Ultrasound-guided stellate ganglion blockade: an appealing tactic for cardiac el

Zi-Hao LAI, Li-Hui ZHENG, Yan YAO

Arrhythmia Center, Fuwai Hospital, National Center for Cardiovascular Diseases, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing, China

Ventricular arrhythmia (VA) is a life-threatening cardiac emergency.When VA occurs three times or more within 24 h and interventions are required, it is defined as an electrical storm (ES) characterized by refractoriness and recurrence.[1]For patients with implantable cardioverter defibrillator (ICD), the notion is redefined as no fewer than three appropriate and separate (at least 5 min for each interval) ICD interventions given within 24 h.

ES often leads to poor quality of life and high rates of hospitalization and mortality.[2,3]The acknowledged pathogenesis involves complex interactions among triggers, cardiac substrates, and autonomic vulnerability.Triggered behaviors predispose patients to ES, whereas cardiac substrate maintains ES.[4]Cardiac disorders may cause structural and electrical remodeling of heterogenic myocytes, which could lead to functional reentry and an increase in the incidence of ES.[5,6]

Sympatho-excitation plays a crucial role in ES genesis.Researchers found an elevated sympathetic tone induces arrhythmogenic changes as well as sizable reduction in heart rate variability prior to the onset of ventricular tachycardia (VT) in canines.[7,8]Another pathologic aspect is sympathetic alteration in form of hyperinnervation.[9]Recently, stellate ganglion (SG) in the autonomic nervous system is recognized as a crucial role among the pathophysiological mechanism.

To stabilize patients’ hemodynamics during acute management, advanced cardiac life support and external defibrillation may be required.When necessary, sedation and intubation are added.There is evidence that two ICD therapy modalities introduced during ES increase mortality for those who have ICD installation as palliative prevention.[10]

β-blockers and other antiarrhythmic drugs are mainstay for treatment.β-blockers are the first-line pharmacologic therapy advised for ES management, among which nonselective β-blockers exert better antiarrhythmic efforts.[1,11]Nademanee,et al.[12]discovered that patients who underwent β-blockade had a remarkably greater survival rate than those who received conservative antiarrhythmic therapy.However, the efficacy of β-blockers is less systematically specific and limited by side effects like drugs intolerance.Patients afflicted with acute heart failure,end-stage organ failure, or pulmonary edema are not amenable to β-blockers.

Cardiac sympathetic denervation (CSD) permanently suppresses sympathetic main flow to the heart.Two systematic reviews reported it freed near or more than 60% of patients from VT events in the postoperative period.[13,14]Recent studies have suggested that CSD may provide a moderately additional mid- to long-term benefit before or after catheter ablation (CA).[15,16]Even though CA and CSD proved to be effective, they are not always carried out as intended.Hemodynamically compromised or critically ill sufferers hardly tolerate surgeries and transportation to operating rooms.Besides, CSD is unavailable in many basic medical institutions and CA is frequently inaccessible.According to a survey by the European Heart Rhythm Association, only 16.5% of affiliated hospitals offer CA around the clock.[17]

The inferior cervical ganglion and the first thoracicganglion integrate into the intrathoracic oval-shaped SG, which is located near several vital blood vessels and soft tissues in 70%-80% of the population and serves as the primary source of cardiac sympathetic activities as well as the signal station to the head and upper extremities.[18,19]

SG is highly associated with VA.A study on ambulatory animals showed that 86.3% of VT and sudden cardiac death episodes were preceded by discharges from the left SG (LSG).[20]Another research found that there was a temporal correlation between large and sustained skin sympathetic nerve activities and VA episodes.[21]Furthermore, animal studies revealed that LSG is more dominant over the posterior ventricular walls while right SG (RSG)predominates the anterior ones.[22,23]Schwartz,et al.[24]showed that deactivated RSG decreased the ventricular fibrillation threshold and that disposed LSG raised the threshold.

The stellate ganglion blockade (SGB) procedure has been updated from being landmark-based to image-guided and ultrasound-guided SGB was first introduced in 1995.[25]The ideal blockade site is at C6, which guards against unintended puncture of vital viscera and the loss of control of local anesthetics (LA) spreading.A left unilateral blockade typically initiates the initial blockade.Bilateral blockade is indicated when it fails, or when patients are under general anesthesia or intubated.

Medium- and long-acting anesthetic agents are commonly used for blockade.Some physicians favor compound LA to augment anesthesia or addition of adrenaline to limit the risk of LA.Previous experience indicated that 5-8 mL would be a suitable LA dosage range for blockade, and even 2 mL was sufficient for procedural success.[25-28]Except for single bolus,continuous infusion may also lower VA burden without repetitive punctures, but benefit should be weighed against possible risk of infection and coagulation.[29]

The main steps of an ultrasound-guided SGB procedure are described in previous studies as follows:[26,28,30-33]

(1) Prepare the armamentarium and set the patient in a preoperative position.

(2) Place the echo probe on the cricoid cartilage and gradually move it to the blockade side to distinguish vital structures and C6 level.

(3) Identify precise positioning of key structures(carotid sheath, longus colli muscle, and carotid tubercle of C6) and determine the puncture plane.

(4) Puncture by an in-plane or out-of-plane technique after individual evaluation under real-time monitoring.

(5) Terminate the tip within interspace between prevertebral fascia and longus colli muscle.

(6) Inject LA after confirming safety using negative aspiration.A continuous caudal spread to the SG can be observed when successful.

Horner’s syndrome is generally regarded as a sign of operational success because it occurs soon after the blockade is finished, though it is unspecific and not noticeable when patients are sedated or unconscious.Other objective substitutes include the perfusion index measured by pulse oximetry and vascular condition detected by pulsed-wave Doppler ultrasound.[34,35]More reliable parameters need to be further established to validate blockade success.

In people with structural heart diseases and primary electrical diseases, sports, alarms, and prompt changes to orthostatic position are common triggers of VA or sudden cardiac death[1].Cardiac surgeries are sources of stress that predispose patients to malignant or refractory VA in the postoperative period as well as a high mortality rate.[36,37]Patients with these diseases or conditions can be considered as an indicative group of SGB since adrenergic surge is what causes ES attacks mentioned above.

Cardioversion or defibrillation can be life-saving bailout in terminating malignant VAs.However,there might be benefits to ultrasound-guided SGB over repeated shocks.Patients experience less physical and psychological distress due to reduced invasiveness and lack of electrical discharge from SGB.Multiple external shocks panic patients and heighten hyperadrenergic activities, which tend to increase VA burden and create a vicious cycle.Additionally,cardioversion is not applicable to patients with repetitive non-sustained VT and if there is a substantial risk of anesthesia and/or sedation is high, cardioversion should be reconsidered.[1]

SGB may be a feasible alternative that temporarily halts maladaptive sympathetic activities in emergency when conventional strategies fail, definitivetreatment is unavailable, or sufferers are ineligible for it.Besides, SGB can be a non-permanent transition for surgical patients during the acute phase whose autonomic imbalance is transient until further additional procedures and ICD implantation are reevaluated.

SGB is theoretically and technically feasible.SGB benefits patients regardless of the etiology and type of cardiomyopathy, the type of ventricular rhythm,the degree of cardiac contractibility and left ventricular ejection fraction.[38]Compared to β-blockers, its suppressive period lasts longer, which ranges from 6 hours to 4 weeks, depending on the selected types of LA, dose concentration, and volume.[39]Anatomical vision of ultrasound-guided SGB allows for accurate penetration and minimizes anesthesia, consequently restraining the risk of adverse events (AE).Since SG sitting varies from person to person, the successful completion of the procedure is determined by the actual location of the tissues as visible on the ultrasound images.

Anesthesiologists or skilled cardiologists can efficiently finish blockage at the patient's bedside with the aid of portable apparatuses.The flowchart displays the proposed ES treatment order and the suggested time for SGB deployment (Figure 1).

SGB has been effectively used to treat vascular diseases, pain conditions, and hyperhidrosis.To reduce pain and attenuate the resting heart rate, it has also been used to treat sympathetic-associated pain and inappropriate sinus tachycardia.[40]There have been only a few cases in emergency department and intensive care units, and retrospective studies hint that SGB may be able to lessen VA burden.[41,42]Fudim,et al.and Meng,et al.systematically reviewed different cases respectively and inferred the effectiveness of SGB.[38,39]The largest cohort study subsequently reported the short-term and long-term effect of SGB.[43]Furthermore, Fudim,et al.attested the effectiveness and safety of bilateral SGB, and Sav-astano,et al.illustrated that repeated blockade may bring additional benefits.[32,44]Recently, a cohort from Sanghai,et al.[29]showed that the continuousinfusion blockade was comparatively more effective and practical than single injection.

The short-term suppressive effect on VA and decrease in death rate are the efficacy main indicators of SGB.The percentage of targeted patients receiving explicit therapies and that of postoperative AE and serious AE (SAE) are also examined.The outcomes from some representative studies have been summarized in the following text.The timeframe of“short-term” among the included articles vary, ranging from 1 h to 96 h and more data are needed to determine the appropriate scope.

The VA burden is commonly set as the primary endpoint in studies with external or internal defibrillation serving as another viable evaluation indicator.The immediate outcomes of SGB are displayed in Figure 2 and Figure 3.[29,32,39,43-45]After SGB, the number of VA episodes dropped by over 90% and some patients had no more occurrences.Episodes of internal or external defibrillation show a similar trend of reduction.SGB shows potential in effectively alleviating short-term VA burden and decreases the frequency of defibrillation.

Figure 2 Short-term VA burden reduction.VA: ventricular arrhythmia.

Figure 3 Short-term defibrillation reduction.SGB: stellate ganglion blockade.

The potential effectiveness of SGB can also be elucidated in other parameters.Previous studies in Figure 4 have stated that the proportion of patients without reemergence after blockade reached over 60% in a short-term period and that of VA-induced mortality dropped to less than 10%.[12,29,32,39,43,44]SGB help bridge around 30%-50% of the patients to undergo therapies including CA, CSD, heart transplantation,and curatives for primary cardiac diseases.However,the occurrence still exists, ranging from 17% to 55%,and it probably associates with the presence of primary cardiac substrate and the nature of ES.SGB represents possibility on decreasing VA-induced mortality and recurrences extrapolated from limited findings.It can serve to stabilize patients to receive further treatment.Because antiarrhythmic treatment has been used prior to SGB, it is difficult to distinctly identify contribution of SGB to the overall efficacy.This positive trend should be further consolidated by prospective randomized clinical trials.

Figure 4 The consequent outcome of SGB.SGB: stellate ganglion blockade.

The two main categories of AE are those related to operations and those related to drugs, the latter of which can be further divided into local and systemic events.The most common systemic side effects of image-guided SGB are hoarseness and light-headedness, whereas hematoma formation is frequently found to be a local adverse event.[46]Percentages of AE and SAE among the selected articles are shown in Figure 5.[29,32,43-45]Sonographic imaging optimizesthe medication protocol and the insertion process.Approximately less than 10% of patients tolerate post-SGB AE (hoarseness, hypotension, arm weakness, and ptosis have been reported) and there are no life-threatening SAE demanding extended hospitalization or intensified interventions.AE encountered by the patients are temporary and/or reversible, have minor negative impacts, and can be treated with general management.

Figure 5 The proportion of AE and SAE.AE: adverse events; CI: continuous infusion; SAE: serious adverse events; SI: single injection.

In conclusion, when conservative means are unsatisfactory or contraindicated, ultrasound-guided SGB can be considered to diminish VA burden and times of defibrillation, short-term VA recurrence rate, and mortality rate, which maintains patients to be admitted to definitive modalities.Though the short-term outcome is clear, its validity needs to be verified through large sample randomized controlled studies.The current technique requires continuous refinement, and normalized SGB treatment guidelines should be established.

ACKNOWLEDGMENTS

This work is supported by a grant (Z191100006619019)from the Capital Municipal Science and Technology Commission and a grant (2022-GSP-QZ-4) from the Chinese Academy of Medical Sciences Fuwai Hospital Top-level Hospital Clinical Scientific Research Funds.