Ineffective Shock Research Articles

Do Implantable Cardioverter-Defibrillators Prevent Sudden Cardiac Death in End-Stage Renal Disease Patients on Dialysis?

Chronic kidney disease patients appear to be predisposed to heart rhythm disorders, including atrial fibrillation/atrial flutter, ventricular arrhythmias, and supraventricular tachycardias, which increase the risk of sudden cardiac death. The pathophysiological factors underlying arrhythmia and sudden cardiac death in patients with end-stage renal disease are unique and include timing and frequency of dialysis and dialysate composition, vulnerable myocardium, and acute proarrhythmic factors triggering asystole. The high incidence of sudden cardiac deaths suggests that this population could benefit from implantable cardioverter-defibrillator therapy. The introduction of implantable cardioverter-defibrillators significantly decreased the rate of all-cause mortality; however, the benefits of this therapy among patients with chronic kidney disease remain controversial since the studies provide conflicting results. Electrolyte imbalances in haemodialysis patients may result in ineffective shock therapy or the appearance of non-shockable underlying arrhythmic sudden cardiac death. Moreover, the implantation of such devices is associated with a risk of infections and central venous stenosis. Therefore, in the population of patients with heart failure and severe renal impairment, periprocedural risk and life expectancy must be considered when deciding on potential device implantation. Harmonised management of rhythm disorders and renal disease can potentially minimise risks and improve patients' outcomes and prognosis.

C6 VENTRICULAR FIBRILLATION SPECTRAL AREA (AMSA) AND LOW–ENERGY SHOCK SUCCESS PREDICTION IN PATIENTS WITH OUT–OF–HOSPITAL CARDIAC ARREST

Abstract Introduction In case of cardiac arrest due to ventricular fibrillation (VF) or pulseless ventricular tachycardia (pVT), the optimal energy level for defibrillation is that which achieves defibrillation and minimize the current–induced myocardial damage. Therefore, it would be reasonable to reduce the energy level as well as the number of shocks. ECG–based VF waveform analysis features such as amplitude spectral area (AMSA) have been recently introduced as predictors of shock success but their predictivity for shock success with low energy level is not known. We aimed to assess whether AMSA of VF is able to predict the efficacy of low energy level for defibrillation in out–of–hospital cardiac arrest (OHCA) patients. Methods All the OHCAs with at least one shockable rhythm occurred from January 2015 to December 2020 in the province of Pavia, Italy, were considered. AMSA values were calculated by retrospectively analyzing the data collected by the Corpuls 3 monitors/defibrillators and by using a 2–second–pre–shock ECG interval. Results Among 4619 OHCA, AMSA values and energy for defibrillation were documented in 791 shocks, of which 45% received a shock at low energy (<= 150J) and 55% at high energy (>150J). The rate of efficacy between the two groups did not differ significantly (44% vs 38%, p=0.102), however in patients efficaciously treated with low energy, AMSA was higher compared to those efficaciously treated with high energy [13.2 mV·Hz (12.5–14.2) vs 10.8 (10.1–11.5), p<0.001]. Moreover, AMSA was found to be different even when comparing ineffective shock at low energy with effective shock at high energy [(6.6 (4.6–10) vs 10.8 (8.1–13.8), p<0.001] and similar when comparing ineffective shock at low and at high energy [6.6 (4.6–10) vs 6.3 (4.5–8.7), p=0.21]. By dividing AMSA values into three tertiles the rate of shock success at low energy was found to be different: [T1 (0.7–6.2) 4.2%; T2 (6.2–10.8) 13%; T3 (10.8–63.2) 42%, Chi squared p<0.001 and p for trend <0.001]. After correction for age, sex, amiodarone use, call to shock time, AMSA values corresponding to the third and second tertile were associated with higher probability of shock success compared with the values in the lowest tertile [T3 OR 15 (95%CI 7–30), p< 0.001; T2 OR 3 (95%CI 1–7), p= 0.002]. Conclusion Amplitude spectral area of VF is a predictor of shock success at low energy. This could be useful to optimize the choice of energy limiting the current related myocardial injury.

1105 VENTRICULAR FIBRILLATION SPECTRAL AREA (AMSA) AND LOW-ENERGY SHOCK SUCCESS PREDICTION IN PATIENTS WITH OUT-OF-HOSPITAL CARDIAC ARREST

Abstract Introduction In case of cardiac arrest due to ventricular fibrillation (VF) or pulseless ventricular tachycardia (pVT), the optimal energy level for defibrillation is that which achieves defibrillation and minimize the current-induced myocardial damage. Therefore, it would be reasonable to reduce the energy level as well as the number of shocks. ECG-based VF waveform analysis features such as amplitude spectral area (AMSA) have been recently introduced as predictors of shock success but their predictivity for shock success with low energy level is not known. We aimed to assess whether AMSA of VF is able to predict the efficacy of low energy level for defibrillation in out-of-hospital cardiac arrest (OHCA) patients. Methods All the OHCAs with at least one shockable rhythm occurred from January 2015 to December 2020 in the province of Pavia, Italy, were considered. AMSA values were calculated by retrospectively analyzing the data collected by the Corpuls 3 monitors/defibrillators and by using a 2-second-pre-shock ECG interval. Results Among 4619 OHCA, AMSA values and energy for defibrillation were documented in 791 shocks, of which 45% received a shock at low energy (<= 150J) and 55% at high energy (>150J). The rate of efficacy between the two groups did not differ significantly (44% vs 38%, p=0.102), however in patients efficaciously treated with low energy, AMSA was higher compared to those efficaciously treated with high energy [13.2 mV·Hz (12.5-14.2) vs 10.8 (10.1-11.5), p<0.001]. Moreover, AMSA was found to be different even when comparing ineffective shock at low energy with effective shock at high energy [(6.6 (4.6-10) vs 10.8 (8.1-13.8), p<0.001] and similar when comparing ineffective shock at low and at high energy [6.6 (4.6-10) vs 6.3 (4.5-8.7), p=0.21]. By dividing AMSA values into three tertiles the rate of shock success at low energy was found to be different: [T1 (0.7-6.2) 4.2%; T2 (6.2-10.8) 13%; T3 (10.8-63.2) 42%, Chi squared p<0.001 and p for trend <0.001]. After correction for age, sex, amiodarone use, call to shock time, AMSA values corresponding to the third and second tertile were associated with higher probability of shock success compared with the values in the lowest tertile [T3 OR 15 (95%CI 7-30), p< 0.001; T2 OR 3 (95%CI 1-7), p= 0.002]. Conclusion Amplitude spectral area (AMSA) of VF is a predictor of shock success at low energy. This could be useful to optimize the choice of energy limiting the current related myocardial injury.

Ventricular fibrillation amplitude spectral area as a guide to deliver the optimal energy level for defibrillation

Abstract Introduction In case of cardiac arrest due to ventricular fibrillation (VF) or pulseless ventricular tachycardia (pVT), the optimal energy should be the lowest energy effective to achieve defibrillation minimizing the current-induced myocardial damage. Therefore, it would be ideal to minimize the energy level as well as the number of shocks during resuscitation. ECG-based VF waveform analysis features such as amplitude spectral area have been recently introduced as predictors of shock success, but their predictivity for shock success with low energy level is not known. Purpose To assess whether amplitude spectral area (AMSA) of VF is able to predict the efficacy of low energy level defibrillation in out-of-hospital cardiac arrest (OHCA) patients. Methods All the OHCAs with at least one shockable rhythm that occurred from January 2015 to December 2020 were considered. AMSA values were calculated by retrospectively analyzing the data collected by the Corpuls 3 monitors/defibrillators and by using a 2-second-pre-shock ECG interval. Results Among 4619 OHCAs, resuscitation was attempted in 2982 (64%) and at least one shock was delivered in 697 (15%). AMSA values and defibrillation energy were available for 791 shocks, of which 45% received shock at low energy (>150J) and 55% at high energy (>150J). The rate of efficacy between the two groups was similar (44% vs 38%, p=0.102). However, in patients efficaciously treated with shock at low energy, AMSA was higher compared to those treated with shock at high energy [13.2 mV Hz (IQR 10.2–17) vs 10.8 mV Hz (IQR 8–13.8), p<0.001]. Moreover, AMSA values were significantly different when comparing ineffective shock at low energy with effective shock at high energy [6.6 mV Hz (IQR 4.6–10) vs 10.8 mV Hz (IQR 8.1–13.8), p<0.001] and similar when comparing ineffective shock at low and high energy [6.6 mV Hz (IQR 4.6–10) vs 6.3 mV Hz (IQR 4.5–8.7), p=0.21]. By dividing AMSA values into three tertiles, the rate of shock success at low energy was statistically different: [T1 (0.7–6.2 mV Hz) 4.2%; T2 (6.2–10.8 mV Hz) 13%; T3 (10.8–63.2 mV Hz) 42%; Chi-squared p<0.001 and p for trend <0.001]. After correction for age, sex, amiodarone use and call to shock time, AMSA values corresponding to the third and second tertile were associated with higher probability of shock success at low energy compared to the lowest tertile [T3 OR 15 (95% CI 7–30), p<0.001; T2 OR 3 (95% CI 1–7), p=0.002]. Conclusion Ventricular fibrillation amplitude spectral area is a predictor of shock success at a low energy level. This could be useful to optimize both time and dose-energy to patients, yielding the highest chance for successful defibrillation while reducing the number of futile shocks and thus limiting the total current myocardial energy as well as CPR interruptions. Funding Acknowledgement Type of funding sources: None.

Safety of omitting defibrillation efficacy testing with subcutaneous defibrillators: a propensity matched case-control study

Abstract Funding Acknowledgements Type of funding sources: None. Background Defibrillation efficacy testing (DT) is recommended at implantation of subcutaneous implantable cardioverter–defibrillators (S-ICD). However, prior works found that adherence to this recommendation is declining in clinical practice. Purpose To compare survival from all-cause death and first ineffective shock (primary endpoint) and the composite of all-cause death, ineffective shock, inappropriate shock and device-related complication (secondary endpoint) between patients who underwent DT and those with omitted DT. Methods We analyzed 1652 consecutive patients who underwent S-ICD implantation in 60 Italian centers from 2013 to 2019. Results DT was not performed in 325 (20%) patients (no-DT patients). As compared with the DT group, these patients were older (51 ± 16 vs. 48 ± 15 years; p < 0.01) and had lower ejection fraction (37 ± 16% vs. 46 ± 16%; p < 0.01). The 325 no-DT patients were propensity matched with 325 patients of the DT group. During a median follow up of 19 months, 27 (4.2%) patients died for any-cause. During follow-up, 34 (5.2%) patients received appropriate shocks to treat discrete episodes of VT/VF. The first shock was effective in 30 out of 34 patients (88%), whereas a second shock was required to terminate VT/VF in 3 patients and a third shock in the last one. The primary endpoint occurred in 31 (4.8%) patients, and the risk was not significantly increased in the no-DT cohort (HR = 1.26, 95%CI:0.62-2.55, p = 0.522). Inappropriate shocks were reported in 36 (5.5%) patients and device-related complications in 25 (3.8%) patients during follow-up. Survival from the composite secondary endpoint was comparable between groups (HR = 0.86, 95%CI:0.57-1.32, p = 0.500). Conclusions Our data confirmed that DT is frequently omitted in current clinical practice, especially in older patients with worse systolic function. A strategy that omits DT did not appear to compromise the effectiveness of the S-ICD and no additional risk seems associated with DT omission at a mid-term follow-up. These data suggest that routine DT at S-ICD implant might not be necessary. Randomized trials are needed to confirm this finding.

Analysis of Atrial Fibrillation Recidivity under Successive Attempts of Electrical Cardioversion Based on Fibrillatory Wave Amplitude and Dominant Frequency

Atrial fibrillation (AF) is the most common cardiac arrhythmia in clinical practice. One frequent and very effective alternative to revert AF back to a normal sinus rhythm (NSR) is external electrical cardioversion (ECV). However, conventional ECV protocols do not consider effects of electrical shocks on the atrial activity (AA) and its evolution during the procedure. The present study analyzes the feasibility of using the fibrillatory wave amplitude (fWA) and the dominant atrial frequency (DAF), extracted from the AA, to noninvasively detect AF recurrence under successive attempts of ECV and to predict the effectiveness of each shock in the ECV protocols. Results show that the effects of the first ineffective shock are only notably found in the fWA. The percentage of patients who needed several attempts who were correctly classified into patients who relapsed to AF, maintained NSR, and had an ineffective procedure was 64.3% for the fWA analyzed before the first shock, and increased to 89.3% for the same analysis after the first shock. Additionally, by jointly considering the patients who needed only one and several shocks, the discriminant ability increased when the values after the first ineffective attempt were used for the prediction. For the fWA, the diagnostic accuracy increased from 79.4% to 85.7%, for the DAF, from 65.1% to 71.4%, and for their combination, from 82.5% to 87.3%. The effect of the first unsuccessful shock is crucial for determining whether NSR will be restored through successive cardioversion attempts and predicting AF recurrence in patients undergoing ECV protocols. fWA and DAF can thus provide valuable information to improve the effectiveness of conventional ECV protocols, in which the effect of unsuccessful shocks is not taken into account at present.

Shock Efficacy of Subcutaneous Implantable Cardioverter-Defibrillator for Prevention of Sudden Cardiac Death

Background— Recently, subcutaneous implantable cardioverter-defibrillator (S-ICD) has become available. The aim of our study was to assess the efficacy of S-ICD in a clinical setting. Methods and Results— Between June 2010 and July 2011, 40 consecutive patients (42±15 years; body mass index, 27±6 kg/m 2 ; left ventricular ejection fraction, 47±15%; 28 men) received an S-ICD for primary (n=17) or secondary prevention (n=23 [58%]) at 3 institutions in Germany. Intraoperative defibrillation efficacy testing failed in 1 patient with severely reduced left ventricular ejection fraction; testing was effective in all other patients. All episodes stored in the S-ICD were analyzed for appropriate and inappropriate detection, as well as effective shock delivery to convert ventricular tachyarrhythmia into sinus rhythm. During a median follow-up of 229 (interquartile range, 116–305) days, 4 patients experienced 21 episodes, with correct detection of ventricular tachyarrhythmia and subsequent shock therapy. A total of 28 shocks were delivered in these 4 patients. Mixed logistic regression modeling revealed a shock efficacy of 96.4% (95% CI, 12.8%–100%). The efficacy of first shocks, however, was only 57.9% (95% CI, 35.6%–77.4%). Four episodes were incorrectly classified as ventricular tachyarrhythmia, which led to inappropriate shock delivery in 2 patients. Conclusions— Ineffective shock delivery may occur in patients with S-ICD, even after successful intraoperative testing. Multicenter trials are required with close monitoring of safety and efficacy end points to identify patients who may be at risk for shock failure.

Abstract 16979: Impact of ICD Shock Testing and Non-Testing on Arrhythmia Therapy Efficacy

Background: Defibrillation testing is often performed during implantation of implantable cardioverter defibrillators (ICD) to confirm therapy efficacy, even though there are no prospective data suggesting that outcome is improved by this procedure when modern ICDs are implanted. The aim of the study was to investigate whether shock testing during ICD implantation is feasible for predicting future effectiveness of ICD therapy. Methods: The retrospective analysis included a cohort of consecutive patients who received an ICD device with telemedicine capacity in our clinic, with each tachycardia episode monitored and evaluated online. All devices were implanted by means of standard surgical techniques, and shock testing was conducted or desisted due to the attending cardiologist's and surgeon's discretion. Results: 357 patients who received either an ICD or CRT-ICD with home monitoring capacity could be enclosed in the study. From 219 patients, in which ICD shock testing was performed during implantation, initial shock testing revealed satisfactory results in 210 cases; otherwise, additional surgical measures led to shock testing success. 138 patients were not tested. Compared to the shock testing group, implantation for primary prevention was more common in the non-testing group. In the shock testing group, 124 patients had VT/VF requiring ICD shock therapy. First shock efficacy was 99% for the first VT event in this group, with only one patient undergoing an ineffective first shock delivery. In this patient, the VT could be terminated with the second shock. However, in the long run 7 patients had at least one documented episode with an ineffective shock, despite the fact that previous shocks had been successful. In the non-testing group, 76 patients required ICD shock therapy and first shock efficacy was 100% for the first VT event in this group. Accordingly, there was no significant difference regarding first shock efficacy between patients with ICD for primary or secondary prevention. Conclusions: Shock efficacy for treatment of the first ventricular tachycardia was generally high, regardless whether shock testing was performed during implantation or not. This result challenges the current paradigm of ICD shock testing during implantation.

정상족과 편평족의 Arch Support 사용에 따른 운동역학적 분석

The purpose of this study was to the kinetic variables effects from the use of arch support inserts on low-arched people. We selected 10 people for the research and separated them into 2 groups, 5 people for the normal arched group and 5 people for the low arched group. Each group wear shoes which have a 3 step convertible arch support (level 0, level 2, level 5) and we measured their foot pressure and 3D motion analysis data. As a result, we found that the mean pressure at the heel of the low arched group was decreased when using the arch supports. The arch support induced the correct grounding area for the foot and dispersion of foot pressure. 3D motion analysis found that as the height of the arch support was increased, the movement of the Y-axis(inversion-eversion) was increased to relieve the shock to the heel. The arch support insert limited the range of motion(ROM) of the Z-axis(abduction-adduction) of the low arched person's ankle joint and prevented ankle injury caused by the excessive eversion when walking. Low arched people are seen to be easily tired due to the ineffective shock absorption of the knees and abnormal walking motion. In order to improve the problems, a 3 step convertible arch support(level 5) insert would improve the low-arched people's walking ability. In other words, the low arched people should be expected to walk as well as normal arched people when they wear shoes with the arch support insert.

Remote implantable cardioverter defibrillator monitoring in a Brugada syndrome population

The diagnosis of Brugada syndrome (BS) is typically made in a young and otherwise healthy population. In patients with a high risk of sudden cardiac death (SCD), the only currently recommended therapy is an implantable cardioverter defibrillator (ICD), but these are not without complications. We investigated whether remote ICD monitoring could simplify follow-up and detect potential complications in these patients. Thirty-five consecutive patients (26 males, 44 +/- 11 years) implanted with an ICD for BS with a remote monitoring ['Home Monitoring' (HM), Biotronik, Germany] system were prospectively enrolled in this study. They were matched for age, sex, and follow-up duration with 35 BS patients implanted with an ICD without this capability. During a mean follow-up of 33 +/- 17 months, the number of cardiology consultations was significantly lower in the HM group (3 +/- 2 vs. 7 +/- 3; P < 0.001). Inappropriate shock(s) [IS(s)] occurred in three patients (8.5%) in the HM group vs. six (17%) in the control group (P = NS). Ten patients in the HM group had a median of four alerts ('ventricular tachycardia/ventricular fibrillation detection' in all patients, 'shock' in three, 'ineffective shock' in two patients with shock on noise, 'extreme ventricular pacing impedance' in one patient due to lead failure, and 'deactivated therapy' in two patients with lead failure before replacement). In 5 of these 10 patients, prompt reprogramming of the ICD may have prevented IS(s). Remote ICD monitoring in patients with BS decreases outpatient consultations and may help prevent ISs.

Non-determinable defibrillation threshold and inefficacy of implantable cardioverter/defibrillator shocks due to defective connections of the defibrillator lead terminals in the device header port

Inefficacy of implantable cardioverter/defibrillator (ICD) shocks or inappropriate shocks in ICD patients may occur due to mechanical or technical failure of the device. In our unusual case of ICD defibrillation failure, faulty insertion and configuration of the defibrillation lead in the header port resulted in ineffective shock therapies and a non-determinable defibrillation threshold. In cases of successless defibrillations during or after ICD implantation, this problem should be considered.

Lessons From the Failure and Recall of an Implantable Cardioverter-Defibrillator

Multiple clinical trials have shown that a properly functioning implantable cardioverter-defibrillator (ICD) is capable of interrupting sudden death caused by ventricular tachyarrhythmias. Unfortunately, ICDs are complex medical devices, and they do not always perform as expected. For example, only 5% of ICD batteries last >7 years, and most dual-chamber ICD models must be replaced for battery depletion every 3 to 5 years.1 Normal battery depletion, however, is reliably predicted by routine follow-up methods before an ICD fails. In contrast, electronic malfunctions are unpredictable and may not be detected by standard follow-up techniques before an ICD is unable to deliver effective therapy. Thus, sudden cardiac arrest or death may be the first and only sign that an ICD has failed.2 Recently, we reported the death of a 21-year-old patient who received a Prizm 2 DR model 1861 ICD pulse generator (Guidant, Inc) in 2001 to prevent sudden cardiac death resulting from hypertrophic cardiomyopathy.3 In March 2005, this young man experienced a witnessed arrest and could not be resuscitated. His ICD was returned to Guidant, which found that the device had failed during the delivery of a shock. The cause of failure was massive electronic damage caused by electrical overstress that occurred when a short circuit developed between a high-voltage wire and a tube used to test the housing during manufacturing (see the Figure). At the time of our patient’s death, Guidant had knowledge of 25 similar Prizm 2 DR model 1861 failures in patients, 3 of whom had required rescue defibrillation. Indeed, Guidant had first observed this mode of failure 3 years earlier, in February 2002, when 2 returned Prizm 2 DR pulse generators exhibited the same short circuiting that caused our patient’s device to fail. Guidant was sufficiently concerned about these failures that manufacturing changes were made …

Atrial Fibrillation in Patients with a Dual Defibrillator: Characteristics of Spontaneous and Induced Episodes and Effect of Ventricular Tachyarrhythmia Induction

The pattern of FF intervals during atrial fibrillation (AF) has been analyzed in induced and spontaneous AF episodes, after the induction of ventricular fibrillation (VF) and after atrial shock, in order to suggest practical considerations for AF management in patients implanted with antitachycardia devices. In 13 patients implanted with a dual-chamber defibrillator, FF intervals were analyzed during two separate induced AF episodes, before and after VF induction over AF, as well as during spontaneous AF episodes and after unsuccessful atrial shocks. The following parameters were considered: mean atrial cycle length (CL), atrial CL stability, and standard deviation of the atrial cycle. The AF pattern had comparable characteristics considering two separate inductions of AF, as well as spontaneous AF episodes. Ventricular tachyarrhythmia induction resulted in a shortening of atrial CL (P < 0.02) and in a less organized AF pattern (P < 0.005). Changes in the FF interval after ineffective shock therapy showed a shortening of AF cycles after shocks with energies far below the defibrillation threshold. (a) The AF pattern is reproducible in separate inductions of sustained AF and in spontaneous episodes, (b) dynamic changes involving a shortening of the AF cycle and an evolution to a less homogeneous pattern occur after VF induction, revealing a complex interplay between AF and VF, and (c) FF interval analysis after ineffective shock delivery may allow the relationship between delivered shock energy and effective defibrillation energy to be estimated, thereby providing practical suggestions for step-up protocols in atrial cardioversion.