Long‐Term Outcomes of Inducible Very Fast Ventricular Tachycardia (Cycle Length 200–250 ms) in Patients With Ischemic Cardiomyopathy

Very Fast Ventricular Tachycardia. Background: The long‐term outcomes of patients with inducible very fast ventricular tachycardia (VFVT) of cycle length (CL) 200 to 250 ms have not been well studied. Methods: Consecutive patients with ischemic cardiomyopathy with a left ventricular ejection fraction (LVEF) of ≤40% (n = 300) underwent programmed ventricular stimulation (PVS) and were divided into 4 groups based on results of the study. Group A were noninducible, had induced ventricular fibrillation (VF), or polymorphic VT (CL < 200 ms); group B had inducible VFVT (200–250 ms); group C had inducible fast ventricular tachycardia (FVT; CL 251–320 ms); and group D had inducible slow VT (CL >320 ms). The primary endpoint was spontaneous ventricular arrhythmia or sudden death. Results: The mean age was 63 ± 12 years and mean LVEF was 29 ± 7%. At mean follow‐up of 38 ± 25 months (median 30 months), the primary endpoint rate was 6.6%, 34%, 44%, and 71% in groups A, B C, and D, respectively (P < 0.001). Neither mode of induction of VT nor LVEF altered the observed pattern in the primary endpoint. There was no significant difference in the primary endpoint among implanted cardioverter defibrillator recipients in groups B and C (38% vs 45%, P = 0.43). Adjusted hazard ratios for the primary endpoint compared to group A were 3.2, 3.5, and 7.0 in groups B, C, and D, respectively (P < 0.05). Conclusions: Inducible VFVT (200–250 ms) is a clinically significant arrhythmia with adverse long‐term outcomes and should not be considered a nonspecific finding of PVS. (J Cardiovasc Electrophysiol, Vol. 21, pp. 262–269, March 2010)     

Implantable Cardioverter‐Defibrillator in Patients With Hypertrophic Cardiomyopathy: Efficacy and Complications of the Therapy in Long‐Term Follow‐up

ICD in Hypertrophic Cardiomyopathy Patients. Introduction: Although implantable cardioverter‐defibrillators (ICDs) are used in sudden cardiac death (SCD) prevention in high‐risk patients with hypertrophic cardiomyopathy (HCM), long‐term results as well as precise risk stratification are discussed in a limited number of reports. The aim of the study was to assess the incidence of ICD intervention in HCM patients with relation to clinical risk profile. Methods and Results: We studied 104 consecutive patients with HCM implanted in a single center. The mean age of study population was 35.6 (SD, 16.2) years with the average follow‐up of 4.6 (SD, 2.6) years. ICD was implanted for secondary (n = 26) and primary (n = 78) prevention of SCD. In the secondary prevention group, 14 patients (53.8%) experienced at least 1 appropriate device intervention (7.9%/year). In the primary prevention (PP) group appropriate ICD discharges occurred in 13 patients (16.7%) and intervention rate was 4.0%/year. Nonsustained VT was the only predictive risk factor (RF) for an appropriate ICD intervention in the PP (positive predictive value 22%, negative predictive value 96%). No significant difference was observed in the incidence of appropriate ICD discharges between PP patients with 1, 2, or more RF. Complications of the treatment included: inappropriate shocks (33.7%), lead dysfunction (12.5%), and infections: 4.8% of patients. Four patients died during follow‐up. Conclusion: ICD therapy is effective in SCD prevention in patients with HCM, although the complication rate is significant. Nonsustained ventricular tachycardia seems to be the most predictive RF for appropriate device discharges. Number of RF did not impact the incidence of appropriate ICD interventions. (J Cardiovasc Electrophysiol, Vol. 21, pp. 883‐889, August 2010)     

Long‐term follow‐up of adult patients with congenital heart disease and an implantable cardioverter defibrillator

Objective: Sudden cardiac death is common in the adult congenital heart disease (ACHD) population. Knowledge and experience about the use of implantable cardio‐ verter defibrillators (ICD) in ACHD patients is very limited. We aimed to characterize a cohort of patients with ACHD and ICDs.
Design: Thirty consecutive ACHD patients submitted to an ICD implantation in a single tertiary center were evaluated. Data on baseline clinical features, heart defect, indication for ICD, type of device, appropriate therapies, ICD‐related complication, and mortality during follow‐up were collected.
Results: Of the 30 patients, 56.7% received appropriate therapies due to ventricular tachycardia (VT) or ventricular fibrillation (VF). The rate of inappropriate therapies and device‐related complications was 33.3%. Secondary prevention and primary pre‐ vention patients with class I indications for ICD had more appropriate therapies than complication, but this relationship was reversed for patients with class II indications. Remote monitoring played an important role in diagnosing new atrial arrhythmias be‐ fore scheduled visits in 46.2% of patients, leading to a change in medication. VT/VF episodes were associated with a composite of death, cardiac transplantation, and hos‐ pital admission (OR 13.0; 95% CI: 2.1‐81.5).
Conclusion: ICDs are not only useful in preventing SCD, but also have a major role in diagnosing atrial tachyarrhythmias ahead of scheduled visits. Although improve‐ ments in ICD technology might reduce complications and inappropriate therapies, adequate selection of candidates for primary prevention still remains difficult be‐ cause of the lack of clear indications.     

Programming Antitachycardia Pacing for Primary Prevention in Patients With Implantable Cardioverter Defibrillators: Results From the PROVE Trial

Programming ATP for ICD Patients. Objectives: The PROVE trial was designed to determine if antitachycardia pacing (ATP) is clinically beneficial for primary prevention in patients who have implantable cardioverter defibrillators (ICDs) or cardiac resynchronization therapy defibrillators (CRT‐Ds). Background: Use of ICDs and CRT‐Ds reduces mortality in patients with ventricular dysfunction and mild to moderate heart failure. However, in studies of the primary prevention population, shock‐only ICDs are predominantly used, without ATP programming for less painful termination of ventricular tachycardia (VT). Methods: We conducted a prospective, nonrandomized, multicenter study using market‐released ICDs and CRT‐Ds. Patients received devices programmed to deliver ATP for VT cycle lengths of 270–330 ms. Follow‐up evaluation was performed at 3, 6, and 12 months. The incidence of VT and the rate of successful termination by ATP were analyzed. Results: Of 830 patients in the study population (men, 73%; mean age, 67.3 ± 12 years), 32% received single‐chamber ICDs, 44% dual‐chamber ICDs, and 24% CRT‐Ds. ATP was attempted for 112 VT episodes in 71 patients, and 103 (92%) of the VT episodes were successfully terminated. Three VT episodes were accelerated by ATP and required termination by ICD shock; 6 episodes terminated spontaneously or by ICD shock. Conclusions: VT is common in patients without a history of this arrhythmia who have received ICDs or CRT‐Ds for primary prevention indications. Programming ICDs for ATP therapy at the time of implantation could potentially terminate most VT episodes and reduce the number of painful shocks for these patients. (J Cardiovasc Electrophysiol, Vol. 21, pp. 1349‐1354, December 2010)     

Feasibility of Defibrillation and Automatic Arrhythmia Detection Using an Exclusively Subcutaneous Defibrillator System in Canines

Subcutaneous Defibrillation in Canines. Introduction: This study reports the experimental process leading to development of an automatic totally subcutaneous implantable cardioverter defibrillator (SICD) system engineered for human use. Methods and Results: Two studies were conducted to test defibrillation and detection feasibility of an SICD system located in the left chest. In the first study, 2 pockets were created in 15 canines for placement of an anterior electrode adjacent to the left edge of the sternum and a lateral electrode at the site along the axillary line between the 4th and 6th intercostal space. Stainless steel flat electrodes with active surface areas of 5, 10, 20, and 25 cm² or rod electrodes were subsequently positioned and the defibrillation threshold (DFT) was measured for multiple combinations. In the second study, the ability to induce, detect, and provide shock delivery in response to ventricular fibrillation (VF) using an SICD system engineered for clinical use was tested in 5 canines. One hundred and three DFT tests with 11 different dual electrode combinations were performed. All combinations terminated VF with a DFT of 35 ± 16 J (range: 9–79 J). Nineteen VF episodes were induced and recognized by the chronic SICD, leading to automatic capacitor charge and shock delivery in all cases. Conclusions: Subcutaneous defibrillation using different electrode combinations with shock energies less than 80 J terminated all induced VFs. An automatic SICD proved effective in detecting and activating shock delivery in all cases. (J Cardiovasc Electrophysiol, Vol. 24, pp. 77‐82, January 2013)     

Effect of elapsed time from coronary revascularization to implantation of a cardioverter defibrillator on long-term survival in the MADIT-II trial

Coronary Revascularization and Long‐Term Mortality in MADIT‐II. Introduction: Coronary revascularization (CR) may reduce arrhythmia risk and improve long‐term outcome in patients with left ventricular dysfunction. This study was designed to evaluate the effect of elapsed time from CR on long‐term mortality and arrhythmic risk among patients who receive an implantable cardioverter defibrillator (ICD). Methods and Results: We evaluated the risk of 8‐year mortality by elapsed time from CR to ICD implantation (categorized as: no CR; recent CR [<2 years]; or nonrecent CR [≥2 years], and assessed as a continuous measure) among 720 ICD recipients enrolled in the Multicenter Automatic Defibrillator Trial‐II. At 8years of follow‐up, patients who did not undergo CR and those who underwent nonrecent CR had significantly higher mortality rates than patients who underwent recent CR (54%, 54%, and 36%, respectively; P < 0.001). Multivariate analysis demonstrated that no‐ and nonrecent CR were associated with respective 48% (P = 0.022) and 67% (P < 0.001) increases in mortality risk compared with recent CR. Assessment of time from CR as a continuous measure showed that every year elapsed from CR was associated with an adjusted 6% increase in 8‐year mortality (P < 0.001), and in respective 6% (P < 0.001) and 6% (P = 0.003) increased risk for in‐trial appropriate ICD therapy of ventricular tachyarrhythmias and appropriate ICD shocks. Conclusions: We observed a direct relationship between elapsed time from CR and long‐term mortality following ICD implantation. The favorable long‐term effect on outcome of recent CR may be related to a time‐dependent effect of CR on ventricular arrhythmic burden and the need for appropriate ICD shocks. (J Cardiovasc Electrophysiol, Vol. pp. 1‐6)     

Description and Evaluation of the Res-QTM Arrhythmia Control Device

The Res-Q^TM Arrhythmia Control Device. The Res-Q^TM Arrhythmia Control Device (Intermedics Inc.) is one of the latest entries into the growing implantable cardioverter defibrillator (ICD) market. Dysrhythmias are classified according to their zone of detection, with a bradycardia zone, up to 3 tachycardia zones, and a fibrillation zone. Detection criterion, therapies, and redetection criterion within each zone are independently programmable, tailoring the setup to each individual's needs. In a hierarchical manner, this allows efficacy, urgency, and patient comfort to be appropriately balanced. Tachycardia therapy options include antitachycardia pacing (ATP), low-energy cardioversion, and high-energy shock, while VVI pacing provides bradycardia therapy. ATP programming is extremely flexible. Biphasic waveform and a maximum output of 700 V have yielded a high rate of successful implantation. Unique features include the multiprogrammable sensing autogain, which tracks evoked T waves during pacing, as well as the use of the pulse generator to perform implant testing. Major strengths include programming flexibility and individualized therapy for multiple dysrhythmias. The major shortcoming relates to a lack of stored electrograms. Although long-term follow-up is not yet available, the Res-Q^TM appears to be a capable challenger to a peer group of advanced generation ICDs.     

Atrial fibrillation in patients with a dual defibrillator: characteristics of spontaneous and induced episodes and effect of ventricular tachyarrhythmia induction

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