Patient, Physician, and Procedural Factors Influencing the Use of Defibrillation Testing during Initial Implantable Cardioverter Defibrillator Insertion: Findings from the NCDR®

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.

Defibrillation Safety Margin Testing in Patients With Congenital Heart Disease: Results From the NCDR

OBJECTIVES

This study analyzed the predictors of defibrillation safety margin (DSM) testing at the time of implantable cardioverter-defibrillator (ICD) insertion and factors associated with inadequate DSM in patients with congenital heart disease (CHD).

BACKGROUND

There are few data about the prevalence and safety of DSM testing in those with CHD.

METHODS

A retrospective analysis was performed of all patients with atrial or ventricular septal defect, tetralogy of Fallot, transposition of the great vessels, Ebstein anomaly, or common ventricle undergoing a transvenous ICD procedure in the National Cardiovascular Data Registry (NCDR) ICD Registry from April 2010 to March 2016, and DSM testing was assessed. Inadequate DSM was defined as a lowest successful energy tested <10 J than the maximum output of the ICD generator.

RESULTS

Of all ICD recipients (N = 7,024), DSM testing was performed in 52.0% (n = 3,654). The mean lowest successful energy tested was 20.7 ± 7.3 J. Of those with DSM adequacy data available (n = 3,623), an inadequate DSM occurred in 13.8% (n = 501). After multivariable adjustment, DSM testing was not associated with in-hospital complications or death (odds ratio [OR]: 1.00; 95% confidence interval [CI]: 0.79 to 1.28) but was associated with lower odds of prolonged hospital stay (>3 days) (OR: 0.71; 95% CI: 0.60 to 0.84; p < 0.0001). An inadequate DSM was not associated with in-hospital death or complications (OR: 1.27; 95% CI: 0.79 to 2.04) or prolonged hospital stay (OR: 1.34; 95% CI: 0.995 to 1.81).

CONCLUSIONS

DSM testing is being performed less frequently over time and seems safe in those with CHD. An inadequate DSM was not associated with worse in-hospital outcomes.

Analysis of Temporal Trends and Variation in the Use of Defibrillation Testing in Contemporary Practice

IMPORTANCE

Defibrillation testing (DFT) is performed during implantable cardioverter-defibrillator (ICD) implantation to assess the capacity of the device to detect and terminate ventricular arrhythmias. However, DFT can result in complications and omission of its use has been shown to be safe.

OBJECTIVE

To describe temporal trends and variation in the use of DFT in contemporary practice in the United States.

DESIGN, SETTING, AND PARTICIPANTS

This multicenter cross-sectional study used data from the National Cardiovascular Data Registry ICD Registry. A total of 499 211 patients from 1794 different facilities undergoing first-time ICD implantation from April 2010 to December 2015 were included. Data analysis was performed from May 20, 2015, to August 15, 2019.

EXPOSURE

Defibrillation testing was assessed using the National Cardiovascular Data Registry ICD Registry.

MAIN OUTCOMES AND MEASURES

Defibrillation testing rates and median odds ratios (MORs) were assessed over time. The MOR represents the odds that a randomly selected patient receiving testing at a hospital with high testing rates would be tested compared with if he or she had received care at a hospital with low testing rates.

RESULTS

Of the 499 211 patients from 1794 different facilities included in this analysis, the mean (SD) age of the population was 65.5 (13.4) years and 356 681 patients (71.4%) were men. The use of DFT declined from 71.6% in the first calendar quarter of 2010 to 36.4% in the fourth quarter of 2015 (P < .001). Patients undergoing DFT were more likely than those without testing to have ischemic heart disease (170 569 [58.1%] vs 116 295 [56.6%]), ventricular tachycardia (91 500 [31.2%] vs 58 949 [28.7%]), and less advanced heart failure (New York Heart Association class I and II, 153 188 [52.2%] vs 91 215 [44.4%]) (P < .001 for all). The MOR for the use of defibrillation testing was 3.78 (95% CI, 3.54-4.03) in 2010, increasing to 6.05 (95% CI, 5.61-6.52) in 2015, indicating that by 2015 a randomly selected patient receiving testing at a hospital with high testing rates would have a 6-fold higher odds of being tested than if they had received care at a hospital with low testing rates.

CONCLUSIONS AND RELEVANCE

Defibrillation testing at the time of ICD placement in the United States may have declined over time; however, institutional variation in its use appears to be marked and increased. This variability in the reduced use of defibrillation testing could reflect differences in individual or institutional cultures of practice.

Sedation strategies for defibrillation threshold testing: safety outcomes with anaesthesiologist compared to proceduralist-directed sedation: an analysis from the SIMPLE study

Aims

No standard practice exists with respect to anaesthesiologist-directed sedation (ADS) vs. sedation by proceduralist (PDS) for defibrillation threshold (DT) testing. We aimed to evaluate adverse events and safety outcomes with ADS vs. PDS for DT testing.

Methods and results

A post hoc analysis of the Shockless Implant Evaluation (SIMPLE) study was performed among the 1242 patients who had DT testing (624 ADS and 618 PDS). We evaluated both intraoperative and in-hospital adverse composite events and two safety composite outcomes at 30-days of the main trial. Propensity score adjusted models were used to compute odds ratio (OR) and 95% confidence interval (CI) to evaluate the association between adverse and safety outcomes with method of sedation and independent predictors for use of ADS. Compared to PDS, patients who received ADS were younger (62 ± 12 years vs. 64 ± 12 years, P = 0.01), had lower ejection fraction (left ventricular ejection fraction 0.31 ± 13 vs. 0.33 ± 13, P = 0.03), were more likely to receive inhalational anaesthesia, propofol, or narcotics (P < 0.001, respectively) and receive an arterial line (43% vs. 8%, P = <0.0001). Independent predictors for ADS sedation were presence of coronary artery disease (OR 1.69, 95% CI 1.0-2.72; P = 0.03) and hypertrophic cardiomyopathy (OR 2.64, 95% CI 1.19-5.85; P = 0.02). Anaesthesiologist directed sedation had higher intraoperative adverse events (2.2% vs. 0.5%; OR 4.47, 95% CI 1.25-16.0; P = 0.02) and higher primary safety outcomes at 30 days (8.2% vs. 4.9%; OR 1.72 95% CI 1.06-2.80; P = 0.03) and no difference in other outcomes compared to PDS.

Conclusion

Proceduralist-directed sedation is safe, however, this could be result of selection bias. Further research is needed.

Defibrillation testing and clinical outcomes after implantable cardioverter-defibrillator implantation in patients in atrial fibrillation at the time of implant: An analysis from the SIMPLE trial

BACKGROUND

The Shockless IMPLant Evaluation (SIMPLE) trial showed that defibrillation testing (DT) at the time of implantable cardioverter-defibrillator (ICD) implant did not improve shock efficacy or reduce mortality. There are no data regarding the risk of complications, including stroke, among patients with atrial fibrillation (AF) who undergo DT.

OBJECTIVE

The purpose of this prospectively planned substudy of SIMPLE was to evaluate the effect of DT vs no DT on clinical outcomes among patients with AF.

METHODS

We compared efficacy (failed appropriate shock/arrhythmic death) and safety between patients who had AF on their immediate preprocedural ECG to the rest of the study patients. Then among patients with AF we compared these outcomes between patients randomized to DT vs no DT.

RESULTS

Of the 2500 patients enrolled in SIMPLE, 251 (10%) were in AF immediately before ICD implant. AF patients had an increased risk of failed appropriate shock/arrhythmic death (adjusted hazard ratio [HR] 1.64; 95% confidence interval [CI] 1.13-2.39; P = .009) and higher all-cause mortality (adjusted HR 1.58; 95% CI 1.2-2.08; P = .001). Among AF patients, perioperative complications and stroke did not significantly differ between DT vs no-DT groups (9.2% vs 5.4%; P = .2; and 1.7% vs 1.5%; P >.999, respectively). Failed appropriate shock or arrhythmic death occurred in 35 of 251 AF patients (14%), and the no-DT group proved not inferior to the DT group (HR 0.58; 95% CI 0.30-1.15; P_{noninferiority} = .006).

CONCLUSION

ICD recipients with AF are at increased risk for adverse outcomes; however, DT does not improve arrhythmic survival or shock efficacy. There is no evidence that DT increased the occurrence of perioperative stroke.

Effect of defibrillation threshold testing on effectiveness of the subcutaneous implantable cardioverter defibrillator

BACKGROUND

Defibrillation threshold (DFT) testing is recommended with the subcutaneous implantable cardioverter defibrillator (SICD).

OBJECTIVE

To describe first shock efficacy for appropriate SICD therapies stratified by the presence of implant DFT testing.

METHODS

We reviewed all patients receiving SICDs at our institution and stratified them based on whether implant DFT testing was performed. Appropriate shocks were reviewed to see if ventricular tachycardia/ventricular fibrillation (VT/VF) terminated with a single shock. First shock efficacy was stratified by implant DFT status.

RESULTS

178 patients implanted with SICDs and followed in our center were included in this study. Of these, 135 (76%) underwent DFT testing (DFT (+) group). In the DFT (+), 80 appropriate shocks were needed to treat 69 episodes of VT/VF. The first shock was effective in 61 out of 69 episodes (88.4%), whereas multiple shocks were required to terminate VT/VF in the remaining eight episodes. Among 43 patients without implant DFT testing (DFT (-) group), 20 appropriate shocks to treat 17 episodes of VT/VF occurred in seven patients. VT/VF was successfully terminated with the first shock in 16 out of 17 episodes (first shock efficacy 94.1 %). There was no significant difference in first shock effectiveness between those with and without implant DFT testing (P  =  0.97).

CONCLUSION

A strategy that omits DFT testing at implant did not appear to compromise the effectiveness of the SICD. These data suggest that routine DFT testing at SICD implant might not be necessary. Randomized trials are needed to confirm this finding.

Ventricular Fibrillation Conversion Testing After Implantation of a Subcutaneous Implantable Cardioverter Defibrillator: Report From the National Cardiovascular Data Registry

BACKGROUND

Compared with transvenous implantable cardioverter defibrillators (ICDs), subcutaneous (S)-ICDs require a higher energy for effective defibrillation. Although ventricular fibrillation conversion testing (CT) is recommended after S-ICD implantation to ensure an adequate margin between the defibrillation threshold and maximum device output (80J), prior work found that adherence to this recommendation is declining.

METHODS

We studied first-time recipients of S-ICDs (between September 28, 2012, and April 1, 2016) in the National Cardiovascular Database Registry ICD Registry to determine predictors of use of CT, predictors of an insufficient safety margin (ISM, defined as ventricular fibrillation conversion energy >65J) during testing, and inhospital outcomes associated with use of CT. Multivariable logistic regression analysis was used to predict use of CT and ISM. Inverse probability weighted logistic regression analysis was used to examine the association between use of CT and inhospital adverse events including death.

RESULTS

CT testing was performed in 70.7% (n=5624) of 7960 patients with S-ICDs. Although deferral of CT was associated with several patient characteristics (including increased body mass index, increased body surface area, severely reduced ejection fraction, dialysis dependence, warfarin use, anemia, and hypertrophic cardiomyopathy), the facility effect was comparatively more important (area under the curve for patient level versus generalized linear mixed model: 0.619 versus 0.877). An ISM occurred in 6.9% (n=336) of 4864 patients without a prior ICD and was more common among white patients and those with ventricular pacing on the preimplant ECG, higher preimplant blood pressure, larger body surface area, higher body mass index, and lower ejection fraction. A risk score was able to identify patients at low (<5%), medium (5% to 10%), and high risk (>10%) for ISM. CT testing was not associated with a composite of inhospital complications including death.

CONCLUSIONS

Use of CT testing after S-ICD implantation was driven by facility preference to a greater extent than patient factors and was not associated with a composite of inhospital complications or death. ISM was relatively uncommon and is associated with several widely available patient characteristics. These data may inform ICD system selection and a targeted approach to CT.

Implantable Cardioverter Defibrillator Implantation with or Without Defibrillation Testing

Defibrillation testing (DFT) during implantable cardioverter-defibrillator (ICD) implantation is still considered standard of care in some, but in increasingly fewer centers. The goal is to ensure that the device system functions as intended by testing in the controlled laboratory setting. Although safe, complications can occur and DFT is associated with an increased procedural time and cost. DFT is useful in assessing device function when programming changes or patient characteristics raise concerns regarding ICD efficacy. DFT remains standard of practice following implantation of subcutaneous ICDs and other specific circumstances. Implanting physicians should remain familiar with the process of DFT and situations where it is useful for individual patients.

Cardioverter defibrillator implantation without induction of ventricular fibrillation: a single-blind, non-inferiority, randomised controlled trial (SIMPLE)

BACKGROUND

Defibrillation testing by induction and termination of ventricular fibrillation is widely done at the time of implantation of implantable cardioverter defibrillators (ICDs). We aimed to compare the efficacy and safety of ICD implantation without defibrillation testing versus the standard of ICD implantation with defibrillation testing.

METHODS

In this single-blind, randomised, multicentre, non-inferiority trial (Shockless IMPLant Evaluation [SIMPLE]), we recruited patients aged older than 18 years receiving their first ICD for standard indications at 85 hospitals in 18 countries worldwide. Exclusion criteria included pregnancy, awaiting transplantation, particpation in another randomised trial, unavailability for follow-up, or if it was expected that the ICD would have to be implanted on the right-hand side of the chest. Patients undergoing initial implantation of a Boston Scientific ICD were randomly assigned (1:1) using a computer-generated sequence to have either defibrillation testing (testing group) or not (no-testing group). We used random block sizes to conceal treatment allocation from the patients, and randomisation was stratified by clinical centre. Our primary efficacy analysis tested the intention-to-treat population for non-inferiority of no-testing versus testing by use of a composite outcome of arrhythmic death or failed appropriate shock (ie, a shock that did not terminate a spontaneous episode of ventricular tachycardia or fibrillation). The non-inferiority margin was a hazard ratio (HR) of 1·5 calculated from a proportional hazards model with no-testing versus testing as the only covariate; if the upper bound of the 95% CI was less than 1·5, we concluded that ICD insertion without testing was non-inferior to ICD with testing. We examined safety with two, 30 day, adverse event outcome clusters. The trial is registered with ClinicalTrials.gov, number NCT00800384.

FINDINGS

Between Jan 13, 2009, and April 4, 2011, of 2500 eligible patients, 1253 were randomly assigned to defibrillation testing and 1247 to no-testing, and followed up for a mean of 3·1 years (SD 1·0). The primary outcome of arrhythmic death or failed appropriate shock occurred in fewer patients (90 [7% per year]) in the no-testing group than patients who did receive it (104 [8% per year]; HR 0·86, 95% CI 0·65-1·14; pnon-inferiority <0·0001). The first safety composite outcome occurred in 69 (5·6%) of 1236 patients with no-testing and in 81 (6·5%) of 1242 patients with defibrillation testing, p=0·33. The second, pre-specified safety composite outcome, which included only events most likely to be directly caused by testing, occurred in 3·2% of patients with no-testing and in 4·5% with defibrillation testing, p=0·08. Heart failure needing intravenous treatment with inotropes or diuretics was the most common adverse event (in 20 [2%] of 1236 patients in the no-testing group vs 28 [2%] of 1242 patients in the testing group, p=0·25).

INTERPRETATION

Routine defibrillation testing at the time of ICD implantation is generally well tolerated, but does not improve shock efficacy or reduce arrhythmic death.

FUNDING

Boston Scientific and the Heart and Stroke Foundation (Ontario Provincial office).

Incidence of defibrillator shocks after elective generator exchange following uneventful first battery life

Background

A significant number of implantable cardioverter‐defibrillator (ICD) patients do not experience shocks after ICD implant. Elective generator exchange (GE) has been associated with increased risk of infection and ICD lead failure. There is a paucity of contemporary data reporting on shock incidence with replacement devices.

Methods and Results

Patients undergoing elective GE (n=24 203) who transmit data remotely via a remote monitoring system were analyzed to determine the incidence of ICD shocks after GE. A total of 16 230 patients (67%) did not experience a shock with the first ICD (group A), and 7973 (33%) received at least 1 shock (group B). Patients in group A were older (71.3 versus 68.8 years, P<0.001) and more often female (71% versus 77% male, P<0.001). Over an average follow‐up of 1.9±1.2 years after GE, the proportion of patients with shocks and risk of ICD shocks was lower for those who did not receive a shock during the first battery life (group A: 9.9% versus 27.7%, hazard ratio 0.36, 95% CI 0.34 to 0.38, P<0.001). The cumulative rate of ICD shocks at 5 years after GE was 25.7% in group A and 51.1% in group B.

Conclusions

In this large cohort of ICD patients implanted across the United States, two thirds did not receive ICD shock therapy prior to GE. The occurrence of ICD shocks prior to GE is an important predictor of shocks after GE; however, even among those without shocks during first battery life, the incidence of shocks at 5 years following GE is >25%. These data should support informed decision making for patients and physicians at the time of ICD generator end of service.