Antitachycardia pacing for spontaneous rapid ventricular tachycardia in patients with prophylactic cardioverter-defibrillator therapy

AIMS: Antitachycardia pacing (ATP) has not routinely been used in patients who received implantable cardioverter defibrillators (ICDs) for primary prevention of sudden death. This study investigated the efficacy of empirical ATP to terminate rapid ventricular tachycardia (VT) in heart failure patients with prophylactic ICD therapy. METHODS AND RESULTS: Ninety-three patients with a mean left ventricular ejection fraction of 22 +/- 7% (range: 9-35%) due to nonischemic or ischemic cardiomyopathy received prophylactic ICDs with empiric ATP. At least 2 ATP sequences with 6-pulse burst pacing trains at 81% of VT cycle length (CL) were programmed in one or two VT zones for CL below 335 +/- 23 ms and above 253 +/- 18 ms. Ventricular flutter and fibrillation (VF) with CL below 253 +/- 18 ms were treated in a separate VF zone with ICD shocks without preceding ATP attempts. During 38 +/- 27 months follow-up, 339 spontaneous ventricular tachyarrhythmias occurred in 36 of 93 study patients (39%). A total of 232 VT episodes, mean CL 293 +/- 22 ms, triggered ATP in 25 of 36 patients with ICD interventions (69%). ATP terminated 199 of 232 VT episodes (86%) with a mean CL of 294 +/- 23 ms in 23 of 25 patients (88%) who received ATP therapy. ATP failed to terminate or accelerated 33 of 232 VT episodes (14%) with a mean CL of 287 +/- 19 ms in 12 of 25 patients (48%) who received ATP therapy. CONCLUSIONS: Painfree termination of rapid VT with empirical ATP is common in heart failure patients with prophylactic ICD therapy. The occasional inability of empiric ATP to terminate rapid VT in almost 50% of patients who receive ATP for rapid VT warrants restrictive ICD programming with regard to the number of ATP attempts in order to avoid syncope before VT termination occurs.     

Delayed detection of ventricular tachycardia in a dual chamber rate adaptive pacing implantable cardioverter defibrillator: a case of intradevice interaction

Ventricular tachycardia detection is delayed due to concomitant programming of rate adaptive dual chamber pacing. Underlying timing cycle constraints as well as programming precautions and pitfalls are reviewed.     

Radiofrequency ablation of fast ventricular tachycardia causing an ICD storm in an infant with hypertrophic cardiomyopathy

An implantable cardioverter defibrillator (ICD) storm involves very frequent arrhythmia episodes and ICD shocks, and it is associated with poor short‐term and long‐term prognosis. Radiofrequency catheter ablation can be used as an effective rescue treatment for patients with an ICD storm. To our knowledge, this is the first report of an infant with hypertrophic cardiomyopathy presenting with an ICD storm and undergoing successful radiofrequency catheter ablation salvage treatment for the fast left posterior fascicular ventricular tachycardia.     

Inactivation of a ventricular tachycardia preventive algorithm during automatic mode switching for atrial tachyarrhythmia

A patient with a dual chamber implantable defibrillator and pause dependent VT in whom a rate smoothing algorithm failed to operate during automatic mode switching due to device idiosyncrasy is reported. Preventive measures are discussed.     

Inappropriate pacing due to autoperpetuation of the ventricular rate stabilization algorithm: a manifestation of T wave oversensing by ICDs

Preventive pacing algorithms designed to eliminate the pause that follows a premature ventricular depolarization have been incorporated in current implantable defibrillators. We report a patient in whom intermittent T wave oversensing frequently invoked the ventricular rate stabilization algorithm and resulted in periods of inappropriate VVI pacing. The problem was solved by decreasing the maximum sensitivity from 0.3 mV to 0.45 mV. Implant testing had revealed adequate sensing of ventricular fibrillation with a maximum sensitivity of 1.2 mV.     

Importance of initiation pattern of polymorphic ventricular tachycardia in patients with implantable cardioverter defibrillators

BACKGROUND: Stored intracardiac electrograms (ICEGs) are helpful in understanding the initiation mechanisms of sustained ventricular arrhythmias and in determining the appropriateness of the therapy delivered by implantable cardioverter defibrillators (ICDs). AIM: We investigated the initiation pattern of sustained polymorphic ventricular tachycardia (PVT) and the features of the therapy delivered by ICDs. METHODS: Sixty-six patients (mean age of 67 +/- 8 years) with 97 stored ICEGs showing PVT were evaluated. Cardiovascular diagnosis included coronary artery disease in 72.7% of the patients. The average left ventricular ejection fraction was 33+/-6%. RESULTS: Nonsudden onset episodes were more common than sudden onset episodes (63 episodes, 65% vs 34 episodes, 35%, P < 0.001). More PVT episodes were required multiple shock delivery if they had nonsudden onset initiation (28.6% vs 23.6%, P < 0.01). The mean shock energy delivered for arrhythmia termination was higher in PVT with nonsudden onset (20 +/- 4 vs 14 +/- 5 J, P < 0.01). CONCLUSIONS: The stored ICEGs demonstrate that PVT is most often preceded by ventricular ectopy. To be reverted, nonsudden onset episodes require higher levels of shock energy and more frequently multiple shock achievements than sudden onset episodes.     

Inappropriate tachycardia detection by a biventricular implantable cardioverter defibrillator

This case describes "double counting" of intrinsic conduction due to the combination of intraventricular conduction delay and the merging of the electrograms from the right and left ventricle (coronary sinus) leads in a biventricular cardioverter defibrillator. This situation prompted asymptomatic antitachycardia pacing. Lengthening of AV conduction by betablocker solved the problem.     

His-Purkinje System Reentry As a Pro arrhythmic Effect of Flecainide

We report a case of tachycardia due to reentry within the His-Purkinje system (HPS) occurring after introduction of flecainide. The patient presented with a mild mitral regurgitation and normal left ventricular function. He had incomplete left bundle branch block with left-axis deviation. At the electrophysiology study, a prolonged HV interval was observed at baseline, and the tachycardia could be reproduced after ajmaline infusion. Six months after interruption of flecainide, the patient remains free of arrhythmia recurrence. The authors emphasize that proarrhythmic effects of flecainide may include reentry within the HPS in patients with underlying HPS disease.     

Bundle brunch reentrant ventricular tachycardia with two distinct conduction patterns in a patient with complete right bundle branch block

We report a rare case of bundle branch reentrant ventricular tachycardia [BBRVT]. A 67-year-old female was admitted for management of wide QRS tachycardia (right bundle branch block [RBBB] and a southwest axis). The mapping procedure revealed the tachycardia circuit consisted of the left anterior fascicle (LAF) as an antegrade, and the right bundle as a retrograde pathway. She presented RBBB during sinus rhythm. LAF ablation changed the tachycardia configuration to a northwest axis and prolonged the cycle length. Left posterior fascicle ablation terminated the tachycardia, and complete atrioventricular block occurred, which showed the unidirectional conduction over the right bundle.     

Discriminatory therapy for very fast ventricular tachycardia in patients with implantable cardioverter defibrillators

Objectives: We assessed the efficacy of antitachycardia pacing (ATP) and low-energy (5J) shock for very fast ventricular tachycardia (VFVT), cycle length 200–250 ms, in patients with implantable cardioverter defibrillators (ICDs).
Methods and Results: One hundred and fifty-two consecutive patients with standard indications for ICD therapy were enrolled. Before discharge from the hospital each patient had an electrophysiological study (EPS) performed through the device, to assess the efficacy of ATP and low-joule shock at terminating VFVT. Initial therapy for VFVT consisted of three bursts of ATP followed by low-energy shock, and high-energy shocks as required. The mean age of enrolled patients was 63 ± 13 years, and the mean left ventricular ejection fraction (LVEF) was 31 ± 13%. During the predischarge EPS, a total of 125 VT episodes were induced in 64 patients. In patients with VFVT, the success rate of ATP was 30% (14/46), the acceleration rate was 26% (12/46), and the success rate of low-energy shock was 86% (25/29). In patients with fast ventricular tachycardia (FVT), cycle lengths 251–320 ms, the success rate of ATP was 62% (24/39), the acceleration rate was 18% (7/39), and the success rate of low-energy shock was 94% (17/18).
Conclusions: This study has demonstrated for the first time that ATP and low-energy shock are effective, as an alternative to high-energy shock, to revert induced VFVT. Low-energy shock has a very high success rate for VT slower than VFVT. Clinical studies are required prior to consideration for empiric programming.     

Safety and efficacy of a dual chamber implantable cardioverter defibrillator capable of slow ventricular tachycardia discrimination: a randomized study

New developments in dual chamber implantable cardioverter defibrillators (ICD) have increased the specificity of therapy delivery. This study was performed to examine the performance of an algorithm, focusing on its ability to distinguish slow ventricular tachycardia (VT) from sinus rhythm or supraventricular tachyarrhythmias. The patient population included 77 men and 13 women, 63 +/- 11 years old, treated with ICDs after episodes of spontaneous or inducible ventricular tachyarrhythmias. They were randomized to programming of the ICD to a lower limit of VT detection at 128 beats/min (group I, n = 44), versus 153 beats/min II (group II, n = 46). The primary endpoint of the study consisted of comparing the specificity and sensitivity of the algorithm between the two groups of patients. Over a 10.1 +/- 3.5 months follow-up, 325 episodes were detected in the Tachy zone in group I, versus 106 in group II. The sensitivity and specificity of the algorithm in group I were 98.8% and 94.4%, respectively, versus 100% and 89% in group II (NS). A single episode of VT at a rate of 132 beats/min was diagnosed as SVT in group I. The sensitivity and specificity of the algorithm for tachycardias <153 beats/min were 97.4% and 94.5%, respectively. Overall VT therapy efficacy was 100% in both groups. The performance of this algorithm in the slow VT zone supports the programming of a long Tachy detection interval to document slow events, and allows to treat slow VT, if necessary, without significant risk of inappropriate interventions for sinus tachycardia.     

Spontaneous polymorphic ventricular tachycardia after administration of pilsicainide in a patient resuscitated from ventricular fibrillation

We performed a pilsicainide challenge test in a 38-year-old man who was resuscitated from ventricular fibrillation without apparent baseline electrocardiogram (ECG) abnormality. His father had a history of ventricular fibrillation and his brother had multiple episodes of syncope. Pilsicainide (1 mg/kg) induced short coupled ventricular premature beats followed by repetitive polymorphic ventricular tachycardia without apparent J wave and ST elevation, and excessive changes in QRS duration and QT interval. An implantable cardioverter defibrillator was implanted.     

Termination of ventricular tachycardia by far-field stimulation in humans: a feasibility study

Background: Although a low‐energy cardioversion (LEC) shock from an implantable cardioverter‐defibrillator (ICD) can terminate ventricular tachycardia (VT), it frequently triggers ventricular fibrillation (VF) and is therefore not used in clinical practice. We tested whether a modified LEC shock with a very short duration (0.12–0.36 ms), termed “field stimulus,” can terminate VT without triggering VF. Methods: In 13 sedated patients with implanted ICDs, we attempted to induce VT and to terminate the arrhythmias by field stimuli during hospital predischarge tests. Results: In eight patients, 27 VT episodes were induced and treated with a total of 46 high‐voltage (25–200 V) field stimuli, which terminated 11 VT episodes (41% efficacy) and never accelerated VT into VF. VT episodes slower than 230 beats per minute (bpm) (median rate) were terminated more successfully than faster arrhythmia episodes (69% vs 15%, P < 0.01). The strength of the field stimulus had no major influence on the effectiveness. We therefore postulate that suboptimal timing of field stimuli (delivered simultaneously with a sensed event in the right ventricular apex) was the main reason for failed VT terminations. Conclusion: A short (0.12–0.36 ms), high‐voltage (50–100 V) field stimulus delivered from the shock coil of an implanted ICD system can safely terminate VT, especially for VT rates below 230 bpm. We believe that it would be reasonable to test the effectiveness of automatic field‐stimulus therapy from implanted ICDs in VT episodes up to 230 bpm that are not susceptible to termination by antitachycardia pacing. (PACE 2010; 33:1540–1547)     

Alleviation of central sleep apnea by ventricular pacing in a patient with an implanted cardioverter defibrillator

A 75-year-old man with a single chamber cardioverter defibrillator implanted for the management of sustained ventricular tachycardia developing after a healed myocardial infarction was admitted for evaluation of a sleep disorder. Polysomnography confirmed the presence of severe predominant central sleep apnea syndrome. The apnea-hypopnea index score decreased from 43.3 during spontaneous cardiac rhythm to 24.6 during VVI pacing at a rate of 70 beats/min. Ventricular pacing reduced the number of episodes of central sleep apnea/hypopnea without reducing the total sleep time, though it had no effect on episodes of obstructive sleep apnea/hypopnea.     

Antitachycardia pacing for rapid VT during ICD charging: a method to prevent ICD shocks

In patients with ICDs, rapid VTs are usually treated with shocks. It is unknown, if antitachycardia pacing (ATP) delivered once for rapid VT during capacitor charging can avoid painful shocks without increasing the risk of syncope. In patients in whom rapid monomorphic VT (cycle length 300-220 ms) could be reproducibly induced during predischarge ICD testing, the success of cardioversion (defibrillation threshold plus 10 J) and a single ATP attempt (burst with 8 or 16 stimuli) was compared using a randomized crossover study design. Consciousness of the patients was checked by the signal from a button constantly pushed by the patient. In 20 patients (ejection fraction 0.50 +/- 0.19) rapid VTs (253 +/- 26 ms) were reproducibly induced. A single burst successfully terminated 11 (55%) of 20 rapid VTs, 6 episodes could not be terminated with a single burst pacing and 3 VTs accelerated. Rapid VTs not terminated by ATP were significantly faster than those that could be terminated (246 vs 258 ms, P = 0.026). Cardioversion (19 +/- 3 J) terminated the VTs in all cases. No patient suffered syncope during rapid VTs. A single ATP may terminate rapid VT with cycle lengths < 300 ms in 55% of patients without increasing the risk of syncope. Therefore, in rapid VTs one attempt of ATP may be suitable as an additional therapy option during ICD capacitor charging to avoid painful shocks without compromise of safety. Thus, future ICDs should implement the option of ATP during charging of capacitors.     

Implantation of an epicardial dual chamber ICD following unsuccessful percutaneous extraction of a failed ventricular shocking electrode

This report describes the case of a 22-year-old patient presenting with ICD electrode failure where attempted percutaneous electrode extraction was unsuccessful. In view of the patient's young age, an operative approach was considered most appropriate. The failed electrode was surgically extracted and a new epicardial pacing/defibrillator system inserted.