Risk stratification and prevention of sudden death in hypertrophic cardiomyopathy

Opinion statement Sudden cardiac death is the most devastating manifestation of hypertrophic cardiomyopathy (HCM) and often occurs in young and previously asymptomatic patients. Therefore, risk stratification for sudden death has a major role in the management of HCM and has acquired even greater relevance since the implantable cardioverter-defibrillator (ICD) has proved to be highly effective in preventing sudden death in this disease. The ICD is definitely indicated for secondary prevention of sudden death in patients with HCM who have survived a cardiac arrest with documented ventricular fibrillation, or experienced one or more episodes of sustained ventricular tachycardia. However, uncertainties persist regarding the precise selection of patients for primary prophylactic ICD implantation. A number of risk markers are used to assess the magnitude of risk, including family history of premature sudden death; extreme left ventricular (LV) hypertrophy (> 30 mm) in young patients; nonsustained ventricular tachycardia on Holter electrocardiographic recording; unexplained (not neurally mediated) syncope, particularly in young patients; and blood pressure decrease or inadequate increase during upright exercise. Multiple risk factors convey a definite increase in risk. However, a single risk factor such as family history of multiple sudden deaths, massive LV hypertrophy in a young patient, or frequent and/or prolonged runs of nonsustained ventricular tachycardia on Holter, may also justify consideration of a prophylactic ICD.     

Cardioverter-defibrillator implantation in high-risk patients with hypertrophic cardiomyopathy.

BACKGROUND: Implantable cardioverter-defibrillators (ICDs) are used with increasing frequency in hypertrophic cardiomyopathy (HCM) patients of all ages for primary and secondary sudden death prevention. Concerns may arise regarding the safety of device implantation because of unique clinical and phenotypic expressions of HCM. OBJECTIVES: The purpose of this study was to assess the efficacy and safety of ICD placement in high-risk patients with HCM. METHODS: We analyzed the experience with ICDs and transvenous lead systems in 75 consecutive HCM patients at the Minneapolis Heart Institute from 1993 to 2004. RESULTS: The age of the study group patients was 12 to 79 years (mean 36 +/- 16). Patients received ICDs for secondary (n = 4, after cardiac arrest) or primary prevention (n = 71, with > or = 1 risk factor). Thirty-one patients demonstrated disease features that potentially impacted methodology and safety of the implant procedure, most commonly massive left ventricular (LV) hypertrophy and outflow obstruction > or = 50 mmHg. There were no procedure-related deaths; defibrillator implants were successful and uneventful in 71 of 75 patients (95%). In 3 of the 75 patients (4%), defibrillation was unsuccessful because of high thresholds, associated with extreme hypertrophy (wall thickness > 45 mm) and/or ongoing amiodarone therapy. In two of these patients, thoracotomy with epicardial lead placement achieved successful defibrillation; ICD therapy was abandoned in the other patient. CONCLUSION: ICD placement in children and adults with HCM is generally safe and effective. However, in some patients with massive LV hypertrophy and/or prior administration of amiodarone, transvenous defibrillation proved difficult, and epicardial lead placement was required. High-energy ICD devices and defibrillation threshold testing are recommended for most high-risk HCM patients.     

Early automatic remote detection of combined lead insulation defect and ICD damage

Lead and implantable cardioverter defibrillator (ICD) devicefailure is a severe problem in ICD therapy and may occur withoutpreceding signs of deterioration. Insulation lead failure andsubsequent ICD defect 7 months after ICD implantation for secondaryprevention of sudden cardiac death (SCD) in a 70-year-old malewas automatically detected with the Home Monitoring system.Immediate lead and device replacement was performed. This caseillustrates the benefit of permanent automatic remote monitoringof implanted active devices.     

Echocardiographic parameters to predict inadequate defibrillation safety margin in patients receiving implantable cardioverter defibrillators for primary prevention

Background

Implantable cardioverter defibrillators (ICDs) have become an important part of the management of patients with congestive heart failure. At the time of ICD implantation, ventricular fibrillation (VF) is induced to assess adequate energy required for defibrillation. There are multiple parameters which influence the defibrillation safety margin (DSM); however, these factors are not well-established when ICDs are implanted for the primary prevention of sudden cardiac death (SCD) in patients with severe systolic dysfunction. We evaluated multiple clinical and echocardiographic parameters as predictors of adequate DSM in patients referred for ICD implantation for the primary prevention of SCD.

Methods

We prospectively enrolled 41 patients for ICD implantation with clinical indications for the primary prevention of SCD. Two blinded independent readers evaluated the prespecified echocardiographic parameters. These included left ventricular (LV) mass, indices of right ventricular and LV systolic and diastolic functions, and LV geometric dimensions. Basic clinical demographics, including age, gender, comorbidities, and etiology of cardiomyopathy, were also evaluated. DSM was established using our standard protocol for defibrillation testing which includes VF with successful first shock terminating VF at a value at least 10 J below the maximum output of the implanted device. High defibrillation thresholds (DFT) were defined as >21 J.

Results

The mean age is 61.8?±?14.7 years, with men comprising the majority of the patients (73 %). The only clinical variables which predicted the high DFT were age (in years) (54.5?±?17.5 vs. 65.7?±?11.3, p?=?0.044), QRS duration (in milliseconds) (116.0?±?29.5 vs. 110.5?±?21.8, p?=?0.03), LV mass (in grams) (241.0?±?77.9 vs. 181.9?±?52.3, p?=?0.006), and LV mass index (in grams per square meter) (111.1?±?38.2 vs. 86.4?±?21.1, p?=?0.02). On multivariate logistic regression analysis, LV mass was the only independent predictor of low DFT (≤22 J) in patients with ICD implanted for the primary prevention of SCD.

Conclusion

LV mass may help predict an adequate DSM in patients who are referred for ICD implantation for the primary prevention of SCD. These results may help distinguish the patients who may require high-energy devices prior to the implantation procedure. These results may help distinguish patients requiring high-energy devices, coils, or advanced programming prior to implantation and appropriate referral to electrophysiologists.     

Implantable cardioverter-defibrillators in children

BACKGROUND: Implantable cardioverter-defibrillators (ICD) have been increasingly used in adult patients for the prevention of sudden cardiac death (SCD). The usefulness and feasibility of ICD implantation in children have been less well established. AIM: To analyse indications, results and safety of ICD therapy in children. METHODS: ICDs were implanted in seven children, aged from 6 to 17 years. All patients underwent cardiological evaluation which included analysis of medical history, physical examination, chest X-ray, standard ECG, 24-hour Holter ECG monitoring and echocardiography. RESULTS: In five children devices were implanted due to aborted sudden death (ventricular fibrillation) whereas in the remaining two - as a primary prevention of SCD. Three children had hypertrophic cardiomyopathy, one - dilated cardiomyopathy, one - mitral valve prolapse and QT prolongation, one - congenital long QT syndrome and the remaining patient - idiopathic ventricular tachycardia. Single-chamber devices were implanted in six children, and dual-chamber system - in one patient. In all patients endocardial leads were implanted and ICD pocket was formed under the greater pectoral muscle. During follow-up ranging between four months to 5.4 years, four children developed ventricular fibrillation or ventricular tachycardia which were terminated by appropriate ICD discharges. CONCLUSIONS: 1. ICD implantation in children is effective in the prevention of SCD. 2. In our population, the most frequent indications for device implantation were life-threatening ventricular arrhythmias occurring in patients with cardiomyopathy. 3. Cardiac arrest due to ventricular fibrillation may occur in children without a history of aborted SCD. 4. ICD implantation in children is feasible and safe.     

Habitual cocaine use is associated with high defibrillation threshold during ICD implantation

Background: Habitual cocaine use can lead to dilated cardiomyopathy (DCM) and sudden cardiac death. Based on prior clinical observations, we hypothesized that prior habitual cocaine use is a strong predictor of high defibrillation threshold (DFT) during implantable cardioverter-defibrillator (ICD) implant.
Methods: We reviewed the medical records of 130 consecutive patients undergoing initial ICD implantation or revision at Parkland Hospital and the Dallas VA Hospital, Dallas, TX, from January 2002 to November 2005. Patient characteristics and DFT data were collected retrospectively.
Results: The study group includes 11 patients (8.46%) who were identified as having a history of prior habitual cocaine use as demonstrated by history and urine toxicology; the rest (119 patients) form the control group. Cocaine-using patients tended to be younger (48.2 ± 10 vs 60.1 ± 12.3 years; P = 0.0026), were less likely to have coronary disease (36.3% vs 72.2%; P = 0.032), and had less comorbidity. The average DFT was 27.9 ± 7.8 J for all cocaine-using patients and 14.5 ± 4.1 J for noncocaine-using patients (P = 0.00018). In the cocaine-using group, three out of 11 patients required a subcutaneous array compared to none in the control group.
Conclusions: Our results suggest that patients with a history of habitual cocaine use may be at increased risk to have a high DFT during ICD implantation. This is the first study to demonstrate such association. ICD implantation in patients with this history should be planned with these findings in mind, as larger output generators or subcutaneous arrays might be required.     

心脏三腔起搏除颤器的临床应用

目的　评价具有心脏再同步化治疗 (CRT)和置入式心脏复律除颤器 (ICD)功能起搏器(CRT D)置入的安全性和有效性。方法　共 11例患者纳入研究。年龄 4 8～ 84 (71 6± 9 5 )岁 ,男 7例 ,女 4例。患者有心脏猝死或室性心动过速或电生理检查出现室性心动过速或心室颤动 ;左室射血分数≤ 35 % ,QRS≥ 12 0ms。所有患者置入的CRT D是美敦力INSYNCⅡMARQUIS 72 89,左心室电极置于冠状静脉窦左心室侧后壁分支或左后壁分支。右心房电极和右心室电极都使用主动螺旋电极 ,后者置于室间隔上部。手术在全麻下进行。术后次日在心脏超声指导下进行AV优化。结果　所有患者顺利度过手术 ,无并发症。放射时间为 19～ 73(44 7± 19 9)min。心房电极的振幅、阻抗和阈值分别为 (2 4 7± 0 77)mV、(5 90± 12 6 )Ω、(1 37± 0 71)V。右心室电极的振幅、阻抗和阈值分别为 (11 0 0± 3 4 8)mV、(5 86± 116 )Ω、(0 6 9± 0 2 1)V。左心室电极的振幅、阻抗和阈值分别为(15 37± 5 .15 )mV、(6 0 2± 12 5 )Ω、(1 6 2± 1 5 9)V。除颤阈 2 0J和 6J的各 3例 ,15J、12J和 3J各 1例。 1例患者因为原有除颤电极失效而更换为皮下电极 ,但仍除颤失败。另 1例患者因为出现心电图ST T变化而暂时未测定除颤阈值。所有患者除颤能量     

Implantation of an automatic cardioverter-defibrillator in small children--two case reports

Implantation of an automatic cardioverter-defibrillator (ICD) in children may be challenging due to the increased risk of periprocedural and long-term complications. ICD was implanted in two boys with hypertrophic cardiomyopathy, aged 6 and 9 years, with of a body weight of 20 and 25 kg, respectively. In one patient an ICD was implanted due to a history of ventricular fibrillation whereas the second patient underwent prophylactic ICD implantation due to a family history of sudden cardiac death. No short- or mid-term complications were recorded. Difficulties and risks of ICD implantation in children are discussed.     

Risk of thromboembolic complications in patients with permanent atrial fibrillation undergoing cardioverter-defibrillator implantation

BACKGROUND: Cardioversion of atrial fibrillation (AF) carries the risk of thromboembolic complications and, therefore, anticoagulation therapy is routinely administered before and after this procedure. In patients with permanent AF who undergo implantation of cardioverter-defibrillator (ICD), anticoagulants are usually withdrawn during the perioperative period. However, in some patients sinus rhythm may be restored during defibrillation threshold (DFT) testing which potentially may increase the risk of thromboembolic complications. AIM: To assess the frequency of sinus rhythm restoration during ICD implantation in patients with permanent AF and the rate of both thromboembolic events and local bleeding complications which may occur due to temporary withdrawal of anticoagulation therapy and its re-initiation early after the procedure. METHODS: Permanent AF was present in 23 (12%) of 193 patients selected for ICD implantation. All patients received prolonged oral anticoagulation according to the generally accepted standards. Anticoagulation therapy was stopped few days before the procedure and replaced by low molecular weight heparin which was administered up to 24 hours before ICD implantation and re-initiated 12-24 hours afterwards. RESULTS: During DFT testing sinus rhythm was restored in 5 (21.7%) patients with AF. Clinical and DFT characteristics were similar in those who were converted to sinus rhythm and those who remained in AF. No thromboembolic events were noted in either group. Local haematoma at the site of ICD implantation occurred in two (8%) patients. CONCLUSIONS: Sinus rhythm was restored in 21.7% of patients with permanent AF who underwent ICD implantation. Temporary withdrawal of anticoagulation therapy did not increase the risk of thromboembolic complications, however, its early re-initiation after implantation resulted in an increase in local bleeding complication rate.     

The implantable cardioverter-defibrillator and hypertrophic cardiomyopathy. Experience at three centers

INTRODUCTION AND OBJECTIVES: Although implantable cardioverter-defibrillators (ICDs) are recommended for high-risk patients with hypertrophic cardiomyopathy (HCM), there is no agreement on their general use. Moreover, little information is available on ICD use in this setting in Spain. Our aims were to describe the characteristics of HCM patients who received ICDs at three hospitals in Spain, and to study indications for device implantation and the results of follow-up in device users. METHODS: We evaluated risk factors for sudden death in HCM patients with ICDs, including family history of sudden death, recurrent syncope, maximum wall thickness > or =30 mm, left ventricular outflow pressure gradient >30 mmHg, abnormal blood pressure response to exercise, and nonsustained ventricular tachycardia. During regular follow-up, appropriate and inappropriate administration of ICD therapy was recorded. RESULTS: Of 726 HCM patients, 45 (6.2%) had an ICD (mean age 43 [20] years). The proportion of patients with ICDs at the three centers studied was highly variable despite patients' clinical characteristics being similar. The indication for implantation was primary prevention in 27 patients and secondary prevention in 18. During follow-up (median 32 months), ICD therapy was administered appropriately in 10 (22.0%) patients (in nine, as secondary prevention and, in one, as primary prevention). The annual appropriate ICD therapy rate was 11.1% for secondary prevention and 1.6% for primary prevention. Two patients received an ICD to treat ventricular fibrillation and eight, to treat sustained ventricular tachycardia. The only significant predictor of appropriate ICD therapy was a history of sustained ventricular tachycardia or ventricular fibrillation (hazard ratio =13.3, P=.014). CONCLUSIONS: The percentage of HCM patients undergoing ICD implantation at Spanish hospitals was highly variable, possibly due to different selection criteria. When used as secondary prevention, ICD therapy was administered appropriately in a high proportion of cases (50% in 3 years).     

Defibrillation testing and early neurologic outcome

During implantable cardioverter-defibrillator (ICD) implantation, ventricular defibrillation testing (DFT) is considered a standard procedure. This procedure often requires multiple ventricular fibrillation (VF) inductions. These repeated short episodes of circulatory arrest with global cerebral ischemia may cause neurological damage. In the present study, patients undergoing initial ICD implantation and limited induction of VF for defibrillation safety margin testing were evaluated for pre- and postoperative cognitive and neurologic functions. In addition, the serum neuron specific enolase (NSE) level, which is a biochemical marker of cerebral injury, was evaluated. The study was performed on 16 patients undergoing initial elective transvenous insertion of an ICD. A neurologic examination and cognitive assessment tests were performed 24 to 48 hours before and after ICD. NSE was determined before (NSE 1) and at the end of the surgery (NSE 2), as well as 2 hours (NSE 3), 24 hours (NSE 4), and 48 hours (NSE 5) after implantation. A total of 29 internal shocks (average, 1.8 +/- 0.4) with energy ranging from 14 to 41 J (mean, 20 +/- 5; median, 20 J ) were delivered in the ICD group patients. In one patient, 3 external (50, 200 and 360 J) shocks were required for fast VT induced during ICD lead positioning. The mean duration of VF was 10 +/- 4 seconds and the mean cumulative time in VF was 16 +/- 5 seconds. The mean recovery time between VFs was 5.3 +/- 0.6 minutes. NSE levels were not different from the baseline at any time point in the patients of the group that completed the 48-hour observation period (P > 0.05). The patients did not report any new neurological symptoms after ICD implantation, and repeat examination after the procedure showed no abnormal findings other than those detected in the previous one. There were no statistically significant differences between the preoperative and postoperative scores obtained in the cognitive assessment. Single or two VF inductions and the brief arrest of cerebral circulation during ICD implantation are not associated with permanent neurological injury. However, further studies are needed to confirm this finding.     

Relation between extent of left ventricular hypertrophy and occurrence of sudden cardiac death in hypertrophic cardiomyopathy

Sudden unexpected death can be the first clinical manifestation of hypertrophic cardiomyopathy and is the most devastating feature of the natural history of the disease. Left ventricular hypertrophy appears to be an important determinant of many clinical features of hypertrophic cardiomyopathy, but the relation between its magnitude and the occurrence of sudden cardiac death has not been clearly defined. In this study, the magnitude of hypertrophy was assessed with two-dimensional echocardiography in 29 asymptomatic or mildly symptomatic patients with hypertrophic cardiomyopathy who subsequently died suddenly or experienced cardiac arrest with documented ventricular fibrillation. Findings were compared with those obtained in a control group of 95 patients of similar age and symptomatic state. Maximal left ventricular wall thickness was significantly greater in patients with sudden death (26 +/- 7 mm) than in control patients (21 +/- 5 mm, p less than 0.001). Left ventricular wall thickness index, a quantitative expression of the overall extent of hypertrophy, was also greater in patients with sudden death (76 +/- 20 mm) than in surviving control patients (62 +/- 13 mm, p less than 0.001). Particularly marked and diffuse hypertrophy, with maximal wall thickness greater than or equal to 30 mm or wall thickness greater than or equal to 25 mm in two or more of the four segments into which the left ventricle had been divided, was eight times more common in patients with sudden death (11 [38%] of 29) than in control patients (5 [5%] of 95, p less than 0.001).(ABSTRACT TRUNCATED AT 250 WORDS)     

心律转复除颤器植入术后电风暴的发生及其对预后的影响

目的调查单中心心律转复除颤器（ICD）植入术后电风暴（ES）的发生率、发作特征和危险因素，并探讨其对患者预后的影响。方法对本中心123例植入ICD的患者进行随访。Es定义为24h内出现3次或3次以上的快速室性心律失常（VA）导致ICD治疗，或ICD监测到持续30s以上的VA但未发放治疗。结果在（26．9±21．3）个月的随访期间，共有41（33．3％）例患者（ES组）发作139次ES（3．4±3．9）次／例，其中29（70．7％）例患者的首次发作在植入后1年内出现，Es发作呈现出6：00—10：00和14：00～17：00两个高峰。多因素Logistic回归分析表明植入ICD作为心脏性猝死二级预防是ES发生的独立危险因素（OR=4．797，P=0．044）。本组共15（12．2％）例患者死亡，Es组死亡率较无Es组（24．4％对6．1％，P=0．003）显著增高，Kaplan—Meier生存曲线分析显示Es组累计生存概率明显低于无Es组（Log—rank检验P〈0．001）。结论Es发作表现为上午和下午两个高峰，可导致死亡率增高，其首次发作多在ICD植入后1年内。植入ICD作为心脏性猝死二级预防是Es发生的独立危险因素。     

Is the determination of the defibrillation threshold in patients with an implantable cardioverter�Cdefibrillator still required?

Background

Intraoperative testing of implantable cardioverter?Cdefibrillators (ICDs) is time consuming and associated with risks. In the present study, we elucidated whether the initial implantation of an ICD with high energy output makes intraoperative defibrillation threshold testing (DFTT) unnecessary even though antiarrhythmic (AA) therapy is needed in the future.

Methods

A total of 111 patients (94 men, 17 women) receiving an ICD with subsequent AA therapy (mexiletine, amiodarone, sotalol, flecainide) were analyzed retrospectively. DFT was performed during ICD implantation and after AA drug therapy. In a second step, DFT results from the study cohort were analyzed for implantation of virtual ICDs with either low (???30?J, LOD), intermediate (34?J, IOD), or high energy output (36?J, HOD).

Results

In the study cohort, all patients reached the safety margin (SM) of 10?J between DFT and maximal shock energy of the ICD. After loading of AA agents, 6?patients (12%) with a LOD, 3?patients (11%) with an IOD, and 3 (13%) patients with a HOD failed the 10?J SM. Using virtual ICDs, 6 (5.5%) patients with a LOD, 1?patient (1%) with an IOD, and no patients with a HOD would have failed the 10?J SM. After loading of AA agents, 18?patients (16%) with a virtual LOD, 12?patients (10.8%) with an IOD, and still 9?patients (8%) with a HOD would have failed the 10?J SM.

Conclusion

Our results demonstrate that the 10?J SM would have been achieved intraoperatively in all patients with virtual HOD ICDs. Thus, determination of the DFT during implantation does not seem to be obligatory. However, in patients receiving AA agents, DFT testing is still required.     

埋藏式心脏转复除颤器安置的临床经验

总结非开胸经锁骨下静脉穿刺安置埋藏式心脏转复除颤器 (ICD)的手术方法、除颤阈值 (DFT)测定及ICD工作参数设置等临床经验。 10例患者 ,6例有反复晕厥病史。 2例晕厥时心电图证实为心室颤动 (简称室颤 ) ,体外电除颤成功 ,另 8例心内电生理均诱发出持续性室性心动过速或室颤。其中冠心病 8例 (1例合并Brugada综合征 ) ,扩张性心肌病 1例 ,原发性室颤 1例。 5例术前口服胺碘酮治疗。结果 :全部经锁骨下静脉置入ICD ,术中所有患者成功诱发室颤 ,并一次电击成功。手术时间 92± 2 7min。DFT≤ 2 0J,电击阻抗 4 1.2± 15 .3Ω ,R波高度 16 .3± 6 .6mV ,无手术并发症。结论 :经锁骨下静脉置入ICD方法简单 ,安全可靠 ;术前口服适量胺碘酮对术中诱发室颤无影响。     

单中心植入埋藏式心脏转复除颤器患者的随访

目的了解本中心植入埋藏式心脏转复除颤器(ICD)/双室同步起搏+除颤器(CRT-D)患者的临床特征,并进行长期随访以期了解其患者的预后和转归。方法对57例植入ICD/CRT-D的患者,其中一级预防23例,二级预防34例,收集其基本资料及相关病史,记录入院期间检查结果及治疗情况,并对其死亡率和恶性室性心律失常发生率进行随访。结果一级预防恶性心律失常发生率低于二级预防(21.7%vs 43.8%),所有患者无心律失常死亡,治疗成功率近100%。结论 ICD/CRT-D能减低患者恶性心律失常死亡。     

Síncope e padrão de Brugada intermitente

Brugada syndrome is a rare syndrome, with an estimated prevalence in Europe of 1-5/10 000 population, whose initial clinical presentation can be sudden death. Although it has a characteristic electrocardiographic pattern, this can be intermittent. The authors present the case of a 32-year-old man, with no family history of syncope or sudden death, who went to the emergency department for syncope without prodromes. The initial electrocardiogram (ECG) in sinus rhythm documented an isolated and non-specific ST-segment elevation in V2. During further diagnostic studies, a repeat ECG revealed type 1 Brugada pattern. This pattern was later seen in a more marked form during a respiratory infection. The patient subsequently underwent electrophysiological study, followed by implantation of an implantable cardioverter-defibrillator (ICD), with an episode of ventricular fibrillation converted via ICD shock two months after implantation.     

Implantable cardioverter-defibrillators should be used routinely in the elderly

Implantable cardioverter-defibrillators (ICDs) reduce mortality in selected high-risk populations by reducing the risk of sudden death. No clinical trial examining ICD efficacy has focused specifically on benefits and risks in the elderly, but all trials have included substantial numbers of older patients. The author addresses several issues: Is the risk of sudden death different for the elderly than in younger patients? Is ICD implantation feasible in the elderly? Is there evidence that ICD use in the elderly improves survival? The author's research indicates that while total mortality is higher for the elderly, there does not appear to be a specific predilection for arrhythmic death. Recent reports indicate that while ICDs can be implanted in a Medicare population, ICD implantation is associated with significant mortality (0.9%), as well as periprocedural complications (10.8%). In spite of the risks, both secondary and primary prevention trials demonstrate that the survival benefit associated with ICD use in the study populations was at least as great for elderly patients as for younger persons. Thus, published data support judicious ICD use in elderly patients at high risk for sudden death.     

Is ICD-programming for double intraoperative defibrillation threshold energy safe and effective during long-time follow-up? Results of a prospective randomized multicenter study (Low-Energy Endotak Trial--LEET)

The aim of this prospective and randomized study was to evaluate the safety and efficacy of a reduced shock strength in transvenous implantable defibrillator therapy. So far clinical data concerning the safety margin of the shock energy in ICD therapy do not exist. The shock energy tested during long-term follow-up in this study was twice the intraoperatively measured defibrillation threshold (DFT). A total number of 176 consecutive patients representing a typical cohort of ICD patients were evaluated. All patients received a non-thoracotomy lead system (CPI, Endotak 0070, 0090) and a biphasic cardioverter-defibrillator with the ability to store episodes (Cardiac Pacemakers Inc., Ventac TM PRx II, PRx III). The intraoperative defibrillation threshold (DFT) was evaluated in a step-down protocol (15, 10, 8, 5 J) and had to be < or = 15 J for inclusion into the study. The lowest effective energy terminating induced ventricular fibrillation had to be confirmed and was defined as DFT+ augmented defibrillation threshold. The DFT+ value was tested immediately after successful implantation, at discharge, and after a follow-up period of one year. Prior to implantation the patients were randomized into two groups. The energy of the first shock in the study group was programmed at twice DFT+ and in the control group at the maximum energy output (34 J). The efficacy of the first shock and its reproducibility in DFT testings and in spontaneous episodes during long-term follow-up of the study group were compared to those in the control group. A DFT+ value was found to be < or = 15 J in 166 of 176 patients (94%). The DFT+ in the study group was 9.6 +/- 3.2; in control group 10.1 +/- 3.5 J. The prohability of successful defibrillation at DFT+ level after one year was 84%. The success rate of the first shock meant to terminate induced ventricular fibrillation (VF) was 99.5% in the study group (217 of 218 episodes) and 99% in the control group (201 of 203 episodes). During follow-up of 24 +/- 9 months spontaneous episodes in the study group, 83/86 (96.5%) monomorphic ventricular tachycardias (MVT) and 38/40 (95%) VF-episodes were converted successfully by the 2x DFT+ shock. In the control group the first shock was successful in 151/156 (96.8%) spontaneous MVTs and in 30/33 (91%) VF episodes. The efficacy of the first shock was not influenced by clinical data such as the underlying cardiac disease, left ventricular function, ongoing antiarrhythmic therapy with amiodarone, or the number of spontaneous episodes per day or by the DFT itself. At a mean follow-up of two years there was no significant difference between the two groups concerning the incidence of sudden cardiac death (2.4% in the study group vs. 3.8% in the control group). In conclusion programming the first shock with the ICD lead system used in this study at 2x DFT+ is as efficient as a shock energy of 34 J in order to terminate induced and spontaneous episodes of VT/VF. Thus, the safety of ICD-therapy is not impaired when programming the shock energy at the 2x DFT+ value.     

Safety and Long-term Outcomes of Defibrillator Therapy in Patients With Right-Sided Implantable Cardiac Devices in Adults With Congenital Heart Disease

BackgroundImplantable cardioverter-defibrillators (ICDs) have been proven to prevent sudden cardiac death in adult congenital heart disease (ACHD) patients. Although the left side is chosen by default, implantation from the right side is often required. However, little is known about the efficacy and safety of right-sided ICDs in ACHD patients.MethodsIn this study we reviewed a total of 191 ACHD patients undergoing ICD/cardioverter resynchronisation therapy-defibrillator (CRT-D) implantation at our hospital between 2001 and 2019 (134 men and 57 women; age [mean ± standard deviation], 41.5 ± 14.8 years).ResultsTwenty-seven patients (14.1%) had right-sided devices. The most common causes of right-sided implantation were persistent left superior vena cava and vein occlusion (37.0%). Although procedure time (202.8 ± 60.5 minutes vs 143.8 ± 69.1 minutes, P = 0.008) was longer and the procedural success was lower (92.6% vs 99.4%, P = 0.008) for right-sided devices, no difference in R-wave and pacing threshold were noted. Among the 47 patients (24.6%) who underwent defibrillation threshold testing (DFT), no difference in DFT was observed (25.2 ± 5.3 J vs 23.8 ± 4.1 J, P = 0.460). During the median follow-up of 42.4 months, appropriate ICD therapy was observed in 5 (18.5%) and 30 (18.3%) patients for right- and left-sided ICDs/CRTDs, respectively (P = 0.978). No significant difference was seen in complications between them.ConclusionsImplantation of an ICD on the right side is technically challenging, but it is feasible as an alternative approach for ACHD patients with contraindications to left-sided device implantation.