Significance of Supraventricular Tachyarrhythmias in Patients with Implanted Pacing Cardioverter Defibrillators

Eighty-six patients were treated with an implantable cardioverter defibrillator (ICD) because of sustained ventricalar tachycardia (VT) or ventricular fibrillation (VF). In 27 patients an epicardial system was used, in 59 patients a transvenous system with a subcutaneous patch electrode was implanted. During a mean follow-up time of 17 ± 9 months, inappropriate activations of the ICD due to supraventricular tachycardia were documented by Holter monitoring in 14 patients (16%). In 8 patients paroxysmal atrial fibrillation (AF), in 2 patients chronic AF, in 1 patient atrial flutter, and in 3 patients sinus tachycardia triggered antitachycardia pacing functions (12 patients) or internal defibrillation (2 patients). In 3 patients (5%) VT was induced by inappropriate antitachycardia pacing. In an additional 18 patients (21%) inappropriate activation of antitachycardia functions due to atrial tachyarrhythmias were suspected based on telemetry readouts or the patient's history. Inappropriate activation of ICD therapy triggered by intermittent supraventricular tachyarrhythmias is common. Further improvements of detection algorithms for supraventricular tachycardia are required in future device generations.     

New ICD-Technologies: First Clinical Experience with Dual-Chamber Sensing for Differentiation of Supraventricular Tachyarrhythmias

Inappropriate ICD therapy for supraventricular arrhythmias remains an unsolved problem and may lead to serious clinical situations. Current algorithms for differentiation of supraventricular and ventricular arrhythmias are based on ventricular sensing solely and, therefore, lack semitivity and specificity. This preliminary analysis from a multicenter trial comprises data from the first 26 patients who received a Res-Q? Micron active-can ICD (Stdzer Intermedics) with a ventricular defibrillation lead and an additional bipolar lead for atrial sensing. Digitized atrial and ventricular waveform storage as well as interval charts from 102 induced and 30 spontaneous arrhythmia episodes were prospectively collected and analyzed with regard to appropriateness of ICD therapy. From all 132 arrhythmia episodes, high-quality stored dual-chamber intracardiac electrograms (JFXJM) could be retrieved for further analysis: in 40 (30%) episodes, atrial fibrillation (AF with rapid ventricular response 22, AF with VT9, AF with VF 9) was identified as the underlying intrinsic rhythm, and inappropriate ICD therapy was delivered in 4/22 (18%) episodes of AF with rapid ventricular response. In the remaining 92 (70%) episodes, sinus rhythm was the underlying atrial rhythm (SR with VT 13, SR with VF 79), and no inappropriate therapy was observed. Three of 22 (15%) high-energy shocks delivered for ventricular arrhythmias (VT 9, VF 9, rapid AF 4) terminated AF at the same time. In total, there were 3 complications (2 atrial lead dislodgments, I revision for bleeding). Both atrial lead dislodgments occurred in the 2 patients with passive-fixation leads compared to none in the 24 patients with active-fixation leads (p - 0.003). In conclusion, dual-chamber sensing and waveform storage of the new Res-Q? Micron offer very helpful diagnostic tools for the detection of inappropriate ICD-therapy. Placement of an additional atrial lead is safe and does not interfere with proper ICD function. However, for avoidance of atrial lead dislodgment, active fixation leads are recommended With the tested active-can lead configuration, the efficacy of successful atrial cardioversion by high-energy shocks delivered for ventricular arrhythmias seems to be low.     

Characteristics and relevance of clustering ventricular arrhythmias in defibrillator recipients

INTRODUCTION: Studies of recurrent ventricular tachycardia and ventricular fibrillation (VT/VF) have been limited to "electrical storms," where recurrent arrhythmias necessitate repeated external cardioversions or defibrillations. Patients with an implantable cardioverter-defibrillator (ICD) may also suffer frequently recurrent arrhythmias. The aim of this study was to analyze the temporal pattern and the clinical relevance of clustering ventricular arrhythmias in ICD recipients. METHODS: The incidence and the type of arrhythmias were determined by reviewing stored electrograms. VT/VF clusters were defined as the occurrence of three or more adequate and successful ICD interventions within 2 weeks. Two hundred and fourteen consecutive ICD recipients were followed during an average of 3.3 +/- 2.2 years (698 patient-years). RESULTS: Fifty-one patients (24%) suffered 98 VT/VF clusters 21 +/- 22 months after ICD implantation, 93% of these clusters consisting of recurrent regular VT. Monomorphic VT as index event leading to ICD implantation was the only factor predicting VT/VF clusters. Kaplan-Meier estimates of the combined end-point of death or heart transplantation showed a 5-year event-free survival of 67% versus 87% in patients with and without clusters, respectively (P = 0.026). Adjusted hazard ratios for death or heart transplantation in the group with arrhythmia clusters was 3.5 (95% confidence interval 1.5-7.9 P = 0.003). CONCLUSIONS: VT/VF clusters are frequent late after ICD implantation particularly in patients who had VT as index-event. As arrhythmias and recurrent ICD interventions are responsible for an important morbidity, there is a possible role for a prophylactic intervention. Furthermore, VT/VF clusters are an independent marker of increased risk of death or need for heart transplantation.     

Ventricular Arrhythmia Inducibility Predicts Subsequent ICD Activation in Nonischemic Cardiomyopathy Patients: A DEFINITE Substudy

Objectives: We evaluated whether electrophysiologic (EP) inducibility predicts the subsequent occurrence of spontaneous ventricular tachycardia (VT) or ventricular fibrillation (VF) in the Defibrillators in Nonischemic Cardiomyopathy Treatment Evaluation (DEFINITE) trial.
Background: Inducibility of ventricular arrhythmias has been widely used as a risk marker to select implantable cardioverter defibrillator (ICD) candidates, but is believed not to be predictive in nonischemic cardiomyopathy patients.
Methods: In DEFINITE, patients randomized to the ICD arm, but not the conventional arm, underwent noninvasive EP testing via the ICD shortly after ICD implantation using up to three extrastimuli at three cycle lengths plus burst pacing. Inducibility was defined as monomorphic or polymorphic VT or VF lasting 15 seconds. Patients were followed for a median of 29 ± 14 months (interquartile range = 2–41). An independent committee, blinded to inducibility status, characterized the rhythm triggering ICD shocks.
Results: Inducibility, found in 29 of 204 patients (VT in 13, VF in 16), was associated with diabetes (41.4% vs 20.6%, P = 0.014) and a slightly higher ejection fraction (23.2 ± 5.9 vs 20.5 ± 5.7, P = 0.021). In follow-up, 34.5% of the inducible group (10 of 29) experienced ICD therapy for VT or VF or arrhythmic death versus 12.0% (21 of 175) noninducible patients (hazard ratio = 2.60, P = 0.014).
Conclusions: In DEFINITE patients, inducibility of either VT or VF was associated with an increased likelihood of subsequent ICD therapy for VT or VF, and should be one factor considered in risk stratifying nonischemic cardiomyopathy patients.     

An adaptive interval-based algorithm for withholding ICD therapy during sinus tachycardia

Avoiding inappropriate ICD therapy during supraventricular tachycardia (SVT) while assuring 100% sensitivity for VT/VF remains a challenge. Inappropriate VT/VF therapy during sinus tachycardia (ST) is particularly distressing to the patient because the full sequence of ICD therapies is often delivered. ST or 1:1 atrial tachycardia (AT) with long PR intervals and ST or AT with atrial oversensing of far-field R waves cause the majority of inappropriate therapy in the Medtronic GEM DR (Model 7271) ICD. The goals of the present effort were to define an adaptive interval-based algorithm for withholding VT/VF therapy in dual chamber ICDs during ST and to compare performance of the adaptive algorithm with that of the original ST withholding algorithm in the GEM DR. The adaptive algorithm uses a combination of 1:1 atrial to ventricular conduction pattern, changes in RR intervals and changes in intrinsic PR intervals to establish evidence for or against the presence of ST. Performances of the adaptive and original ST withholding algorithms were compared on 3 databases collected by implanted GEM DR devices. The first database included 684 spontaneous VT/VF episodes. The second database included 216 spontaneous SVT episodes that received inappropriate VT/VF therapy. These databases included up to 2,000 atrial or ventricular sensed or paced events preceding the spontaneous tachycardias. The third database included 320 spontaneous ST/AT episodes for which therapy was appropriately withheld by the GEM DR. Performance of the adaptive algorithm on the third database was predicted rather than directly computed because of record length limitations. VT/VF therapy was classified as "withheld" if evidence of ST remained high for one algorithm (i.e., at least 7 more beats to VT/VF detection) at the point of VT/VF detection by the other algorithm. For the 684 true VT/VF episodes, the original algorithm withheld VT/VF therapy in 5 episodes and the adaptive algorithm withheld VT/VF therapy in 3 episodes. The 95% confidence interval for the difference in VT/VF sensitivity between the adaptive and original algorithms was [-0.5 to + 1.1%]. Twelve of the 320 ST/AT episodes (3.8%) that were appropriately classified by the original algorithm were predicted to receive inappropriate therapy by the adaptive algorithm. However, relative to the original algorithm, the adaptive algorithm appropriately withheld VT/VF therapy for 76 of 216 true SVT episodes (i.e., incremental specificity of 35.2%). For the specific SVT episodes that were the targets for improvement by the adaptive ST algorithm (ST/AT with long PR intervals and ST/AT with intermittent atrial oversensing of far-field R waves), the adaptive algorithm reduced inappropriate therapy by 63.2%.     

A prospective randomized-controlled trial of ventricular fibrillation detection time in a DDDR ventricular defibrillator. Ventak AV II DR Study Investigators

Implantable cardioverter defibrillators (ICDs) with dual chamber and dual chamber rate responsive pacing may offer hemodynamic advantages for some ICD patients. Separate ICDs and DDDR pacemakers can result in device to device interactions, inappropriate shocks, and underdetection of ventricular fibrillation (VF). The objectives of this study were to compare the VF detection times between the Ventak AV II DR and the Ventak AV during high rate DDDR and DDD pacing and to test the safety of dynamic ventricular refractory period shortening. Patients receiving an ICD were randomized in a paired comparison to pacing at 150 beats/min (DDD pacing) or 175 beats/min (DDDR pacing) during ICD threshold testing to create a "worst case scenario" for VF detection. The VF detection rate was set to 180 beats/min, and VF was induced during high rate pacing with alternating current. The device was then allowed to detect and treat VF. The induction was repeated for each patient at each programmed setting so that all patients were tested at both programmed settings. Paired analysis was performed. Patient characteristics were a mean age of 69 +/- 11 years, 78% were men, coronary artery disease was present in 85%, and a mean left ventricular ejection fraction of 0.34 +/- 0.11. Fifty-two episodes of VF were induced in 26 patients. Despite the high pacing rate, all VF episodes were appropriately detected. The mean VF detection time was 2.4 +/- 1.0 seconds during DDD pacing and 2.9 +/- 1.9 seconds during DDDR pacing (P = NS). DDD and DDDR programming resulted in appropriate detection of all episodes of VF with similar detection times despite the "worst case scenario" tested. Delays in detection may be seen with long programmed ventricular refractory periods which shorten the VF sensing window and may be avoided with dynamic ventricular refractory period shortening.     

Enhanced specificity of a dual chamber ICD arrhythmia detection algorithm by rate stability criteria

Inappropriate therapy remains an important limitation of implantable cardioverter defibrillators (ICD). PARAD+ was developed to increase the specificity conferred by the original PARAD detection algorithm in the detection of atrial fibrillation (AF). To compare the performances of the two different algorithms, we retrospectively analyzed all spontaneous and sustained episodes of AF and ventricular tachycardia (VT) documented by state-of-the-art ICDs programmed with PARAD or PARAD+ at the physicians' discretion. The results were stratified according to tachycardia rates <150 versus > or =150 beats/min. The study included 329 men and 48 women (64 +/- 10 years of age). PARAD was programmed in 263, and PARAD+ in 84 devices. During a mean follow-up of 11 +/- 3 months, 1,019 VT and 315 AF episodes were documented among 338 devices. For tachycardias with ventricular rates <150 beats/min, the sensitivity of PARAD versus PARAD+ was 96% versus 99% (NS), specificity 80% versus 93% (P < 0.002), positive predictive value (PPV) 94% versus 91% (NS), and negative predictive value (NPV) 86% versus 99% (P < 0.0001). In contrast, in the fast VT zone, the specificity and PPV of PARAD (95% versus 84% and 100% versus 96%) were higher than those of PARAD+ (NS, P < 0.001). Among 23 AF episodes treated in 16 patients, 3 episodes triggered an inappropriate shock in 3 patients, all in the PARAD population. PARAD+ significantly increased the ICD algorithm diagnostic specificity and NPV for AF in the slow VT zone without compromising patient safety.     

心源性猝死一级预防植入心律转复除颤器前非持续室性心动过速与植入后恰当治疗的关系

  目的  探讨植入型心律转复除颤器(implantable cardioverter defibrillator, ICD)用于心源性猝死一级预防时, 植入前发生非持续性室性心动过速(non-sustained ventricular tachycardia, NSVT)与植入后ICD恰当治疗的关系。  方法  本研究为单中心回顾性队列研究, 连续纳入2006年1月至2017年12月在北京协和医院住院植入ICD用于一级预防的心脏病患者, 患者在住院期间ICD植入前均完善Holter检查。根据Holter检查是否出现NSVT, 将患者分为NSVT组及无NSVT组。门诊或电话随访至2018年8月, 随访事件包括全因死亡、植入后ICD放电治疗及抗心动过速起搏(antitachycardia pacing, ATP)治疗情况。  结果  纳入60例符合入选和排除标准的患者, 随访时间37(14~61)个月, Kaplan-Meier生存曲线及Log-Rank检验提示, NSVT组与无NSVT组相比, 全因死亡率无统计学差异(P=0.108), NSVT组恰当治疗的风险高于无NSVT组(P=0.033), NSVT和左心室射血分数与ICD恰当治疗独立相关(NSVT:HR=5.099, 95% CI:1.399~18.588, P=0.014;左心室射血分数:HR=1.077, 95% CI:1.013~1.145, P=0.018)。  结论  ICD一级预防患者植入前出现NSVT提示接受ICD恰当治疗的风险增加。     

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.     

The Value of Electrophysiology Study and Prophylactic Implantation of Cardioverter Defibrillator in Patients with Hypertrophic Cardiomyopathy

Fifty-three consecutive patients with hypertrophic cardiomyopathy (HCM) and no history of sudden death underwent electrophysiology (EP) study. Sustained polymorphic ventricular tachycardia (VT) or ventricular fibrillation (VF) was induced in 19 patients (35%). Patients with prior syncope or near syncope had a higher incidence of VT/VF inducibility. An implantable cardioverter defibrillator (ICD) was placed in 14 of the 19 patients. Of the remaining 5 patients with inducible VT/VF, three refused ICD implantation, while two underwent septal myectomy and VT/VF was no longer inducible afier the operation. None of the patients received antiarrhythmic drugs. During a mean follow-up period of 47 ± 31 (2–117) months, no events occurred in the 34 patients with negative EP study. Three events occurred among the 19 patients with inducible VT/VF. One patient died suddenly, one developed wide complex tachycardia which required resuscitation, and one patient received an appropriate ICD shock. In conclusion, sustained polymorphic VT/VF was inducible in about one-third of patients with HCM. Noninducibility of VT/VF appeared to predict a favorable prognosis. Although the overall event rate was low in patients with inducible VT/VF, prophylactic ICD implantation in patients with multiple risk factors may be appropriate.     

Risk assessment of R-on-T event based on modeled QT-RR relationship

Background: R‐on‐T event is a well‐known trigger of ventricular tachycardia (VT) and ventricular fibrillation (VF). We propose a method to estimate the risk of R‐on‐T event from the inter‐beat (RR) intervals based on modeled QT‐RR relationship. Methods: We retrospectively analyzed the Spontaneous Ventricular Tachyarrhythmia Database and the HAWAI Registry, which include a total of 397 RR interval recordings from 116 implantable cardioverter defibrillator patients. For each RR interval time series, QT intervals were estimated from the weighted average of preceding RR intervals using Bazett, Fridericia, and linear formulas. The risk score (RS) of each cycle was calculated to quantify the probability of R‐on‐T event based on the timing of R‐wave relative to the estimated T‐end. We identified 52,440 ectopic beats (EBs) episodes, 280 nonsustained VT (NSVT) episodes, and 352 sustained VT/VF episodes. The RS of episode onset and the prematurity index (PMI) of the initiating beat were compared. Results: Using different QT‐RR models, R‐on‐T events were respectively detected in 9% EB, 45% NSVT, 69% VT/VF (Bazett); in 6% EB, 41% NSVT, 65% VT/VF (Fridericia); and in 7% EB, 42% NSVT, 66% VT/VF (linear). No R‐on‐T event was found in normal beats. Consistent among three QT‐RR models, the RS of episode onset rises sharply from EB to NSVT and to VT/VF episodes. In contrast, no trend in PMI is found. Conclusions: The risk of R‐on‐T can be estimated from RR intervals, based on modeled QT‐RR relationship. An episode onset with higher RS has increased risk of developing into NSVT or VT/VF. (PACE 2011; 700–708)     

Do Traditional VT Zones Improve Outcome in Primary Prevention ICD Patients?

Aims: We reviewed outcomes in our primary prevention implantable cardioverter defibrillator (ICD) population according to whether the device was programmed with a single ventricular fibrillation (VF) zone or with two zones including a ventricular tachycardia (VT) zone in addition to a VF zone. Methods: This retrospective study examined 137 patients with primary prevention ICDs implanted at our institution between 2004 and 2006. Device programming and events during follow‐up were reviewed. Outcomes included all‐cause mortality, time to first shock, and incidence of shocks. Results: Eighty‐seven ICDs were programmed with a single VF zone (mean >193 ± 1 beats per minute [bpm]) comprising shocks only. Fifty ICDs had two zones (mean VT zone >171 ± 2 bpm; VF zone >205 ± 2 bpm), comprising antitachycardia pacing (100%), shocks (96%), and supraventricular (SVT) discriminators (98%) . Discriminator “time out” functions were disabled. Mean follow‐up was 30 ± 0.5 months and similar in both groups. All‐cause mortality (12.6% and 12.0%) and time to first shock were similar. However, the two‐zone group received more shocks (32.0% vs 13.8% P = 0.01). Five of 16 shocks in these patients were inappropriate for SVT rhythms. The single‐zone group had no inappropriate shocks for SVTs. Eighteen of 21 appropriate shocks were for ventricular arrhythmias at rates >200 bpm (three VF, 15 VT). This suggests that primary prevention ICD patients infrequently suffer ventricular arrhythmias at rates <200 bpm and that ATP may play a role in terminating rapid VTs. Conclusions: Patients with two‐zone devices received more shocks without any mortality benefit. (PACE 2010; 1353–1358)     

High incidence of appropriate and inappropriate ICD therapies in children and adolescents with implantable cardioverter defibrillator

Appropriate and inappropriate therapies of implantable cardioverter defibrillators have a major impact on morbidity and quality of life in ICD recipients, but have not been systematically studied in children and young adults during long-term follow-up. ICD implantation was performed in 20 patients at the mean age of 16 +/- 6 years, 11 of which had prior surgical repair of a congenital heart defect, 9 patients had other cardiac diseases. Implant indications were aborted sudden cardiac death in six patients, recurrent ventricular tachycardia in 9 patient, and syncope in 5 patients. Epicardial implantation was performed in 6 and transvenous implantation in 14 patients. Incidence, reasons and predictors (age, gender, repaired congenital heart disease, history of supraventricular tachycardia, and epicardial electrode system) of appropriate and inappropriate ICD therapies were analyzed during a mean follow-up period of 51 +/- 31 months range 18-132 months. There were a total 239 ICD therapies in 17 patients (85%) with a therapy rate of 2.8 per patient-years of follow-up. 127 (53%) ICD therapies in 15 (75%) patients were catagorized as appropriate and 112 (47%) therapies in 10 (50%) patients as inappropriate, with a rate of 1.5 appropriate and 1.3 inappropriate ICD therapies per patient-years of follow-up. Time to first appropriate therapy was 16 +/- 18 months. Appropriate therapies were caused by ventricular fibrillation in 29 and ventricular tachycardia in 98 episodes. Termination was successful by antitachycardia pacing in 4 (3%) and by shock therapy in 123 episodes (97%). Time to first inappropriate therapy was 16 +/- 17 months. Inappropriate therapies were caused by supraventricular tachycardia in 77 (69%), T wave oversensing in 19 (17%), and electrode defect in 16 episodes (14%). It caused shocks in 87 (78%) and only antitachycardia pacing in 25 episodes (22%). No clinical variable could be identified as predictor of either appropriate or inappropriate ICD therapies. There is a high rate of ICD therapies in young ICD recipients, the majority of which occur during early follow-up. The rate of inappropriate therapies is as high as 47% and is caused by supraventricular tachycardia and electrode complications in the majority of cases. Prospective trials are required to establish preventative strategies of ICD therapies in this young patient population.     

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.     

Variability of Holter electrocardiographic findings in patients fulfilling the noninvasive MADIT criteria. Multicenter Automatic Defibrillator Implantation Trial

In the MADIT study, a selected group of postinfarction patients with asymptomatic nonsustained ventricular tachycardia (NSVT) has been shown to benefit from prophylactic ICD treatment. The present study analyzed the variability of NSVT in a patient population fulfilling the non-invasive MADIT criteria. Three consecutive Holter ECGs were performed in weekly intervals in 68 postinfarction patients with an LVEF < or = 0.35. Patients with NSVT underwent programmed ventricular stimulation (PVS); patients were implanted with an ICD if sustained VT or VF was inducible. If NSVT was found in at least two recordings, the arrhythmia was defined as reproducible. In 28 (41%) of the 68 patients, NSVT was found in at least one recording. Seventeen patients revealed NSVT in the first, the remaining 11 in the second registration; no patient had NSVT only in the third Holter. Of the patients with NSVT, 50% had only one, 39% had two, and 11% had three positive recordings. Thus, reproducible NSVT was found in only 50% of the patients with NSVT. Predictors for reproducibility were LVEF > 0.27, NYHA Class I, absence of digitalis therapy, and > 2 NSVT per 24-hour period. Reproducible NSVT was not associated with risk factors such as elevated mean heart rate, reduced heart rate variability, late potentials, or inducibility of sustained VT during PVS. During 17 +/- 9 months of follow-up, seven (10%) patients experienced arrhythmic events: two without and five with previously documented NSVT. In the latter patients, first occurrence of NSVT was consistently in the first Holter; only two of them had reproducible NSVT. In postinfarction patients, the risk factor NSVT exhibits marked spontaneous variability, especially in those with a low number of NSVT per 24-hour period, LVEF < 0.27 or NYHA III, which limits its clinical value as a selection criterion for PVS. Reproducibility of NSVT itself does not seem to be an independent risk factor.     

Failure of Third-Generation Implantable Cardioverter Defibrillators to Abort Shock Therapy for onsustained Ventricular Tachycardia Due to Shortcomings of the VF Confirmation Algorithm

Unnecessary shocks by ICDs for rhythms other than sustained VT or VF have been described as the most frequent adverse event in ICD patients. To avoid unnecessary shocks for self-terminating arrhythmias, the third-generation Jewel PCD defibrillators 7202, 7219, and 7220 Plus use a specially designed VF confirmation algorithm after charge end. The purpose of this study was to determine the ability of this VF confirmation algorithm to recognize nonsustained VT, and to analyze the reasons for failure of the PCD device to abort shock therapy for nonsustained VT despite use of this VF confirmation algorithm. Analysis of stored electrograms of electrical events triggering high voltage capacitor charging in the programmed VF zone of the device showed 36 spontaneous episodes of nonsustained VT (227 ± 21 beats/mm) during 18 ± 7 months follow-up in 15 patients who had a Jewel PCD implanted at our hospital. Intracardiac electrogram recordings and simultaneously retrieved marker channels demonstrated that the ICD shock was appropriately aborted according to the VF confirmation algorithm in 24 (67%) of 36 episodes of nonsustained VT. Twelve episodes (33%) of nonsustained VT, however, were followed by a spontaneous ICD shock in 6 (40%) of the 15 study patients. The only reason for all 12 shocks for nonsustained VT was the inability of the device to recognize the absence of VT after charge end due to shortcomings of the VF confirmation algorithm: 11 of the 12 shocks for nonsustained VT were triggered by the occurrence of paced beats during the VF confirmation period and 1 shock for nonsustained VT was triggered by the occurrence of 2 premature beats after charge end. Thus, better VF confirmation algorithms need to be incorporated in future PCD devices to avoid unnecessary shocks for nonsustained VT.     

Ventricular tachyarrhythmias in patients receiving an implantable cardioverter-defibrillator for primary versus secondary prophylaxis indications

Introduction: Data on the mechanisms of sudden cardiac death are limited and may be biased by delays in rhythm recording and selection bias in survivors. As a result, the relative contributions of monomorphic ventricular tachycardia (VT) (cycle length [CL] > 260 ms), monomorphic fast VT (FVT) (CL ≤ 260 ms), and polymorphic VT (PMVT)/ventricular fibrillation (VF) have not been well characterized nor compared in patients with and without prior arrhythmic events. Methods: A retrospective cohort study of implantable cardioverter‐defibrillator (ICD) recipients with primary or secondary implant indications was used to evaluate intracardiac electrograms (EGMs) for the first spontaneous VT/VF resulting in appropriate ICD therapy. EGMs were categorized into VT, FVT, and PMVT/VF based on CL and morphologic criteria. Results: Of 616 implants, 145 patients (58 [40%] primary indications) received appropriate ICD therapy for VT/VF over mean follow‐up of 3.8 ± 3.2 years. Primary implants had more diabetes (28% vs 12%; P = 0.02) and less antiarrhythmic use (15% vs 33%; P = 0.02). In those patients with spontaneous arrhythmia, PMVT/VF occurred in 20.7% of primary versus 21.8% of secondary implants, FVT in 19.0% versus 21.8%, and VT in 60.3% versus 56.4%, respectively (P = 0.88). Spontaneous VT CL was similar regardless of implant indication (284 ± 56 [primary] vs 286 ± 67 ms [secondary]; P = 0.92). Conclusions: Monomorphic VT is the most common cause of appropriate ICD therapy regardless of implant indication. These results provide insight into the mechanisms of sudden cardiac death and have implications for the use of interventions designed to limit ICD shocks. (PACE 2011; 34:571–576)     

Chronic experiences with a single lead dual chamber implantable cardioverter defibrillator system

Monitoring of atrial rhythm in patients implanted with ICDs may improve accuracy in identifying supraventricular arrhythmias and, therefore, prevent inappropriate therapies. Since difficulties were found in dual chamber ICDs with separate leads, a new designed single lead dual chamber ICD system was tested. Twenty-five patients implanted with a Deikos A+ (single coil defibrillation lead with two atrial sensing rings combined with a dual chamber ICD with a high amplifying atrial channel) were tested. Atrial and ventricular signals were analyzed during sinus rhythm (SR) and sinus tachycardias (STs), atrial flutter and AF, and VT or VF. Follow-ups were performed after 1, 3, 6, 9, and 12 months after implantation. Analysis of EGM amplitudes of stored episodes revealed that atrial signals during atrial flutter (2.1 +/- 0.51 mV) were comparable to those of ST (2.2 +/- 0.5 mV). Atrial amplitudes during AF were significantly lower (0.81 +/- 0.5 mV, P<0.01). During VF atrial "sinus" signals (2 +/- 0.8 mV) were stable. Ventricular parameters did not differ from a standard ICD lead; defibrillation threshold was 11.4 +/- 4.5 J (16 patients). During intraoperative and prehospital discharge measurements, 97.1% of SR-P waves and 99.2% of atrial flutter waves were detected correctly. In AF 91.11% of atrial signals were detected. Analysis of 505 stored episodes showed that 96.8% of ST and 100% of atrial flutter and 100% of AF episodes have been classified correctly and no underdetection of VT/VF was found. The first experiences with the new VDD-ICD system show an increase of the specificity to detect ventricular tachycardias to a level comparable to dual chamber ICDs with two leads. The reliability of this system has to be proven in a prospective randomized study.     

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)     

Efficacy of implantable cardioverter defibrillator therapy for primary and secondary prevention of sudden cardiac death in hypertrophic cardiomyopathy

Risk stratification and effectiveness of implantable cardioverter-defibrillator (ICD) therapy are unresolved issues in hypertrophic cardiomyopathy (HCM), a cardiac disease that is associated with arrhythmias and sudden death. We assessed ICD therapy in 132 patients with HCM: age at implantation was 34 +/- 17 years, and 44 (33%) patients were aged 相似文献