Increased defibrillation threshold with right-sided active pectoral can

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).

Predictors of a high defibrillation threshold test during routine ICD implantation

BACKGROUND

There is growing evidence that routine defibrillation threshold (DFT) testing during implantable cardioverter defibrillator (ICD) implantation is not necessary. However a small group of patients might be at risk if no DFT testing is performed.

METHODS

Patients with a new pectoral ICD implantation in our hospital between 2006 and 2014 were included in a retrospective registry. A clinical high DFT was defined as a safety margin <10 J of the maximal device output. Logistic regression for prediction of high DFT was performed using patient characteristics, clinical, echocardiographic and device-related parameters.

RESULTS

DFT testing was performed in 788/864 (91.2%) procedures. In 76 (8.8%) patients no DFT testing was performed mainly due to atrial fibrillation, intra-cardiac thrombus, hemodynamic instability or logistical reasons. A high DFT was present in 44 (5.6%) patients. A QRS duration ≥150 ms, a low left ventricular ejection fraction (LVEF ≤25%), a severely dilated left ventricle ≥60 mm and right sided pre-pectoral implantations were univariate predictors of a high DFT. Independent predictors of a high DFT were a LVEF ≤25% (HR 2.195, 95%CI 1.085-4.443) and right sided pre-pectoral implantations (HR 3.135, 95% CI 1.186-8.287).

CONCLUSIONS

A high DFT is still present in about 5% of patients and is more frequent in patients with a severely dilated left ventricle, a very low LVEF, right sided pre-pectoral implantation and wider QRS duration. It might be clinically important to continue DFT testing in these high risk patients.

ICD implantation without intraoperative testing does not increase the rate of system modifications and does not impair defibrillation efficacy tested in follow-up

AIM

The need for implantable cardioverter-defibrillator (ICD) defibrillation testing (DT) and subsequent intraoperative system modifications is discussed controversially. The study's goal was to prove that consequent abdication of intraoperative DT does not impair defibrillation efficacy and does not increase the rate of postoperative system revisions.

METHODS

In a prospective single-center observational study, 609 out of 648 consecutive patients underwent transvenous ICD implantation (left-sided, active can, dual coil lead, and biphasic shock waveform) waiving intraoperative DT. Defibrillation efficacy was validated prior to hospital discharge (PHD) by applying two 10 J safety margin (SM) shocks.

RESULTS

Following "schockless" implantation 580 out of 609 patients (95.2 %) met a 10 J SM with default programming. Shock path reversal provided 10 J SM in 13 out of 29 cases with initially failed DT. In four patients (0.7 %) maximum energy shocks were ineffective. There was no morbidity or mortality related to DT. The total rate of surgical ICD revisions was 1.8 %.

CONCLUSION

Routine ICD implantation without intraoperative DT does not lead to an increased rate of postoperative system modifications and does not decrease defibrillation efficacy as tested PHD.

Significance of intraoperative testing in right-sided implantable cardioverter-defibrillators

Background

Implantation of implantable cardioverter-defibrillators (ICD) from the left pectoral region is the standard therapeutical method. Increasing numbers of system revisions due to lead dysfunction and infections will consecutively increase the numbers of right-sided implantations. The reliability of devices implanted on the right pectoral side remains controversially discussed, and the question of testing these devices remains unanswered.

Methods

In a prospectively designed study all 870 patients (60.0±14 years, 689 male) who were treated with a first ICD from July 2005 until May 2012 and tested intraoperatively according to the testing protocol were analyzed. The indication for implantation was primary prophylactic in 71.5%. Underlying diseases included ischemic cardiomyopathy (50%), dilative cardiomyopathy (37%), and others (13%). Mean ejection faction was 27±12%. Implantation site was right in 4.5% and left in 95.5%.

Results

Five patients supplied with right-sided ICD (13%, p = 0.02 as compared to left-sided) failed initial intraoperative testing with 21 J. 3 patients were male. The age of the patients failing intraoperative testing with right-sided devices appeared higher than of patients with left-sided devices (p = 0.07). The ejection fraction was 28±8%. All patients reached a sufficient DFT ≤ 21 J after corrective procedures.

Conclusion

Implantation of ICDs on the right side results in significantly higher failure rate of successful termination of intraoperatively induced ventricular fibrillation. The data of our study suggest the necessity of intraoperative ICD testing in right-sided implanted ICDs.

Evaluation of defibrillation safety margin in modern implantable cardioverter defibrillators after administration of amiodarone

AIM

The adjunctive medication with amiodarone plays a major role in patients with an implantable cardioverter defibrillator (ICD). Amiodarone as class III antiarrhythmic drug may significantly alter the defibrillation threshold (DFT). Conflicting results exist on the clinical relevance of a DFT rise on amiodarone. The only prospective study on this issue included only a small number of patients on amiodarone. The purpose of this study was to assess the safety and clinical relevance of repeat defibrillator testing after initiation of amiodarone in modern defibrillator systems.

METHODS AND RESULTS

We assessed risks and clinical consequences of retesting defibrillation safety margin after initiation of amiodarone in 130 consecutive patients. All patients underwent intraoperative testing at the time of first ICD implantation. A repeated VF induction and defibrillator test (by protocol with a single shock and 10 J safety margin) after a total dose of at least 10 g amiodarone 4-6 weeks after initiation of medication was performed. DFT testing after initiation of amiodarone was safe as there were no complications that led to a prolonged hospital stay. In 4 of 114 patients with a left-sided device (1.6%) and 3 of 7 patients with a right-sided device (42.8%), a 10 J safety margin could not be achieved. As a result 4 patients (3.1% of study collective) had a revision of the system.

CONCLUSION

Repeat defibrillation testing after administration of amiodarone therapy rarely fails in patients with left-sided devices. We observed a higher test failure in patients with a device in the right-subpectoral position although this subgroup was small. Repeat defibrillator testing is safe as no relevant complications were observed.

Additional coronary sinus defibrillation lead with a right pectoral ICD and high DFT : a case report

We report the case of a 63-year-old man with ischemic cardiomyopathy having an implantable cardioverter defibrillator (ICD) implanted for repeated ventricular tachycardia (VT). After several revisions of the ICD lead, a thrombosis of the left venous system was diagnosed. A right pectoral ICD device was implanted, and a sufficient defibrillation threshold (DFT) could not be achieved during the operation. Thus, a further defibrillation lead was implanted into the coronary sinus, which successfully terminated ventricular fibrillation.

Cardiac defibrillator implantation via persistent left superior vena cava - sometimes this approach is facile. A case report

We report a case of persistent left superior vena cava (PLSVC) incidentally recognized during the implantation of a cardioverter-defibrillator. PLSVC is the most common venous anomaly of the thorax and drains into the right atrium. There are a lot of publications reporting success of pacemaker or defibrillator lead implantations via PLSVC. In this article we present the technique of approaching the right ventricle and right atrium via PLSVC; sometimes this method can be as straightforward as the classical way. Therefore, if PLSVC is recognized intra-operatively, we suggest continuing left-sided implantation, and considering a right venous access only in case of failure.

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.

Implantation of a biventricular pacing and defibrillator device via a persistent left superior vena cava

A persistent left superior vena cava was discovered in a 66-year-old man with heart failure undergoing implantation of a biventricular pacing and defibrillator device. An active fixation right ventricular defibrillator lead was placed through a curved guiding catheter. A sub-selection catheter and a guidewire allowed the engagement of a posterior-lateral branch of the coronary sinus, performance of an angiogram without an occlusive balloon, and optimal lead placement. The right atrial lead was positioned using a standard stylet. Despite the technical challenges, implantation of a biventricular pacing and defibrillator device via a persistent left superior vena cava is safe and feasible.

Active-can implantable cardioverter defibrillator placement from a femoral approach

This report describes a case of an active-can ICD placed in the thigh. A 74-year-old man on chronic renal dialysis had no venous access from cephalic, subclavian, or jugular approaches. Using long active-fixation leads the device was placed from a femoral approach with good sensing, pacing, and defibrillation parameters.

Left superior vena cava persistence in patients undergoing pacemaker or cardioverter-defibrillator implantation: a 10-year experience

OBJECTIVE

The persistence of a left superior vena cava (LSVC) has been observed in 0.3% of the general population as established by autopsy. In the adult population, it is an important anatomic finding if a left superior approach to the heart is considered. The aim of the study was to evaluate the prevalence of a LSVC in patients undergoing pacemaker (PM) and cardioverter-defibrillator (CD) implantation.

DESIGN

We observed the prevalence of LSVC during a 10-year period; each patient undergoing PM or transvenous CD implantation received a left cephalic/left subclavian venous approach to the heart. With this technique, LSVC persistence is easily diagnosed during lead placement.

RESULTS

A total of 1,139 patients consecutively underwent PM implantation during 10 years: 4 patients had persistent LSCV (0.34%). Among 115 patients undergoing CD implantation, 2 patients with LSVC (1.7%) were observed. Overall LSVC persistence was found in 6 of 1,254 patients (0.47%). Two patients, one of whom had no right superior vena cava (RSVC), received a left-sided PM, whereas two other patients received right-sided devices. Both CD patients received a left-sided active-can device: the first patient with a right-sided lead tunneled to the left pectoral pocket, as a result of poor catheter handling through the LSVC and coronary sinus, and the second patient with a screw-in lead from LSVC. Long-term follow-up of these patients (average +/- SD, 41 +/- 26 months) revealed absence of lead dislodgment and appropriate device function regardless of lead implantation site.

CONCLUSIONS

Persistence of LSVC in adults undergoing PM/CD implantation is similar to that of the general population (0.47% in our study). The left-sided implant can be achieved by stylet shaping and by use of active fixation leads in most patients, with a reliable outcome at short term in addition to appropriate device performance at follow-up. Assessment of the RSVC is advisable when planning a right-sided implantation, since a minority of patients lacks this vessel.