Effects of chronic amiodarone therapy on defibrillation threshold

Emergency Management of Electrical Storm: A Practical Overview

Electrical storm is a medical emergency characterized by ventricular arrythmia recurrence that can lead to hemodynamic instability. The incidence of this clinical condition is rising, mainly in implantable cardioverter defibrillator patients, and its prognosis is often poor. Early acknowledgment, management and treatment have a key role in reducing mortality in the acute phase and improving the quality of life of these patients. In an emergency setting, several measures can be employed. Anti-arrhythmic drugs, based on the underlying disease, are often the first step to control the arrhythmic burden; besides that, new therapeutic strategies have been developed with high efficacy, such as deep sedation, early catheter ablation, neuraxial modulation and mechanical hemodynamic support. The aim of this review is to provide practical indications for the management of electrical storm in acute settings.

Single beta-blocker or combined amiodarone therapy in implantable cardioverter-defibrillator and cardiac resynchronization therapy-defibrillator patients: Insights from the German DEVICE registry

BACKGROUND

Because of its antiarrhythmic potency and due to the lack of alternatives, amiodarone is often used for antiarrhythmic therapy in patients with implantable cardioverter-defibrillator (ICD) or cardiac resynchronization therapy-defibrillator systems. To date, robust data on the safety and clinical benefit of amiodarone therapy in these patients are missing.

OBJECTIVE

The purpose of this study was to assess the periprocedural and postprocedural outcomes of combined therapy with beta-blockers plus amiodarone compared to treatment with single beta-blockers in the "real-life" cohort of ICD recipients of the German DEVICE registry.

METHODS

A total of 4499 patients who underwent ICD implantation, revision, or upgrade in 49 centers participating in the German DEVICE registry were enrolled from March 2007 to February 2014.

RESULTS

Amiodarone had no significant effect on the success of defibrillation testing. Early implantation-associated complications were similar between the groups. However, 1-year overall mortality was significantly higher in the beta-blocker plus amiodarone cohort (adjusted hazard ratio 2.09; P <.001). Interestingly, among the surviving patients, amiodarone was not associated with a significantly reduced risk of ICD discharges or syncopal events. Furthermore, the occurrence of ventricular tachycardia (VT) storm or incessant VTs and the number of patients scheduled for intracardiac ablation did not differ among both groups, whereas the rate of rehospitalization was lower in the cohort with only beta-blockers.

CONCLUSIONS

Although amiodarone has no adverse effect on the success of defibrillation testing, our data suggest an increased all-cause mortality under amiodarone therapy, especially in the subgroups of patients with sinus rhythm or severely reduced left ventricular function. In surviving patients, rates of arrhythmic events were comparable.

Effectiveness and safety of mexiletine in patients at risk for (recurrent) ventricular arrhythmias: a systematic review

While mexiletine has been used for over 40 years for prevention of (recurrent) ventricular arrhythmias and for myotonia, patient access has recently been critically endangered. Here we aim to demonstrate the effectiveness and safety of mexiletine in the treatment of patients with (recurrent) ventricular arrhythmias, emphasizing the absolute necessity of its accessibility. Studies were included in this systematic review (PROSPERO, CRD42020213434) if the efficacy or safety of mexiletine in any dose was evaluated in patients at risk for (recurrent) ventricular arrhythmias with or without comparison with alternative treatments (e.g. placebo). A systematic search was performed in Ovid MEDLINE, Embase, and in the clinical trial registry databases ClinicalTrials.gov and ICTRP. Risk of bias were assessed and tailored to the different study designs. Large heterogeneity in study designs and outcome measures prompted a narrative synthesis approach. In total, 221 studies were included reporting on 8970 patients treated with mexiletine. Age ranged from 0 to 88 years. A decrease in ventricular arrhythmias of >50% was observed in 72% of the studies for pre-mature ventricular complexes, 64% for ventricular tachycardia, and 33% for ventricular fibrillation. Electrocardiographic effects of mexiletine were small; only in a subset of patients with primary arrhythmia syndromes, a relative (desired) QTc decrease was reproducibly observed. As for adverse events, gastrointestinal complaints were most frequently observed (33% of the patients). In this systematic review, we present all the currently available knowledge of mexiletine in patients at risk for (recurrent) ventricular arrhythmias and show that mexiletine is both effective and safe.

Mexiletine for recurrent ventricular tachycardia in adult patients with structural heart disease and implantable cardioverter defibrillator: an EHRA systematic review

The aim of the study was to systematically review evidence on the effectiveness and safety of oral mexiletine administered in monotherapy or in combination with other antiarrhythmic drugs for recurrent ventricular arrhythmia (ventricular tachycardia/ventricular fibrillation, VT/VF) in adult patients with structural heart disease (SHD) and implantable cardioverter defibrillators (ICDs). We systematically searched MEDLINE, Embase, and CENTRAL databases from inception to 27 August 2021 for prospective and retrospective studies investigating mexiletine in the target population. The main outcome was the reduction of ICD therapy. The main safety outcome was the presence of any serious adverse events (SAEs) leading to mexiletine discontinuation. Study quality was assessed using the Cochrane risk of bias tool or the Newcastle–Ottawa scale. Four studies comprising 86 mexiletine recipients were included in the review. We also obtained individual data of 50 patients from two studies. Ischaemic cardiomyopathy (ICM) was present in 86% of patients. The quality of included studies was moderate/low. A narrative review was undertaken as studies varied widely in terms of study population and treatment. Across studies, mexiletine treatment (with or without amiodarone) seemed to consistently reduce the number of ICD therapies especially in a population where catheter ablation (CA) was unsuccessful or contraindicated. In ICM patients deemed eligible for CA, mexiletine seemed to be inferior to CA. Mexiletine was discontinued in 14% of cases, mainly for gastrointestinal or neurological SAE. Mexiletine seems to be an option for the long-term treatment of recurrent VT/VF in adult patients with SHD, especially ICM, and ICD in whom CA was unsuccessful or not suitable.

Recent insights into mechanisms and clinical approaches to electrical storm

Electrical storm, characterized by repetitive ventricular tachycardia/fibrillation (VT/VF) over a short period, is becoming commoner with widespread use of implantable cardioverter-defibrillator (ICD) therapy. Electrical storm, sometimes called "arrhythmic storm" or "VT-storm", is usually a medical emergency requiring hospitalization and expert management, and significantly affects short- and long-term outcomes. This syndrome typically occurs in patients with underlying structural heart disease (ischemic or non-ischemic cardiomyopathy) or inherited channelopathies. Triggers for electrical storm should be sought but are often unidentifiable. Initial management is dictated by the hemodynamic status, while subsequent management typically involves ICD interrogation and reprogramming to reduce recurrent shocks, identification/management of triggers like electrolyte abnormalities, myocardial ischemia, or decompensated heart failure, and antiarrhythmic-drug therapy or catheter ablation. Sympathetic nervous system activation is central to the initiation and maintenance of arrhythmic storm, so autonomic modulation is a cornerstone of management. Sympathetic inhibition can be achieved with medications (particularly beta-adrenoreceptor blockers), deep sedation, or cardiac sympathetic denervation. More definitive management targets the underlying ventricular arrhythmia substrate to terminate and prevent recurrent arrhythmia. Arrhythmia targeting can be achieved with antiarrhythmic medications, catheter ablation or more novel therapies such as stereotactic radiation therapy that targets the arrhythmic substrate. Mechanistic studies point to adrenergic activation and other direct consequences of ICD-shocks in promoting further arrhythmogenesis and hypocontractility. Here, we review the pathophysiologic mechanisms, clinical features, prognosis, and therapeutic options for electrical storm. We also outline a clinical approach to this challenging and complex condition, along with its mechanistic basis.

Electrical storm: Prognosis and management

Electrical storm is present when a cluster of ventricular arrhythmias (VAs) occurs within a short time frame. The most widely accepted definition is 3 or more episodes of VA within a 24-h period, although prognostic risk begins to rise when 2 or more events occur within 3months. Electrical storm often presents as a medical emergency in the form of recurrent implantable cardiac defibrillator (ICD) shocks, recurrent syncope in patients with no ICD or low cardiac output symptoms. Management often requires a multimodality approach including ICD management, pharmacologic therapy, catheter ablation and modulations of the autonomic nervous system. In this article, we review the definition, prognosis and management of electrical storm.

Antiarrhythmic Drugs or Catheter Ablation in the Management of Ventricular Tachyarrhythmias in Patients With Implantable Cardioverter-Defibrillators: A Systematic Review and Meta-Analysis of Randomized Controlled Trials

BACKGROUND

In patients with an implantable cardioverter-defibrillator (ICD), shocks are associated with increased morbidity and mortality. Therefore, we conducted this study to evaluate the efficacy and safety of antiarrhythmic drugs and catheter ablation (CA) in the treatment of ventricular tachyarrhythmias (VT) in patients with an ICD.

METHODS

An electronic database search for randomized controlled trials that evaluated antiarrhythmic drugs and CA in patients with ICD was conducted. The primary outcome was recurrent VT. Secondary outcomes were ICD shocks and any deaths. Bayesian and frequentist network meta-analyses were performed to calculate hazard ratios (HRs) and 95% credible intervals (CrIs)/CIs.

RESULTS

Twenty-two randomized controlled trials were identified (3828 total patients; age 64.3±11.4; 79% males). The use of amiodarone was associated with a significantly reduced rate of VT recurrence compared with control (HR=0.34 [95% CrI=0.15-0.74]; absolute risk difference=-0.23 [95% CrI=-0.23 to -0.09]; number needed to treat=4). Sotalol was associated with increased risk of VT recurrence compared with amiodarone (HR=2.88 [95% CrI=1.35-6.46]). Compared with control, amiodarone (HR=0.33 [95% CrI=0.15-0.76]; absolute risk difference=-0.17 [95% CrI=-0.32 to -0.06]; number needed to treat=6) and CA (HR=0.52 [95% CrI=0.30-0.89; absolute risk difference=-0.12 [95% CrI=-0.24 to -0.03]; number needed to treat=8) were associated with significantly reduced ICD shocks. Compared with amiodarone, sotalol was associated with significantly increased ICD shocks (HR=2.70 [95% CrI=1.17-6.71]). The rate of death was not significantly different between the competing strategies. The node-splitting method showed no inconsistency.

CONCLUSIONS

Among patients with an ICD, amiodarone significantly reduced VT recurrence and ICD shocks, while CA reduced ICD shocks. Sotalol significantly increased VT recurrence and ICD shocks compared with amiodarone. The long-term side effects of amiodarone and early complications of CA should be weighed carefully according to specific patient characteristics.

[Clinical aspects of treatment with amiodarone]

Amiodarone has multiple and complex electrophysiological effects that render it a very effective antiarrhythmic drug for the treatment of both, supraventricular and ventricular arrhythmias. Proarrhythmic effects of amiodarone in patients with structural heart disease are rare. However, extracardiac adverse effects occurring in association with amiodarone treatment are frequent and feared. These adverse effects have usually been related to total amiodarone exposure (i. e., dose and duration of treatment). Parallel to a more frequent use of lower amiodarone maintenance doses (100-200 mg/day), the incidence of severe unwanted extracardiac side effects has decreased. High-dose maintenance regiments (daily dose ≥300 mg) are usually obsolete. This paper discusses recommendations regarding the monitoring of cardiac and extracardiac side effects of amiodarone. They need to be regarded by physicians using amiodarone to ensure long-term safety of amiodarone therapy.

Defibrillation Threshold Testing: Current Status

When the transvenous ICD initially came into use for primary and secondary prevention of sudden cardiac death, defibrillation threshold (DFT) testing was universally performed. However, DFT testing is no longer routinely recommended for transvenous ICD implantation except in certain situations. Risk scores can help guide the decision to perform DFT testing. The subcutaneous ICD represents an area of uncertainty, with limited data available regarding the role of DFT testing in these devices. Current guidelines give a class I recommendation for performing DFT testing at the time of implant. Further studies are needed before this recommendation can be safely dismissed.

Long-term performance of right ventricular pacing leads: risk factors associated with permanent right ventricular pacing threshold increase

Purpose

Right ventricular pacing threshold (RVPT) may rise over time accompanied by the increased use of implantable cardiac pacemakers. However, risk factors for permanent RVPT increase are not fully clarified in patients without definite lead fracture and dislodgment. We aimed to evaluate the long-term performance of RV pacing leads and identify risk factors associated with the occurrence of permanent RVPT increase in this population.

Methods

Patients with first implantation of cardiac pacemakers from January 2008 to June 2016 were consecutively enrolled. Follow-up for RVPT increase was until December 2017. The clinical data, specific data on the pacemaker implantation, and routine follow-up were retrieved.

Results

During a follow-up duration of 5.4 ± 2.1 years, permanent RVPT increase (except lead fracture and dislodgment) was found in 8.4% (87/1033) patients. Patients with permanent RVPT increase had higher prevalence of myocardial infarction (MI), diabetes, and the use of amiodarone. The risk factors independently associated with permanent RVPT increase were MI (HR = 1.094, 95% CI 1.014–1.180, p = 0.031), diabetes (HR = 2.804, 95% CI 1.064–3.775, p = 0.003). MI patients with RVPT increase had higher prevalence of multivessel disease and atrioventricular block. Diabetic patients with RVPT increase exhibited higher serum fasting blood glucose (FBG) and hemoglobin A1c (HbA1c) levels, which were correlated with the maximum RVPT (p < 0.001).

Conclusions

Our data showed that permanent RVPT increases (except lead fracture and dislodgement) during long-term follow-up after pacemaker implantation. The likely risk factors predisposing to chronic permanent RVPT increase are MI and diabetes with higher FBG and HbA1c levels.

The Selective Late Sodium Current Inhibitor Eleclazine, Unlike Amiodarone, Does Not Alter Defibrillation Threshold or Dominant Frequency of Ventricular Fibrillation

INTRODUCTION

We examined the effects of the selective late INa inhibitor eleclazine on the 50% probability of successful defibrillation (DFT50) before and after administration of amiodarone to determine its suitability for use in patients with implantable cardioverter defibrillators (ICDs).

METHODS AND RESULTS

In 20 anesthetized pigs, transvenous active-fixation cardiac defibrillation leads were fluoroscopically positioned into right ventricular apex through jugular vein. ICDs were implanted subcutaneously. Dominant frequency of ventricular fibrillation was analyzed by fast Fourier transform. The measurements were made before drug administration (control), and at 40 minutes after vehicle, eleclazine (2 mg/kg, i.v., bolus over 15 minutes), or subsequent/single amiodarone administration (10 mg/kg, i.v., bolus over 10 minutes). Eleclazine did not alter DFT50, dominant frequency, heart rate, or mean arterial pressure (MAP). Subsequent amiodarone increased DFT50 (P = 0.006), decreased dominant frequency (P = 0.022), and reduced heart rate (P = 0.031) with no change in MAP. Amiodarone alone increased DFT50 (P = 0.005; NS compared to following eleclazine) and decreased dominant frequency (P = 0.003; NS compared to following eleclazine).

CONCLUSION

Selective late INa inhibition with eleclazine does not alter DFT50 or dominant frequency of ventricular fibrillation when administered alone or in combination with amiodarone. Accordingly, eleclazine would not be anticipated to affect the margin of defibrillation safety in patients with ICDs.

Electrical Storm in Patients with Implantable Cardioverter-defibrillators: A Practical Overview

Electrical storm (ES) is an increasingly common medical emergency characterized by clustered episodes of sustained ventricular arrhythmias (VAs) that lead to repeated appropriate implantable cardioverter-defibrillator (ICD) therapies. A diagnosis of ES can be made with the occurrence of three or more sustained episodes of VAs, or of three or more appropriate ICD therapies within 24 hours in patients with implanted devices. ES is associated with poor outcomes in patients with structural heart disease, particularly those with severe left ventricular dysfunction. In large clinical trials involving patients with ICDs for primary and secondary prevention, ES appears to be a predictor of cardiac death, with notably higher rates of mortality soon after the event. ES management is challenging and requires special medical attention with accurate patient risk stratification and a multidisciplinary approach that includes the use of pharmacologic therapies such as antiarrhythmic drugs (AADs) and interventional approaches like catheter ablation, surgical ablation, or sympathetic neuromodulation. Initial management involves determining and addressing the underlying ischemia, any electrolyte imbalances, and/or other causative factors. Hemodynamic support needs to be considered in high-risk patients with unstable VAs or those with severe comorbidities such as low left ventricular ejection fraction, advanced New York Heart Association class, and/or chronic pulmonary disease. Following the acute phase of ES, treatment should shift towards maximizing therapeutic efforts to address heart failure, performing revascularization, and preventing subsequent VAs. In the present manuscript, we offer an overview of the most relevant clinical aspects of ES with regard to novel therapeutic strategies.

Amiodarone versus other pharmacological interventions for prevention of sudden cardiac death

BACKGROUND

Sudden cardiac death (SCD) is one of the main causes of cardiac death. There are two main strategies to prevent it: managing cardiovascular risk factors and reducing the risk of ventricular arrhythmias. Implantable cardiac defibrillators (ICDs) constitute the standard therapy for both primary and secondary prevention; however, they are not widely available in settings with limited resources. The antiarrhythmic amiodarone has been proposed as an alternative to ICD.

OBJECTIVES

To evaluate the effectiveness of amiodarone for primary or secondary prevention in SCD compared with placebo or no intervention or any other antiarrhythmic drugs in participants at high risk (primary prevention) or who have recovered from a cardiac arrest or a syncope due to Ventricular Tachycardia/Ventricular Fibrillation, or VT/VF (secondary prevention).

SEARCH METHODS

We searched the Cochrane Central Register of Controlled Trials (CENTRAL), MEDLINE (OVID), EMBASE (OVID), CINAHL (EBSCO) and LILACS on 26 March 2015. We reviewed reference lists of included studies and selected reviews on the topic, contacted authors of included studies, screened relevant meetings and searched in registers for ongoing trials. We applied no language restrictions.

SELECTION CRITERIA

Randomised and quasi-randomised trials assessing the efficacy of amiodarone versus placebo, no intervention, or other antiarrhythmics in adults. For primary prevention we considered participants at high risk for SCD. For secondary prevention we considered participants recovered from cardiac arrest or syncope due to ventricular arrhythmias.

DATA COLLECTION AND ANALYSIS

Two authors independently assessed the trials for inclusion and extracted relevant data. We contacted trial authors for missing data. We performed meta-analyses using a random-effects model. We calculated risk ratios (RR) for dichotomous outcomes with 95% confidence intervals (CIs). Three studies included more than one comparison.

MAIN RESULTS

We included 24 studies (9,997 participants). Seventeen studies evaluated amiodarone for primary prevention and six for secondary prevention. Only three studies used an ICD concomitantly with amiodarone for the comparison (all of them for secondary prevention).For primary prevention, amiodarone compared to placebo or no intervention (17 studies, 8383 participants) reduced SCD (RR 0.76; 95% CI 0.66 to 0.88), cardiac mortality (RR 0.86; 95% CI 0.77 to 0.96) and all-cause mortality (RR 0.88; 95% CI 0.78 to 1.00). The quality of the evidence was low.Compared to other antiarrhythmics (three studies, 540 participants), amiodarone reduced SCD (RR 0.44; 95% CI 0.19 to 1.00), cardiac mortality (RR 0.41; 95% CI 0.20 to 0.86) and all-cause mortality (RR 0.37; 95% CI 0.18 to 0.76). The quality of the evidence was moderate.For secondary prevention, amiodarone compared to placebo or no intervention (two studies, 440 participants) appeared to increase the risk of SCD (RR 4.32; 95% CI 0.87 to 21.49) and all-cause mortality (RR 3.05; 1.33 to 7.01). However, the quality of the evidence was very low. Compared to other antiarrhythmics (four studies, 839 participants) amiodarone appeared to increase the risk of SCD (RR 1.40; 95% CI 0.56 to 3.52; very low quality of evidence), but there was no effect in all-cause mortality (RR 1.03; 95% CI 0.75 to 1.42; low quality evidence).Amiodarone was associated with an increase in pulmonary and thyroid adverse events.

AUTHORS' CONCLUSIONS

There is low to moderate quality evidence that amiodarone reduces SCD, cardiac and all-cause mortality when compared to placebo or no intervention for primary prevention, and its effects are superior to other antiarrhythmics.It is uncertain if amiodarone reduces or increases SCD and mortality for secondary prevention because the quality of the evidence was very low.

The Effect of Direct Current Stimulation versus T-Wave Shock on Defibrillation Threshold Testing

INTRODUCTION

There are several methods to induce ventricular fibrillation (VF) during defibrillation threshold (DFT) testing. Delivering a shock at a critical time during the T wave (T-shock) is the conventional approach, while delivering a constant direct current voltage (DC stim) from the implantable cardioverter defibrillator is an alternative method. Only a few reports compare VF induction methods. The purpose of this study was to evaluate the effects and safety of DC stim versus T-shock.

METHODS

We retrospectively investigated 414 consecutive patients undergoing DFT testing. We compared the two groups (DC stim and T-shock) with respect to clinical characteristics, electrocardiogram (ECG) changes, and complications.

RESULTS

Ventricular arrhythmia, including ventricular tachycardia (VT) and VF, was induced by DC stim in 93 patients or T-shock in 321 patients. No more than three attempts were performed during one procedure. There was no significant difference in the baseline ECG, induced tachycardia cycle length (TCL), or complications between the two groups. However, the induced TCL was significantly shorter than the clinical TCL regardless of induction method (P = 0.001). Five patients suffered major complications (i.e., electromechanical dissociation or incessant VT). A history of atrial fibrillation was significantly greater in patients with major complications than the others (80% vs 24%, P = 0.004), and was an independent predictor on multivariate analysis.

CONCLUSIONS

There is no significant difference in induced TCL or complications between the DC stim and T-shock. The induced TCL is significantly shorter than clinical TCL regardless of induction method.

Optimal antiarrhythmic drug therapy for electrical storm

Electrical storm, defined as 3 or more separate episodes of ventricular tachycardia or ventricular fibrillation within 24 hours, carries significant morbidity and mortality. These unstable ventricular arrhythmias have been described with a variety of conditions including ischemic heart disease, structural heart disease, and genetic conditions. While implantable cardioverter defibrillator implantation and ablation may be indicated and required, antiarrhythmic medication remains an important adjunctive therapy for these persons.

Implantable cardioverter-defibrillator shock prevention does not reduce mortality: a systemic review

BACKGROUND

Mortality is increased among implantable cardioverter-defibrillator (ICD) recipients who receive shocks; however, whether shocks cause this increase or are simply a marker of risk is unknown. Antiarrhythmic medications, catheter ablation, and enhanced ICD programming all may reduce ICD shocks, but whether shock reduction decreases mortality is unknown.

OBJECTIVE

The purpose of this study was to conduct a meta-analysis to estimate the impact of ICD shock reduction on survival.

METHODS

Two independent reviewers searched MEDLINE, EMBASE, and clinicaltrials.gov and extracted data from randomized controlled trials assessing the efficacy of interventions to prevent ICD shocks.

RESULTS

Seventeen randomized trials were included in this analysis, including 5875 patients. Mean ejection fraction of all trial participants was 32%, and 25% of the patients received ICD therapy for primary prophylaxis. Antiarrhythmic medications (odds ratio [OR] 0.59, 95% confidence interval [CI] 0.36-0.96, P = .03) and catheter ablation of ventricular tachycardia (OR 0.35, 95% CI 0.19-0.62, P = .0004) significantly reduced the proportion of patients receiving shocks. However, there was no significant reduction in mortality among trials of antiarrhythmic medications (OR 1.07, 95% CI 0.72-1.59, P = .73) or catheter ablation (OR 0.72, 95% CI 0.32-1.64, P = .44). The 5 ICD programming trials had sufficiently heterogeneous interventions that pooling of their results was not performed. However, only the PAINFREE-II (Pacing Fast Ventricular Tachycardia Reduces Shock Therapies) trial demonstrated a significant reduction in shocks (OR 0.38, 95% CI 0.22-0.65), but this was not associated with any significant reduction in mortality (OR 1.41, 95% CI 0.81-2.45).

CONCLUSION

There is no compelling evidence that existing interventions that reduce ICD shocks significantly improve survival.

[Is the determination of the defibrillation threshold in patients with an implantable cardioverter-defibrillator still required?]

BACKGROUND

Intraoperative testing of implantable cardioverter-defibrillators (ICDs) is time consuming and associated with risks. In the present study, we elucidated whether the initial implantation of an ICD with high energy output makes intraoperative defibrillation threshold testing (DFTT) unnecessary even though antiarrhythmic (AA) therapy is needed in the future.

METHODS

A total of 111 patients (94 men, 17 women) receiving an ICD with subsequent AA therapy (mexiletine, amiodarone, sotalol, flecainide) were analyzed retrospectively. DFT was performed during ICD implantation and after AA drug therapy. In a second step, DFT results from the study cohort were analyzed for implantation of virtual ICDs with either low (≤ 30 J, LOD), intermediate (34 J, IOD), or high energy output (36 J, HOD).

RESULTS

In the study cohort, all patients reached the safety margin (SM) of 10 J between DFT and maximal shock energy of the ICD. After loading of AA agents, 6 patients (12%) with a LOD, 3 patients (11%) with an IOD, and 3 (13%) patients with a HOD failed the 10 J SM. Using virtual ICDs, 6 (5.5%) patients with a LOD, 1 patient (1%) with an IOD, and no patients with a HOD would have failed the 10 J SM. After loading of AA agents, 18 patients (16%) with a virtual LOD, 12 patients (10.8%) with an IOD, and still 9 patients (8%) with a HOD would have failed the 10 J SM.

CONCLUSION

Our results demonstrate that the 10 J SM would have been achieved intraoperatively in all patients with virtual HOD ICDs. Thus, determination of the DFT during implantation does not seem to be obligatory. However, in patients receiving AA agents, DFT testing is still required.

Inappropriate Implantable Cardioverter-Defibrillator Therapy

Although improvements in implantable cardioverter-defibrillator (ICD) therapy have taken place, many challenges do remain. Inappropriate delivery of therapy is a big problem that impacts the quality of life of ICD recipients. Although there is now a clear understanding that atrial arrhythmias are the main cause of inappropriate ICD therapies, physicians have not been very successful in preventing them. Additionally, although many tachycardia detection discriminators have been shown to be helpful, it is not clear that there is a particular combination that is ideal for all patients. Until such an algorithm is developed (which may not be possible), a detailed knowledge and use of all available programming options, guided by special characteristics of each unique patient, are the only foreseeable solutions. Finally, one must face the prospect that this problem cannot be vanquished, but only ameliorated.

The dilemma of ICD implant testing

Ventricular fibrillation (VF) has been induced at implantable cardioverter defibrillator (ICD) implant to ensure reliable sensing, detection, and defibrillation. Despite its risks, the value was self-evident for early ICDs: failure of defibrillation was common, recipients had a high risk of ventricular tachycardia (VT) or VF, and the only therapy for rapid VT or VF was a shock. Today, failure of defibrillation is rare, the risk of VT/VF is lower in some recipients, antitachycardia pacing is applied for fast VT, and vulnerability testing permits assessment of defibrillation efficacy without inducing VF in most patients. This review reappraises ICD implant testing. At implant, defibrillation success is influenced by both predictable and unpredictable factors, including those related to the patient, ICD system, drugs, and complications. For left pectoral implants of high-output ICDs, the probability of passing a 10 J safety margin is approximately 95%, the probability that a maximum output shock will defibrillate is approximately 99%, and the incidence of system revision based on testing is < or = 5%. Bayes' Theorem predicts that implant testing identifies < or = 50% of patients at high risk for unsuccessful defibrillation. Most patients who fail implant criteria have false negative tests and may undergo unnecessary revision of their ICD systems. The first-shock success rate for spontaneous VT/VF ranges from 83% to 93%, lower than that for induced VF. Thus, shocks for spontaneous VT/VF fail for reasons that are not evaluated at implant. Whether system revision based on implant testing improves this success rate is unknown. The risks of implant testing include those related to VF and those related to shocks alone. The former may be due to circulatory arrest alone or the combination of circulatory arrest and shocks. Vulnerability testing reduces risks related to VF, but not those related to shocks. Mortality from implant testing probably is 0.1-0.2%. Overall, VF should be induced to assess sensing in approximately 5% of ICD recipients. Defibrillation or vulnerability testing is indicated in 20-40% of recipients who can be identified as having a higher-than-usual probability of an inadequate defibrillation safety margin based on patient-specific factors. However, implant testing is too risky in approximately 5% of recipients and may not be worth the risks in 10-30%. In 25-50% of ICD recipients, testing cannot be identified as either critical or contraindicated.

Comparison of efficacy of sotalol and nifekalant for ventricular tachyarrhythmias

BACKGROUND

Suppression of implantable defibrillator discharges associated with ventricular tachyarrhythmia (VTA) has been reported for sotalol. This study aimed to investigate the efficacy of intravenous nifekalant hydrochloride in predicting the effects of oral sotalol.

METHODS AND RESULTS

The present study included 14 patients who had sustained VTA associated with structural heart disease. All patients also had inducible VTA. To compare the effects of nifekalant and sotalol, programmed electrical stimulation was performed, in the basal state, after nifekalant administration, and after sotalol administration. Nifekalant and sotalol similarly prolonged the corrected QT interval and ventricular effective refractory periods, but the heart rate was slowed by sotalol only. In 4 of 5 patients whose VTA became non-inducible by nifekalant, subsequent treatment with sotalol also suppressed the inducible VTA. In all of the 9 patients non-responding to nifekalant, VTA remained inducible during sotalol treatment. Nifekalant accurately predicted the response to sotalol during electrophysiologic study in 13 of 14 patients. Of 11 patients who remained on sotalol, VTA recurred in 3 non-responders during a follow-up of 46 +/- 11 months.

CONCLUSIONS

Nifekalant and sotalol had similar effects on inducible VTA. The response of inducible VTA to nifekalant may predict the clinical efficacy of sotalol.

Comparing intravenous amiodarone or lidocaine, or both, outcomes for inpatients with pulseless ventricular arrhythmias*

OBJECTIVE

To compare survival rates of patients with in-hospital cardiac arrest due to pulseless ventricular tachycardia/ventricular fibrillation treated with lidocaine, amiodarone, or amiodarone plus lidocaine.

DESIGN

Multicenter retrospective medical record review.

SETTING

Three academic medical centers in the United States.

PATIENTS

Hospitalized adult patients who received amiodarone, lidocaine, or a combination for pulseless ventricular tachycardia/ventricular fibrillation between August 1, 2000, and July 31, 2002.

MEASUREMENTS AND MAIN RESULTS

Data were collected according to the Utstein style. In-hospital proportion of patients living at 24 hrs and discharge were analyzed using chi-square analysis. Of the 605 patient medical records reviewed, 194 met criteria for inclusion (n=79 for lidocaine, n=74 for amiodarone, n=41 for combination). Available data showed no difference in proportion of patients alive 24 hrs post-cardiac arrest (p=.39). Cox regression analysis indicated a decreased likelihood of survival in patients with pulseless ventricular tachycardia/ventricular fibrillation as an initial rhythm as compared with those who presented with bradycardia followed by pulseless ventricular tachycardia/ventricular fibrillation and in those patients who received amiodarone as compared with lidocaine. However, only 14 patients (25%) in the amiodarone group received the recommended initial 300-mg intravenous bolus, and amiodarone was administered an average of 8 mins later in the code compared with lidocaine (p<.001).

CONCLUSIONS

These results generate the hypothesis that inpatients with cardiac arrest may have different benefits from lidocaine and amiodarone than previously demonstrated. Inadequate dosing and later administration of amiodarone in the code were two confounding factors in this study. Prospective studies evaluating these agents are warranted.

The Effect of Induction Method on Defibrillation Threshold and Ventricular Fibrillation Cycle Length

INTRODUCTION

Since no clinical data are available on the comparison of the "shock on T-wave" and "high frequency burst" ventricular fibrillation (VF) induction modes during defibrillation threshold (DFT) testing, we aimed to compare these two methods during implantable cardioverter defibrillator implantation.

METHODS

The DFT was determined with a step-down protocol using biphasic, anodal polarity (100%, 40%, 20% voltage control) shocks. Patients were randomized: VF was induced by 50 Hz burst in group B (n = 45) and T-wave shock in group T (n = 41). The DFT was defined as the lowest energy level that terminated VF; confirmed DFT (DFTc) was defined as the minimal energy level that consecutively terminated VF twice. Success rate of DFTc was calculated during an intraindividual test for the alternate induction method.

RESULTS

A total of 546 episodes of VF were induced: n = 278 (B) vs n = 268 (T). Incidence of VT during inductions was 9.9% (B) vs 2.7% (T), P < 0.05. Neither the DFT, 8.8 +/- 4.0 J (B) vs 9.7 +/- 4.2 J (T), nor the DFTc, 10.6 +/- 5.1 J (B) vs 10.8 +/- 4.2 J (T), proved to be significantly different. A significant correlation was found between VF cycle length (CL) and the concomitant DFT (r = 0.298, P < 0.05) in group T only. Subgroup analysis of patients under chronic class III antiarrhythmic treatment showed no increase of the DFT in either group and significantly lower incidence of VT induction in group T regardless of antiarrhythmic treatment.

CONCLUSION

The DFT and the VFCL proved to be independent of the VF induction method. The T-wave shock was more unlikely to induce VT during DFT testing. These results suggest that both methods are reliable in DFT determination, though T-wave shock application is a more reliable method for DFT testing.

Randomized double-blind trial of sotalol versus lignocaine in out-of-hospital refractory cardiac arrest due to ventricular tachyarrhythmia

AIM

We aimed to compare the efficacy of sotalol versus lignocaine for the treatment of patients with out-of-hospital ventricular fibrillation refractory to > or = 4 defibrillatory shocks.

BACKGROUND

The outcome of patients in ventricular fibrillation refractory to > or = 4 defibrillatory shocks is poor. In a previous randomized trial, sotalol was superior to lignocaine for acute termination of ventricular tachycardia not causing loss of consciousness.

METHODS

Patients of the Ambulance Service of New South Wales treated by paramedics with continued ventricular fibrillation despite standard resuscitation and > or = 4 defibrillatory monophasic shocks were eligible. Drug doses were sotalol 100 mg or lignocaine 100 mg, given as i.v. boluses. A further 2 min of cardiopulmonary resuscitation was given and then defibrillation was repeated twice. If this failed, half the initial dose of the trial drug was repeated and a further > or = 2 shocks were given.

RESULTS

Sixty patients were randomized to sotalol and 69 randomized to lignocaine. There was no significant difference between the two groups in the clinical characteristics of the patients or in the number of shocks received. Outcomes in the sotalol and lignocaine groups were survival to hospital admission in 7 (12%) and 16 (23%), respectively (P = 0.09), and survival to hospital discharge in 2 (3%) and 5 (7%), respectively (P = 0.33).

CONCLUSIONS

Sotalol is not superior to lignocaine for treatment of ventricular fibrillation refractory to multiple shocks. The overall outcome of this group of patients is poor regardless of the pharmacological intervention (lignocaine or sotalol).

Antiarrhythmic drugs in patients with implantable cardioverter-defibrillators

Antiarrhythmic drugs need to be initiated in up to 70% of patients with implantable cardioverter-defibrillators (ICDs) in order to treat atrial tachyarrhythmias, decrease the frequency of defibrillator shocks, and terminate ventricular arrhythmias along with antitachycardia pacing. trial fibrillation (AF) occurs in about 20% of patients with ICDs (the majority with congestive heart failure [CHF]). Antiarrhythmic drugs are initiated for this indication in 2-20% of the ICD population. Data from CHF-STAT (Congestive Heart Failure: Survival Trial of Antiarrhythmic Therapy; amiodarone vs placebo) and DIAMOND-AF (Danish Investigations of Arrhythmia and Mortality ON Dofetilide--rial Fibrillation; dofetilide vs placebo) support the approach that restoration and maintenance of sinus rhythm might be beneficial in CHF, even though no study has specifically addressed the CHF population with ICDs. Further clarification on potential benefits of rhythm control in CHF-associated AF will come from the AF-CHF (Atrial Fibrillation and Congestive Heart Failure) trial that is currently underway. The vast majority of patients with ICDs will have discharges of their devices during follow-up. Although class III antiarrhythmic drugs are widely considered to be effective for prophylaxis against frequent shocks, there are surprisingly few controlled studies that demonstrate this. In contrast to conflicting amiodarone data, sotalol has been found to be effective in preventing shocks from ICDs in prospective, randomized, placebo-controlled studies. A large study (SHIELD; SHock Inhibition Evaluation with azimiLiDe) has shown that azimilide significantly reduces ventricular tachyarrhythmia recurrence, thereby reducing the burden of symptomatic ventricular tachyarrhythmia. Other novel antiarrhythmic drugs, such as dofetilide or dronedarone, as well as different strategies (e.g. in the OPTIC [Optimal Pharmacological Therapy in Implantable Cardioverter] trial; beta-adrenoceptor antagonist therapy alone, amiodarone plus beta-adrenoceptor antagonist therapy, or sotalol alone) for the prevention of ICD shocks are under evaluation. The majority of antiarrhythmic drugs, including sotalol, dofetilide, and azimilide, have no effect on, or are even associated with a decrease in, defibrillation thresholds in humans. Amiodarone, in contrast, has been shown to be related to higher defibrillation thresholds at implant and during follow-up of monophasic devices. Potential cardiac (e.g. ventricular proarrhythmia, negative inotropic effect) and drug-specific non-cardiac adverse effects are a frequent cause for drug discontinuation and need to be considered when initiating and maintaining antiarrhythmic drug therapy. In conclusion, antiarrhythmic drugs are frequently used in ICD patients, the main indications being treatment of atrial tachyarrhythmias and prevention of ICD shocks. Despite potential adverse effects, antiarrhythmics can be administered safely, as long as ICD/drug interactions are appreciated. Controlled studies that will further define the role of concomitant antiarrhythmic drug utilization in patients with ICDs are underway.

Interactions of antiarrhythmic drugs and implantable devices in controlling ventricular tachycardia and fibrillation

Implantable cardioverter defibrillators (ICDs) have proven highly successful in the treatment of life-threatening ventricular arrhythmias. Despite the efficacy of the ICD in terminating ventricular arrhythmias, antiarrhythmic drugs remain an important adjunct to ICD therapy. The use of antiarrhythmic drug therapy in combination with the ICD is synergistic in terms of beneficial effects, but also has the potential for some adverse interactions. Knowledge and recognition of these potential interactions is important for any physician managing patients with an ICD. This review summarizes the benefits and adverse effects of ICD in combination with antiarrhythmic drug therapy, and provides guidelines to ensure safe application of this hybrid therapy.

Electrical storms in an ICD-recipient with 429 delivered appropriate shocks: therapeutic management with antiarrhythmic drug combination

The case of a 65 year old man with ischemic cardiomyopathy, an ICD device and recurrent electrical storms is presented. The patient had been implanted with an ICD device due to aborted sudden death. The first electrical storm occurred 12 months later. It was terminated by the administration of intravenous amiodarone and the patient was discharged on maintenance dose amiodarone and b-blocker. After a period of 3 months during which the patient remained asymptomatic, a second arrhythmic clustering occurred and it was controlled by the addition of mexiletine. A total number of 429 appropriate shocks had been delivered by the device. Thereafter and for a seven month follow-up period, the patient remains asymptomatic under this combination of antiarrhythmic drugs.

Efficacy of amiodarone for the termination of chronic atrial fibrillation and maintenance of normal sinus rhythm: a prospective, multicenter, randomized, controlled, double blind trial

OBJECTIVE

We sought to assess the efficacy and safety of amiodarone for restoration and maintenance of sinus rhythm in patients with chronic atrial fibrillation in a prospective, randomized, double blind trial.

BACKGROUND

Restoration and preservation of sinus rhythm is difficult in patients with chronic atrial fibrillation. The efficacy of oral amiodarone has not been conclusively established.

METHODS

Ninety-five patients with chronic atrial fibrillation, lasting an average of 35.6 months, were randomized to either amiodarone (600 mg/d) (47 patients) or placebo (48 patients) during four weeks. Nonresponders underwent electric cardioversion, and those who reverted continued with amiodarone (200 mg/d) or placebo. End-points were successful cardioversion and sinus rhythm maintenance.

RESULTS

Sixteen patients (34.04%) in the amiodarone group reverted within 27.28 +/- 8.85 days in comparison with 0% in the placebo group (P < 0.000009). The conversion rate rose to 51.72% in patients with chronic atrial fibrillation lasting less than 12 months. Twenty-eight patients in the amiodarone group and 39 in the placebo group underwent electric cardioversion, which was successful in 19 patients (67.8%) of the amiodarone group and in 15 (38.46%) of the placebo group (P = 0.017). Altogether, conversion was obtained in 79.54% of the amiodarone group patients and in 38.46% of the placebo group patients (P < 0.0001). During follow-up, atrial fibrillation relapsed in 13 (37.14%) of 35 patients of the amiodarone group within 8.84 +/- 8.57 months and in 12 (80%; P = 0.009) of 15 patients of the placebo group within 2.74 +/- 3.41 months.

CONCLUSIONS

Oral amiodarone restored sinus rhythm in one third of patients with chronic atrial fibrillation, increased the success rate of electric cardioversion, decreased the number of relapses and delayed their occurrence.

T Wave Alternans for Predicting Adverse Effects of Amiodarone in a Patient With Dilated Cardiomyopathy

An implantable cardioverter defibrillator (ICD) was used in a 62-year-old man with dilated cardiomyopathy (DCM) because of hemodynamically intolerable ventricular tachycardia (VT). Amiodarone was administered after a second episode of ICD discharge. Three weeks later, incessant VT appeared, and DC discharge failed to terminate it. Microvolt T wave alternans (TWA), measured by a spectral method, was observed in this patient with and without amiodarone administration. The onset heart rate with TWA was lower and the alternans voltage was higher with amiodarone than without it. The effects of amiodarone appeared to be related to the exacerbation of VT and an increased defibrillation threshold. TWA might be useful in predicting the proarrhythmic effects of amiodarone in similar cases.

High defibrillation threshold at cardioverter defibrillator implantation under amiodarone treatment: favorable effects of D, L-sotalol

A 57-year-old man with primary dilated cardiomyopathy and obesity received an implantable cardioverter defibrillator because of recurrent, poorly tolerated ventricular tachycardia despite continuous treatment with amiodarone. When the device was implanted, assessment of the ability to defibrillate induced ventricular fibrillation showed high energy requirements, with a lack of conventional safety margin between energies effective at defibrillation testing and maximal device output. Treatment with oral amiodarone was withdrawn and substituted with oral sotalol. A repeat defibrillation test, performed 54 days after amiodarone withdrawal and during D,L -sotalol treatment, showed a reduction in defibrillation energy requirements. In view of this experience, replacement of amiodarone treatment with an alternate class III agent (D,L -sotalol or other agents, if available) can be considered as a possible option in case of high defibrillation threshold at the time of the implantation in a patient receiving continuous amiodarone treatment.

Implantable Cardioverter Defibrillator: Current Progress and Management

With greater technologic advances during the past decade, use of the implantable cardioverter defibrillator (ICD) has increased to more than 200,000 implants worldwide to date. Indications for ICD implant have expanded to include both patients who have survived sudden cardiac death (secondary prevention of cardiac arrest) and those who are at high risk for experiencing lethal arrhythmias (primary prevention of cardiac ar rest). Thus, it is likely that physicians will encounter defibrillators in their clinical practice and must be familiar with their indications for implant, basic opera tion, and long-term management of devices. Several prospective clinical trials have recently shown the long- term efficacy of ICD therapy at aborting sudden death in the high-risk patient population. Although still evolving, general guidelines and indications for ICD implant have been put forth and are discussed in this review. From the first defibrillation in humans during surgery in 1947 to the sophisticated dual-chamber pacing and memory functions of the modern device, ICD development has led to ever smaller devices with more complex technol ogy. The implant procedure of current ICDs parallels that used to place pacemakers. However, the anesthe sia team plays a vital role in initial ICD implantation by monitoring cardiopulmonary status during defibrilla tion threshold (DFT) testing. Additionally, long-term management of ICDs often requires repeat DFT testing with anesthesia involvement. Finally, possible electro magnetic (environmental) interactions with the ICD of which physicians should be aware are described in this article.

Effect of chronic amiodarone therapy on defibrillation energy requirements in humans

INTRODUCTION

The effect of oral amiodarone therapy on defibrillation energy requirements in patients with an implantable defibrillator has not been established.

METHODS AND RESULTS

Twenty-one consecutive patients with implantable biphasic waveform defibrillators underwent a step-down determination of the defibrillation energy requirement 211 +/- 12 days before and 73 +/- 22 days after initiation of amiodarone therapy (mean total dose 26.7 +/- 11.1 g). Serum amiodarone and desethylamiodarone concentrations were measured at the time of defibrillation energy requirement determination. The mean defibrillation energy requirement before amiodarone therapy was 9.9 +/- 4.6 J. After initiation of amiodarone therapy, the mean defibrillation energy requirement increased to 13.7 +/- 5.6 J (P = 0.004). A linear relationship between the amiodarone (P = 0.02, r = 0.6), desethylamiodarone (P = 0.02, r = 0.6), and combined amiodarone-desethylamiodarone concentrations (P = 0.01, r = 0.6) and the defibrillation energy requirement was noted. Stepwise regression analysis demonstrated that the combined amiodarone-desethylamiodarone concentration was the only independent predictor of increase in the defibrillation energy requirement.

CONCLUSION

Chronic oral amiodarone therapy increases the defibrillation energy requirement by approximately 62% in patients with an implantable defibrillator. The combined amiodarone-desethylamiodarone concentration is directly related to the increase in the defibrillation energy requirement.

Hybrid therapy for ventricular arrhythmia management

Optimum arrhythmia management has evolved to couple ICD therapy with catheter ablative and drug therapy to attempt to eliminate or reduce arrhythmia risk. No longer should the clinician approach such therapy as a choice among single alternative strategies only. Optimum patient management includes not only recognition of the indications and benefits of such hybrid therapy but also a complete understanding of potential pitfalls of such therapy.

Intravenous sotalol decreases transthoracic cardioversion energy requirement for chronic atrial fibrillation in humans: assessment of the electrophysiological effects by biatrial basket electrodes

OBJECTIVES

This study was undertaken to assess the effects of sotalol on the transthoracic cardioversion energy requirement for chronic atrial fibrillation (AF) and on the atrial electrograms during AF recorded by two basket electrodes.

BACKGROUND

The effects of sotalol infusion on transthoracic electrical cardioversion for chronic atrial fibrillation in humans have not been well investigated.

METHODS

We included 18 patients with persistent AF for more than three months. Atrial electrograms were recorded by two basket electrodes positioned in each atrium respectively. Transthoracic cardioversion was performed before and after sotalol 1.5 mg/kg i.v. infusion.

RESULTS

In the 14 patients whose AF could be terminated by cardioversion before sotalol infusion, the atrial defibrillation energy was significantly reduced after sotalol infusion (236 +/- 74 jules [J] vs. 186 +/- 77 J; p < 0.01). Atrial fibrillation was refractory to cardioversion in four patients at baseline and was converted to sinus rhythm by cardioversion after sotalol infusion in two of them. We further divided the patients into two groups. Group A consisted of 10 patients in whom the energy requirement was decreased by sotalol while group B consisted of eight patients in whom the energy requirement was not decreased. The mean A-A (atrial local electrogram) intervals during AF were significantly increased after sotalol infusion in both groups, but the increment of A-A interval was significantly larger in group A than it was in group B patients (36 +/- 13 ms vs. 22 +/- 8 ms for the right atrium; 19 +/- 7 ms vs. 9 +/- 7 ms for the left atrium; both p < 0.05). The spatial and temporal dispersions of A-A intervals were not significantly changed after sotalol infusion in both atria in both groups.

CONCLUSIONS

Sotalol decreases the atrial defibrillation energy requirement by increasing atrial refractoriness but not by decreasing the dispersion of refractoriness.

Combining antiarrhythmic drugs and implantable devices therapy: benefits and outcome

At least 50% of patients who received an ICD have been treated with antiarrhythmic drugs (AAD). The potential indications for combining antiarrhythmic drugs and ICD are generally the following: reduction of the number of episodes of ventricular tachycardia or ventricular fibrillation and therefore of the number of shocks, improving patient's quality of life and extending the battery life of the ICD, prevention of supraventricular arrhythmias and/or control of their rate, lengthening of the tachycardia cycle length to allow ventricular tachycardia conversion by antitachycardia pacing and reduction of the number of episodes of syncope. Although previous papers reported conflicting results about pharmacologic therapy in reducing the frequency of iCD shocks, some recent randomized prospective studies showed the efficacy of pharmacologic therapy in reducing the frequency of ICD shocks. The use of antiarrhythmic drugs can have also adverse effect: an increase in the defibrillation threshold, an increase in the pacing threshold and an increase in the VT cycle length leading to detection failure. We have also to consider that some advantages derived from antiarrhythmic drugs can be reached by the new devices with atrial sensing and pacing and/or the possibility of atrial defibrillation or by using catheter ablation as adjunctive therapy to ICD. For these reasons, the concomitant use of antiarrhythmic drugs and ICD should be evaluated in each patient in relation to specific clinical and electrophysiologic features including: the frequency, the rate and the clinical presentation of the ventricular arrhythmia, the effect of the selected drug on the defibrillation threshold, the defibrillation threshold at the implant, the effect of the selected drug on the ventricular function and the likelihood of proarrhythmic events.

Multicenter evaluation of implantable cardioverter defibrillator testing after implant: the Post Implant Testing Study (PITS)

To reassess the function of the implantable cardioverter defibrillator (ICD) many electrophysiology centers perform a second test after the initial test at implant. A prospective multicenter study evaluated the necessity and yield of routine postimplant defibrillator testing. The results of 843 postimplant defibrillator tests were collected from 31 centers. The 764 routine tests in which ventricular fibrillation was successfully induced were analyzed. Variables examined included patient age, presenting arrhythmia, underlying heart disease, left ventricular ejection fraction, defibrillator age, make and model of ICD, electrode system, defibrillation threshold, polarity, and waveform. The overall failure rate was 3.1% (24/764). Units tested later than 365 days after implant tended to have a higher failure rate than those tested within the first month or the next eleven months (6.5%, 3.0%, 2.3%, respectively, P = 0.374). The failure rate was higher in patients with left ventricular ejection fraction < 40% than those with higher ejection fractions (3.8% vs 2.0%, P = 0.167). These trends did not reach statistical significance. No other baseline characteristic was associated with higher failure rates. Routine testing of ICDs reveals an overall failure rate of 3.1%. While the rate was low, defibrillator failure places the patient at high risk for sudden cardiac death. As any failure in this population is associated with a high risk of sudden cardiac death, routine defibrillator testing may be justified.