Preoperative Prediction of Shock Impedance for Subcutaneous Implantable Cardioverter Defibrillator Using Chest Computed Tomography.

BACKGROUND: High shock impedance is associated with conversion failure among patients with subcutaneous implantable cardioverter defibrillators (S-ICD). Currently, there is no preoperative assessment method for predicting high shock impedance. This study examined the efficacy of chest computed tomography (CT) as a preoperative evaluation tool to assess the shock impedance of S-ICDs. METHODS AND RESULTS: The amount of adipose tissue adjacent to the device and anteroposterior diameter at the basal heart region were measured preoperatively using chest CT. We examined the correlation between these measurements and shock impedance at the conversion test. We enrolled 43 patients with S-ICDs (mean [±SD] age 54±15 years; body mass index 23±4 kg/m2; PRAETORIAN score 30-270 points; amount of adipose tissue 1,250±716 cm3), who underwent intraoperative conversion tests by inducing ventricular fibrillation, which was terminated with a 65-J shock. A sufficient concordance correlation coefficient was observed between the shock impedance and the amount of adipose tissue (r=0.616, P<0.01) and anteroposterior diameter (r=0.645, P<0.01). In multiple regression analysis, the amount of adipose tissue (ß=0.439, P=0.009) and anteroposterior diameter (ß=0.344, P=0.038) were identified as independent predictive factors of shock impedance. CONCLUSIONS: The preoperative CT-measured amount of adipose tissue and basal heart anteroposterior diameter are independent predictors of shock impedance. These parameters may be more accurate in identifying higher shock impedance in patients with S-ICDs.

The relationship between the incision line and position of the latissimus dorsi muscle for subcutaneous implantable cardioverter-defibrillator intermuscular implantations.

INTRODUCTION: Intermuscular implantations of subcutaneous implantable cardioverter-defibrillators (S-ICD) have been recommended, but the position of the anterior border of the latissimus dorsi muscle (LDM) has not previously been evaluated in establishing an incision line to facilitate the intermuscular approach. The objective of this study is to evalua the position and trend of the anterior border of the LDM in patients who are candidates for implantable cardioverter-defibrillators. METHODS: The distance from the back to the anterior border of the LDM (A) and the anterior-posterior width of the chest wall (B) were measured on computed tomography retrospectively, and the ratio (=A/B) was used as the position of the anterior border of the LDM. In addition, the variability and factors affecting the values were evaluated. RESULTS: An analysis was performed on 78 patients, and the position of the anterior border of the LDM (=A/B) exhibited a normal distribution, with a mean value of 0.53 ± 0.062 (0.41-0.69). The position of the anterior border of the LDM tended to be more anterior in younger, taller, male, primary prevention, nonheart failure, low brain natriuretic peptide level, and nondiabetic patients. CONCLUSION: The position of the anterior border of the LDM varied from case to case with variable results. Conventional incisions on the midaxillary line may be inappropriate for intermuscular implantations, and the position of the anterior border of the LDM should be evaluated in each individual case to establish the incision line.

Additional coils mitigate elevated defibrillation threshold in right-sided implantable cardioverter defibrillator generator placement: a simulation study.

AIMS: The standard implantable cardioverter defibrillator (ICD) generator (can) is placed in the left pectoral area; however, in certain circumstances, right-sided cans may be required which may increase defibrillation threshold (DFT) due to suboptimal shock vectors. We aim to quantitatively assess whether the potential increase in DFT of right-sided can configurations may be mitigated by alternate positioning of the right ventricular (RV) shocking coil or adding coils in the superior vena cava (SVC) and coronary sinus (CS). METHODS AND RESULTS: A cohort of CT-derived torso models was used to assess DFT of ICD configurations with right-sided cans and alternate positioning of RV shock coils. Efficacy changes with additional coils in the SVC and CS were evaluated. A right-sided can with an apical RV shock coil significantly increased DFT compared to a left-sided can [19.5 (16.4, 27.1) J vs. 13.3 (11.7, 19.9) J, P < 0.001]. Septal positioning of the RV coil led to a further DFT increase when using a right-sided can [26.7 (18.1, 36.1) J vs. 19.5 (16.4, 27.1) J, P < 0.001], but not a left-sided can [12.1 (8.1, 17.6) J vs. 13.3 (11.7, 19.9) J, P = 0.099). Defibrillation threshold of a right-sided can with apical or septal coil was reduced the most by adding both SVC and CS coils [19.5 (16.4, 27.1) J vs. 6.6 (3.9, 9.9) J, P < 0.001, and 26.7 (18.1, 36.1) J vs. 12.1 (5.7, 13.5) J, P < 0.001]. CONCLUSION: Right-sided, compared to left-sided, can positioning results in a 50% increase in DFT. For right-sided cans, apical shock coil positioning produces a lower DFT than septal positions. Elevated right-sided can DFTs may be mitigated by utilizing additional coils in SVC and CS.

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

OBJECTIVE: 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). BACKGROUND: 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. METHODS: 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. RESULTS: 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). CONCLUSION: 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.

High Internal Atrial Defibrillation Threshold Is Related to a High Risk of Recurrence After Catheter Ablation for Long-Standing Persistent Atrial Fibrillation But Not for Persistent Atrial Fibrillation.

BACKGROUND: The atrial defibrillation threshold (ADFT) for internal cardioversion is theoretically related to the critical mass for sustaining atrial fibrillation (AF). OBJECTIVE: This study aimed to investigate the association of ADFT for internal cardioversion with the outcome of catheter ablation for non-paroxysmal AF (non-PAF). METHODS: We included 368 consecutive patients who underwent first-time catheter ablation for non-PAF. Based on the degree of ADFT recorded by the internal cardioversion before pulmonary vein isolation, we divided the patients into low ADFT (<20 J) and high ADFT (≥20 J) groups and analysed the association between ADFT and atrial tachyarrhythmia recurrence. RESULTS: There were 234 and 134 patients in the low and high ADFT groups, respectively. Of these, 39 patients (16.7%) and 41 (30.6%) patients, respectively, had atrial tachyarrhythmia recurrence during the 2.6±1.0 year follow-up. The high ADFT group showed a significantly higher atrial tachyarrhythmia recurrence than the low ADFT group (p=0.002). This finding was also noted in patients with long-standing persistent AF (p=0.032) but not in patients with persistent AF (p=0.159). The significant predictors of arrhythmia recurrence on multivariate analysis were high ADFT (p=0.004) and long-standing persistent AF (p=0.011). In multivariate analysis within the long-standing persistent AF group, only ADFT remained a significant risk factor for AF recurrence (p=0.035). CONCLUSIONS: The high ADFT of internal cardioversion was found to be a risk factor for post-catheter ablation recurrence in patients with long-standing persistent AF but not in those with persistent AF.

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

BACKGROUND: The 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 PRESENTATION: A 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. CONCLUSION: Frequent S-ICD shocks for VF storms might cause various pathological changes around the device and lead to a high DFT.

A cracking complication: Displacement of existing clavicle fracture complicating subcutaneous implantable cardioverter defibrillator implantation.

An 18 year old male with an incompletely healed clavicle fracture presented with unexplained syncope. Subsequent investigations were consistent with a diagnosis of arrhythmogenic right ventricular cardiomyopathy (ARVC). A subcutaneous implantable cardioverter-defibrillator (S-ICD) was successfully implanted and defibrillation threshold (DFT) testing performed as per standard protocol. Shortly following the procedure, the patient complained of pain and swelling over the left clavicle. A radiograph revealed aggravation and displacement of the underlying clavicle fracture. Surgical reduction and internal fixation was performed one week later.

Minimal defibrillation thresholds and the correlation with implant position in subcutaneous implantable-defibrillator patients.

BACKGROUND: Since the introduction of the subcutaneous implantable-defibrillator (S-ICD) knowledge of factors elevating the defibrillation threshold (DFT), have increased. Optimal device positioning most likely results in a decrease in DFT. The PRAETORIAN score is a tool to systematically evaluate S-ICD implant position and predict conversion success by estimating the DFT on a chest X-ray. The objective of this study is to determine DFT in de novo S-ICD patients. METHODS: De novo S-ICD patients were enrolled with DFT testing using a single 30 J shock or a prespecified step-down protocol. Chest X-rays were obtained and implant position was evaluated using the PRAETORIAN score. RESULTS: Fifteen patients, age 47 (±18) years and body mass index (BMI) 25(±3) kg/m2 , underwent conversion testing with a single 30 J shock. Fourteen patients (93%) converted successfully. Implant position was optimal in all patients, PRAETORIAN score of 30 (100%). Twelve patients were available for analysis in the step-down DFT cohort, age 46 years (±15), left ventricular ejection fraction 50% (±15%) and a median BMI of 25.7 kg/m2 (range 23.8-29.1 kg/m2 ). No complications occurred during DFT testing. Mean DFT was 29 J (±12 J). Time to shock was 11 seconds (±2 seconds) for a 20 J shock compared with 17 seconds in case of a 70 J shock output. Nearly all patients were implanted with optimal device positioning with the lowest possible PRAETORIAN score of 30 (92%). CONCLUSION: DFT in S-ICD patients with optimal device positioning is lower than previously reported. Conversion testing using a low shock output reduced time to therapy by 6 seconds on average.

The Saga of Defibrillation Testing: When Less Is More.

PURPOSE OF REVIEW: In the current era of implantable cardioverter-defibrillator procedures, the decision of whether or not to perform defibrillation threshold testing at the time of implantation is now less of a clinical conundrum. In this paper, we summarize this current practice, beginning with the physiology of defibrillation, followed by a review of the salient data, and discussion of specific situations where defibrillation threshold testing remains a clinical consideration. RECENT FINDINGS: Two prospective randomized trials demonstrated no mortality difference and no overall complication rate difference between patients who underwent defibrillation testing at implant compared with patients who underwent no defibrillation testing. Current recommendations support eliminating routine defibrillation testing in left-sided transvenous implantable cardioverter-defibrillator primary prevention implants. Defibrillation testing remains indicated in subcutaneous defibrillator implants in the absence of contraindications.

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.

Prognostic Implications of Defibrillation Threshold Testing in Patients With Hypertrophic Cardiomyopathy.

INTRODUCTION: In hypertrophic cardiomyopathy (HCM) patients the need for defibrillation threshold (DFT) testing at the time of ICD implantation is debated. Moreover, its prognostic implications have never been explored. In a cohort of HCM patients we sought to (a) investigate factors prompting DFT testing, (b) evaluate ICD efficacy by testing DFT, (c) compare DFT in patients with and without massive LVH, and (d) assess whether DFT testing predicts shock efficacy for spontaneous VT/VF. METHODS AND RESULTS: We retrospectively analyzed a cohort of HCM patients implanted with an ICD. DFT was tested at the discretion of the implanting physician with a 10 J safety margin. During follow-up, ICD interventions were evaluated. The study population included 66 patients. DFT was determined in 25 (38%) patients. Age (HR: 0.95; 95%CI: 0.92-0.98; P = 0.004) and massive LVH (HR: 6.0; 95%CI: 2.03-18.8; P = 0.001) affected the decision to test DFT. DFT was at least 10 J less than maximal ICD output in 25/25. Safety margin was similar among patients with and without massive LVH (15 ± 3 J vs. 14 ± 2 J; P = 0.42). During follow-up (median 53 months) 15 shocks were delivered for 12 VT/VF in 7 patients. One VF ended spontaneously after a failed shock. Of 4 unsuccessful shocks, 2 occurred in 1 patient with DFT testing and 2 were delivered in 2 patients without. All unsuccessful shocks were ≤35 J. CONCLUSION: Young age and massive LVH prompt DFT testing. Contemporary ICDs are safe and effective in HCM patients independently from the magnitude of LVH. DFT testing does not predict shock efficacy for spontaneous VT/VF.

Contemporary rates and outcomes of single- vs. dual-coil implantable cardioverter defibrillator lead implantation: data from the Israeli ICD Registry.

AIMS: Dual-coil leads were traditionally considered standard of care due to lower defibrillation thresholds (DFT). Higher complication rates during extraction with parallel progression in implantable cardioverter defibrillator (ICD) technology raised questions on dual coil necessity. Prior substudies found no significant outcome difference between dual and single coils, although using higher rates of DFT testing then currently practiced. We evaluated the temporal trends in implantation rates of single- vs. dual-coil leads and determined the associated adverse clinical outcomes, using a contemporary nation-wide ICD registry. METHODS AND RESULTS: Between July 2010 and March 2015, 6343 consecutive ICD (n = 3998) or CRT-D (n = 2345) implantation patients were prospectively enrolled in the Israeli ICD Registry. A follow-up of at least 1 year of 2285 patients was available for outcome analysis. The primary endpoint was all-cause mortality. Single-coil leads were implanted in 32% of our cohort, 36% among ICD recipients, and 26% among CRT-D recipients. Secondary prevention indication was associated with an increased rate of dual-coil implantation. A significant decline in dual-coil leads with reciprocal incline of single coils was observed, despite low rates of DFT testing (11.6%) during implantation, which also declined from 31 to 2%. In the multivariate Cox model analysis, dual- vs. single-coil lead implantation was not associated with an increased risk of mortality [hazard ratio (HR) = 1.23; P= 0.33], heart failure hospitalization (HR = 1.34; P=0.13), appropriate (HR = 1.25; P= 0.33), or inappropriate ICD therapy (HR = 2.07; P= 0.12). CONCLUSION: Real-life rates of single-coil lead implantation are rising while adding no additional risk. These results of single-coil safety are reassuring and obtained, despite low and contemporary rates of DFT testing.

Defibrillation thresholds with right pectoral implantable cardioverter defibrillators and impact of waveform tuning (the Tilt and Tune trial).

AIMS: Assess defibrillation thresholds (DFTs) with right active pectoral implantable cardioverter defibrillator (RICDs). Defibrillation thresholds in patients receiving RICDs are regarded as 'high' and potentially improved by waveform optimization (tuning). However, this has not been systematically tested. METHODS AND RESULTS: Patients receiving RICDs [Single chamber (VVI) = 16, DDD = 32, cardiac resynchronization therapy (CRT) = 43] were randomized to either 50/50% fixed tilt (FT) or tuned waveform (3.5 ms time constant based). Defibrillation threshold was tested with a binary search protocol in single coil anodal configuration. Then RICDs were compared with left-sided placements. Baseline patient characteristics in FT (n = 54) and tuned (n = 37) were similar (65 ± 14 years, 71% male, Left ventricular ejection fraction 31 ± 13%; and proportions VVI/DDD/Cardiac resynchronization therapy defibrillator). Tuning reduced Phase 1 by 15% and Phase 2 by 45%. For FT vs. tuned: high voltage impedance was 61.9 ± 13.2 vs. 64.5 ± 12.7 Ω (P = 0.33) and mean DFT 14.2 ± 8.8 vs. 14.9 ± 9.2 J (P = 0.8). When high voltage impedance was >62 Ω (mean 73.6 ± 8.6 Ω), DFT was identical [FT 13.0 ± 7.9 J vs. tuned 12.0 ± 5.9 J (P= 0.7)]. Defibrillation thresholds exceeded 20 J (600 V) in >20% of patients [FT 11/54 (20.4%) vs. tuned 12/37 (32%) patients]. Defibrillation threshold with RICD was greater and exhibited wider dispersion compared with left ICDs (n = 54) under similar conditions. CONCLUSION: This first randomized trial investigating DFTs with right ICDs confirms relatively higher DFTs with RICDs than reported for left pectoral ICDs. However, DFTs were generally unaffected by 3.5 ms time constant-based waveform tuning compared with a 50% tilt waveform. Implant testing may be preferred with RICDs. CLINICAL TRIAL NUMBER: NCT00873691.

Impact of the Relationship between the Defibrillation Threshold (DFT) and Clinical Outcomes in Recipients of Modern Era Implantable Cardioverter Defibrillator (ICD).

Defibrillation threshold (DFT) testing during implantable cardioverter defibrillator (ICD) implantations is considered necessary for appropriate shock therapy and to measure the safety margin. However, the relationship between the DFT with modern era devices and the clinical outcome, including the total mortality is limited, which may lead to DFT testing itself being questioned. This study aimed to evaluate the relationship between the DFT and clinical outcome in ICD recipients.We enrolled 81 consecutive patients (66 males, aged 64.6 ± 13.8 years) who received an ICD implantation and underwent DFT testing. The DFT was measured with a step-by-step method in the patients upon implant. Further, we evaluated the relationship between the DFT and the clinical outcome, which included major cardiac adverse events and any cause of death.The mean DFT was 11.6 ± 9.24J in total. In 40 patients (49.4%), VF was terminated by a low output (5J), whereas 11 patients (13.6%) had a high DFT. The rates of atrial fibrillation were significantly higher in the high DFT group (63.6% versus 24.2%, P = 0.007). During the observational period (median 432 days; range from 151 days to 1146 days), the incidence of clinical events occurred in 22 patients (27.2%) in total. In a multivariate analysis, a high DFT was the only predictive factor for the incidence of the clinical outcome (OR 4.54, 95% CI 1.03-21.9, P = 0.045).

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

INTRODUCTION: Identification 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. METHODS: We 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. RESULTS: The 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. CONCLUSIONS: Planning 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.

Changes of Atrial Natriuretic Peptides after Defibrillation Threshold Testing Predicted Future Ventricular Arrhythmia Event.

BACKGROUND: We investigated the change of natriuretic peptides during defibrillation threshold (DFT) testing and its relationship with future ventricular arrhythmia (VA) events in patients implanted with an implantable cardioverter defibrillator (ICD). METHODS: Atrial natriuretic peptide (ANP), brain natriuretic peptide (BNP), and c-type natriuretic peptide (CNP) were measured in 21 patients (mean age 61 ± 13 years; 67% male) undergoing ICD implantation. Blood samples of the patients were drawn at pre-implantation, 30 minutes, 60 minutes, and 24 hours after DFT testing. The patients were followed and divided into two groups according to the occurrence of VA in 18 months. The biomarker levels and their changes were compared in patients with and without further VA. RESULTS: The pre-implantation ANP levels were higher at pre-implantation and increased significantly at 30 minutes after DFT testing (Δ30minANP) among patients with VA events. The BNP and CNP levels did not change significantly after DFT testing in both groups. The area under curve was 0.82 for the change in Δ30minANP determining further ventricular events. The optimal Δ30minANP cutoff value was 0.51 pg/ml, with sensitivity of 0.83 and specificity of 0.68. Multivariable analysis confirmed that patients with Δ30minANP more than 0.51 pg/ml have a higher risk of further ventricular events (hazard ratio 39.8, 95% confidence interval: 2.87-553.01, p = 0.006). The pre-implantation ANP level could not predict future VA events (hazard ratio 1.06, 95% CI: 1.00-1.14, p = 0.06). CONCLUSIONS: The increase of ANP concentration after DFT testing predicted future VA events after ICD implantation while the BNP and CNP levels did not predict future VA events.

Risk Factors for Inadequate Defibrillation Safety Margins Vary With the Underlying Cardiac Disease: Implications for Selective Testing Strategies.

INTRODUCTION: In view of the shift from routine toward no or selective defibrillation testing, optimization of the current risk stratification for inadequate defibrillation safety margins (DSMs) could improve individualized testing decisions. Given the pathophysiological differences in myocardial substrate between ischemic and nonischemic heart disease (IHD/non-IHD) and the accompanying differences in clinical characteristics, we studied inadequate DSMs and their predictors in relation to the underlying etiology. METHODS AND RESULTS: Cohort of routine defibrillation tests (n = 785) after first implantable cardioverter defibrillator (ICD)-implantations at the Radboud UMC (2005-2014). A defibrillation threshold >25 J was regarded as an inadequate DSM. In total, 4.3% of patients had an inadequate DSM; in IHD 2.5% versus 7.3% in non-IHD (P = 0.002). We identified a group of non-IHD patients at high risk (13-42% inadequate DSM); the remainder of the cohort (>70%) had a risk of only 2% (C-statistic entire cohort 0.74; C-statistic non-IHD 0.82). This was based upon two identified interaction terms: (1) non-IHD and age (aOR 0.94 [95% CI 0.91-0.97]); (2) non-IHD and the indexed left ventricular (LV) internal diastolic diameter (aOR 3.50 [95% CI 2.10-5.82]). CONCLUSION: The present study on risk stratification for an inadequate DSM not only confirms the importance of making a distinction between IHD and non-IHD, but also shows that risk factors in an entire cohort (LV dilatation, age) may only apply to a subgroup (non-IHD). Appreciation of this concept could favorably affect current risk stratification. If confirmed, our approach may be used to optimize individualized testing decisions in an upcoming era of non-routine testing.

Monitored Anesthesia Care for Subcutaneous Cardioverter-Defibrillator Implantation: A Single-Center Experience.

BACKGROUND: To date, general anesthesia has been suggested as the preferred approach for implantation of a subcutaneous implantable cardioverter-defibrillator (S-ICD). The purpose of this study was to assess the use of monitored anesthesia care (MAC) for S-ICD implantation. The goals were to assess adequate sedation and analgesia (efficacy endpoints) and major perioperative airway or hemodynamic compromise (safety endpoints). The authors hypothesized that MAC may provide adequate sedation and analgesia and no major perioperative airway or hemodynamic compromise during S-ICD implantation and multiple defibrillation threshold (DFT) testing. METHODS: Prospectively collected data of patients who underwent S-ICD implantation with MAC from 2015 to 2016 were analyzed retrospectively. The efficacy endpoints were the provision of an optimal depth of sedation and analgesia to facilitate S-ICD implantation without intra-procedure patient discomfort or awareness, and the absence of "severe" pain at the lead tunneling and the generator insertion sites post-procedure. The safety endpoints included: (1) periprocedural hypotension, as defined by a mean arterial pressure (MAP)<60 mmHg refractory to conventional pharmacotherapy, (2) heart rate (HR)<45 bpm requiring pharmacologic support, and (3) sedation-induced airway compromise requiring endotracheal intubation. MEASUREMENTS: MAP and HR were recorded during S-ICD implantation and DFT testing. The maximum and minimum infusion rates of propofol, supplemental sedatives, and analgesics, and doses of vasopressor and/or inotropic agents administered intra-procedurally were recorded. Post-procedure pain scores also were noted. RESULTS: Ten patients underwent S-ICD implantation with MAC (mean age, 56 years; 50% men; mean left ventricular ejection fraction was 39%). Implantation of the S-ICD system using MAC was successful in all patients without any major adverse events. The mean baseline MAP was 92.8 mmHg, and the mean end-procedure MAP was 88 mmHg (p = 0.26). When compared to baseline and end-procedure, the mean lowest intra-procedure MAP was significantly lower (67.4 mmHg; p = 0.0001). The mean baseline HR was 65.7 bpm, and the mean end-procedure HR was 70.1 bpm (p = 0.28). When compared to baseline and end-procedure, the mean lowest intra-procedure HR was significantly lower (55.8 bpm; p<0.001). MAC was not associated with airway compromise in any patient, and post-procedure pain was rated as no greater than "mild". CONCLUSIONS: Among a heterogeneous patient population undergoing S-ICD implantation and DFT testing, the use of MAC is efficacious, feasible, and safe.