Azygos Vein Lead Implantation:. A Novel Adjunctive Technique for Implantable Cardioverter Defibrillator Placement

Patients with a high defibrillation threshold: Approaches to management

Implantable cardioverter-defibrillators (ICDs) have revolutionized the prognosis for patients at elevated risk of ventricular tachyarrhythmias. For safety, defibrillation should be effective with a minimum of 10 J below the device's maximum energy. While modern ICDs rarely deliver ineffective shocks in primary prevention, the surge in managing severe heart failure patients has led to an increased number of patients with high defibrillation thresholds (DFTs). This article elucidates the potential causes of high DFT, including clinical factors, lead and device placement, the presence of a Left Ventricular Assist Device (LVAD), prolonged ventricular arrhythmias, shock vectors, waveform tilt, medications, and manufacturer-specific options. We also detail management strategies, highlighting alternative shock coil placements, practical recommendations, and case studies from our institution. Our management algorithm suggests addressing preventable causes, re-evaluating coil positions, considering non-invasive system modifications, upgrading to a higher-capacity device, and adding extra coil(s).

Cases of Azygous Coil Extraction

Background

Procedural and clinical outcomes of patients undergoing extraction or removal of azygous coils are not well characterized.

Objective

Evaluate outcomes in patients who undergo device extraction with an azygous coil in situ.

Methods

Patients undergoing extraction with an azygous coil in situ between May 2015 and January 2021 were included in this retrospective single-center analysis. Outcomes included procedural success, use of laser and mechanical cutting tools during the procedure, procedural complications, and mortality.

Results

We identified 2 patients undergoing device extraction with an azygous coil in situ with a dwell time greater than 12 months. The patients were male, aged 73 and 83 years. Both had a history of hypertension, atrial fibrillation, heart failure (ejection fractions <15% and 20%), and cardiomyopathy (nonischemic and ischemic), and presented with an infection (case 1 with a single-chamber ICD and Staphylococcus aureus bacteremia, case 2 with a cardiac resynchronization therapy defibrillator pocket infection). The mean dwell time of all 6 leads extracted was 6.43 years (range 1.33–12.63 years), and the 2 azygous coils had dwell times of 1.33 and 6.04 years. In case 1, the azygous coil was inferior to the cardiac silhouette, while in case 2 it was superior. A 14F laser sheath was employed to remove both azygous coils. Both extractions were a complete procedural success in which all leads were removed completely without intraoperative complications.

Conclusion

These cases demonstrate the variable courses of azygous coils, provide proof of concept that they can be removed safely, and illustrate that azygous coils can be removed with the same techniques that are commonly used to remove other types of leads.

Azygous Vein Coil Implantation in Left Ventricular Assist Device Patients: A Hands-on Approach

Recently, there have been reports of left ventricular assist device (LVAD) patients presenting with multiple ineffective implantable cardioverter-defibrillator (ICD) shocks. In such patients, the placement of an azygous vein coil by providing an alternative anteroposterior trajectory of the electrical shock vector can enable successful defibrillation. This review discusses a hands-on approach to azygous vein coil implantation. Additionally, we compare our tools and technique to those that have been previously described by other operators. From 2018 to 2021, eight patients were identified who underwent azygous vein coil implantation at MedStar Washington Hospital Center using a specific technique and tools. Demographic and procedural data were obtained by a retrospective review of patient charts, procedure logs, fluoroscopy, and venography performed during coil implantation. The indication for azygous vein coil implantation was ineffective ICD shocks in seven patients. The presenting rhythm was ventricular fibrillation in six (75%) cases and sustained ventricular tachycardia in two (25%) cases. Using the approach described, we were able to successfully implant an azygous vein coil in all eight (100%) patients. There were no procedure-related complications. Postimplantation, defibrillation threshold (DFT) testing was successfully performed in six of eight (75%) patients. One patient failed DFT testing despite placement of an azygous vein coil. In another patient, DFT testing was not performed because the patient was in atrial fibrillation and was not systemically anticoagulated. In conclusion, the placement of an azygous vein coil in LVAD patients with failed ICD shocks using the tools and technique described in this report is safe and highly efficacious (successful in 100% of cases).

Non-traditional implantable cardioverter-defibrillator configurations and insertion techniques: a review of contemporary options

Implantable cardioverter-defibrillators (ICDs) have revolutionized the treatment of acquired or inherited cardiac diseases associated with a high risk of sudden cardiac death due to ventricular tachyarrhythmias. Contemporary ICD devices offer reliable arrhythmia detection and discrimination algorithms and deliver highly efficient tachytherapies. Percutaneously inserted transvenous defibrillator coils with pectoral generator placement are the first-line approach in the majority of adults due to their extensively documented clinical benefit and efficiency with comparably low periprocedural implantation risks as well as the option of providing pain-free tachycardia treatment via anti-tachycardia pacing (ATP), concomitant bradycardiaprotection, and incorporation in a cardiac resynchronization therapy if indicated. Yet, expanding ICD indications particularly among younger and more complex patient groups as well as the increasingly evident long-term consequences and complications associated with intravascular lead placements promoted the development of alternative ICD configurations. Most established in daily clinical practice is the subcutaneous ICD but other innovative extravascular approaches like epicardial, pericardial, extra-pleural, and most recently substernal defibrillator coil placements have been introduced as well to overcome shortcomings associated with traditional devices and allow for individualized treatment strategies tailored to the patients characteristics and needs. The review aims to provide practical solutions for common complications encountered with transvenous ICD systems including restricted venous access, high defibrillation/fibrillation thresholds (DFTs), and recurrent device infections. We summarize the contemporary options for non-traditional extravascular ICD configurations outlining indications, advantages, and disadvantages.

Completely epicardial implantable cardioverter/defibrillator (ICD) and CRT-D systems: A case series and systematic literature review

BACKGROUND

Epicardial ICD systems and CRT-Ds using high voltage coils represent an alternative to transvenous systems in patients without central venous access and prior device complications including infection.

OBJECTIVE

We present a case series in the adult population of epicardial ICD/CRTD systems using high voltage epicardial coils. We summarize the existing data regarding techniques, efficacy, and safety.

METHODS

A retrospective board approved medical record review was conducted for all patients undergoing epicardial ICD/CRTD placement at our institution between January 2010 and May 2020. The literature was reviewed for prior published trials, case reports, and case series of epicardial high voltage coil insertions.

RESULTS

Eleven patients (six female, mean age 48 years) underwent epicardial ICD/CRTD implant including 5/11 completely epicardial CRTD systems. The procedure was performed via median sternotomy in eight patients, left anterior thoracotomy in two patients, and sub-xiphoid approach in one patient. After a mean follow up of 35 months, appropriate successful shocks were delivered in two (18%) patients and no patients received an inappropriate shock. Three of five (60%) patients had volumetric remodeling with CRT with significant improvement of LV EF. Device-related complications requiring a surgical/percutaneous revision or another DFT test occurred in six patients (54%). One patient died during follow up due to refractory heart failure. No cases of epicardial device infection, coronary artery compression, constrictive pericarditis, or erosion of defibrillator coils into intrathoracic organs were reported. No randomized studies comparing safety and efficacy of traditional transvenous or subcutaneous ICD systems and epicardial ICD systems using contemporary high voltage coils were found nor any studies directly comparing epicardial defibrillator patches versus epicardial coils. Thirteen case series and 24 single case reports published between 2004 and 2020 were identified describing in total a heterogenous group of 188 patients with ICD systems incorporating one or more epi- or pericardially positioned shock coils.

CONCLUSION

The use of epicardial defibrillation coils for ICD/CRT-D is a feasible treatment option for patients with either failed or contraindicated transvenous ICD systems. Dedicated epicardial high voltage leads with integrated pace-sense electrodes and specialized delivery tools for minimal invasive implantations may improve longer term outcomes.

Coronary vein defibrillator coil placement in patients with high defibrillation thresholds

BACKGROUND

Elevated defibrillation threshold (DFT) occurs in 2%-6% of patients undergoing implantable cardioverter defibrillator (ICD) implantation. Adding a defibrillation coil in the coronary sinus (CS) or its branches can result in substantial reductions in the mean DFT. However, data regarding acute success and long-term stability remain lacking. We report our experience with this bailout strategy.

METHODS

Patients with elevated DFT at implantation (safety margin at implantation <10 J) and those with failed ICD shocks for ventricular arrhythmias (VA) referred for high DFT underwent placement of an additional defibrillation coil in the CS. DFT testing was performed at the completion of the implantation procedure. External potentially reversible factors were excluded. High-output devices were systematically used.

RESULTS

Four patients with high DFT at implantation and two with several failed shock attempts underwent placement of a defibrillation coil in the CS. Mean age was 41.8 (23-78). They presented a mean LVEF of 21% (15-30), QRS-complex duration of 109.8 milliseconds (87-168), body surface area of 1.96 m2 (1.45-2.58), and a mean R wave of 16.3 mV (8-27). Defibrillation coil implantation in the CS (final shocking configuration of right ventricle as anode and left ventricle (LV) plus can as cathode) was associated with successful DFT testing in all. Three patients had a concomitant LV lead for biventricular pacing. During a mean follow-up of 54.67 months (10-118), two patients experienced successful ICD shocks for VA (one of them also presented inappropriate shocks because of the fast conducting atrial fibrillation).

CONCLUSIONS

Positioning of a defibrillation coil in the CS can result in a substantial reduction in mean DFT and associates with optimal long-term stability.

Defibrillation Threshold Testing: Current Status

When the transvenous ICD initially came into use for primary and secondary prevention of sudden cardiac death, defibrillation threshold (DFT) testing was universally performed. However, DFT testing is no longer routinely recommended for transvenous ICD implantation except in certain situations. Risk scores can help guide the decision to perform DFT testing. The subcutaneous ICD represents an area of uncertainty, with limited data available regarding the role of DFT testing in these devices. Current guidelines give a class I recommendation for performing DFT testing at the time of implant. Further studies are needed before this recommendation can be safely dismissed.

An inappropriate pacing threshold increase after repeated electrical storm in a patient with implantable cardioverter defibrillator

BACKGROUND

Implantable cardioverter defibrillators (ICD) are capable of effectively terminating malignant ventricular arrhythmia and are the most effective way to prevent sudden cardiac death. However, some evidences demonstrated that both anti-tachycardia pacing (ATP) and ICD shock can also bring adverse prognosis.

CASE PRESENTATION

A 66-year-old Han Chinese man with prior ICD implantation was admitted to our hospital because of frequent ICD shocks. Although intravenous amiodarone and esmolol succinate were administered daily, the patient suffered 155 episodes of VT/VF during 8 weeks after implantation. After repeated discharge of the device, the pacing threshold of the patient increased gradually. Considering the inappropriate increase of the pacing threshold, we decided to reposition the right ventricular (RV) lead with good sensing and threshold parameters confirmed. Subsequent 22 months interrogation follow-up revealed a stable lead position and electrical specifications. Furthermore, antiarrhythmic drugs were maximally increased, while ATP burst was remarkably decreased and the inappropriate ICD shock never occurred until now.

CONCLUSION

An inappropriate pacing threshold was increased secondary to repeated ICD electrical storm. A timely active lead position adjustment reduced the pacing threshold and eliminated the risk of premature battery depletion.

Successful reduction of a high defibrillation threshold by a combined implantation of a subcutaneous array and azygos vein lead

A 72-year-old man with nonischemic cardiomyopathy was referred because his implantable cardioverter defibrillator had failed to terminate spontaneous ventricular fibrillation (VF). Defibrillation threshold (DFT) testing confirmed that 830-V shocks failed to defibrillate VF despite optimization of the biphasic waveform and reversal of shock polarity. The placement of a new right ventricular lead and the addition of a subcutaneous array failed to defibrillate VF at 830 V. The combination of a subcutaneous array and azygos vein coil successfully defibrillated VF. The mechanism for successful DFT reduction was likely greater current supplied to the posterior basal left ventricle by the azygos vein lead.

Managing patients with ICD shocks and programming tachycardia therapies during acute heart failure syndromes

We review the pharmacologic, interventional and device programming treatment options for patients with implantable cardioverter-defibrillators who present with acute heart failure and implantable cardioverter-defibrillator shocks.

Atypical Placement of Hemodialysis Catheters in Patients with Complete and Irreversible Obstruction of Central Venous Vessels

Purpose

This article describes the approach to atypical placement of central venous catheters (CVC) in dialysis patients with complete untreatable obstruction of central venous vessels.

Methods

Five patients with complete obstruction of central venous vessels underwent CT venography and digital venous angiography. After ultrasound-guided and radioscopic-assisted cannulation of the internal jugular vein, permanent CVCs were placed in atypical locations: in two patients a preliminary venous angioplasty was performed to facilitate the catheter positioning in a mediastinal enlarged collateral vein and in a persistent left superior vena cava; in three patients the CVC was placed in the azygos vein, enlarged because of the obstruction of the superior vena cava.

Results

In all cases, we achieved satisfactory morphological and functional immediate results. Hemodialysis (HD) was carried out long term in all patients except one who presented a non-functioning CVC after 4 months. In one case the catheter, still functioning well after 9 months, was removed due to kidney transplantation. The CVC in the left superior vena cava was replaced with a longer one after 12 months, and it is still functioning well 3 months after replacement. The patency of the other two catheters has to date been kept for 9 and 18 months.

Conclusions

The placement of CVC for HD in atypical sites can be considered a viable option in extreme cases; adequate imaging support is paramount in order to facilitate the procedure and to avoid complications.

Limitations of the DF-4 defibrillator connector necessitating device removal

The DF-4 implantable defibrillator connector was recently released for clinical practice. This connector facilitates lead to device connection, reduces bulk in the device pocket, and eliminates the risk of incorrect device connection. Unfortunately, new technology often introduces new challenges. We report the case of a 63-year-old male with chronic systolic heart failure referred for cardiac resynchronization therapy-defibrillator implant. Limitations implicit to the current iteration of this technology include a lack of additional connectivity. In the present case, these limitations ultimately warranted device removal and reimplant with a traditional trifurcating IS-1/DF-1 connector.

Image based modeling of defibrillation in children

Volume imaging, defibrillation electrode models, and finite element modeling are employed in patient-specific procedural modeling in pediatric patients with cardiac arrhythmias. Due to variable size and anatomy, these patients may not be well-served by devices designed for adult defibrillation. A pipeline for rapid creation of image based models that can be interactively interrogated to determine optimal defibrillation scenarios and preliminary proof-of-concept work are presented. This approach has potential clinical applications for therapy planning and broad applications for finite element modeling in anatomical models. Clinical studies investigating the effects of body size, habitus, and anatomical variation on myocardial voltage gradients are planned.

The dilemma of ICD implant testing

Ventricular fibrillation (VF) has been induced at implantable cardioverter defibrillator (ICD) implant to ensure reliable sensing, detection, and defibrillation. Despite its risks, the value was self-evident for early ICDs: failure of defibrillation was common, recipients had a high risk of ventricular tachycardia (VT) or VF, and the only therapy for rapid VT or VF was a shock. Today, failure of defibrillation is rare, the risk of VT/VF is lower in some recipients, antitachycardia pacing is applied for fast VT, and vulnerability testing permits assessment of defibrillation efficacy without inducing VF in most patients. This review reappraises ICD implant testing. At implant, defibrillation success is influenced by both predictable and unpredictable factors, including those related to the patient, ICD system, drugs, and complications. For left pectoral implants of high-output ICDs, the probability of passing a 10 J safety margin is approximately 95%, the probability that a maximum output shock will defibrillate is approximately 99%, and the incidence of system revision based on testing is < or = 5%. Bayes' Theorem predicts that implant testing identifies < or = 50% of patients at high risk for unsuccessful defibrillation. Most patients who fail implant criteria have false negative tests and may undergo unnecessary revision of their ICD systems. The first-shock success rate for spontaneous VT/VF ranges from 83% to 93%, lower than that for induced VF. Thus, shocks for spontaneous VT/VF fail for reasons that are not evaluated at implant. Whether system revision based on implant testing improves this success rate is unknown. The risks of implant testing include those related to VF and those related to shocks alone. The former may be due to circulatory arrest alone or the combination of circulatory arrest and shocks. Vulnerability testing reduces risks related to VF, but not those related to shocks. Mortality from implant testing probably is 0.1-0.2%. Overall, VF should be induced to assess sensing in approximately 5% of ICD recipients. Defibrillation or vulnerability testing is indicated in 20-40% of recipients who can be identified as having a higher-than-usual probability of an inadequate defibrillation safety margin based on patient-specific factors. However, implant testing is too risky in approximately 5% of recipients and may not be worth the risks in 10-30%. In 25-50% of ICD recipients, testing cannot be identified as either critical or contraindicated.

Azygos Tip Placement for Hemodialysis Catheters in Patients with Superior Vena Cava Occlusion

Chronic central venous access is necessary for numerous life-saving therapies. Repeated access is complicated by thrombosis and occlusion of the major veins, such as the superior vena cava (SVC), which then require novel vascular approaches if therapy is to be continued. We present two cases of catheterization of the azygos system in the presence of an SVC obstruction. We conclude that the azygos vein may be used for long-term vascular access when other conduits are unavailable and that imaging studies such as magnetic resonance venography, contrast-enhanced computed tomography or conventional venography can be employed prior to the procedure to aid with planning and prevent unforeseen complications.