Unnecessary Implantable Cardioverter-defibrillator Research Articles

Are We Implanting Too Many Primary-Prevention Implantable Cardioverter-Defibrillators?

Canadian Cardiovascular Society/Canadian Heart Failure Society guidelines recommend optimizing patients with heart failure with reduced ejection fraction (HFrEF) on guideline directed medical therapy (GDMT) prior to implanting primary prevention implantable cardioverter defibrillators (ICDs). However, often GDMT is suboptimal at the time of ICD implantation, and is associated with reduced survival. Furthermore, with evidence for declining sudden cardiac death (SCD) rates in patients with cardiomyopathy, there is a need for better risk stratification to determine the indication for ICD.1 This raises concern for potentially unnecessary ICD implantation in this population, and efforts are needed to address this issue in clinical practice.

Reducing inappropriate and unnecessary implantable cardioverter-defibrillator therapy: Is patient confirmation via a mobile application the solution?

Reducing inappropriate and unnecessary implantable cardioverter-defibrillator therapy: Is patient confirmation via a mobile application the solution?

Machine learning-derived cycle length variability metrics predict spontaneously terminating ventricular tachycardia in implantable cardioverter defibrillator recipients.

Implantable cardioverter defibrillator (ICD) therapies have been associated with increased mortality and should be minimized when safe to do so. We hypothesized that machine learning-derived ventricular tachycardia (VT) cycle length (CL) variability metrics could be used to discriminate between sustained and spontaneously terminating VT. In this single-centre retrospective study, we analysed data from 69 VT episodes stored on ICDs from 27 patients (36 spontaneously terminating VT, 33 sustained VT). Several VT CL parameters including heart rate variability metrics were calculated. Additionally, a first order auto-regression model was fitted using the first 10 CLs. Using features derived from the first 10 CLs, a random forest classifier was used to predict VT termination. Sustained VT episodes had more stable CLs. Using data from the first 10 CLs only, there was greater CL variability in the spontaneously terminating episodes (mean of standard deviation of first 10 CLs: 20.1 ± 8.9 vs. 11.5 ± 7.8 ms, P < 0.0001). The auto-regression coefficient was significantly greater in spontaneously terminating episodes (mean auto-regression coefficient 0.39 ± 0.32 vs. 0.14 ± 0.39, P < 0.005). A random forest classifier with six features yielded an accuracy of 0.77 (95% confidence interval 0.67 to 0.87) for prediction of VT termination. Ventricular tachycardia CL variability and instability are associated with spontaneously terminating VT and can be used to predict spontaneous VT termination. Given the harmful effects of unnecessary ICD shocks, this machine learning model could be incorporated into ICD algorithms to defer therapies for episodes of VT that are likely to self-terminate.

Implantable Devices in Genetic Heart Disease: Disease-Specific Device Selection and Programming.

Diagnosis and risk stratification of rare genetic heart diseases remains clinically challenging. In many cases, there are few data and insufficient numbers to support randomized controlled trials. While implantable cardioverter defibrillator (ICD) use is vital to protect higher-risk individuals from life-threatening ventricular arrhythmias, low-risk individuals also require protection from unnecessary ICDs and their associated complications. Once an ICD has been implanted, appropriate device programming is essential to ensure maximal protection while balancing the risks of inappropriate therapy.

Potential for delayed improvement of left ventricular ejection fraction in newly diagnosed heart failure under optimized therapy depends on etiology - data from the PROLONG-II study

Abstract Funding Acknowledgements Type of funding sources: None. Introduction Patients with a first diagnosis of heart failure with reduced ejection (HFrEF) have potential for improvement under appropriate therapy. We and others have previously suggested to extend the time of therapy optimization beyond 3 months before considering implantation of a primary preventive implantable cardioverter-defibrillator (ICD), in order to avoid unnecessary ICD implantations. This sub-analysis of the PROLONG-II study sought to investigate which patients show recovery of left ventricular ejection fraction (LVEF) beyond 3 months under optimized therapy. Methods Patients with newly diagnosed HFrEF with either ischemic cardiomyopathy (ICM), dilated cardiomyopathy (DCM), peripartum cardiomyopathy (PPCM) or myocarditis at our center between 2012 and 2017 were included. All patients received a wearable cardioverter defibrillator (WCD) for temporary protection from sudden cardiac death. Follow-up (FU) data were analyzed after 3 months and at last available FU, and included WCD data, clinical status, medication, echocardiography and ECG. Results 353 patients (69% male) with newly diagnosed HFrEF (LVEF 25±8%) were followed for 2.8±1.5 years: 126 patients with ICM (35%), 169 patients with DCM (48%), 27 patients with PPCM (7%), 24 patients with myocarditis (7%) and 7 patients with other diagnoses (2%). LVEF improvement within the first 3 months was observed in all subgroups but was more pronounced in patients with DCM (9±9%) compared to ICM (5±8%) and in PPCM (20±10%) and myocarditis (15±9%) compared to both DCM and ICM. In patients with DCM and PPCM, LVEF continued to improve significantly beyond 3 months (another 10% each). Conclusion Potential for delayed LVEF improvement in newly diagnosed HFrEF under optimized therapy depends on etiology. Patients with PPCM and DCM seem to be particularly eligible for an extended period of therapy optimization and risk stratification before considering an ICD.

Delayed Improvement of Left Ventricular Function in Newly Diagnosed Heart Failure Depends on Etiology-A PROLONG-II Substudy.

In patients with newly diagnosed heart failure with reduced ejection fraction (HFrEF), three months of optimal therapy are recommended before considering a primary preventive implantable cardioverter-defibrillator (ICD). It is unclear which patients benefit from a prolonged waiting period under protection of the wearable cardioverter-defibrillator (WCD) to avoid unnecessary ICD implantations. This study included all patients receiving a WCD for newly diagnosed HFrEF (n = 353) at our center between 2012 and 2017. Median follow-up was 2.7 years. From baseline until three months, LVEF improved in patients with all peripartum cardiomyopathy (PPCM), myocarditis, dilated cardiomyopathy (DCM), or ischemic cardiomyopathy (ICM). Beyond this time, LVEF improved in PPCM and DCM only (10 ± 8% and 10 ± 12%, respectively), whereas patients with ICM showed no further improvement. The patients with newly diagnosed HFrEF were compared to 29 patients with a distinct WCD indication, which is an explantation of an infected ICD. This latter group had a higher incidence of WCD shocks and poorer overall survival. All-cause mortality should be considered when deciding on WCD prescription. In patients with newly diagnosed HFrEF, the potential for delayed LVEF recovery should be considered when timing ICD implantation, especially in patients with PPCM and DCM.

Comparing clinical performance of current implantable cardioverter-defibrillator implantation recommendations in arrhythmogenic right ventricular cardiomyopathy.

AimsArrhythmogenic right ventricular cardiomyopathy (ARVC) patients have an increased risk of ventricular arrhythmias (VA). Four implantable cardioverter-defibrillator (ICD) recommendation algorithms are available The International Task Force Consensus (‘ITFC’), an ITFC modification by Orgeron et al. (‘mITFC’), the AHA/HRS/ACC guideline for VA management (‘AHA’), and the HRS expert consensus statement (‘HRS’). This study aims to validate and compare the performance of these algorithms in ARVC.Methods and resultsWe classified 617 definite ARVC patients (38.5 ± 15.1 years, 52.4% male, 39.2% prior sustained VA) according to four algorithms. Clinical performance was evaluated by sensitivity, specificity, ROC-analysis, and decision curve analysis for any sustained VA and for fast VA (>250 b.p.m.). During 6.4 [2.8–11.5] years follow-up, 282 (45.7%) patients experienced any sustained VA, and 63 (10.2%) fast VA. For any sustained VA, ITFC and mITFC provide higher sensitivity than AHA and HRS (94.0–97.8% vs. 76.7–83.5%), but lower specificity (15.9–32.0% vs. 42.7%-60.1%). Similarly, for fast VA, ITFC and mITFC provide higher sensitivity than AHA and HRS (95.2–97.1% vs. 76.7–78.4%) but lower specificity (42.7–43.1 vs. 76.7–78.4%). Decision curve analysis showed ITFC and mITFC to be superior for a 5-year sustained VA risk ICD indication threshold between 5–25% or 2–9% for fast VA.ConclusionThe ITFC and mITFC provide the highest protection rates, whereas AHA and HRS decrease unnecessary ICD placements. ITFC or mITFC should be used if we consider the 5-year threshold for ICD indication to lie within 5–25% for sustained VA or 2–9% for fast VA. These data will inform decision-making for ICD placement in ARVC.

B-PO02-057 DEVICE NURSE-LED INTERVENTION TO INCREASE GUIDELINE-CONCORDANT PRIMARY PREVENTION IMPLANTABLE CARDIOVERTER-DEFIBRILLATOR PROGRAMMING

Implantable cardioverter-defibrillators (ICDs) are highly effective in reducing mortality in patients at risk for life-threatening arrhythmias. However, studies have shown that delivery of unnecessary or inappropriate ICD therapies for non-sustained ventricular tachycardia and supraventricular tachycardia (SVT) is associated with increased morbidity and mortality. Thus, professional societies have issued guidelines on appropriate ICD programming for primary prevention of sudden cardiac death. We previously demonstrated that patients with primary prevention ICDs with guideline-concordant (GC) ICD programming had significantly lower ICD therapy rates compared to patients with guideline-discordant (GD) ICD programming. However, the rate of GC programming was very low. This study aims to assess the effect of a device nursing-led intervention on the rate of GC versus GD primary prevention ICD programming at one large academic center. A device nurse-led intervention was deployed in the cardiac device clinic at a large tertiary care center in January 2018. This intervention involved device nurse review of patients’ ICD programming at each clinic visit with alert of the covering electrophysiology provider if programming was GD. Consecutive patients undergoing primary prevention ICD implantation between 2018-2020 were assessed for rates of GC and NGC ICD programming. Kaplan-Meier analysis and Cox proportional hazard models were used to estimate freedom from first ICD therapy and shock. Comparisons were made to a control period before implementation of the intervention (consecutive patients with primary prevention ICD implantation between 2014-2016). A total of 241 patients underwent primary prevention ICD implementation during the study period. Of these, 215 (89.2%) had GC programming. Compared to the control period, rates of GC ICD programming significantly increased (31% of 310 patients versus 89.2% of 241 patients, respectively; p <0.01). A device nursing-led intervention successfully increased the rates of guideline-concordant primary prevention ICD programming at a large tertiary care center.

Primary hyperparathyroidism associated with acquired long QT interval and ventricular tachycardia.

SummaryWe present a 54-year-old patient admitted to the emergency department due to loss of consciousness. The initial ECG registered monomorphic ventricular extrasystoles and prolonged QT interval (QT corrected (QTc) >500 ms). Sustained ventricular tachycardia (VT) was registered on 24-h Holter ECG monitoring, which clinically was presented as a crisis of consciousness. Coronary angiography and other visualization methods were normal. Implantable cardioverter-defibrillator (ICD) implantation was planned for the purpose of secondary prevention of sudden cardiac death (SCD). Laboratory and hormonal analyzes revealed primary hyperparathyroidism (PHPT), chronic kidney disease, and hypokalemia. Neck ultrasound showed a 25 mm, sharply outlined homogenous tumor mass which was separated from thyroid gland (TG) and exerted a mild impression on lower parts of the left lobe. Dual wash technetium-99m sestamibi parathyroid scintigraphy with single-photon emission CT (SPECT)/CT also showed the uptake of tracer behind the lower half of the left lobe of the TG. Surgical treatment, lower left parathyroidectomy, was performed, and pathohistological analysis verified parathyroid adenoma. The patient was rhythmically and hemodynamically stable for 7 days after surgery, without additional complaints, and was discharged from the hospital. Timely diagnosis of PHPT, correct assessment and surgical treatment, did not lead our patient to unnecessary ICD implantation. Our case suggests an additional intertwining of electrolyte disorders and ventricular arrhythmias in PHPT and more importantly emphasizes the need for caution when indicating ICD, even in patients with the most serious life-threatening arrhythmias.Learning pointsElectrolyte abnormalities in PHPT can have highly malignant consequences, and the occurrence of hypokalemia in the presence of hypercalcemia is underestimated in PHPT, and the consequences can be life-threatening.Although hypercalcemia causes shortened QT interval, concomitant severe hypokalemia may overcome hypercalcemia and prolong QT interval, even in the absence of structural heart disease or LQTS.Timely diagnosis of PHPT, correct assessment and surgical treatment, do not lead to unnecessary ICD implantation.

High mean entropy calculated from cardiac MRI texture analysis is associated with antitachycardia pacing failure.

Antitachycardia pacing (ATP), which may avoid unnecessary implantable cardioverter-defibrillator (ICD) shocks, does not always terminate ventricular arrhythmias (VAs). Mean entropy calculated using cardiac magnetic resonance texture analysis (CMR-TA) has been shown to predict appropriate ICD therapy. We examined whether scar heterogeneity, quantified by mean entropy, is associated with ATP failure and explore potential mechanisms using computer modeling. A subanalysis of 114 patients undergoing CMR-TA where the primary endpoint was delivery of appropriate ICD therapy (ATP or shock therapy) was performed. Patients receiving appropriate ICD therapy (n=33) were dichotomized into "successful ATP" versus "shock therapy" groups. In silico computer modeling was used to explore underlying mechanisms. A total of 16 of 33 (48.5%) patients had successful ATP to terminate VA, and 17 of 33 (51.5%) patients required shock therapy. Mean entropy was significantly higher in the shock versus successful ATP group (6.1 ± 0.5vs 5.5 ± 0.7, P=.037). Analysis of patients receiving ATP (n=22) showed significantly higher mean entropy in the six of 22 patients that failed ATP (followed by rescue ICD shock) compared to 16 of 22 that had successful ATP (6.3 ± 0.7vs 5.5 ± 0.7, P=.048). Computer modeling suggested inability of the paced wavefront in ATP to successfully propagate from the electrode site through patchy fibrosis as a possible mechanism of failed ATP. Our findings suggest lower scar heterogeneity (mean entropy) is associated with successful ATP, whereas higher scar heterogeneity is associated with more aggressive VAs unresponsive to ATP requiring shock therapy that may be due to inability of the paced wavefront to propagate through scar and terminate the VA circuit.

Diagnosing arrhythmogenic right ventricular cardiomyopathy by 2010 Task Force Criteria: clinical performance and simplified practical implementation.

AimsArrhythmogenic right ventricular cardiomyopathy (ARVC) is diagnosed by a complex set of clinical tests as per 2010 Task Force Criteria (TFC). Avoiding misdiagnosis is crucial to prevent sudden cardiac death as well as unnecessary implantable cardioverter-defibrillator implantations. This study aims to validate the overall performance of the TFC in a real-world cohort of patients referred for ARVC evaluation.Methods and resultsWe included patients consecutively referred to our centres for ARVC evaluation. Patients were diagnosed by consensus of three independent clinical experts. Using this as a reference standard, diagnostic performance was measured for each individual criterion as well as the overall TFC classification. Of 407 evaluated patients (age 38 ± 17 years, 51% male), the expert panel diagnosed 66 (16%) with ARVC. The clinically observed TFC was false negative in 7/66 (11%) patients and false positive in 10/69 (14%) patients. Idiopathic outflow tract ventricular tachycardia was the most common alternative diagnosis. While the TFC performed well overall (sensitivity and specificity 92%), signal-averaged electrocardiogram (SAECG, P = 0.43), and several family history criteria (P ≥ 0.17) failed to discriminate. Eliminating these criteria reduced false positives without increasing false negatives (net reclassification improvement 4.3%, P = 0.019). Furthermore, all ARVC patients met at least one electrocardiogram (ECG) or arrhythmia criterion (sensitivity 100%).ConclusionThe TFC perform well but are complex and can lead to misdiagnosis. Simplification by eliminating SAECG and several family history criteria improves diagnostic accuracy. Arrhythmogenic right ventricular cardiomyopathy can be ruled out using ECG and arrhythmia criteria alone, hence these tests may serve as a first-line screening strategy among at-risk individuals.

Outcomes in Brugada Syndrome Patients With Implantable Cardioverter-Defibrillators: Insights From the SGLT2 Registry.

Background and ObjectivesBrugada syndrome (BrS) is a cardiac ion channelopathy with characteristic electrocardiographic patterns, predisposing affected individuals to sudden cardiac death (SCD). Implantable cardioverter-defibrillator (ICD) is used for primary or secondary prevention in BrS, but its use remains controversial amongst low-risk asymptomatic patients. The present study aims to examine indicators for ICD implantation amongst BrS patients with different disease manifestations.MethodsThis study included BrS patients who received ICDs between 1997 and 2018. The cohort was divided into three categories based on presentations before ICD implantation: asymptomatic, syncope, ventricular tachycardia/ventricular fibrillation (VT/VF). Univariate and multivariate Cox-regression analysis were performed to identify independent predictors of appropriate and inappropriate shock delivery.ResultsA total of 136 consecutive patients were included with a median follow-up of 95 (IQR: 80) months. Appropriate shocks were delivered in 34 patients (25.0%) whereas inappropriate shocks were delivered in 24 patients (17.6%). Complications occurred in 30 patients (22.1%). Type 1 Brugada pattern were found to be an independent predictor of appropriate shock delivery, whilst the presence of other arrhythmia was predictive for both appropriate and inappropriate ICD shock delivery under multivariate Cox regression analysis.ConclusionICD therapy is effective for primary and secondary prevention of SCD in BrS. Whilst appropriate shocks occur more frequently in BrS patients presenting with VT/VF, they also occur in asymptomatic patients. Further research in risk stratification can improve patient prognosis while avoid unnecessary ICD implantation.

2019 HRS/EHRA/APHRS/LAHRS focused update to 2015 expert consensus statement on optimal implantable cardioverter-defibrillator programming and testing

The 2015 HRS/EHRA/APHRS/SOLAECE Expert Consensus Statement on Optimal Implantable Cardioverter-Defibrillator Programming and Testing provided guidance on bradycardia programming, tachycardia detection, tachycardia therapy, and defibrillation testing for implantable cardioverter-defibrillator (ICD) patient treatment. The 32 recommendations represented the consensus opinion of the writing group, graded by Class of Recommendation and Level of Evidence. In addition, Appendix B provided manufacturer-specific translations of these recommendations into clinical practice consistent with the recommendations within the parent document. In some instances, programming guided by quality evidence gained from studies performed in devices from some manufacturers was translated such that this programming was approximated in another manufacturer’s ICD programming settings. The authors found that the data, although not formally tested, were strong, consistent, and generalizable beyond the specific manufacturer and model of ICD. As expected, because these recommendations represented strategic choices to balance risks, there have been reports in which adverse outcomes were documented with ICDs programmed to Appendix B recommendations. The recommendations have been reviewed and updated to minimize such adverse events. Notably, patients who do not receive unnecessary ICD therapy are not aware of being spared potential harm, whereas patients in whom their ICD failed to treat life-threatening arrhythmias have their event recorded in detail. The revised recommendations employ the principle that the randomized trials and large registry data should guide programming more than anecdotal evidence. These recommendations should not replace the opinion of the treating physician who has considered the patient’s clinical status and desired outcome via a shared clinical decision-making process.

2019 HRS/EHRA/APHRS/LAHRS focused update to 2015 expert consensus statement on optimal implantable cardioverter-defibrillator programming and testing.

The 2015 HRS/EHRA/APHRS/SOLAECE Expert Consensus Statement on Optimal Implantable Cardioverter-Defibrillator Programming and Testing provided guidance on bradycardia programming, tachycardia detection, tachycardia therapy, and defibrillation testing for implantable cardioverter-defibrillator (ICD) patient treatment. The 32 recommendations represented the consensus opinion of the writing group, graded by Class of Recommendation and Level of Evidence. In addition, Appendix B provided manufacturer-specific translations of these recommendations into clinical practice consistent with the recommendations within the parent document. In some instances, programming guided by quality evidence gained from studies performed in devices from some manufacturers was translated such that this programming was approximated in another manufacturer's ICD programming settings. The authors found that the data, although not formally tested, were strong, consistent, and generalizable beyond the specific manufacturer and model of ICD. As expected, because these recommendations represented strategic choices to balance risks, there have been reports in which adverse outcomes were documented with ICDs programmed to Appendix B recommendations. The recommendations have been reviewed and updated to minimize such adverse events. Notably, patients who do not receive unnecessary ICD therapy are not aware of being spared potential harm, whereas patients in whom their ICD failed to treat life-threatening arrhythmias have their event recorded in detail. The revised recommendations employ the principle that the randomized trials and large registry data should guide programming more than anecdotal evidence. These recommendations should not replace the opinion of the treating physician who has considered the patient's clinical status and desired outcome via a shared clinical decision-making process.

2019 HRS/EHRA/APHRS/LAHRS focused update to 2015 expert consensus statement on optimal implantable cardioverter-defibrillator programming and testing.

The 2015 HRS/EHRA/APHRS/SOLAECE Expert Consensus Statement on Optimal Implantable Cardioverter-Defibrillator Programming and Testing provided guidance on bradycardia programming, tachycardia detection, tachycardia therapy, and defibrillation testing for implantable cardioverter-defibrillator (ICD) patient treatment. The 32 recommendations represented the consensus opinion of the writing group, graded by Class of Recommendation and Level of Evidence. In addition, Appendix B provided manufacturer-specific translations of these recommendations into clinical practice consistent with the recommendations within the parent document. In some instances, programming guided by quality evidence gained from studies performed in devices from some manufacturers was translated such that this programming was approximated in another manufacturer's ICD programming settings. The authors found that the data, although not formally tested, were strong, consistent, and generalizable beyond the specific manufacturer and model of ICD. As expected, because these recommendations represented strategic choices to balance risks, there have been reports in which adverse outcomes were documented with ICDs programmed to Appendix B recommendations. The recommendations have been reviewed and updated to minimize such adverse events. Notably, patients who do not receive unnecessary ICD therapy are not aware of being spared potential harm, whereas patients in whom their ICD failed to treat life-threatening arrhythmias have their event recorded in detail. The revised recommendations employ the principle that the randomized trials and large registry data should guide programming more than anecdotal evidence. These recommendations should not replace the opinion of the treating physician who has considered the patient's clinical status and desired outcome via a shared clinical decision-making process.

Implantable cardioverter-defibrillators in patients with long QT syndrome: a multicentre study.

Implantable cardioverter-defibrillator (ICD) therapy has been proven effective in the prevention of sudden cardiac death, but data on outcomes of ICD therapy in the young and otherwise healthy patients with long QT syndrome (LQTS) are limited. We sought to collect data on appropriate and inappropriate ICD discharges, risk factors, and ICD-related complications. All LQTS patients implanted with an ICD in 14 centres were investigated. Demographic, clinical, and ICD therapy data were collected. The study included 67 patients (88% female). Median age at ICD implantation was 31 years (12-77 years). ICD indication was based on resuscitated cardiac arrest in 46 patients, syncope in 18 patients, and malignant family history in three patients. During a median follow-up of 48 months, 39 (58%) patients received one or more ICD therapies. Time to first appropriate discharge was up to 55 months. Inappropriate therapies were triggered by fast sinus rhythm, atrial fibrillation, and T-wave oversensing. No predictors of inappropriate shocks were identified. Risk factors for appropriate ICD therapy were: (1) recurrent syncope despite b-blocker treatment before ICD implantation, (2) pacemaker therapy before ICD implantation, (3) single-chamber ICD, and (4) noncompliance to b-blockers. In 38 (57%) patients, at least one complication occurred. ICD therapy is effective in nearly half the patient population; however, the rates of early and late complica-tions are high. Although the number of unnecessary ICD shocks and reimplantation procedures may be lowered by modern programming and increased longevity of newer ICD generators, other adverse events are less likely to be reduced.

Therapy optimization in patients with heart failure: the role of the wearable cardioverter-defibrillator in a real-world setting

BackgroundThe wearable cardioverter-defibrillator (WCD) has emerged as a valuable tool to temporarily protect patients at risk for sudden cardiac death (SCD). The aim of this study was to determine the value of the WCD for therapy optimization of heart failure patients.MethodsOne hundred five consecutive patients that received WCD between 4/2012 and 9/2016 were included in the study. All patients were followed for clinical outcome and echocardiographic parameters during WCD therapy and had continued follow-up after WCD therapy, irrespective of subsequent implantable cardioverter-defibrillator (ICD) implantation.ResultsThe most common indication for WCD were newly diagnosed ischemic (ICM) or non-ischemic cardiomyopathy (NICM) with left ventricular ejection fraction (LVEF) ≤35%. Mean WCD wear time was 68.8 ± 50.4 days with a mean daily use of 21.5 ± 3.5 h. Five patients (4.8%) received a total of five appropriate WCD shocks.During WCD wear, patients with ICM and NICM showed significant improvement in LVEF, reducing the proportion of patients with a need for primary preventive ICD implantation to 54.8% (ICM) and 48.8% (NICM). An ICD was finally implanted in 51.4% of the study patients (24 trans-venous ICDs, 30 subcutaneous ICDs).After discontinuation of WCD therapy, all patients were followed for a mean of 18.6 ± 12.3 months. 5.6% of patients with implanted ICDs received appropriate therapies. No patient with subcutaneous ICD needed change to a trans-venous device. None of the patients without an implanted ICD suffered from ventricular tachyarrhythmias and no patient died suddenly.In patients with NICM a significant LVEF improvement was observed during long-term follow-up (from 34.8 ± 11.1% to 41.0 ± 10.2%).ConclusionsWCD therapy successfully bridged all patients to either LVEF recovery or ICD implantation. Following WCD, ICD implantation could be avoided in almost half of the patients. In selected patients, prolongation of WCD therapy beyond 3 months might further prevent unnecessary ICD implantation. The WCD as an external monitoring system contributed important information to optimize device selection in patients that needed ICD implantation.

Sudden Cardiac Death: Lessons Learned from Cardiac Implantable Rhythm Devices.

Trials have demonstrated that implantable-cardioverter defibrillators (ICDs) are effective in preventing sudden cardiac death (SCD). The degree of left ventricular dysfunction is the only parameter to identify primary prevention populations at higher risk of SCD in which ICDs may reduce longitudinal mortality risk. Clinical application of current stratification approaches based on left ventricular ejection fraction (LVEF) alone has failed to prevent most SCD in the general population. This lack of specificity has resulted in a significant number of potentially unnecessary ICDs. Future studies should focus on newer risk markers to improve the predictive value of LVEF and SCD prevention.

Optimal Implantable Cardioverter Defibrillator Programming.

Optimal programming of implantable cardioverter defibrillators (ICDs) is essential to appropriately treat ventricular tachyarrhythmias and to avoid unnecessary and inappropriate shocks. There have been a series of large clinical trials evaluating tailored programming of ICDs. We reviewed the clinical trials evaluating ICD therapies and detection, and the consensus statement on ICD programming. In doing so, we found that prolonged ICD detection times, higher rate cutoffs, and antitachycardia pacing (ATP) programming decreases inappropriate and painful therapies in a primary prevention population. The use of supraventricular tachyarrhythmia discriminators can also decrease inappropriate shocks. Tailored ICD programming using the knowledge gained from recent ICD trials can decrease inappropriate and unnecessary ICD therapies and decrease mortality.

A novel algorithm for ventricular arrhythmia classification using a fuzzy logic approach.

In the present study, it has been shown that an unnecessary implantable cardioverter-defibrillator (ICD) shock is often delivered to patients with an ambiguous ECG rhythm in the overlap zone between ventricular tachycardia (VT) and ventricular fibrillation (VF); these shocks significantly increase mortality. Therefore, accurate classification of the arrhythmia into VT, organized VF (OVF) or disorganized VF (DVF) is crucial to assist ICDs to deliver appropriate therapy. A classification algorithm using a fuzzy logic classifier was developed for accurately classifying the arrhythmias into VT, OVF or DVF. Compared with other studies, our method aims to combine ten ECG detectors that are calculated in the time domain and the frequency domain in addition to different levels of complexity for detecting subtle structure differences between VT, OVF and DVF. The classification in the overlap zone between VT and VF is refined by this study to avoid ambiguous identification. The present method was trained and tested using public ECG signal databases. A two-level classification was performed to first detect VT with an accuracy of 92.6%, and then the discrimination between OVF and DVF was detected with an accuracy of 84.5%. The validation results indicate that the proposed method has superior performance in identifying the organization level between the three types of arrhythmias (VT, OVF and DVF) and is promising for improving the appropriate therapy choice and decreasing the possibility of sudden cardiac death.