Defibrillation Threshold Testing Research Articles

Utility of routine follow-up defibrillation safety margin testing in young patients with epicardial implantable cardioverter-defibrillators.

Routine defibrillation threshold testing (DFT) of transvenous implantable defibrillators (ICDs) has largely been in decline. In patients with non-transvenous ICDs that utilize subcutaneous and pleural ICD leads, serial DFT testing can detect a significant number of failures. Data about the utility of follow-up defibrillation safety margin testing (DSM) testing in pediatric patients and young adults with an epicardial ICD are lacking. Patients aged<25 years old who underwent epicardial ICD placement at Mayo Clinic from 2014 to 2023 with at least one follow-up DSM test were included. The patients were divided into a "routine" (R) and "clinically indicated" (CI) group based on the index of clinical concern. Inadequate DSM was defined as unsuccessful defibrillation at an output of less than 10 J below the maximum output of the device. The purpose of this study was to assess the utility of follow-up DSM testing. An epicardial ICD system was placed in 122 patients. A total of 26 patients met inclusion criteria and underwent a total of 47 DSM follow up tests. Inadequate DSM occurred in 1/33 (3%) in the R group and 2/14 (14%) DSM tests in the CI group. The median follow-up period was 54 and 36 months for the R and CI group, respectively. Our data suggest that epicardial ICDs are reliable and routine follow-up DSM testing may not be necessary for all patients. DSM testing should be performed in individuals with epicardial ICD systems when there is clinical concern about lead or coil performance.

Acute human defibrillation performance of a subcutaneous implantable cardioverter-defibrillator with an additional coil electrode

The subcutaneous implantable cardioverter-defibrillator (S-ICD) delivers 80 J shocks from an 8 cm left-parasternal coil to a 59 cm3 left lateral pulse generator (PG). A system that defibrillates with lower energy could significantly reduce PG size. Computer modeling and animal studies suggested that a second shock coil either parallel to the left-parasternal coil or transverse from the xiphoid to the PG pocket would significantly reduce the defibrillation threshold. The purpose of this study was to acutely assess the defibrillation efficacy of parallel and transverse configurations in patients receiving an S-ICD. Testing was performed in patients receiving a conventional S-ICD system. Success at 65 J was required before investigational testing. A second electrode was temporarily inserted from the xiphoid incision connected to the PG with an investigational Y-adapter. Phase 1 (n = 11) tested the parallel configuration. Phase 2 (n = 21) tested both parallel and transverse configurations in random order. This study enrolled 35 patients (76% male; mean age 52 ± 17 years; left ventricular ejection fraction 40% ± 15%; body mass index 26 ± 4 kg/m2; prior myocardial infarction 50%; congestive heart failure 53%; cardiomyopathy 56%). Compared to the conventional S-ICD system, mean shock impedance decreased for both parallel (69 ± 15 Ω vs 86 ± 20 Ω; n = 33; P < .001) and transverse (56 ± 14 Ω vs 81 ± 21 Ω; n = 20; P < .001) configurations. Shock success rates at 20, 30, and 40 J were 55%, 79%, 97%, and 25%, 70%, 90% for parallel and transverse configurations, respectively. Defibrillation threshold testing was well tolerated with no serious adverse events. Adding a second shock coil, particularly in the parallel configuration, significantly reduced the impedance and had a high likelihood of defibrillation success at energies ≤40 J. This may enable the development of a smaller S-ICD.

Single center experience with subcutaneous ICD in combination with previously implanted endocardial or epicardial antibradycardia or cardiac resynchronization devices

Abstract Funding Acknowledgements Type of funding sources: None. Background Subcutaneous ICD (S-ICD) is an established therapy for prevention of sudden cardiac death due to ventricular arrhythmias (VA). One major drawback of the S-ICD is the lack of antibradycardia pacing. Theroretically the S-ICD can be used in combination with endocardial or epicardial pacemaker (PM), or even cardiac resinchronization (CRT) devices, but recently there are only few case reports available on this topic. Purpose To evaluate the feasibility and safety of concomitant use of endocardial or epicardial PM or CRT devices and S-ICD in a single center patient cohort. Methods Fifty-seven patients underwent S-ICD implantation in our center between 2017 and 2022. Based on individualized decision making-process, six out of these patients underwent the S-ICD implantation without explantation of previuosly implanted transvenous devices, or after epicardial PM or CRT implantation (group 1). The procedural and follow-up data of these patients were compared with data of the other 51 patients (group 2). All patients underwent successful S-ICD screening before implantation. Patients with previously implanted devices were screened either in bipolar pacing mode and either during intrinsic rhythm, if present. S-ICD implantations were performed under general anaesthesia (33 %) or under deep sedation with ultrasound guided regional nerve blocks (66 %) using intermuscular generator placement and two incision technique. Defibrillation threshold test was performed successfully in all the 57 patients. Results All S-ICD implantations were performed successfully without any procedural complications. There were no significant difference between group 1 and group 2 in terms of age (52,3±20 yrs vs. 37,7±18,5 yrs, p=0,75), ejection fraction (49,2±25,6 % vs. 46,5±21 %, p=0,77), procedure duration (57±9,7 min. vs. 52,2±15,5 min., p=0,46), and the mean follow-up duration (20,5±23,6 months vs. 25±18,8 months, p=0,59). During follow-up, one patient in group 1 (17%), and 10 patients in group 2 (19,6 %) experienced adequate ICD therapies due to VA. There were no inadequate ICD therapy in group 1, but eight patients (15,6 %) in group 2 suffered from inadequate ICD shocks caused by T wave oversensing (3/8), atrial fibrillation (2/8) myopotential oversensing (2/8,) and S-ICD lead fracture (1/8). In group 1, no interferences occured between the implanted devices, and no missed S-ICD therapy were observed during induced or spontaeous VA due to pacing artefact oversensing by the S-ICD caused by undersensing of the VA by the pacemakers. Non of the patients in group 2 experienced symptomatic bradycardia required antibradycardia pacing during follow up. Conclusion Based on our observations, S-ICD implantation after previously implanted endocardial or epicardial pacemaker or CRT systems seems feasible and safe. After individualized decision-making, with careful screening and device programming the potential interference between the implanted devices can be prevented.

Post-shock acute electrical parameters of left bundle branch area defibrillation (LBBAD) leads

Abstract Funding Acknowledgements Type of funding sources: None. Background Conduction system pacing is a growing field in bradycardia-treatment. Evidence for His bundle pacing (HBP) and left bundle branch area pacing (LBBAP) to prevent pacing induced cardiomyopathy is growing. Promising data is also emerging to use CSP as an additional tool in cardiac-resynchronisation therapy (CRT). (1-5). Very often patients requiring an ICD also have an indication for bradycardia or resynchronisation pacing. Adding CSP-treatment to these patients requires an additional pacing lead (HBP or LBBAP) and the use of a CRT-D device. As opposed to HBP, in LBBAP atrial oversensing cannot occur. Using an ICD-lead in this position could reduce the number of intracardiac leads needed while maintaining the possibility of sensing and treating ventricular arrhythmias. Purpose We evaluated the acute electrical parameters before and after delivering an ICD shock with an ICD-lead positioned in the left bundle branch area (LBBA). As this ICD-lead position has never been described before, no data is available on dislocation after shock-delivery. We looked at the electrical parameters of the successful LBBAP ICD-lead implants in our LBBAD (Left Bundle Branch Area Defibrillator) pilot-trial which is a proof-of-concept study for LBBA-ICD lead implantation. Methods In the LBBAD pilot trial, we implant an ICD lead in the LBBA to evaluate for feasibility of implantation and functionality of defibrillation. As this is a proof of concept trial, after testing the lead is re-implanted in a conventional ventricular position. In this abstract we report the evaluation of the electrical parameters of the first 3 successfully implanted LBBAD-leads (n=3). Results After LBBA implantation initial electrical parameters were measured. The pacing threshold was 0,8 +/- 0,6 V @ 0,4 ms, while the sensed R-wave and the impedance measured 7,0 +/- 2,7 mV and 512,3 +/- 38,8 Ohms respectively. The shock-coil impedance was 68,0 +/- 7,0 Ohms. All these parameters are in range with the parameters seen in conventional ICD-lead implantation. After performing the defibrillation threshold test (DFT) all electrical parameters were re-evaluated. Sensing, threshold and impedance were 7,6 +/- 2,2 mV, 0,8 +/- 0,7 V @ 0,4 ms, 516,3 +/- 47,8 Ohms and 71,7 +/- 8,2 Ohms respectively. These post-shock measurements remained stable within normal ICD-lead functioning range precluding acute dislocation. Conclusions Our LBBAD pilot trial is the first-in-human experience with ICD-leads implanted in the LBBA. This pilot trial evaluates for implant-feasibility and also looked at the pre- and post shock electrical parameters of the ICD-lead. As the parameters remained in normal working range, precluding acute shock-induced dislocation, these results open the possibility in patients with an LBBAP-indication as well as an ICD-indication, for a follow-up study to implant an LBBAD-lead and perform longer-term evaluation.

Standard and extended electrocardiographic screening for the subcutaneous implantable cardioverter-defibrillator

Abstract Funding Acknowledgements Type of funding sources: None. Background The subcutaneous implantable cardioverter-defibrillator (SICD) is effective therapy for sudden cardiac death prevention. The condition for implantation is an electrocardiographic screening test before procedure (ECG-s). Patients who don’t pass are regarded to be at risk of inappropriate detection of tachyarrhythmias with inappropriate interventions. A patient is considered suitable for implant if at least one surface ECG lead (sense vector) is acceptable for all tested postures. Objective The aim of the study was to identify the incidence of failure, the predicting factors and clinical importance of extended ECG-s with right sided lead position and lying on the left and right side of the body. Methods ECG-s to determine suitability for SICD is based and performed using a manufacturer –specific measurement tool. We performed this test in 75 consecutive pts with indication for SICD therapy on the basis of standard manufacturer protocol(lead at the left sternum border: sitting, standing and lying position), and extended for right sternal lead location and two additional body position: lying on the left and right side (10 position for each individual). We analyzed: age, gender, body mass index(BMI), heart rate, heart rhythm(sinus/atrial fibrillation), QRS duration, PR interval, corrected QT interval(QTc), echocardiography parameters, etiology. Results ECG-s failure occurred in 6/75(8%) of patients. Screening results: 1 vector failure rate with the standard device and lead positions: primary(P) 12%, seconadary(S) 17%, alternative(A) 40%, P vs. A and S vs. A p&amp;lt;0,001. Testing with an electrode positioned on the right sternum border- 1 vector failure: (P) 10%,seconadary(S) 17%, alternative(A) 48%, P vs. A and S vs. A p&amp;lt;0,001. In case of failure on left side 50%, 14% and 6% of pts passed the test with the right sided lead position for P, S and A vector respectively, p&amp;lt;0.001. Identified factors predicting ESG-s passing vs. failure included: QTc interval 445,32±35,4 vs. 480,6±37,6 ms for any vector(p=0,034), BMI:26,7±4,7 vs. 29,9±4,7 for vector A( p=0,008 ), EF: 43,3±20,1 vs. 34,0±16,2 for vector A( p=0,027). Sense vector failure rate with the left sternal lead location lying on the left and right side of the body was concordant with the rate lying on the back, p=0,05. For the right parasternal lead location the rate failure was lower lying on the right side for all sense vectors: P, S and A(p=0,045; 0,083 and 0,020) respectively. Conclusions ECG screening failure rate for SICD is comparable with previous reports. The right sternal lead location screening is effective and enables important clinical findings before implantation and in case of lead reposition( defibrillation threshold test failure) during procedure. We recommend to screen routinely on both sternum borders. Some additional body position testing: lying on the left and right side of the body, mimicking sleeping/rest could be an important element to determine eligibility for SICD.

PO-03-011 LEFT BUNDLE BRANCH AREA DEFIBRILLATION (LBBAD): EVALUATION OF ACUTE DEFIBRILLATION PERFORMANCE

Conduction system Pacing (CSP) is a promising technique to prevent pacing-induced cardiomyopathy and is a valuable additional tool in cardiac-resynchronization therapy. Patients requiring an ICD for underlying structural heart disease often have a concomitant bradycardia pacing indication. As RV pacing is to be avoided in these patients, CSP is a promising option. A combined left bundle branch area (LBBA) pacing/defibrillation lead would be desirable over an additional CSP pacing lead. We evaluated defibrillation threshold testing (DFT) with a classical ICD lead (Boston Scientific Reliance 4-Front 0693/64cm) positioned in the LBBA. In our LBBAD feasibility pilot trial we evaluated the implantability of an ICD lead in the LBBA and looked at the acute performance of an ICD lead temporarily implanted in this position. One of the tests performed was DFT testing by VF induction using a shock-on-T with decreasing energy (ULV). This value was subsequently used to program the energy of the first shock to treat the induced VF (see Figure). After all tests were performed the lead was removed from the septum and implanted in a conventional location. We present the DFT results of the first 3 successfully implanted LBBAD leads. All three patients received an ICD in primary prevention for ischemic cardiomyopathy (mean EF of 25 ± 3.3%). Induction shock to initiate VF (ULV) was 14 ± 2.4 J (mean induced VF heart rate of 259 ± 13.9 bpm). Time to VF detection was 5.5 ± 1.2 s with a mean capacitor charging time of 4.9 ± 1.0 s to deliver 28 ± 4.7 J. All VF episodes were successfully terminated by the first programmed shock. The impedance over the shock-lead measured 68 ± 4,99 Ω. No complications occurred. Our LBBAD pilot trial is the first experience in man with ICD leads (temporarily) implanted in an LBBA position. Besides evaluation of the implant feasibility of an ICD lead in the LBBA, we also looked at the acute electrical performance of the lead in this position.

PO-04-084 LOW SHOCK IMPEDANCE OF SUBCUTANEOUS IMPLANTABLE CARDIAC DEFIBRILLATOR (S-ICD) IN THE SETTING OF ACUTE DECOMPENSATED HEART FAILURE

Shock impedance represents the resistance between the coil and generator of subcutaneous ICDs. It is an important metric to predict device defibrillation success. Several factors have been implicated in determining system impedance of S-ICDs such as generator-lead distance, body habitus as well as generator position (subcutaneous vs. intermuscular pocket). We present a case report highlighting the impact of volume status on shock impedance. N/A A 60-year-old female presents to the office. She has a past medical history of obesity, Heart Failure with Preserved Ejection Fraction (HFpEF), ventricular fibrillation followed by implantation of transvenous ICD. This was complicated by device infection requiring device extraction and implantation of S-ICD. She has been having progressive shortness of breath with minimal exertion weeks prior to presentation. She denied chest pain, palpitations or dizziness but endorsed generalized fatigue as well as significant weight gain. She usually weighs around 165-170 lbs, but was 220 lbs on presentation. Her physical exam was remarkable for elevated jugular venous pressure, anasarca with crackles in the lung bases as well as abdominal ascites and lower extremity edema. Interrogation of her device was performed which showed no significant arrythmias. However, device detected low system impedance of <30 ohms. Her previous interrogation about 3 months earlier showed impedance of 50 Ohms. She was admitted for inpatient intravenous diuresis. Chest radiograph demonstrated normal position of the generator in the posterolateral chest wall and normal lead position in the parasternal area. Serial device interrogations were performed during the hospitalization showing gradual improvement in system impedance up to 45 Ohms once euvolemia was achieved (Figure 1). Due to improvement in shock impedance with diuresis, defibrillation threshold testing (DFT) was deferred and patient was discharged home in stable condition. Her repeat interrogation at follow up showed an impedance of 60 ohms. In the setting of heart failure exacerbation, excess fluid accumulation in the chest and abdominal cavities may result in a decrease in S-ICD shock impedance. Interpretation of device impedance should factor in patient’s volume status. Further studies are needed to ascertain if low impedance caused by fluid overload can impact device defibrillation success rate.

Defibrillation Threshold Testing for Right-sided Device Implants: A Review to Inform Shared Decision-making, in Association with the British Heart Rhythm Society.

Prevention of sudden death using ICDs requires the reliable delivery of a high-energy shock to successfully terminate VF. Until more recently, the device implant procedure included conducting defibrillation threshold (DFT) testing involving VF induction and shock delivery to ensure efficacy. Large clinical trials, including SIMPLE and NORDIC ICD, have subsequently demonstrated that this is unnecessary, with a practice of omitting DFT testing having no impact on subsequent clinical outcomes. However, these studies specifically excluded patients requiring devices implanted on the right side, in whom the shock vector is significantly different and smaller studies suggest a higher DFT. In this review, the data regarding the use of DFT testing, focusing on right-sided implants, and the results of a survey of current UK practice are presented. In addition, a strategy of shared decision-making when it comes to deciding on the use of DFT testing during right-sided ICD implant procedures is proposed.

Failed shocks in hypertrophic cardiomyopathy patients: prevalence, predictors and outcome

Abstract Funding Acknowledgements Type of funding sources: None. Introduction An implantable cardioverter-defibrillator (ICD) is used in selected high-risk hypertrophic cardiomyopathy (HCM) patients in order to prevent sudden arrhythmic death. The unique features of this population raise concerns regarding the reliability of successful defibrillation. Purpose To describe the rate and discover potential predictors of failed shocks in HCM patients. Methods We retrospectively evaluated all HCM patients with an ICD from a single tertiary medical center. Clinical, electrocardiographic and echocardiographic data were collected and compared among patients with and without failed shocks. Results A total of 99 patients (77% male, 45±17 years old) were analyzed. Over a median follow up of 6.3 years (IQR 2.6-10.7), 20 patients developed sustained ventricular arrhythmia (VTA). Of those, 18 patients received appropriate shocks from their ICD. VTA was associated with younger age at diagnosis, history of syncope and thicker maximal LV width. Six patients experienced at least one failed shock. The likelihood of failed shocks was similar when single or dual coil electrodes were used (dual coils in 67% of patients with failed shocks and 50% in those without), and the only predictor was increased wall thickness [OR 1.2 (1.07-1.38) per 1 mm]. All-cause mortality was low and similar in patients with an without failed shocks (0% vs 8%, P=0.5) Conclusions Failed shocks are a rare entity in HCM patients. Increased maximal LV width was the only predictor of those events. Our findings support avoiding defibrillation threshold testing routinely, but may indicate its need in patients with extreme LV wall thickening (≥23 mm).

PO-674-05 THE SHOCKING PRACTICES OF PEDIATRIC ELECTROPHYSIOLOGISTS: CONTEMPORARY DFT DATA FROM CIED REGISTRY

Defibrillator threshold (DFT) testing is no longer recommended except in certain circumstances. Data on current national practice pertaining to DFT testing in pediatrics is scarce. To report current implant characteristics, DFT testing practice, and intraprocedural events in pediatric patients undergoing implantable cardiac defibrillator (ICD) placement. We leveraged the pediatric cardiac implantable electronic devices (CIED) registry, a retrospective multicenter study endorsed by PACES, to identify patients (age≤21) who underwent ICD placement between 2017 and 2020. Among 705 patients, 51 underwent new ICD implantation. Median age and median weight at implant were 16 years (IQR 14-18) and 62 kg (53-78) respectively. Cardiomyopathy was diagnosed in 28, congenital heart disease (CHD) in 8, idiopathic VT/VF in 8, channelopathy in 5, and other in 2. An ICD was implanted for secondary prevention in 18 patients. Type of implants were as follows: transvenous in 39, subcutaneous in 8, and epicardial in 4. DFT status was known in 49 patients, of whom 30 (61%) underwent testing. DFT testing was performed in all patients who had a subcutaneous device but there was no difference in those with transvenous vs. epicardial leads (53% vs. 66%, p=0.63). DFT testing was less likely in patients seen at a freestanding Children’s Hospital (48% vs. 87%, p=0.012) but did not vary between diagnoses (CHD 59%, cardiomyopathy 62%, channelopathy 60%, and idiopathic ventricular fibrillation 75%, p=0.68) or type of cardiomyopathy (hypertrophic cardiomyopathy vs. all other types, 62% vs. 55%, p=0.67). Age, weight, mild ventricular dysfunction or greater, history of cardiac arrest, or implant provider were not associated with DFT testing. DFTs failed in 2 patients: inability to induce VT/VF in 1 and inability to defibrillate with an acceptable safety margin in 1. There were no reported complications with DFTs. DFT testing is still performed at implant in the majority of transvenous devices in pediatric patients. Presence of CHD or hypertrophic cardiomyopathy was not associated with higher DFT testing rates. Freestanding children’s hospitals were less likely to perform DFTs.

A Systematic Review and Single-center Experience of Azygos Vein Defibrillator Lead Insertion.

Defibrillation threshold (DFT) testing is performed in individuals with higher predicted risks of defibrillation failure. Many strategies have been explored to overcome the challenge of high DFT, including an insertion of a defibrillator lead into the azygos vein. We performed a systematic review of the literature to evaluate the safety and efficacy of azygos vein implantable cardioverter-defibrillator insertion for high DFT combined with the analysis of a single-center experience of the procedure at our institution. The literature search was performed in PubMed and Embase from database inception to December 2020 to identify all case reports and case series related to azygos vein defibrillator lead insertion. Our search identified 291 records. After excluding duplicate studies and those without DFT thresholds and non-azygos vascular destinations, 12 studies (23 cases) were reviewed from the current database. We also conducted a retrospective analysis of 5 cases performed at our institution, and a total of 28 patients were included in our final analysis. The mean age of the pooled cohort was 47 years (range, 17–88 years). Men composed 92% of the total cases, and the average body mass index was 34 kg/m2. The mean ejection fraction (EF) was 25%, with 78% having non-ischemic cardiomyopathy. The left axillary (36%) or subclavian (48%) vein was the common percutaneous access point. The mean duration of azygos vein access and lead delivery was 22 min (range, 13–60 min). The average DFT prior to azygos coil insertion was 35 J (range, 20–45 J). Fifty-seven percent of cases achieved substantial DFT improvement, whereas 18% achieved relative improvement compared to the pre-procedural threshold. No immediate or remote procedure-related complications were reported in 24 cases where data were available. During an average follow-up period of 18 months, 5 patients had ventricular arrhythmic events requiring device therapy and 4 had successful cardioversion from the device. One patient died from cardiac arrest with variable device therapies of both unsuccessful and successful events. In conclusion, azygos vein defibrillator lead insertion has a considerable rate of success, ease of vascular access with minimal procedural time, and lower risks and complications. Larger studies and longer follow-up periods are warranted to establish its efficacy and safety.

Influence of "high" defibrillation thresholds on patient survival and impact of system modification.

To test whether a high defibrillation threshold (DFT) marks patients with poor outcomes which are improved when DFT is decreased by system modification (subcutaneous coil implant; SM). The electrical substrate generating fast ventricular arrhythmias may generate poor outcomes among patients treated with implantable cardioverter-defibrillators (ICDs), even when arrhythmias are treated successfully. Since patients with high DFTs have increased mortality, we contrasted survival among patients with high DFT treated with and without SM. We studied consecutive patients undergoing ICD implantation and DFT testing at Cleveland Clinic over a 14-year period. High DFT was defined as successful defibrillation by shock strength >25 J or ≤10 J of maximal device output. Mortality was recorded using the Social Security Death Index. Survival was compared among those high DFT patients receiving SM versus the remainder. Out of 6353 patients tested, 191 (3%) had high DFT (32.1 ± 3.7 J)versus 13.9 ± 4.9 J in the remainder ("acceptable DFT,"p < .001). One hundred twenty-one high DFT patients (63%; 33.3 ± 3.4 J) underwent SM, which significantly decreased DFT (24.8 ± 5.9 J; p < .001). Seventy patients (37%; 30.3 ± 3.3 J) did not undergo SM. During follow-up, 38% (2363/6162; 7.8 yrs) patients with acceptable DFT died versus 48% high DFT patients (91/191; 5.6 yrs.; p < .001). Concomitantly, 48% patients with SM (58/121) died, as compared to 47% patients (33/70) without SM (p = .91); median follow-up 4.9 yrs). Patients with high DFT have a higher mortality than those with acceptable DFT. The additional subcutaneous coil implant decreases DFT to an acceptable range but does not appear to improve survival. The electrical substrate underlying high DFT appears to determine survival.

Abstract 9615: Predictors of Impedance During Subcutaneous ICD Defibrillation Testing in Hypertrophic Cardiomyopathy

Introduction: Defibrillation threshold testing (DFT) is generally reserved for populations with perceived concern for defibrillation failure, including in hypertrophic cardiomyopathy (HCM). Higher shock impedance has been associated with risk of DFT failure with subcutaneous defibrillators (SICD). The PRAETORIAN score is a chest radiograph based tool that evaluates device positioning to predict risk of DFT failure. Objective: We assessed predictors of impedance during DFT in a single center HCM SICD cohort. Methods: Data was collected from HCM patients who underwent SICD implantation from 2013 to 2021. Predictors of impedance were evaluated with linear and logistic regression. Results: Impedance was reported in 75 HCM SICD patients during DFT with 65J. DFT was successful in 74 patients with mean impedance of 72.7 ohm and septal thickness of 20.6 mm. Ten patients had massive HCM (&gt; 30 mm) with mean impedance of 66.4 ohm. Septal thickness was not predictive of impedance (β 0.37, 95% CI 1.24-0.50; P = .40). Independent predictors of impedance were BMI (β 1.41, 95% CI 0.61-2.21; P = .0008) and PRAETORIAN score (β 0.14, 95% CI 0.05-0.22; P = .0015). Multivariable regression revealed BMI no longer significant and PRAETORIAN score remaining significant (β 0.10, 95% CI 0.01-1.66; P = .038). Conclusion: In this HCM SICD cohort BMI and PRAETORIAN score were predictive of impedance. However, in a multivariable model, BMI was no longer predictive, highlighting importance of implant technique to improve impedance and DFT. Additionally, patients with massive hypertrophy all had successful DFT and septal thickness was not predictive of impedance. HCM has historically been portrayed as a high DFT population. Further prospective trials are necessary to establish whether standard DFT practice can be applied in HCM.

Abstract 13691: High Burden of Sensing Changes in Periprocedural TAVR Patients With Pre-Existing CIEDs Presents A Unique Challenge

Introduction: The data on the management of patients undergoing transcatheter aortic valve replacement (TAVR) with pre-existing cardiac implantable electronic devices (CIED) is scarce. Objective: We describe the R wave sensing changes following TAVR in a patient with CIED and describe CIED behavior peri procedurally in a high volume center over 8 years. Results: A 64 year old male patient with a history of non-ischemic cardiomyopathy and a secondary prevention dual-chamber ICD presented for generator change. Six months prior, he underwent TAVR (29mm ES S3). Post TAVR, he developed a new RBBB. Device interrogation revealed a significant drop in sensed R waves from 9mV to 1.5mV which temporally correlated with TAVR (Figure 1). Pacing thresholds and impedance were stable. Chest x-rays showed stable lead position. Given drop in R wave sensing, successful defibrillation threshold testing was performed with generator change. Of the 115 patients with pre-existing CIEDs undergoing TAVR between 2012-2020, 23.5% (27 patients) showed changes in sensing (mean 3.0±2.5mV) peri procedurally with minimal change in impedance or threshold with no correlation with QRS changes. Conclusions: To our knowledge, this is the 1st reported case of a change in sensed R waves due to conduction disturbance following TAVR. We hypothesize this occurred due to a change in the activation wavefront sensed by the right ventricular lead following the development of new RBBB. Up to a quarter of patients have sensing fluctuations in our experience. Consideration of pre and post device interrogation with TAVR could be of value.

Azygos Vein ICD Lead Implantation Lowers Defibrillation Threshold in a Patient with Hypertrophic Cardiomyopathy

A 14-year-old boy with hypertrophic cardiomyopathy (HCM) diagnosed at the age of 1 year and with massive left ventricular hypertrophy suffered an episode of ventricular fibrillation during mild effort. He underwent a dual-chamber implantable cardioverter defibrillator (ICD) implantation. The defibrillation threshold testing (DFT) was ineffective. Subcutaneous multi-coli arrays tunneled into the left postero-lateral position and connected to the superior vena cava (SVC) port of the dual-chamber ICD were added to increase the myocardial mass involved in the defibrillation shock pathway. A new DFT was unsuccessful. The patient was transferred to our hospital for myectomy. An epicardial defibrillation patch was placed on the left ventricular lateral wall, but again, DFT testing was ineffective using the right ventricular (RV) coil to lateral patch as shock pathway. Another epicardial defibrillation patch was then placed on the inferior wall. In this case, DFT testing was effective with a defibrillation pathway between the two patches and the can. In November 2015, a high shock impedance alarm was recorded through remote monitoring, thus compromising the safety of the ICD shock pathway. The patient underwent the implant of a new trans-venous defibrillation coil lead in the azygos vein. After few months, the patient developed symptomatic severe aortic regurgitation and underwent an aortic valve replacement. During the operation, DFT testing was performed and was successful. Our case illustrates that azygous vein ICD lead implantation is efficacious in HCM with massive hypertrophy and high DFT, and prompts further studies to systematically investigate its efficacy in this particular subgroup of the HCM population.

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).

B-PO03-015 A CONFUSING TALE OF TWO LEADS

Presenting CRT-D problems do not always indicate the underlying issue. To demonstrate that thorough device interrogations and defibrillation threshold testing (DFTs) are critical to diagnose and treat problems with CRT-D systems. A 33-year-old female was referred for a revision of her CRT-D system. Her original system was implanted for compete heart block and later upgraded to a CRT-D system with an epicardial LV lead after she was diagnosed with non-ischemic cardiomyopathy and VT. A recent device interrogation demonstrated R-waves of 1 mV down from 20 mV prior and therefore she was scheduled for a system revision. In the EP lab, a thorough device interrogation was performed and a slow escape rhythm was demonstrated with R waves between 15-20 mV. The prior 1 mV sensing was felt to be inaccurate as she had become pacemaker dependent, and had no sensed events (at VVI 40) for several months. We then performed DFTs given her history of VT and questions of inadequate RV sensing. Two inductions were performed and her device adequately sensed VF waves that measured 8-10 mV and her device successfully restored sinus rhythm. After DFTs, the shock impedance of the RV lead was noted to be >200 ohms, the LV lead was not capturing at maximum outputs, and the LV lead impedance was >3000 ohms. The epicardial LV lead was a unipolar lead with one pacing configuration from the LV tip to RV coil. We concluded the RV defibrillator lead was damaged by DFTs (although still able to deliver a shock) and LV lead was nonfunctional either because it was also damaged or because the pacing configuration included the RV lead. The patient underwent an extraction and re-implant of a new RV defibrillator lead. Intraprocedural testing demonstrated adequate function of the LV unipolar lead with appropriate sensing, impedance, and capture thresholds with the new RV lead. This patient was referred for system revision for inadequate sensing on her ICD lead, however, after DFTs we determined that she had suffered a conductor fracture in the lead, which also raised questions about her unipolar epicardial LV lead. Revision of the RV lead, although not for the original problem prompting referral, fixed her system.

Single tests of implantable cardioverter defibrillators can be performed in selected patients at a low risk of neuronal damage.

Defibrillator testing (DFT) is still used in selected patients to ensure adequate therapy. To do so, ventricular fibrillation is induced and terminated by the implanted cardioverter defibrillator (ICD). Studies have shown increases in neuronal damage markers without a measurable clinical effect in patients after defibrillator threshold testing with multiple shocks. The aim of this study was to measure clinical outcomes, neuronal damage parameters (NSE and S100), and intraoperative cerebral perfusion (Doppler, near infra-red spectroscopy [NIRS]) in patients undergoing single DFT after transvenous ICD implantation and comparing them to untested patients. We included 23 patients. Nine underwent surgery with a single DFT, 14 were not tested. Cognitive impairment was tested using the Mini-Mental-Status Test (MMST) and the DEMTECt 24h prior and postsurgery. We also measured S100 and Neuron-Specific Enolase (NSE) at these timepoints. During surgery we measured medial cerebral artery velocity and cerebral tissue oxygen saturation (rSO2 ). We found no significant differences between the patient groups except for a significant increase in mean arterial blood pressure and an increase in rSO2 after testing. One patient with cerebral vasculopathy had a significant increase in his NSE values without showing clinical symptoms. This patient also had low rSO2 measurements and a decrease in medial cerebral artery velocity after DFT, other than the other patients. Single DFT did not lead to signs of neuronal damage or cognitive impairment except in one case with pre-existing cerebral vasculopathy. Therefore, our results support the use of DFT in carefully selected patients.

Clinical outcomes and programming strategies of implantable cardioverter-defibrillator devices in paediatric hypertrophic cardiomyopathy: a UK National Cohort Study.

Sudden cardiac death (SCD) is the most common mode of death in paediatric hypertrophic cardiomyopathy (HCM). This study describes the implant and programming strategies with clinical outcomes following implantable cardioverter-defibrillator (ICD) insertion in a well-characterized national paediatric HCM cohort. Data from 90 patients undergoing ICD insertion at a median age 13 (±3.5) for primary (n = 67, 74%) or secondary prevention (n = 23, 26%) were collected from a retrospective, longitudinal multi-centre cohort of children (<16 years) with HCM from the UK. Seventy-six (84%) had an endovascular system [14 (18%) dual coil], 3 (3%) epicardial, and 11 (12%) subcutaneous system. Defibrillation threshold (DFT) testing was performed at implant in 68 (76%). Inadequate DFT in four led to implant adjustment in three patients. Over a median follow-up of 54 months (interquartile range 28-111), 25 (28%) patients had 53 appropriate therapies [ICD shock n = 45, anti-tachycardia pacing (ATP) n = 8], incidence rate 4.7 per 100 patient years (95% CI 2.9-7.6). Eight inappropriate therapies occurred in 7 (8%) patients (ICD shock n = 4, ATP n = 4), incidence rate 1.1/100 patient years (95% CI 0.4-2.5). Three patients (3%) died following arrhythmic events, despite a functioning device. Other device complications were seen in 28 patients (31%), including lead-related complications (n = 15) and infection (n = 10). No clinical, device, or programming characteristics predicted time to inappropriate therapy or lead complication. In a large national cohort of paediatric HCM patients with an ICD, device and programming strategies varied widely. No particular strategy was associated with inappropriate therapies, missed/delayed therapies, or lead complications.

Pediatric SubQ-ICD implantation, a single center review of the inter-muscular technique.

IntroductionPediatric patients with cardiomyopathies are at risk for sudden death and may need implantable cardioverter defibrillators (ICD’s), but given their small size and duration of use, children are at increased risk for complications associated with ICD use. The subcutaneous ICD presents a favorable option for children without pacing indications. Unfortunately, initial pediatric studies have demonstrated a high complication rate, likely due to the 3-incision technique employed.Material and methodsPatients with ICD but no pacing indication were retrospectively reviewed after implantation of subcutaneous ICD via the two-incision technique. In half of the patients, 10-J impedance test was also performed to compare with impedance obtained after defibrillation threshold testing with 65-J.ResultsTwelve patients were included. The median age was 14 years (range 10–16 years) with eight males included (72.7%). The median weight was 55 kg (range 29 kg–75.1 kg). Follow-up had a median of 11.5 months (range 2–27 months). The median body mass index was 18.4 kg/m squared (range 15.5–27.9 kg/m squared). One patient suffered a minor complication after tearing off the incisional adhesive strips early and required a non-invasive repair in clinic. Shock impedance had a median of 55 J (range 48–68 J). There was one appropriate shock/charge and no inappropriate shocks during follow-up.ConclusionThe two-incision, intermuscular technique appears to have a lower acute complication rate than prior reports, in our cohort of 12 pediatric patients.