Correlation between plasma calcium and coronary artery disease burden in patients with preserved renal function

An implantable cardioverter defibrillator (ICD) has been implanted in a 69-year-old patient with arrhythmogenic right ventricular cardiomyopathy (ARVC) for treatment of syncopal ventricular tachycardia (VT). Two types of ICD-related emergencies complicated the clinical course within 15 months. The first arrhythmic event occurred 3 months after ICD implantation as electrical storm with repetitive fast VT, resulting in 87 consecutive shocks at maximal output. Intravenous administration of amiodarone and reprogramming of the device were the measures to control VT. A year later, the patient experienced a cluster of 97 inappropriate shocks. Lead insulation failure produced electrical noise on the ventricular sensing channel and was misidentified as ventricular fibrillation (VF). The depleted ICD and the dual-coil lead were explanted and replaced by a new system. Multiple ICD shocks constitute a medical emergency in ICD patients, which requires immediate device interrogation for differentiation of appropriate and spurious discharges.     

Impact of upgrade to cardiac resynchronization therapy on ventricular arrhythmia frequency in patients with implantable cardioverter-defibrillators.

OBJECTIVES: This study compared cardiac resynchronization therapy's (CRT) impact on ventricular tachyarrhythmia susceptibility in patients who, due to worsening heart failure (HF) symptoms, underwent a replacement of a conventional implantable cardioverter-defibrillator (ICD) with a CRT-ICD. BACKGROUND: Cardiac resynchronization therapy is an effective addition to conventional treatment of HF in many patients with left ventricular systolic dysfunction. However, whether CRT-induced improvements in HF status also reduce susceptibility to life-threatening arrhythmias is less certain. METHODS: Clinical and ICD electrogram data were evaluated in 18 consecutive ICD patients who underwent an upgrade to CRT-ICD. Pharmacologic HF therapy was not altered during follow-up. The definition of ventricular tachycardia (VT) and ventricular fibrillation (VF) for each patient was as determined by device programming. Statistical comparisons used paired t tests. RESULTS: Findings were recorded during two time periods: 47 +/- 21 months (range 24 to 70 months) before and 14 +/- 2 months (range 9 to 18 months) after CRT upgrade. At time of upgrade, patient age was 69 +/- 11 years and ejection fraction was 21 +/- 8%. Before CRT the frequency of VT, VF, and appropriate ICD shocks was 0.31 +/- 1.23, 0.047 +/- 0.083, and 0.048 +/- 0.085 episodes/month/patient, respectively. After CRT-ICD, VT and VF arrhythmia burdens and frequency of shocks were respectively 0.13 +/- 0.56, 0.001 +/- 0.004, and 0.003 +/- 0.016 episodes/month/patient (p = 0.59, 0.03, and 0.05 vs. pre-CRT). CONCLUSIONS: Arrhythmia frequency and number of appropriate ICD treatments were reduced after upgrade to CRT-ICD for HF treatment. Thus, apart from hemodynamic benefits, CRT may also ameliorate ventricular tachyarrhythmia susceptibility in HF patients.     

Hydroquinidine therapy in Brugada syndrome

OBJECTIVES: We sought to assess hydroquinidine (HQ) efficacy in selected patients with Brugada syndrome (BrS). BACKGROUND: Management of asymptomatic patients with BrS and inducible arrhythmias remains a key issue. Effectiveness of class Ia antiarrhythmic drugs, which inhibit the potassium transient outward current of the action potential, has been suggested in BrS. METHODS: From a cohort of 106 BrS patients, we studied 35 who received HQ (32 men; mean age 48 +/- 11 years). Patients had asymptomatic BrS and inducible arrhythmia (n = 31) or multiple appropriate shocks from an implantable cardioverter-defibrillator (ICD) (n = 4). Asymptomatic patients with inducible arrhythmia underwent electrophysiologic (EP)-guided therapy. When ventricular tachycardia (VT)/ventricular fibrillation (VF) inducibility was not prevented, or in case of HQ intolerance, an ICD was placed. RESULTS: Hydroquinidine prevented VT/VF inducibility in 76% of asymptomatic patients who underwent EP-guided therapy. Syncope occurred in two of the 21 patients who received long-term (17 +/- 13 months) HQ therapy (1 syncope associated with QT interval prolongation and 1 unexplained syncope associated with probable noncompliance). In asymptomatic patients who received an ICD (n = 10), one appropriate shock occurred during a follow-up period of 13 +/- 8 months. In patients with multiple ICD shocks, HQ prevented VT/VF recurrence in all cases during a mean follow-up of 14 +/- 8 months. CONCLUSIONS: Hydroquinidine therapy prevented VT/VF inducibility in 76% of asymptomatic patients with BrS and inducible arrhythmia, as well as VT/VF recurrence in all BrS patients with multiple ICD shocks. These preliminary data suggest that preventive treatment by HQ may be an alternative strategy to ICD placement in asymptomatic patients with BrS and inducible arrhythmia.     

Hemodynamically Tolerated Ventricular Tachycardia With Mildly Impaired Ejection Fraction: Do These Patients Have VT/VF Recurrence and ICD Therapies?

BackgroundPatients with hemodynamically tolerated ventricular tachycardia (VT) and minimally reduced left ventricular ejection fraction (LVEF) remain a group that presents a prognostic and therapeutic dilemma.MethodsWe studied patients from our implanted cardioverter-defibrillator (ICD) database who received ICDs for hemodynamically tolerated VT and mildly reduced LVEF (36%-49%) at time of implant between May 2015 and December 2019. Time to appropriate ICD therapy was assessed. Clinical features associated with recurrent VT/ventricular fibrillation (VF) with ICD therapies were explored using binary logistic regression.ResultsAmong 2037 ICDs placed between May 2015 and December 2019, 64 subjects met the inclusion criteria. The mean age of the study group was 68 ± 12 years, and 58 (90.6%) subjects were male. Average ejection fraction was 40% ± 4.4 (range 36%-49%). Twenty-two (34%) subjects received antitachycardia pacing (ATP) for VT at 229 ± 265 days after ICD placement. Fifteen (23%) subjects received appropriate ICD shocks 305 ± 321 days after implant. The rate of recurrent VT/VF among the 37 patients with ICD therapy was 195 ± 39 beats per minute (bpm). This was significantly more rapid than initial presenting VT rates before ICD placement (183 ± 27 bpm) (P = 0.048). Multivariate analysis showed no factors independently associated with recurrent VT/VF.ConclusionsPatients with mildly impaired LV function and hemodynamically tolerated VT receive appropriate ICD therapies over the 3 years following implant. This patient group warrants further investigation, as their recurrent VT/VF rates can be much more rapid, and 23% go on to receive appropriate ICD shocks.     

Appropriate ICD therapy in patients with idiopathic dilated cardiomyopathy: long term follow-up

The implantable cardioverter defibrillator (ICD) has proved effective in preventing sudden death and decreasing mortality in randomised secondary prevention trials. Some nonrandomized studies have reported different incidences and predictors of appropriate ICD therapy in patients with idiopathic dilated cardiomyopathy (DCM). The antiarrhythmic and other medical therapies were different between the published studies and it was reported that not using beta-blockers was a predictor of appropriate ICD therapy. In the present study, we report on our long-term experience with ICD therapy in patients with DCM, the majority of whom were treated with beta-blockers and amiodarone. The study population consisted of 25 patients with DCM who underwent initial transvenous ICD implantation between December 1995 and May 2005. Indications for ICD implantation were monomorphic sustained ventricular tachycardia (VT) in 16 patients (64%), cardiac arrest in 8 patients (32%), and syncope plus inducible VT in one patient. Twenty-four patients underwent an electrophysiologic study (EPS). In 18 patients, the ICDs were programmed to only shocks and in 7 patients an additional antitachycardia pacing program was performed. One patient was lost to follow-up and 24 patients were followed-up primarily in our ICD pacemaker outpatient clinic. Appropriate ICD therapy was defined as antitachycardia pacing therapy or shock for tachyarrhythmia determined by evaluation of the clinical information and by device diagnostics to be either ventricular fibrillation or ventricular tachycardia. The mean follow-up was 39.29 +/- 30.59 months after ICD implantation. At follow-up, 17 patients were using a beta-blocker and 16 patients amiodarone. Appropriate ICD therapy was observed in 14 patients (58%). The detected arrhythmias were VT in 12 patients, ventricular fibrillation (VF) in one, and VT and VF in one patient. The time to first ICD therapy was 15.93 +/- 18.45 (range, 1-74) months. Using the Kaplan-Meier method, the percent survival free of appropriate ICD therapy was 82%, 72%, 66%, and 55% at 1, 2, 3, and 4 years follow-up, respectively. The clinical, echocardiographic, and electrophysiologic characteristics did not differ between those who did and did not receive appropriate ICD therapy. However, the mean QRS duration was significantly longer in patients who received appropriate ICD therapies. Cox regression analysis did not reveal any factors that predicted appropriate ICD therapy. Five patients (21%) died during follow-up. Four deaths were classified as cardiac and one as noncardiac. The cumulative survival from total death was 94%, 82%, 82%, and 69%, and the cumulative survival from cardiac death was 94%, 82%, 82%, and 76% during 1, 2, 3, and 4 years of follow-up, respectively. In summary, in this selected patient population with DCM, the majority of patients were unresponsive to beta-blocker and antiarrhythmic therapy. Most of these patients received appropriate ICD therapy during follow-up. Cox regression analysis did not identify any factors that predicted appropriate ICD therapy. Additional trials with larger patient populations are needed to detect the predictors of appropriate ICD therapy in patients with DCM.     

Death due to an implantable cardioverter defibrillator

Inappropriate therapy due to noise oversensing caused a true ventricular fibrillation (VF) and death of a patient. A 49-year-old patient with a history of dilated cardiomyopathy received a double-chamber implantable cardioverter defibrillator (ICD) in 1991 for a sustained inducible ventricular tachycardia (VT). One appropriate shock delivered in 1994 terminated an episode of VT. The generator was replaced in 1995 and in 2000, and was connected to the initial leads. Three months after the second replacement, the patient received six consecutive shocks related to detection of noise interpreted as VF. Unfortunately, the sixth shock triggered a true VF, which was not treated due to end of the therapeutic sequence, and the patient died. The causes of the dysfunction are discussed.     

埋藏式心脏转复除颤器的随访

目的报道37例埋藏式心脏转复除颤器(ICD)的随访结果。方法对置入ICD的37例患者进行电话询问和门诊随访,通过常规心电图、动态心电图及ICD存储的资料,对患者病情和ICD工作情况进行分析。结果37例患者共发作室性心动过速/心室颤动(VT/VF)917次(VT745次,VF172次),其中911次(99.3%)治疗成功,6次(0.7%)失败。非持续性VT122次(16.4%),发作均自行停止。623次持续性VT(83.6%)中,537次(86.2%)经抗心动过速起搏(ATP)终止,82次(13.2%)经低能量复律(CV)终止,3次(0.4%)在ATP治疗过程中加速为VF,由高能量除颤(DF)终止。172次VF中,167次(97.1%)经DF终止,1例无效放电5次(2.9%)系因电池提前耗竭而更换了ICD脉冲发生器,2例共8次阵发性心房颤动心室率超过设置的VT频率ICD发生误识别,给予ATP治疗。5例术后1~6个月出现心律失常“电风暴”。5例对电击恐惧造成了不同程度的心理障碍,经教导必要时辅以药物治疗后症状得以缓解。共有19例术后因VT发作频繁而服用胺碘酮/美托洛尔,并根据心律失常发作情况调整用药剂量。结论ICD置入后应加强随访,及时调整工作参数,同时辅助药物、改善心功能和心理治疗。     

植入型心律转复除颤器35例次随访

目的报告35例植入型心律转复除颤器（ICD）的随访结果.方法对我院1998年5月至2004年4月植入的31例,另有4例更换ICD患者进行电话询问和门诊随访（3～70个月,平均36.5个月）,通过常规心电图、动态心电图及ICD存储的资料,对患者病情和ICD工作情况进行分析.结果 4例患者死亡.31例患者共发作持续性室性心动过速/心室颤动（VT/VF）725次（VT534次,占73.7%,VF191次,占26.3%）,其中719次（96.8%）治疗成功,6次（3.2%）失败.534次VT中,454次（85.5%）经抗心动过速起搏（ATP）终止,80次（14.5%）经低能量复律（CV）终止.191次VF中,185次（96.9%）经高能量除颤（DF）终止,1例患者无效放电6次.3例患者发生误放电7次.结论 ICD疗效肯定,须密切随访,及时调整工作参数;应高度重视ICD患者的心理治疗.     

Impact of substrate-based ablation for ventricular tachycardia in patients with frequent appropriate implantable cardioverter-defibrillator therapy and dilated cardiomyopathy: Long-term experience with high-density mapping

IntroductionRecurrent ventricular tachycardia (VT) episodes have a negative impact on the clinical outcome of implantable cardioverter-defibrillator (ICD) patients. Modification of the arrhythmogenic substrate has been used as a promising approach for treating recurrent VTs. However, there are limited data on long-term follow-up.AimTo analyze long-term results of VT substrate-based ablation using high-density mapping in patients with severe left ventricular (LV) dysfunction and recurrent appropriate ICD therapy.MethodsWe analyzed 20 patients (15 men, 55% with non-ischemic cardiomyopathy, age 58±15 years, LV ejection fraction 32±5%) and repeated appropriate shocks or arrhythmic storm (>2 shocks/24 h) despite antiarrhythmic drug therapy and optimal heart failure medication. All patients underwent ventricular programmed stimulation (600 ms/S3) to document VT. A sinus rhythm (SR) voltage map was created with a three-dimensional electroanatomic mapping system (CARTO, Biosense Webster, CA) using a PentaRay® high-density mapping catheter (Biosense Webster, CA) to delineate areas of scarred myocardium (ventricular bipolar voltage ≤0.5 mV – dense scar; 0.5-1.5 mV – border zone; ≥1.5 mV – healthy tissue) and to provide high-resolution electrophysiological mapping. Substrate modification included elimination of local abnormal ventricular activities (LAVAs) during SR (fractionated, split, low-amplitude/long-lasting, late potentials, pre-systolic), and linear ablation to obtain scar homogenization and dechanneling. Pace-mapping techniques were used when capture was possible. The LV approach was retrograde in nine cases, transseptal in five and epi-endocardial in four. In two patients ablation was performed inside the right ventricle.ResultsLAVAs and scar areas were modified in all patients. Mean procedure duration was 149 min (105-220 min), with radiofrequency ranging from 18 to 70 min (mean 33 min) and mean fluoroscopy time of 15 min. Non-inducibility was achieved in 75% of cases (in four patients with hemodynamic deterioration and an LV assist device, VT inducibility was not performed). There were two cases of pericardial tamponade, drained successfully. During a follow-up of 50±24 months, 65% had no VT recurrences. Among the seven patients with recurrences, three underwent redo ablation and four, with fewer VT episodes, received appropriate ICD therapy. There were five hospital readmissions due to heart failure decompensation, one patient died in the first week after unsuccessful ablation of a VT storm and three died (stroke and pneumonia) >1 year after ablation.ConclusionCatheter ablation based on substrate modification is feasible and safe in patients with frequent VTs and severe LV dysfunction. This approach may be of clinical relevance, with potential long-term benefits in reducing VT burden.     

植入型心律转复除颤器不适当识别和治疗的发生率及常见原因

目的 植入型心律转复除颤器（ICD）是恶性室性心律失常患者惟一有效的治疗措施。不适当识别和治疗是ICD最常见的并发症，也是导致ICD患者再住院最主要的原因。本文旨在评价本中心的ICD患者不适当识别和治疗的发生率及常见原因。方法 入选2000年1月至2005年12月在本中心因室性心律失常植入ICD并能定期随访的50例患者。根据患者心律失常特点和心功能情况程控ICD的各项参数，定期随访，询问ICD中所有信息，打印、存盘并对储存的腔内电图进行逐条分析，以确定ICD诊断是否准确以及治疗是否有效，判断有无ICD不适当识别和治疗。结果 38例患者在随访期间发生了心律失常事件，ICD共记录到491次室性心动过速（VT）或心室颤动（VF）事件（VT383次，VF108次），其中有11例（22％）发生过≥1次的不适当识别和治疗事件。14．3％（55／383）的VT事件为不适当识别，并导致了78次抗心动过速起搏（ATP）治疗和9次电击治疗。VF不适当识别的发生率为26．9％（28／108），并导致了56次不适当电击事件。结论 植入新一代ICD患者中，不适当识别和治疗发生率仍较高。不适当识别和治疗最常见的原因是心房颤动（房颤）伴快速心室率，占50％以上；其次是由于电磁干扰或肌电干扰所致。     

Ablation of a catecholaminergic polymorphic VT and VF originating from Purkinje fibers--a case report

We describe a case of a 25-year-old woman suffering from recurrent adrenergic polymorphic ventricular tachycardia (PVT). As a 14-year-old the patient suffered from recurrent episodes of syncope during exercise or emotion. On Holter monitoring unsustained runs of PVT were observed. The patient survived SCD (VF) which occurred near the hospital. An ICD was implanted and during the first year over 150 adequate discharges were present. During 9 year follow-up the patient had to have 4 ICDs replaced. She suffered from post-traumatic stress disorder syndrome due to frequent ICD shocks. After age of 23 she was admitted to our hospital and an ablation using the CARTO system was performed. No low voltage areas were observed. During the study ventricular premature beats and VT/PVT runs were observed originating from the Purkinje fibres. RF applications were delivered at those sites, during which abrupt PVT runs were present. After the ablation no ventricular arrhythmia was registered in the ICD memory during 2-year follow-up.     

Implantable defibrillator event rates in patients with idiopathic dilated cardiomyopathy, nonsustained ventricular tachycardia on Holter and a left ventricular ejection fraction below 30%

OBJECTIVES: This study investigated the incidence of appropriate implantable cardioverter defibrillator (ICD) interventions for ventricular tachycardia (VT) or ventricular fibrillation (VF) in patients with idiopathic dilated cardiomyopathy (IDC) and nonsustained VT in the presence of a left ventricular ejection fraction below 30%, versus in patients with syncope and patients with a history of VT or VF. BACKGROUND: To date, only limited information is available about the prophylactic use of ICDs in patients with IDC. METHODS: From January 1993 to July 2000, 101 patients with IDC underwent implantation of ICDs with electrogram storage capability at our institution. Patients were placed into one of three groups according to their clinical presentation: asymptomatic or mildly symptomatic nonsustained VT in the presence of a left ventricular ejection fraction < or = 30% (49 patients, prophylactic group), unexplained syncope or near syncope (26 patients, syncope group) and a history of sustained VT or VF (26 patients, VT/VF group). RESULTS: During 36 +/- 22 months follow-up, 18 of 49 patients (37%) in the prophylactic group received appropriate shocks for VT or VF, compared with 8 of 26 patients (31%) in the syncope group and with 9 of 26 patients (35%) of the VT/VF group. Multivariate Cox analysis of baseline clinical variables identified left ventricular ejection fraction, atrial fibrillation and a history of sustained VT or VF as predictors for appropriate ICD interventions during follow-up. CONCLUSIONS: Patients with IDC and prophylactic ICD implantation for nonsustained VT in the presence of a left ventricular ejection fraction < or = 30% had an incidence of appropriate ICD interventions similar to that of patients with a history of syncope or sustained VT or VF. These findings indicate that ICDs may have a role in not only secondary but also primary prevention of sudden death in IDC.     

埋藏式心脏复律除颤器治疗恶性室性心律失常的随访观察

对２２例埋置了埋藏式心脏复律除颤器（ＩＣＤ）的有晕厥史的恶性室性心律失常患者进行了随访，观察ＩＣＤ的治疗效果。２２例中扩张型心肌病８例、肥厚型心肌病２例、冠心病７例、ＱＴ延长综合症１例，４例未发现器质性心脏病。所有患者均经临床证实有室性心动过速或（和）心室颤动（ＶＴ／ＶＦ）发作。ＩＣＤ具有多项治疗及信息储存记忆功能（即第三代）。随访时通过体外程控仪调出ＩＣＤ储存的资料进行分析。平均随访７．１（１～２３）个月，１１例患者（５０．０％）ＶＴ／ＶＦ发作１１８次，其中５４次为非持续性ＶＴ，均自行终止；接受ＩＣＤ治疗的６４次为ＶＴ／ＶＦ发作，４５次为ＶＴ，２２次由ＩＣＤ的抗心动过速起搏（ＡＴＰ）终止、１６次由低能量（２～１５Ｊ）转复终止、２次发作为窦性心动过速（误判为ＶＴ），其余５次ＶＴ在ＡＴＰ治疗过程中加速转为ＶＦ，由高能量除颤终止。ＩＣＤ诊断的ＶＦ发作共有１９次，发生于４例患者，有１例患者接受除颤１６次，４次系为频率超过ＶＦ感知频率的ＶＴ。１９次发作均被ＩＣＤ有效除颤终止。２例扩张型心肌病患者，１例术后３个月死于心功能衰竭，另１例术后２个月反复发作ＶＦ，多次接受ＩＣＤ除颤治疗，最后死于心功能衰竭。结果表明常规进行?     

T Wave Pacing Inducing Electrical Storm and Multiple Shocks in an ICD-Recipient: A Novel Complication of the Automatic Gain Control Function

Implantable cardioverter-defibrillator (ICD) is highly effective in treating life-threatening ventricular arrhythmias, but it can also have proarrhythmic effect in some cases. We report the case of a 72 years old patient with an ischemic cardiomyopathy in whom an ICD was implanted for a poorly tolerated ventricular tachycardia (Profiles MD—Ventritex). Forty-eight hours after implantation, the patient suddenly received 15 successive shocks. ECG tracings and intracardiac EGM showed the presence of several VT episodes, all induced by the antibradycardia pacing of the ICD: the automatic gain control function of the device failed to detect ventricular premature beats in this patient, leading to a bradycardia pacing falling on the T wave and inducing multiple VTs and shocks.     

窦性心动过速引起植入型心律转复除颤器误放电

目的观察和分析植入型心律转复除颤器（ＩＣＤ）误放电的发生情况。方法对植入ＩＣＤ患者进行随访,应用体外程控仪调出ＩＣＤ存储的资料进行分析。结果３１例植入ＩＣＤ患者随访平均１０个月中,２例患者因窦性心动过速发生ＩＣＤ误放电８次。１例发生在运动过程中,１例发生于静脉滴注多巴酚丁胺时,经程控ＩＣＤ的室性心动过速识别参数后,未再发生误放电。结论植入ＩＣＤ的患者可能会发生误放电,定期的随访及调整合适的ＩＣＤ参数,可避免和减少ＩＣＤ误放电的发生。     

Ventricular tachycardia in arrhythmogenic right ventricular dysplasia/cardiomyopathy: clinical presentation, risk stratification and results of long-term follow-up

BACKGROUND: Not all patients with arrhythmogenic right ventricular dysplasia/cardiomyopathy (ARVD/C) are at risk for sudden cardiac death. The aim of the study was to evaluate the risk stratification in patients with ARVD/C. METHODS AND RESULTS: Programmed ventricular stimulation (PVS) was performed in 34 ARVD/C patients. Twenty-two, 7 and 4 patients had documented sustained monomorphic ventricular tachycardia (smVT), non-smVT and ventricular fibrillation, respectively. One patient experienced syncope only. An implantable cardioverter defibrillator (ICD) was implanted in 11 patients inducible in smVT with hemodynamic compromise, in 4 patients with documented ventricular fibrillation and in one patient with non-smVT (194 ms tachycardia cycle length) (ICD group, n = 16). Ten patients were left without any antiarrhythmic therapy, 5 patients received antiarrhythmic drugs and 3 patients underwent successful VT ablation (non-ICD group, n = 18). Thirteen patients had an abnormal signal averaged ECG. During 6.5 +/- 2.4 years 69% of ICD patients received appropriate discharges and one non-ICD patient had a hemodynamically tolerated smVT recurrence (no sudden cardiac death in both groups). Comparison between the cycle lengths of clinical VT, induced VT and follow-up VT revealed a strong relationship (R = 0.62-0.88). On multivariate analysis abnormal signal averaged ECG and decreased left ventricular ejection fraction were statistically significant predictors for VT recurrence. CONCLUSIONS: In ARVD/C the tachycardia cycle length of clinical VT, PVS-induced VT and follow-up VT correlate well implicating that a PVS-guided approach does not provide additional information. Spontaneous arrhythmia in combination with clinical presentation allows identification of patients in need for an ICD.     

Randomized controlled study of detection enhancements versus rate-only detection to prevent inappropriate therapy in a dual-chamber implantable cardioverter-defibrillator

OBJECTIVES: The purpose of this study was to compare rate-only detection to enhanced detection in a dual-chamber implantable cardioverter-defibrillator (ICD), to discriminate ventricular tachycardia from supraventricular tachycardia. BACKGROUND: ICDs are highly effective in treating ventricular tachycardia (VT) or ventricular fibrillation (VF). However, they frequently deliver inappropriate therapy during supraventricular tachycardia (SVT). METHODS: We conducted a randomized clinical trial of detection enhancements in a dual-chamber ICD compared to control (rate-only) detection to discriminate VT from SVT. Detection enhancements included a specific standardized protocol identical for all patients for programming rate stability, sudden onset, atrial-to-ventricular relationship (sudden onset = 9% and rate stability = 10 ms; V > A "on"), and "sustained rate duration" (3 minutes). The primary endpoint was the time to first inappropriate therapy classified by a blinded events committee. RESULTS: One hundred forty-nine patients had a history of sustained VT or VF. Mean age (+/- SD) was 60 +/- 13 years; 83% were male, and mean ejection fraction was 35 +/- 15%. Control (n = 70) and "enhanced" (n = 79) groups did not differ with regard to age, sex, ejection fraction, or primary arrhythmia. The proportion of patients free of inappropriate therapy over time was significantly higher in the enhanced versus the control group (hazard ratio = 0.47, P = .011). High-energy shocks were reduced from 0.58 +/- 4.23 shocks/patient/month in the control group to 0.04 +/- 0.15 shocks/patient/month in the enhanced group (P = .0425). No patient programmed per protocol failed to receive therapy for VT detected by the ICD (422 VT episodes). CONCLUSIONS: Standardized programming in a dual-chamber ICD leads to a significant and clinically important reduction in inappropriate therapies compared to rate-only detection and does not compromise safety with respect to appropriate treatment of VT.     

Sudden death in implantable cardioverter-defibrillator recipients: clinical context,arrhythmic events and device responses

Objectives. We sought to investigate the nature of terminal events and potential contributory clinical and nonclinical (e.g., device-related) factors associated with sudden death (SD) in recipients of an implantable cardioverter-defibrillator (ICD).Background. The ICD is very effective in terminating ventricular tachycardia (VT) or ventricular fibrillation (VF), but protection against SD is not absolute. Little is known about the nature and potential causes of SD in patients with ICDs.Methods. We analyzed 25 cases of out-of-hospital SD among patients enrolled in the clinical investigation of the Cadence Tiered-Therapy Defibrillator System.Results. All patients (24 men and 1 woman, mean age 62 ± 10 years) received epicardial lead systems. The majority (92%) had coronary artery disease and a previous myocardial infarction (MI), with a mean left ventricular ejection fraction 0.25 ± 0.07. At device implantation, the mean defibrillation threshold was 13 ± 5 J. Sudden death occurred 13 ± 11 months later. Twenty patients (80%) had received appropriate ICD therapies before death, and 18 (72%) were receiving ≥1 antiarrhythmic drugs at the time of death. Sudden death was tachyarrhythmia-associated in 16 patients (64%), non-tachyarrhythmia-associated in 7 (28%) and indeterminate in 2 (8%). In the 16 patients with tachyarrhythmia-associated SD, the overall first therapy success rate in tachycardia and fibrillation zones was 60% and 67%, respectively. However, despite protracted therapies (≥2 shocks) in 7 (66%) of 12 patients who received fibrillation therapies, the final tachyarrhythmic episode was ultimately terminated by the ICD in 15 (94%) of the 16 patients, whereas 1 patient died after multiple (initially successful) internal and external shocks for intractable VT/VF during exercise. In 10 patients (40%) one or more, primarily clinical, factors potentially contributory to SD were identified: heart failure (n = 8), angina (n = 2), hypokalemia (n = 1), adverse antiarrhythmic drug treatment (n = 1) and acute MI (n = 1). An additional 10 patients (40%) had experienced an increase in frequency of ICD shocks within 3 months of SD. Appropriate battery voltages and normal circuitry function were found in all devices interrogated and analyzed after death.Conclusions. In this select group of patients receiving a third-generation ICD, SD was associated with VT or VF events in nearly two-thirds of patients, and death occurred despite ultimately successful, although often protracted, device therapies. These observations, along with evidence of recent worsening clinical status, suggest acute cardiac mechanical dysfunction as a frequent terminal factor. In recipients with ICDs, SD directly attributable to device failure seems to be rare.     

About an implantable cardioverter-fibrillator

A 61-year-old man has been implanted with a Ventritex Profile MD V-186 HV3 ICD for ischemic cardiomyopathy with sustained inducible VT. Three years later, this patient received several inappropriate shocks during the device's interrogation. These shocks provoked ventricular fibrillation. They were caused by a failing soldering between the system random accessory memory (SRAM) module and the hybrid circuit of the device. The device was explanted in emergency.     

Outcome of ventricular tachycardia catheter ablation in ischemic heart disease patients using a high-density mapping substrate-based approach: A prospective cohort study

Introduction and objectiveRadiofrequency catheter ablation (RCA) for ventricular tachycardia (VT) in patients with ischemic heart disease (IHD) is associated with a reduced risk of VT storm and implantable cardioverter defibrillator (ICD) shocks. We aim to report the outcome after a single RCA procedure for VT in patients with IHD using a high-density substrate-based approach.MethodsWe conducted a prospective, observational, single-center and single-arm study involving patients with IHD, referred for RCA procedure for VT using high-density mapping catheters. Substrate mapping was performed in all patients. Procedural endpoints were VT non-inducibility and local abnormal ventricular activities (LAVAs) elimination. The primary end point was survival free from appropriate ICD shocks and secondary end points included VT storm and all-cause mortality.ResultsSixty-four consecutive patients were included (68±9 years, 95% male, mean ejection fraction 33±11%, 39% VT storms, and 69% appropriate ICD shocks). LAVAs were identified in all patients and VT inducibility was found in 83%. LAVA elimination and non-inducibility were achieved in 93.8% and 60%, respectively. After a mean follow-up of 25±18 months, 90% and 85% of patients are free from appropriate ICD shocks at one and two years, respectively. The proportion of patients experiencing VT storm decreased from 39% to 1.6%. Overall survival was 89% and 84% at one and two years, respectively.ConclusionsRCA of VT in IHD using a high-density mapping substrate-based approach resulted in a steady freedom of ICD shocks and VT storm.