PSGB not being widely used. Historically, the techniques have methodically differed in their timing and approach.³ Additionally, because there have only been limited case studies on PSGB, little is known about the generalizability. Finally, the procedure is not currently widely taught during training and provider experience may be limited. The STAR study was designed to measure the effectiveness, safety, and generalizability of the PSGB in refractory ES.

DESIGN

The STAR study is a multicenter, international retrospective and prospective observational longitudinal study. Patients who were experiencing ES refractory to at least one standard treatment between July 2017 and June 2023 were included.

ES was defined as 3 or more separate episodes of VT or VF that were sustained or required treatment. ES was defined as refractory in the case of arrhythmic relapses despite IV administration of antiarrhythmic drugs (AADs). An arrythmic event was defined as an episode of sustained VT or VF treated with antitachycardia pacing (ATP), or with direct current (DC) shock by an internal or external defibrillator.  Sustained ventricular arrhythmias that self-terminated without ATP or shock as well as non-sustained ventricular arrhythmias were not considered.

ES was managed according to standard clinical practice at each institution. Possible treatments included resolution of reversible causes, administration of drugs such as AADs and beta blockers, ICD reprogramming, possible uses of mechanical support devices, and general anesthesia. Centers were free to consider PSGB at any time as long as ES was refractory to the ongoing treatments.

Physicians conducted PSGB on all participants using either anatomical or ultrasound-guided, depending on their own preferences. Operators were also allowed to switch from one technique to the other in cases of repeated procedures. For the anterior anatomical approach, Chassagnac’s tubercle (located at the level of C6) was utilized as the landmark for needle insertion. The needle was advanced perpendicularly to the skin at an anterior paratracheal site to the level of the C6 transverse process site and then slightly retracted just prior to injection. The lateral ultrasound-guided approach utilized an interscalene injection at the longus colli muscle just posterior to the carotid artery. The physician was able to choose their preferred approach. Physicians were also allowed to choose whether to perform a single injection of anesthetic or whether to initiate continuous infusion of anesthetic. For continuous infusions, the catheter was left in place and was connected to an infusion pump. The procedure was performed regardless of anticoagulation or antiplatelet status. In all cases, the first two attempts of PSGB were attempted on the left side while the right side was used only in further recurrences.

Investigators were required to report any other kind of procedure-related side effects. A list of pre-specified complications are listed in the main article. A high-volume center was defined as ≥ 20 patients over the study period.

All of the operators were trained with the same 8-hour course aimed at training cardiologists, intensivists, and emergency physicians. All participating institutions were required to have at least one trained operator and to have received ethical approval prior to enrolling patients in the study.

INCLUSION CRITERIA

• Patients who underwent PSGB for the treatment of refractory ES in a participating center from 07/01/2017 to 06/30/2023

EXCLUSION CRITERIA

• Patients under the age of 18
• Patients with a prior heart transplant
• Patients with a previous surgical cardiac sympathetic denervation
• Patients with a neck non-suitable for procedure (e.g. prior burn, presence of large scar, thyroid goiter)

PRIMARY OUTCOME

• The primary outcome was the effectiveness of PSGB defined as a reduction in arrhythmic events (number of ATPs or DC shocks) by at least 50% in the 12 hours after the block compared to the 12 hours prior to the block.

SECONDARY OUTCOME

• The comparison of the number of shocks in the 12 hours before versus after the PSGB
• The feasibility of the procedure expressed by the number of complications within 12 hours of the procedure
• Comparison of PSGB effectiveness in patients who developed anisocoria versus those who did not
• Difference in effectiveness of PSGB by the anterior anatomical approach versus the lateral ultrasound-guided approach
• Effectiveness of one single-injection PSGB versus continuous PSGB
• Comparison of PSGB effectiveness in high- vs low-volume centers

KEY RESULTS

A total of 133 patients from 19 centers were enrolled in the trial. The final cohort consisted of 131 patients who were mainly male (83.2%) and with a median age of 68 years old. 21% were in cardiogenic shock, 5% in septic shock, and 8% were in cardiac arrest.  A total of 184 PSGBs were performed with 57.6% being from the anatomical approach and 42.4% using an ultrasound-guided approach.

Primary Outcome

• In the 131 patients, 115 of these patients required treatment 12 hours prior to the PSGB for arrhythmias. 106 of these patients (92.2%) had a reduction of treated episodes of ≥50% in the 12 hours after the procedures (median reduction 100%, IQR -100% to -92.3%).

Secondary Outcome

• The median number of treated episodes in the 12 h after the last procedure was significantly lowered compared with the 12 h before the first procedure [0 (IQR 0-1) vs. 6 (IQR 3-15.8), p < 0.001].
• Of the 133 patients studied, there was only one major complication of respiratory depression (0.5%) likely secondary to local anesthetic systemic toxicity (LAST) in a patient on high-dose IV lidocaine that had no further complications after treatment with lipid infusion. Additionally, one episode of bradycardia (0.5%) and one episode of hypotension (0.5%) were also recorded.
• A similar significant reduction of treated arrhythmic episodes in patients who developed anisocoria to those who did not [-2.5 (95% CI -3.5 to -1) vs -2.5 (95% CI -3.5 to -2), p = 0.4].
• Both approaches provided a statistically significant reduction in arrhythmic episodes but there was a significant decrease in arrhythmias were noted in the anatomical when compared to the US-guided approach [-3.5 (95% CI -4.5 to -2.5) vs -1 (95% CI -2 to -0.5), p <0.01]. It is worth noting that in the anatomical group, the number of arrhythmia episodes in the hour prior to the PSGB was higher with the most common arrhythmia being ventricular fibrillation or shorter ventricular tachycardia cycles, and anatomical approach was performed more frequently during cardiac arrest.
• No significant difference between one shot for the PSGB versus a continuous infusion was found [-2.5 (95% CI -3 to -1.5) vs -2 (95% CI -4 to -0.5), p = 0.6].
• Both types of centers (high- and low-volume) centers had a similar and statistically significant reduction in number of arrhythmic episodes [-2.5 (95% CI -3.5 to -2) vs -2 (95% CI -3.5 to -1), p = 0.2]

Safety Outcomes

• One major complication, likely from local anesthetic systemic toxicity (LAST), was observed and treated with lipid infusion without subsequent complications
• Two minor complications of bradycardia and hypotension were observed
• 67% of the PSGB were performed on patients either on dual antiplatelet therapy and/or anticoagulation with no reported complications of bleeding. These are currently a contraindication for thoracic epidural anesthesia (a guideline-recommended alternative to PSGB for management of ES)

LIMITATIONS

• This study is an observational study lacking a control group
• STAR providers decided exactly when to provide PSGB as long as patients had ES
• Different types of local anesthetics were used for PSGB, which varied based on local habits
• There is no information on how implantable devices were programmed or if the programming had been significantly changed after hospital admission
• Data were evaluated and collected by local investigators in the centers who were not blinded to treatment
• ATP and shocks were considered together because the study wanted to compute all treated antiarrhythmic episodes. This prevents the study from differentiating the analysis according to the type of treatment
• Patients were not followed up with after hospital discharge, so it is unclear whether there are any longer-term effects of PSGB

EM TAKE-AWAYS

The STAR study is a multicenter prospective study evaluating the effectiveness of PSGB in terminating electrical storms of VF and VT who have otherwise been generally unresponsive to other antiarrhythmic treatments. In these patients, PSGB has been shown to rapidly reduce the number of arrhythmogenic events, often within the first hour, with 75% of the patients having no recurrence. While a randomized trial is still needed, this study should prompt EM physicians to learn the technique and to consider performing a PSGB in patients with refractory electrical storm.

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