Subcutaneous ICD lead position affects defibrillation threshold

State-of-the-art consensus on non-transvenous implantable cardioverter-defibrillator therapy

Within the last decade, implantable cardioverter-defibrillator (ICD) systems with non-transvenous leads were developed in order to minimize complications related to the cardiovascular position of transvenous ICD leads. This national expert consensus gives an overview of potential indications for the implantation of non-transvenous ICD systems, and provides specific recommendations for implantation, follow-up, and complication management in patients with subcutaneous ICD. Regarding particular issues like the necessity for shock efficacy testing, or the clinical outcome as compared to transvenous ICD, randomized data are expected in the near future.

A Numerical Evaluation of Multi-Lead Subcutaneous Implantable Cardioverter Defibrillator for Low Energy and Less Damage in Swine

In the rescue of patients with sudden cardiac death, cardiac electric defibrillation is usually implemented, but the myocardial damage caused by exceeding defibrillation shock is irreversible. The aim of this study is to provide a numerically implanted optimization of a subcutaneous implantable cardioverter defibrillator (S-ICD) for low shock energy and less myocardial damage. In this paper, three anatomically realistic finite element models of swine were constructed for the evaluation study of six Can-Lead configurations with various number of leads at different placements. For each Can-Lead configuration, corresponding numerical modeling and simulation with the finite element method (FEM) were performed to pre-surgically assess quantitatively the efficiency of a certain defibrillation shock, besed on our previously reported multi-criteria evaluation of cardiac defibrillation. The results show that the outcome of an S-ICD shock depends on numbers of the implanted leads as well as the location of Can-Lead, and suggest that an S-ICD implantation with a left pectoral Can and two leads (located at the midline and at the left last ribs oblique upward) would possess the best efficiency of defibrillation, which could offer another option in clinical practice. In conclusion, on basis of the pre-surgical simulation of an S-ICD configuration, an individual optimization of cardiac defibrillation would be potentially useful for a lower energy and a less myocardial damage compared with current implantations with only the knowledge of clinical practices.

Undetected displacement of a subcutaneous implantable cardioverter-defibrillator lead. importance of performing a chest X-ray during the first weeks post-implant: a case report

Background

In recent years, subcutaneous implantable cardioverter-defibrillator (S-ICD) implants have progressively increased and have been shown to be safe and highly successful, affording low reintervention rates regardless of the technique used.

Case summary

We present a case of S-ICD implantation in a patient diagnosed with idiopathic ventricular fibrillation. In the first follow-up consultation the patient showed appropriate detection parameters in the three configurations. However, chest X-ray revealed lead displacement with a tip migration from the manubrium area of the sternum to the xiphoid process.

Discussion

This case highlights the importance of performing at least one chest X-ray during the first weeks after S-ICD implantation, allowing the detection of a problem such as lead displacement, which can lead to undersensing of ventricular arrhythmias or S-ICD oversensing.

A novel tool to evaluate the implant position and predict defibrillation success of the subcutaneous implantable cardioverter-defibrillator: The PRAETORIAN score

BACKGROUND

Suboptimal positioning of the subcutaneous implantable cardioverter-defibrillator (S-ICD) increases the defibrillation threshold and risk of conversion failure.

OBJECTIVE

Our objective is to develop a tool to evaluate the implant position and predict defibrillation success of the S-ICD: the PRAETORIAN score.

METHODS

The PRAETORIAN score is based on clinical and computer modeling knowledge of determinants affecting the defibrillation threshold: subcoil fat, subgenerator fat, and anterior positioning of the S-ICD generator. The score evaluates these determinants on the postoperative anterior-posterior and lateral chest radiographs and has 3 categories: 30-<90 points representing a low risk, 90-<150 points representing an intermediate risk, and ≥150 points representing a high risk of conversion failure. The score was developed using 2 separate S-ICD data sets for derivation and validation. The performance metrics are the positive and negative predictive values.

RESULTS

The development data set consisted of 181 patients with S-ICD, and the validation cohort consisted of 321 patients from the S-ICD Investigational Device Exemption trial. The distribution of scores was 93%-98% low risk (<90 points), 2%-5% intermediate risk (90-<150 points), and 1% high risk (≥150 points). The positive predictive value for an intermediate or high PRAETORIAN score for a failed conversion test was 51%, while a low PRAETORIAN score predicted a successful conversion in 99.8% of patients.

CONCLUSION

The PRAETORIAN score allows the identification of patients with high defibrillation thresholds by using the routine chest radiograph and provides feedback to implanters on S-ICD positioning. The PRAETORIAN-DFT trial will prospectively validate the score by randomizing to standard conversion testing vs using the score without conversion testing.

Usefulness of lead repositioning from left to right sternal border for a patient with subcutaneous implantable cardioverter defibrillator showing high defibrillation threshold

A 62-year-old man with Brugada syndrome underwent subcutaneous implantable cardioverter defibrillator implantation. The lead was positioned along the left sternal border and defibrillation threshold (DFT) testing was performed. However, ventricular fibrillation (VF) was not terminated with 65 J and 80 J shocks. Shock impedance was 82 ohms. We repositioned the lead to the right sternal border and performed DFT testing again, followed by the VF termination with a 65 J shock. Shock impedance was 59 ohms. The positional relationship among the lead, generator, and heart was changed by lead repositioning, which may have contributed to improved shock impedance and DFT.