The subcutaneous implantable cardioverter-defibrillator: Current trends in clinical practice between guidelines and technology progress

The subcutaneous implantable cardioverter defibrillator (S-ICD) is a valuable alternative to the conventional trans-venous ICD (TV-ICD) for the prevention of sudden cardiac death (SCD). Prospective registries showed that the S-ICD is safe and effective in treating ventricular tachyarrhythmias in high-risk patients without pacing indications. While in earlier studies patients implanted with S-ICDs were young and mostly affected by channelopathies, contemporary S-ICD cohorts include patients with severely impaired left ventricular function and significant comorbidities. This review focuses on S-ICD evidence-based use and highlights current gaps between guidelines recommendations and real-world clinical practice.     

Subcutaneous implantable defibrillator: State-of-the art 2013

The subcutaneous implantable cardioverter-defibrillator(S-ICD)has recently been approved for commercial use in Europe,New Zealand and the United States.It is comprised of a pulse generator,placed subcutaneously in a left lateral position,and a parasternal subcutaneous lead-electrode with two sensing electrodes separated by a shocking coil.Being an entirely subcutaneous system it avoids important periprocedural and long-term complications associated with transvenous implantable cardioverter-defibrillator(TV-ICD)systems as well as the need for fluoroscopy during implant surgery.Suitable candidates include pediatric patients with congenital heart disease that limits intracavitary lead placements,those with obstructed venous access,chronic indwelling catheters or high infection risk,as well as young patients with electrical heart disease(e.g.,Brugada Syndrome,long QT syndrome,and hypertrophic cardiomyopathy).Nevertheless,given the absence of intracavitary leads,the S-ICD is unable to offer pacing(apart from shortterm post-shock pacing).It is therefore not suitable in patients with an indication for antibradycardia pacing or cardiac resynchronization therapy,or with a history of repetitive monomorphic ventricular tachycardia that would benefit from antitachycardia pacing.Current data from initial clinical studies and post-commercialization"real-life"case series,including over 700 patients,have so far been promising and shown that the S-ICD successfully converts induced and spontaneous ventricular tachycardia/ventricular fibrillation episodes with associated complication and inappropriate shock rates similar to that of TV-ICDs.Furthermore,by using far-field electrograms better tachyarrhythmia discrimination when compared to TV-ICDs has been reported.Future results from ongoing clinical studies will determine the S-ICD system’s long-term performance,and better define suitable patient profiles.     

The subcutaneous implantable cardioverter defibrillator in 2019 and beyond

The completely subcutaneous implantable cardioverter defibrillator (S-ICD) is rapidly evolving to become a complete alternative for the transvenous ICD (TV-ICD) leaving the heart and vasculature untouched. Newer trials and registries in cohorts that are similar to real-world ICD patient populations confirm the initial data on safety and efficacy. Technical improvements have resulted in reduced inappropriate shock rates, although more data are warranted, and new developments such as substernal lead positioning, communication between the S-ICD and a leadless cardiac pacemaker and remote monitoring options have evolved to overcome the shortcomings of S-ICD therapy. With these continuing developments, it is expected that within the next years the S-ICD will continue to evolve to a treatment option for ventricular arrhythmia as effective as the TV-ICD overcoming the shortcomings of transvenous leads as well as the drawbacks of the initial system, providing effective shock therapy, pacing capabilities, low complication and inappropriate therapy rates, and automated remote monitoring.     

Estudo Comparativo entre Receptores de Desfibriladores Subcutâneos e Transvenosos em Relação à Tolerância ao Procedimento de Implante e Percepção da Qualidade de Vida

BackgroundThe totally subcutaneous implantable cardioverter-defibrillator (S-ICD) is a safe alternative to the conventional transvenous ICD (TV-ICD) system to prevent sudden death.ObjectiveTo compare the impact of the type of ICD system and surgical technique on patients’ quality of life, as well as the severity of discomfort and pain, between S-ICD and TV-ICD recipients.MethodsConsecutively implanted patients with an S-ICD system were matched with patients with a TV-ICD system. In addition, patients undergoing S-ICD implantation after removal of a TV-ICD due to complications were included. Quality of life (measured with the 12-item short-form health survey) and severity of pain and discomfort were evaluated. Statistical significance was defined as p < 0.05.ResultsA total of 64 patients implanted with S-ICD or TV-ICD under local anesthesia and conscious sedation were analyzed. Patients with S-ICD and TV-ICD systems did not differ significantly in quality of life scores. S-ICD patients had a higher level of perioperative pain; no differences were found regarding severity of intraoperative pain. The magnitude of aesthetic discomfort and sleep disturbances did not differ between groups. An S-ICD was implanted in 7 additional patients after removal of a TV-ICD. All but one of these patients recommended the S-ICD system.ConclusionsThe type of ICD system and the surgical technique have negligible impact on patients’ quality of life. These results suggest that conscious sedation, provided by an experienced electrophysiology team, could be considered as an alternative to general anesthesia to manage patients undergoing S-ICD implantation.     

The Potential Impact of Intrathoracic Impedance on Defibrillation Threshold Testing in S-ICDs

A man with an ischemic cardiomyopathy and chronic obstructive pulmonary disease underwent subcutaneous implantable cardioverter-defibrillator (S-ICD) placement under general anesthesia. Following induction of ventricular fibrillation (VF), defibrillation testing (65J) failed, requiring external rescue. Repeat shock testing with reversed polarity (65J) failed. A third shock and external defibrillation failed (80J and 200J), followed by a second external defibrillation (200J), which did not immediately terminate VF, and a device shock 2 seconds later (80J, successful). Repeat shock testing (80J) under conscious sedation without mechanical ventilation was successful. We discuss this case of failed defibrillation testing during S-ICD placement, potentially due to lung hyperinflation, requiring double sequential defibrillation.     

An Overview of Clinical Outcomes in Transvenous and Subcutaneous ICD Patients

Purpose of Review

Clear guidelines on when to select a subcutaneous ICD (S-ICD) over a transvenous ICD (TV-ICD) are lacking. This review will provide an overview of the most recent clinical data on S-ICD and TV-ICD therapy by pooling comparison studies in order to aid clinical decision making.

Recent Findings

Pooling of observational-matched studies demonstrated an incidence rate ratio (IRR) for device-related complication of 0.90 (95% CI 0.58–1.42) and IRR for lead-related complications of 0.15 (95% CI 0.06–0.39) in favor of S-ICD. The IRR for device infections was 2.00 (95% CI 0.95–4.22) in favor of TV-ICD. Both appropriate shocks (IRR 0.67 (95% CI 0.42–1.06)) and inappropriate shocks (IRR 1.17 (95% CI 0.77–1.79)) did not differ significantly between both groups.

Summary

With randomized data underway, the observational data demonstrate that the S-ICD is associated with reduced lead complications, but this has not yet resulted in a significant reduction in total number of complications compared to TV-ICDs. New technologies are expected to make the S-ICD a more attractive alternative.

     

The 18 cases report of Efficicacy of implantable cardioverter-defibrillator

Objectives Toimplante cardioverter-defibrillator (ICD) in the patients who had life-threantening tachyarrhythmias and with indications of implantation,then analyse and investgate the efficacy ofimplantable ICD to the patients who had life-threantening tachyarrhythmias.Methods From October 2005 to January 2009,our department treated 18 cases that patients had life-threantening tachyarrhythmias.11 cases of Ischemic cardiomyopathy in,7 cases of dilated cardiomyopathy, age from 40-76 years,mean age is(55.77±15.16) years,16 male patients,2 female patients.Etiological diagnosis: CT examination by the coronary angiography or gated cardiovascular,11 cases of clearly ischemic cardiomyopathy, 7 cases of dilated cardiomyopathy.among them there are 3 cases to be implanted ICD After 2 weeks of cardio-pulmonary resuscitation.The others who had life-threantening tachyarrhythmias have history of unexplained syncope or not.Among them,4 received single chamber ICD therapy,5.received dual chambers and9 received cardiac resynchronization therapy-defibrillators.Results All patients were successfully implanted.Operative time was 1.5-5 hours,X-ray exposure time for 19 -62min.shock impedance、pacemaker threshold and R/A amplitude was satisfied.3 patients were induced Ventricular tachycardia(VF) by T-shock,and were converted by 10-20 J shock.During Follow-up of 2-43 months,no death occurred and ICD function was improved.On opration, At the same time use cardoarone,there were total 8 episodes of ventricular tachycardia/ventricular fibrillation(VT/VF) happened in 5 patients,they were terminated by shocks once,2 patient with single chamber ICD were misdiagnosed? atrial fibrillation as a ventricular fibrillation then lead to wrong treatment.We started the stability and the width of two diagnostic functions,follow-up observation of six months,no more misdiagnosis and wrong treatment happened again.9 cases of patients occurred supraventricular tachycardia in observation period and transferred by antitachycardia pacing (ATP).The 9 patients w     

Clinical and electrophysiologic predictors of ventricular tachyarrhythmia recurrence in patients with implantable cardioverter defibrillators

INTRODUCTION: Not all patients experience recurrent sustained ventricular tachyarrhythmias after placement of an implantable cardioverter defibrillator (ICD). We evaluated the clinical and electrophysiologic predictors of ventricular tachycardia (VT) and ventricular fibrillation (VF) recurrence following ICD implantation. METHODS AND RESULTS: Consecutive patients (n = 133) underwent 4 +/- 3 serial electrophysiologic studies (EPS) over 50 +/- 26 months following ICD implantation. Sustained VT/VF could always be induced during follow-up EPS in 49 patients; sustained VT/VF was sometimes induced during follow-up EPS in 47 patients; and sustained VT/VF could never be induced during follow-up EPS in 37 patients. Spontaneous VT/VF requiring ICD therapy occurred in 107 patients during follow-up. Patients with sustained VT/VF that was always inducible or sometimes inducible during follow-up experienced more frequent episodes of VT/VF following ICD implant (20.5, 95% CI 12.7-33.0; and 17.8, 95% CI 11.3-28.1 episodes/patient respectively; vs 3.0, 95% CI 2.0-4.6 episodes/patient for patients with VT/VF never induced, P < 0.001). Inducibility of sustained VT/VF post-ICD implant (P < 0.001) and sustained VT as the presenting arrhythmia (P = 0.02) were independent predictors of spontaneous VT/VF recurrence. CONCLUSION: Reproducibly inducible VT/VF following ICD implantation predicts a high probability of VT/VF recurrence and identifies a cohort of patients who experience frequent episodes of VT/VF over time. Persistent noninducibility of sustained VT/VF identifies a group of patients who experience no or very few episodes of VT/VF recurrence.     

Early Experience with the Subcutaneous ICD

The Subcutaneous Internal Cardiac Defibrillator (S-ICD) represents a major advance in the care of patients who have an indication for an internal cardiac defibrillator without pacing indications. Its main advantage is that it can deliver a shock to cardiovert ventricular arrhythmias utilising a tunnelled subcutaneous lead, negating the risks associated with conventional transvenous systems. Initial studies have shown comparable efficacy in cardioversion of induced and spontaneous ventricular tachycardia (VT) and ventricular fibrillation (VF) when compared to conventional transvenous systems. In addition, inappropriate shocks occurred in a similar percentage of patients to conventional ICD studies. Complication rates are low and relate largely to localised wound infections, treated successfully with antibiotics. The long term efficacy of the device is yet to be ascertained, however, a randomised trial & prospective registries are currently in progress to enable direct comparison with transvenous ICDs. This article summarises the early clinical experience and trials in the implantation of the S-ICD.     

Comparing the safety of subcutaneous versus transvenous ICDs: a meta-analysis

Purpose

The use of transvenous implantable cardioverter defibrillators (TV-ICDs) is associated with multiple risks related to the presence of the defibrillator leads within the venous system and right side of the heart, including endocarditis, venous occlusion, tricuspid regurgitation, and potential lead failure. The emergence of subcutaneous ICDs (S-ICDs) may potentially overcome the aforementioned disadvantages. However, evidence validating the safety of S-ICDs relative to TV-ICDs is limited. The present study aimed to synthesize and analyze available data from published studies to comprehensively compare transvenous and subcutaneous ICDs.

Methods

Different databases were searched for full-text publications with a direct comparison of TV- and S-ICDs. Fixed effect models were applied to pooled data, and no study-to-study heterogeneity was detected.

Results

Data from 7 studies totaling 1666 patients were pooled together. Compared to S-ICDs, the risk of suffering device-related complications was higher in patients with TV-ICDs (OR = 1.71; 95% CI: 1.23–2.38). The number of patients with an S-ICD who suffered inappropriate shocks (IS) was not significantly different than patients with a TV-ICD (OR = 0.92; 95% CI: 0.65–1.30). Subgroup analysis indicated that the TV-ICD group had a higher risk of IS due to supraventricular oversensing (OR = 3.29; 95% CI: 1.92–5.63) while T-wave oversensing tending to cause IS in the S-ICD group (OR = 0.09; 95% CI: 0.03–0.23). The risk of device-related infection in the S-ICD group was not any lower than that in the TV-ICD group (OR = 1.57; 95% CI: 0.67–3.68). The survival rate without any complications during a 1-year follow-up period was similar between the 2 groups (HR = 1.23; 95% CI: 0.81–1.86), although it was assumed that the trend leaned toward more complications in patients with a TV-ICD.

Conclusion

The present study verified the safety of S-ICDs based on pooled data. Although there were no differences between TV- and S-ICDs in the short term, fewer adverse events were found in patients with S-ICDs during long-term follow-up.

     

Voltage gradients in transvenous and subcutaneous defibrillation and their risk of myocardial damage

Introduction

Transvenous implantable cardioverter-defibrillator (ICD) shocks have been associated with cardiac biomarker elevations and are thought in some cases to contribute to adverse clinical outcomes and mortality, possibly from myocardium exposed to excessive shock voltage gradients. Currently, there are only limited data for comparison with subcutaneous ICDs. We sought to compare ventricular myocardium voltage gradients resulting from transvenous (TV) and subcutaneous defibrillator (S-ICD) shocks to assess their risk of myocardial damage.

Methods

A finite element model was derived from thoracic magnetic resonance imaging (MRI). Voltage gradients were modeled for an S-ICD with a left-sided parasternal coil and a left-sided TV-ICD with a mid-cavity, a septal right ventricle (RV) coil, or a dual coil lead (TV mid, TV septal, TV septal + superior vena cava [SVC]). High gradients were defined as > 100 V/cm.

Results

The volumes of ventricular myocardium with high gradients > 100 V/cm were 0.02, 2.4, 7.7, and 0 cc for TV mid, TV septal, TV septal + SVC, and S-ICD, respectively.

Conclusion

Our models suggest that S-ICD shocks produce more uniform gradients in the myocardium, with less exposure to potentially damaging electrical fields, compared to TV-ICDs. Dual coil TV leads yield higher gradients, as does closer proximity of the shock coil to the myocardium.     

Reperfusion ventricular tachyarrhythmias: Correlation with antecedent coronary artery occlusion tachyarrhythmias and duration of myocardial ischemia

The incidence and severity of reperfusion ventricular tachyarrhythmias were correlated with: (1) the duration of antecedent acute coronary artery occlusion and (2) the incidence, severity, and time course of ventricular tachyarrhythmias occurring during the antecedent period of coronary occlusion in 98 dogs studied postligation for 5 to 60 minutes. The incidence of reperfusion ventricular fibrillation (VF) increased significantly as coronary artery ligation periods were lengthened from 5 minutes to either 20 minutes (2 of 19 dogs vs 12 of 18 dogs,p < 0.001) or 30 minutes (16 of 24,p < 0.001), but notably decreased when reperfusion was delayed further from 30 minutes to 60 minutes after coronary artery ligation (4 of 18 dogs,p < 0.001). Seven dogs were resuscitated from VF during coronary ligation and all seven suffered VF on reperfusion, whereas 37 dogs were arrhythmia-free during ligation and only one (3%,p < 0.001) had VF on reperfusion, in addition, reperfusion ventricular tachyarrhythmias correlated with the occurrence of both immediate ventricular tachyarrhythmias (those peaking at 5 to 6 minutes postligation) and delayed ventricular tachyarrhythmias (those peaking at 18 minutes' postligation) of the antecedent acute ligation period. These observations provide a further basis for improved clinical understanding and management of potentially malignant tachyarrhythmias consequent to early myocardial reperfusion following acute myocardial ischemia and infarction.     

Postextrasystolic U Wave Augmentation, a New Marker of Increased Arrhythmic Risk in Patients Without the Long QT Syndrome

Objectives. We attempted to determine the correlation between the presence of postextrasystolic changes in the STU segment and a history of sustained ventricular arrhythmias.

Background. Postextrasystolic U wave augmentation (a marked increment in U wave amplitude after premature ventricular complexes [PVCs]) is an adverse prognostic sign in the “pause-dependent long QT syndrome.” However, the prevalence of postextrasystolic changes in patients without the long QT syndrome is unknown.

Methods. We compared the configuration of the STU segment of the postextrasystolic beat (the sinus beat after a PVC) with the STU configuration during sinus rhythm in three patient groups: 1) 41 patients with spontaneous ventricular tachycardia/fibrillation (VT/VF) (VT/VF group), 2) 63 patients with heart disease and high grade ventricular arrhythmias (control group), and 3) 29 patients with high grade ventricular arrhythmias but no heart disease (reference group).

Results. Postextrasystolic T wave changes did not correlate with a history of ventricular tachyarrhythmias. However, postextrasystolic U wave changes were more common among the patients with VT/VF than among control subjects (39% vs. 8.7%, p < 0.001). By logistic multiple regression analysis, a low left ventricular ejection fraction (p < 0.001) and postextrasystolic U wave changes (p < 0.005) were independent predictors of ventricular tachyarrhythmias.

Conclusions. Postextrasystolic T wave changes are common and lack predictive value. Postextrasystolic U wave changes may be a specific marker of a tendency to the development of spontaneous ventricular arrhythmias. Prospective studies should be performed to confirm this association.

(J Am Coll Cardiol 1996;28:1746–52)>     

Facilitation of ventricular tachyarrhythmia induction by isoproterenol

Ventricular tachyarrhythmia induction was facilitated during infusion of isoproterenol in 21 of 60 patients with ventricular tachycardia (VT) or ventricular fibrillation (VF) in whom programmed electrical stimulation alone failed to reproducibly induce sustained ventricular tachyarrhythmias. Of 44 patients with no ventricular tachyarrhythmias induced before isoproterenol infusion, 11 had a sustained ventricular tachyarrhythmia and 1 patient had unsustained VT induced by isoproterenol alone or by programmed stimulation during the infusion. In 9 of 16 patients in whom nonreproducible or unsustained ventricular tachyarrhythmias were induced before isoproterenol infusion, more reproducible or more sustained ventricular tachyarrhythmias were induced during the infusion. Tachyarrhythmia induction was facilitated by isoproterenol in 20 of 40 patients with sustained VT clinically, but in only 1 of 20 patients with unsustained VT or VF clinically. Among patients with sustained VT clinically, those with exercise-provoked VT and those who had not been tested with stimulation at a second right ventricular site or in the left ventricle were more likely to have induction facilitated by isoproterenol. Drugs effective against induction of isoproterenol-facilitated ventricular tachyarrhythmias were identified in 13 of 25 trials. These drugs were effective during a mean follow-up of 17 months in 7 of 9 long-term trials.     

Spontaneous sustained ventricular tachyarrhythmias during treatment with type IA antiarrhythmic agents

Twenty-six patients who developed their first clinical episode of sustained ventricular tachycardia (VT) or ventricular fibrillation (VF) while taking type IA antiarrhythmic agents for more benign rhythm disturbances were rechallenged with the identical drug during electrophysiologic testing. Patients with these new drug-associated spontaneous ventricular arrhythmias often manifested a preexisting substrate for such arrhythmias: sustained VT or VF was induced in 65% of patients at baseline, and in 58% of patients when tested with their previously taken antiarrhythmic drug. Among those without inducible sustained ventricular arrhythmias in the drug-free state, 78% remained free of inducible sustained arrhythmias when tested with the same drug they had been taking at the time of the clinical arrhythmia. Even patients without a definable electrophysiologic substrate for sustained VT or VF remained at risk for arrhythmia recurrence if treated with alternative antiarrhythmic medications: 40% of such patients who continued to receive an antiarrhythmic agent different from that being administered when their clinical VT or VF occurred had recurrent spontaneous ventricular tachyarrhythmias during follow-up. Thus, patients with drug-associated clinical sustained ventricular tachycardias form a heterogenous group that should be evaluated individually and not empirically managed for a "proarrhythmic effect" simply by antiarrhythmic drug withdrawal or drug substitution.     

Idiopathic ventricular fibrillation

A review of the literature dealing with sudden death revealed 19 articles in which ostensibly healthy patients with documented VF unrelated to any known cardiac or noncardiac etiology are reported. Fifty-four patients fulfilling the criteria for idiopathic VF, including 14 patients investigated at our institution, are described. The mean age of patients for studies that reported age data was 36 years, with a male-to-female ratio of 2.5 to 1. Over 90% of the patients required resuscitation, while syncope due to nonsustained VF occurred in the rest. Diagnosis of VF was preceded by syncope in one fourth of the patients. Holter monitoring and exercise stress tests were often unrewarding. Available electrophysiologic data revealed a 69% inducibility rate of sustained ventricular tachyarrhythmias using nonaggressive protocols of ventricular stimulation in most cases. Induced tachyarrhythmias were poorly tolerated, and were mostly of polymorphic configuration. Class IA antiarrhythmic agents were highly effective in preventing reinduction of these arrhythmias. Available figures suggest an 11% rate of sudden death within 1 year of diagnosis. Appropriate antiarrhythmic therapy appears to improve prognosis. Reviewed data suggest that idiopathic VF represents an underestimated cause of sudden cardiac death in ostensibly healthy patients. An international registry of patients with idiopathic VF is warranted.     

Antiarrhythmia effectiveness of oral sotalol in patients with coronary heart disease and ventricular tachycardias

In order to assess whether Sotalol is an effective drug in patients (pts) with life-threatening ventricular tachyarrhythmias, programmed ventricular stimulation (PVS) was performed in 30 pts with recurrent ventricular tachycardia (VT) or ventricular fibrillation (VF) after myocardial infarction. Prior to Sotalol, pts were treated with a mean of 3.1 +/- 1.2 antiarrhythmic class I drugs. None of these drugs prevented VT or VF. During the control study, sustained VT was induced in 15 pts (50.0%), non-sustained VT in 8 pts (26.7%) and VF in 7 pts (23.3%). Treatment with Sotalol 240-320 mg/day was started and after 3.1 +/- 1.1 weeks PVS was repeated. In none of the pts could VF be induced; sustained VT and non-sustained VT were still inducible in 4 pts (13.3%) and in 6 pts (20.0%) respectively. In 20 pts (66.7%) either no or only a short ventricular response was inducible. Our data show that Sotalol appears to be an effective antiarrhythmic agent in pts with life-threatening ventricular tachyarrhythmias.     

Correlation of Acute and Chronic Defibrillation Threshold with Upper Limit of Vulnerability Determined in Normal Sinus Rhythm

Background: The upper limit of vulnerability (ULV) is the stimulus strength above which ventricular fibrillation cannot be induced, even when the stimulus occurs during the vulnerable period of the cardiac cycle. Determination of ULV using T-wave shocks during ventricular pacing has been shown to closely correlate with the defibrillation threshold (DFT) at ICD implantation. However, there are no data correlating ULV determined in sinus rhythm at ICD implantation, with DFT determined at implantation or during long-term follow-up. This is of clinical importance since ULV may be used to estimate DFT during ICD implantation, both during ventricular pacing or sinus rhythm.Methods and Results: Twenty-one patients receiving a transvenous ICD system were studied prospectively. There were 16 males and 5 females, mean age 68 ± 15 years, with mean ejection fraction 37.4 ± 17.4%. All had structural heart disease. The ULV was defined as the lowest energy that did not induce ventricular fibrillation with shocks at 0, 20 and 40ms before the peak of the T-wave, using a step-down protocol. The initial energy tested was 15J and the lowest energy 2J. DFT was determined following a similar step-down protocol. The DFT was defined as the lowest energy that successfully defibrillated the ventricles. The linear correlation coefficient between ULV and DFT was r = 0.73 (p < 0.001). At implant, mean ULV was 9.2 ± 5J, not statistically different from mean DFT 9.4 ± 4J. ULV plus 5J successfully defibrillated 19 of 21 patients. During long-term follow-up of 10.1 ± 1.8 months in eight patients, DFT was 8.8 ± 5.8J, not significantly different than the DFT of 7.5 ± 4.1J or ULV of 8.0 ± 5.3 at implant.Conclusion: 1) When determined during normal sinus rhythm the ULV significantly correlates with DFT. 2) ULV testing might be used in lieu of standard DFT testing to confirm adequate lead placement thus minimizing or eliminating VF inductions, particularly in hemodynamically unstable patients. 3) Since ULV + 5J has a high probability of successful defibrillation in most patients, programming ICD first shock energy for VF at ULV + 5J may result in lower first shock energies compared to the standard methods of programming first shock energy at twice DFT.Condensed Abstract. The purpose of this study was to determine if the upper limit of vulnerability (ULV) determined during normal sinus rhythm correlates with the defibrillation threshold (DFT), as has been previously shown when determined during ventricular pacing. The linear correlation coefficient between the ULV and DFT was r = 0.73 (p < 0.001). Mean ULV at implant was 9.2 ± 5J, not statistically different from mean DFT of 0.4 ± 4J. During long-term follow-up of 10.1 ± 1.8 months in 8 patients, DFT was 8.75 ± 8J, not significantly different than the DFT of 7.5 ± 4.1J or ULV of 8.0 ± 5.3 at implant. Shocks energies of ULV + 5J successfully defibrillated 19 of 21 patients at implant and 8 of 8 at follow-up. This study indicates that the ULV determined in normal sinus rhythm closely correlates with the DFT, and that ULV + 5J defibrillated most patients. ULV testing could be used to predict DFT and reduce or eliminate the need for DFT testing and VF induction. Programming ICD first shock energy for VF to ULV + 5J will result in lower energy than that used with standard DFT testing.     

Long-term reproducibility of electrophysiologically guided therapy with sotalol in patients with ventricular tachyarrhythmias

OBJECTIVES

Goal of this study was to assess the long-term reproducibility of electrophysiologic drug testing in patients with ventricular tachyarrhythmias (VT/VF).

BACKGROUND

Programmed ventricular stimulation (PVS) is still widely used to guide antiarrhythmic therapy in patients with sustained ventricular tachycardia/fibrillation (VT/VF). Sotalol is considered as one of the most effective drugs for VT/VF. Because there is no proof of long-term reproducibility of a successful drug test with sotalol, we investigated the long-term reproducibility of drug testing with sotalol.

METHODS

Thirty patients with VT/VF (age: 57 ± 11 years, 20 patients with coronary heart disease, 7 patients with no structural heart disease, 3 with others) and reproducible induction of VT/VF (28 patients VT, two patients VF) in a baseline PVS, were suppressible with sotalol (mean dosage 395 ± 137 mg) in a subsequent PVS. After a mean follow-up of 13 ± 10 months a PVS was again performed in patients, who had no evidence of progressive cardiac disease, who did not experience any arrhythmia recurrences or who were drug compliant. Irrespective of the inducibility after long-term therapy with sotalol, all patients were kept on the initial sotalol regimen. All 30 patients had a stable cardiac condition, were free of VT/VF recurrences and were drug compliant.

RESULTS

Despite the clinical efficacy of sotalol, in 12 patients (40%) VT/VF could again be induced after 13 ± 10.2 months. Inducibility was independent of age, heart disease, ejection fraction and follow-up time. During a further follow-up of 22.1 ± 10.9 months, five patients experienced nonfatal VT recurrences independently of the prior inducibility.

CONCLUSIONS

This study shows a lacking long-term reproducibility of an initial effective PVS with sotalol. Despite an uneventful clinical follow-up, late electrophysiologic testing showed a VT/VF inducibility in a high portion of patients. Hence, electrophysiologic testing performed late after the initial drug test may no longer be predictive of outcome.     

Ventricular tachycardia rate and morphology determine energy and current requirements for transthoracic cardioversion.

BACKGROUND. The electrical current and energy required to terminate ventricular tachyarrhythmias are known to vary by arrhythmia: Ventricular tachycardia (VT) is generally considered to require less energy than ventricular fibrillation (VF). The hypothesis of our study was that current requirements for transthoracic termination of VT are further determined by VT rate and QRS complex morphology. METHODS AND RESULTS. We prospectively studied 203 patients who received a total of 569 shocks for VT or VF by following a current-based protocol. This protocol recommended shocks for VT beginning at 18 A (70 +/- 22 J) and shocks for VF beginning at 25 or 30 A (137 +/- 52 J or 221 +/- 70 J). The ventricular tachyarrhythmias were subclassified as monomorphic VT (MVT): uniform QRS complex morphology on surface electrocardiogram and heart rate greater than 100 beats per minute; polymorphic VT (PVT): nonuniform QRS complex morphology and heart rate less than or equal to 300 beats per minute; or VF: nonuniform QRS complex morphology and heart rate greater than 300 beats per minute. We found that shocks of 18 A and 25 A for terminating MVT had success rates of 69% and 82%, respectively, whereas such low-current shocks were less successful for PVT (33% at 18 A) and for VF (19% at 18 A, 53% at 25 A). High-current shocks of 35 A and 40 A were equally successful for the three ventricular tachyarrhythmias. Subdividing MVT revealed that slower MVT (heart rate less than 200 beats per minute) had a significantly better success rate with low-current shocks of 18 A and 25 A than did faster MVT (greater than 200 beats per minute) (89% versus 72% success, p less than 0.01). Bundle branch block morphology, QRS axis, and duration of ventricular tachyarrhythmia did not alter current requirements. CONCLUSIONS. Heart rate and electrocardiographic degree of organization of ventricular tachycardia are important determinants of transthoracic energy and current requirements for cardioversion and defibrillation. Transthoracic termination of MVT requires relatively low current or energy, but PVT behaves more like VF and requires higher electrical current or energy.