High Defibrillation Threshold Research Articles

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).

Exploiting SMART pass filter deactivation detection to minimize inappropriate subcutaneous implantable cardioverter defibrillator therapies: a real-world single-centre experience and management guide.

The SMART Pass™ (SP) algorithm is a high-pass filter that aims to reduce inappropriate therapy (IT) in subcutaneous internal cardiac defibrillator (S-ICD), but SP can deactivate due to low amplitude sensed R waves or asystole. The association between IT and SP deactivation and management strategies were evaluated, hypothesizing SP deactivation increases the risk of IT and device re-programming, or lead/generator re-positioning could reduce this risk. Retrospective single-centre audit of Emblem™ S-ICD devices implanted 2016 to 2020 utilizing health records and remote monitoring data. Cox regression models evaluated associations between SP deactivation and IT. A total of 348 patients (27 ± 16.6 months follow-up) were studied: 73% primary prevention. Thirty-eight patients (11.8%) received 83 shocks with 27 patients (7.8%) receiving a total of 44 IT. Causes of IT were oversensing (98%) and aberrantly conducted atrial fibrillation (2%). SP deactivation occurred in 32 of 348 patients (9%) and was significantly associated with increased risk of IT (hazard ratio 5.36, 95% CI 2.37-12.13). SP deactivation was due to low amplitude R waves (94%), associated with a higher defibrillation threshold at implant and presence of arrhythmogenic right ventricular cardiomyopathy. No further IT occurred 16 ± 15.5 months after corrective interventions, with changing the sensing vector being successful in 59% of cases. To reduce the risk of IT, the cause of the SP deactivation should be investigated, and appropriate reprogramming, device, or lead modifications made. Utilizing the alert for SP deactivation and electrograms could pro-actively prevent IT.

Defibrillation Threshold Testing and Long-term Follow-up in Chagas Disease.

Sudden cardiac death is the most common cause of death in chronic Chagas cardiomyopathy (CCC). Because most CCC patients who are candidates for implantable cardioverter-defibrillators (ICD) meet criteria for high defibrillation threshold values, a defibrillator threshold test (DTT) is suggested. We investigated the use of DTT in CCC patients, focusing on deaths related to ICD and arrhythmic events, as well as treatment during long-term follow-up. We retrospectively evaluated 133 CCC patients who received an ICD mainly for secondary prevention. Demographic, clinical, laboratory data, Rassi score, and DTT data were collected, with p < 0.05 considered significant. The mean patient age was 61 (SD, 13) years and 72% were men. The baseline left ventricular ejection fraction was 40 (SD, 15%) and the mean Rassi score was 10 (SD, 4). No deaths occurred during DTT and no ICD failures were documented. There was a relationship between higher baseline Rassi scores and higher DTT scores (ANOVA = 0.007). The mean time to first shock was 474 (SD, 628) days, although shock was only necessary for 28 (35%) patients with ventricular tachycardia, since most cases resolved spontaneously or through antitachycardia pacing. After a mean clinical follow-up of 1728 (SD, 1189) days, 43 deaths occurred, mainly related to progressive heart failure and sepsis. A routine DTT may not be necessary for CCC patients who receive an ICD for secondary prevention. High DTT values seem to be unusual and may be related to high Rassi scores.

PO-618-03 REDUCTION IN DEFIBRILLATION THRESHOLD BY MODIFICATIONS TO THE SUBCUTANEOUS ICD COIL

Subcutaneous Implantable Cardioverter Defibrillators (S-ICDs) generally have higher defibrillation thresholds (DFTs) than transvenous ICDs, necessitating larger S-ICD generators and with S-ICD VF conversion testing recommended at implantation. We sought to determine whether modifications to the S-ICD coil configuration or characteristics would reduce DFTs compared to the standard S-ICD coil based on a computer model of defibrillation. We utilized a computer model built from MRI images of a normal thorax and simulation of electrical fields generated by defibrillation. The specific electrical properties of tissues and organs were assigned, as well as other characteristics of the shock circuit, with DFT defined as energy required to achieve an electrical field of 4V/cm in > 95% of ventricular myocardium. Coil configurations examined included a standard parasternal S-ICD coil, dual parallel para-sternal coils, dual coils in series (parasternal and along the left ribcage), and a larger flattened parasternal coil. The standard parasternal S-ICD coil configuration (with < 1mm intervening fat under the coil and generator) resulted in an estimated DFT of 33J. The other coil configurations resulted in marked reductions in DFT by as much as 37% (to 21J) (figure), predominantly related to lower shock impedance and improved electrical field distribution. Our modeling work suggests that modifications to the S-ICD coil design could lead to marked reductions in DFT. This could allow for the creation of S-ICDs with lower energy requirements and correspondingly smaller generators compared to current devices and might obviate the need for VF conversion testing with S-ICDs.

The "Defibrillation Testing, Why Not?" survey. Testing of subcutaneous and transvenous defibrillators in the Italian clinical practice.

BackgroundDefibrillation testing (DT) can be omitted in patients undergoing transvenous implantable cardioverter–defibrillator (T-ICD) implantation, but it is still recommended for patients at risk for a high defibrillation threshold and for ICD generator changes. Moreover, DT is still recommended on implantation of subcutaneous ICD (S-ICD). The aim of the present survey was to analyze the current practice of DT during T-ICD and S-ICD implantations.MethodsIn March 2021, an ad hoc questionnaire on the current performance of DT and the standard practice adopted during testing was completed at 72 Italian centers implanting S-ICD and T-ICD.Results48 (67%) operators reported never performing DT during de-novo T-ICD implantations, while no operators perform it systematically. The remaining respondents perform it for patients at risk for a high defibrillation threshold. DT is never performed at T-ICD generator change. At the time of de-novo S-ICD implantation, DT is never performed by 9 (13%) operators and performed systematically by 48 (66%). The remaining operators frequently omit DT in patients with more severe systolic dysfunction. DT is not performed at S-ICD generator change by 92% of operators. DT is conducted by delivering a first shock energy of 65 J by 60% of operators, while the remaining 40% test lower energy values.ConclusionsIn current clinical practice, most operators omit DT at T-ICD implantation, even when still recommended in the guidelines. DT is also frequently omitted at S-ICD implantation, and a wide variability exists among operators in the procedures followed during DT.

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.

Defibrillation testing of subcutaneous versus transvenous defibrillators in the clinical practice: a nationwide survey in Italy

Abstract Aims According to current guidelines, defibrillation testing (DT) for efficacy can be omitted in patients undergoing transvenous implantable cardioverter–defibrillator (T-ICD) implantation. DT is still recommended for patients at risk for a high defibrillation threshold (e.g. hypertrophic cardiomyopathy, arrhythmogenic right ventricular cardiomyopathy, right-sided implantations) and for ICD generator changes. Moreover, a class I recommendation remains to perform DT during the implantation of subcutaneous ICD (S-ICD). The aim of the present survey was to analyze the current practice of DT during T-ICD and S-ICD implantations in Italy. Methods In March 2021, an ad hoc questionnaire on the current performance of DT and the standard practice adopted during testing was completed by 72 operators at Italian centers implanting S-ICD and T-ICD. Results 48 (67%) operators reported never performing DT during de-novo T-ICD implantations, while no operators perform it systematically. The remaining respondents perform it in specific cases: right sided implantations (54%), poor signal sensing (46%), secondary prevention patients (42%), arrhythmic syndromes (13%), hypertrophic cardiomyopathy (8%). DT is never performed at T-ICD generator change. At the time of de-novo S-ICD implantation, DT is never performed by 9 (13%) operators and performed systematically by 48 (66%). The remaining operators perform DT in cases of: secondary prevention patients (73%), sub-optimal S-ICD placement (33%), non-compromised ejection fraction (33%) or obese patients (7%). DT is not performed at S-ICD generator change by 92% of operators. DT is conducted by delivering a first shock energy of 65J by 60% of operators, while the remaining 40% test lower energy values. The most frequently reported conditions for revising the system at the end of de- novo implantation procedure is high shock impedance (54%) and sub-optimal S-ICD placement or high PRAETORIAN score (50%). With adequately low shock impedance and optimal system placement, 37% of operators would accept a defibrillation margin &amp;lt;15J. Conclusion In current clinical practice, the vast majority of operators omit DT at T-ICD implantation, even when still recommended in the guidelines. DT is also frequently omitted at S-ICD implantation. We also report a wide variability among operators in the procedures followed during DT and in the criteria applied for defining the procedural success. Funding Acknowledgement Type of funding sources: None.

Omdlenie i elektrokardiograficzne podejrzenie zawału serca z uniesieniem odcinka ST nad ścianą przednią – pomyśl o zespole Brugadów!

This is a case of 52-year-old male after episode of syncope and with atypical chest pain referred to hospital with acute anterior ST elevation myocardial infarction. Urgent coronary angiography showed normal coronary arteries and only ECG made the next day made us to suspect Brugada syndrome. The patient had ICD implanted and because of high defibrillation threshold, subcutaneous electrode implantation was decided. Our case highlights, that ECG changes in Brugada syndrome can mimic ST elevation in the course of acute coronary syndrome and that subcutaneous electrode implantation may be useful method of lowering defibrillation treshold.

Long term stability of the subcutaneous cardioverter defibrillator implanted by means of the intermuscular two incision technique

Abstract Funding Acknowledgements Type of funding sources: None. Background To ensure effective defibrillation with the subcutaneous implantable cardioverter defibrillator (S-ICD), both the lead and the generator must be adequately positioned extrathoracically. We assessed the long-term adequacy of the S-ICD system position and its stability in a group of patients who received the S-ICD by means of the two-incision intermuscular technique. Methods The PRAETORIAN score uses chest radiography to provide feedback on S-ICD positioning, and identifies patients with high defibrillation thresholds. We compared radiographs taken immediately after implantation and on 12-month follow-up examination. Results We analyzed data from 38 patients with the S-ICD generator positioned in an intermuscular pocket. The median PRAETORIAN score was 38 [25th to 75th percentile: 30 to 60]. Two (5%) patients had a score of 90 (intermediate risk of conversion failure). The thickness of the adipose tissue between the coil and the sternum was ≤1 coil width in 72% of patients, the generator was on, or posterior to, the midline in 94% of patients, and the amount of fat tissue between the generator and the thoracic wall was less than the generator width in 78% of patients. No generator or electrode dislodgments were detected on analyzing radiographs collected at the 12-month visit. In all patients, assessment of the PRAETORIAN score confirmed the values calculated on post-implantation analysis. During follow-up, no ineffective therapies, sudden cardiac or device-related deaths occurred. Conclusions The position of the S-ICD system implanted using the two-incision intermuscular technique was adequate at the time of implantation and remained stable after 12 months.

P529Efficacy and safety of S-ICD implantation without use of defibrillation threshold testing: a retrospective multicentric observational study

Abstract Introduction The subcutaneous ICD (S-ICD) is a valid alternative to transvenous systems (TV-ICD) for the treatment of life-threatening arrhythmias, and the extravascular position of the lead allows a significant reduction of the risk of infection. Current guidelines recommend defibrillation threshold testing (DFT) at the time of S-ICD implantation (class I). Although randomised trials have proven the safety of TV-ICD implantation with no DFT, it is unclear whether such an approach could be adopted for S-ICD as well. The PRAETORIAN score, based on post-implantation chest X-ray, can accurately predict a high defibrillation threshold after S-ICD implantation. The aim of this retrospective multicentre study was to evaluate the efficacy and safety of S-ICD implantation with no DFT. Methods We enrolled 203 consecutive patients undergoing S-ICD implantation in six different centres between October 2012 and January 2019. It was left at discretion of the operator whether performing or not DFT at the time of the procedure. Baseline device settings were collected, and the PRAETORIAN score was retrospectively calculated whenever chest X-ray was available. Both remote or in-clinic device interrogation reports were systemically analysed, and all the shocks and arrhythmia episodes identified. All the patients provided consent form and ethical approval was obtained. Results The population (mean age 57.6 ± 14.2) was divided in two groups, based on whether DFT was performed at the time of the S-ICD implantation: 72 patients (35.4%) underwent DFT (DFT+ group), while 131 patients (64.5%) did not (DFT- group). In the DFT- group, mean LVEF was lower (32 ± 8% vs 42 ± 17%, p &amp;lt; 0.0001) and prevalence of diabetes mellitus and atrial fibrillation higher compared to the DFT+ group (27.5% vs 13.9%, p = 0.04 and 38.9% vs 19.44%, p = 0.007; respectively). In addition, the indication for S-ICD was more frequently primary prevention in the DFT- vs DFT+ group (70.8% vs 90.8%, p = 0.0004; respectively). No differences in terms of device programming were identified between the two cohorts. The PRAETORIAN score was significantly higher in the DFT- vs DFT+ patients (50 ± 26 vs 36 ± 18, p = 0.032; respectively). After a median follow-up of … months, we observed 5 appropriate shocks in 3 patients from the DFT+ group vs. 15 shocks in 8 patients from the DFT- group (p = 0.81). All the life-threatening arrhythmias were successfully recognised and treated by the device. DFT was complicated by pulseless electrical activity in one patient. One patient in the DFT- group suffered from an episode of ventricular tachycardia requiring a total of 4 shocks for being terminated. Six patients in the DFT- group died for non-arrhythmic causes. On the Kaplan-Meier analysis, cumulative survival was comparable between the two groups (log rank p value = 0.13). Conclusions This study suggests that implantation of S-ICD with no DFT might be reasonable. These results should be confirmed in prospective randomised trials.

Refractoriness to subcutaneous implantable cardioverter defibrillator after frequent therapies for ventricular fibrillation storms in a Brugada syndrome case

BackgroundThe subcutaneous implantable cardioverter defibrillator (S-ICD) is an alternative to the transvenous implantable cardioverter defibrillator for the prevention of sudden cardiac death. Here, we report a rare case of refractoriness to an S-ICD after frequent therapies for ventricular fibrillation (VF) storms.Case presentationA 24-year-old man underwent a bout of syncope with vomiting and incontinence at home. He was brought to the emergency room and was witnessed to spontaneously go into VF successfully converted by external defibrillation. Previously, he was diagnosed with a type I Brugada electrocardiogram pattern by a pilsicainide administration test in another hospital. Although he had a family history of sudden cardiac death in 3 relatives, including his brother, he was followed closely without any therapies because he had never had an episode of syncope. He was implanted with an S-ICD without any trouble. Seven months later, frequent S-ICD shocks for VF storms occurred. His VF was controlled by using intravenous amiodarone, which was converted to an oral preparation. However, his VF recurred after another 2 months. The analysis of his S-ICD data revealed that 4 consecutive shock deliveries could not terminate his VF and the final shock delivered could fortunately terminate it because of a high defibrillation threshold test (DFT) due to an increasing shock impedance (64 to 90 Ω). First, we performed an epicardial Brugada syndrome ablation and subsequently replaced and repositioned the S-ICD lead from a left to a right parasternal site. After the re-implantation of the S-ICD, the DFT test improved to within normal range. According to the pathological analysis, infiltration of inflammatory cells and extensive fibrosis were confirmed in the subcutaneous tissue around the shock lead and S-ICD body.ConclusionFrequent S-ICD shocks for VF storms might cause various pathological changes around the device and lead to a high DFT.

EPICARDIAL PASSIVE FIXATION DEFIBRILLATION COIL USING A DURATA LEAD: A UNIQUE APPROACH TO OVERCOMING HIGH DEFIBRILLATION THRESHOLD

Unsuccessful implantable cardioverter defibrillator (ICD) defibrillation due to high defibrillation threshold (DFT) is rare and can be difficult to manage when traditional methods such as azygous vein or epicardial defibrillation fail to provide adequate DFT or long-term durability. A 59-year-old

Coronary vein defibrillator coil placement in patients with high defibrillation thresholds.

BackgroundElevated 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.MethodsPatients 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.ResultsFour 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).ConclusionsPositioning of a defibrillation coil in the CS can result in a substantial reduction in mean DFT and associates with optimal long‐term stability.

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

Suboptimal positioning of the subcutaneous implantable cardioverter-defibrillator (S-ICD) increases the defibrillation threshold and risk of conversion failure. Our objective is to develop a tool to evaluate the implant position and predict defibrillation success of the S-ICD: the PRAETORIAN score. 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. 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. 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.

Should Single-Coil Implantable Cardioverter Defibrillator Leads Be Used in all Patients?

The historical preference for dual-coil implantable cardioverter defibrillator leads stems from high defibrillation thresholds associated with old device platforms. The high safety margins generated by contemporary devices have rendered the modest difference in defibrillation efficacy between single- and dual-coil leads clinically insignificant. Cohort data demonstrating worse lead extraction outcomes and higher all-cause mortality have brought the incremental utility of an superior vena cava coil into question. This article summarizes the current literature and re-evaluates the utility of dual-coil leads in the context of modern device technology.

High defibrillation Thresholds in a Patient with Hypertrophic Cardiomyopathy and implant of a Subcutaneous defibrillator electrode

High defibrillation Thresholds in a Patient with Hypertrophic Cardiomyopathy and implant of a Subcutaneous defibrillator electrode

High defibrillation Thresholds in a Patient with Hypertrophic Cardiomyopathy and implant of a Subcutaneous defibrillator electrode

High defibrillation Thresholds in a Patient with Hypertrophic Cardiomyopathy and implant of a Subcutaneous defibrillator electrode

Predictors of Elevated Defibrillation Threshold with the Subcutaneous Implantable Cardioverter-defibrillator.

There are limited data regarding defibrillation thresholds (DFTs) for the subcutaneous implantable cardioverter-defibrillator (S-ICD), and factors associated with elevated DFTs remain incompletely understood. The objective of this study was to determine the factors associated with elevated DFTs in patients undergoing S-ICD implantation. A retrospective cross-sectional analysis of all patients undergoing S-ICD implantation at our institution between 2013 and 2016 who underwent step-down DFT testing was performed. Factors associated with a higher DFT were analyzed. In total, 56 patients (mean age: 49.3 ± 13.1 years, mean left ventricular ejection rate: 31.1% ± 13.7%) underwent S-ICD implantation in the study period. Full DFT testing was performed in 31 of the 56 patients (55%), with an average DFT of 46.4 joules (J) ± 25.9 J found among this cohort. The DFT was > 65 J in five of the 31 patients (16%). A high DFT was associated with increased body mass index (BMI) (37.7 kg/m2 versus 29.4 kg/m2; p = 0.02) and either increased septal or posterior wall thickness (1.5 cm versus 1.0 cm; p = 0.0003 and 1.4 cm versus 1.1 cm; p= 0.003, respectively). Patients with high DFTs also had higher failed shock impedance values (138 Ω versus 71 Ω; p = 0.005). Renal failure did not appear to affect DFT (51.4 J versus 51.7 J; p = 0.99). BMI, body surface area (BSA), and septal and posterior left ventricular wall thickness predicted elevated DFT on univariate analysis, although findings were not significant with multivariate analysis due to the small sample size. Thus, elevated S-ICD DFT appears to be associated with increased BMI, BSA, and septal or posterior wall thickness. In contrast, dialysis-dependent renal failure is not associated with elevated DFT. Further investigation is necessary in order to better characterize and predict which patients are at-risk for high DFTs.

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.

Higher defibrillation threshold in methamphetamine cardiomyopathy patients with implantable cardioverter-defibrillator

IntroductionIdentification of patients with an increased risk of high defibrillation thresholds (DFTs) is important in planning implantable cardioverter-defibrillator (ICD) procedures. Clinical observations have suggested that patients with methamphetamine cardiomyopathy (MACMP) have significantly elevated defibrillation thresholds. We hypothesized that MACMP patients would have higher DFT thresholds than controls and would require procedural changes during ICD implantation to accommodate higher thresholds. MethodsWe identified consecutive patients with MACMP undergoing ICD implantation at the academic center from 2003 to 2007. We then compared DFTs against age-and sex-matched controls. ResultsThe MACMP (n = 10) group showed significantly increased DFT thresholds (23.7 ± 6.7 J) compared with age and sex-matched controls (14.5 ± 4.6 J, p < 0.005). Additionally, patients with MACMP had evidence of more severe congestive heart failure, with increased B-type natrieutic protein (BNP) levels (1173 ± 784 vs 260 ± 349, p = 0.02) and decreased left ventricular ejection fraction (LVEF) (17.8 ± 9.4 vs 35.9 ± 15.2, p = 0.02). MACMP patients required high output devices than controls (50% versus 0%, p = 0.03). Differences between groups remained significant despite adjusting for LVEF. ConclusionsPlanning for ICD implantation should take into consideration a history of methamphetamine abuse, mandating DFT testing and empiric consideration of high output devices for such patients.