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Selected Abstracts

Title: Psychopathology in Patients with ICDs over Time: Results of a Prospective Study

Introduction: The effects of implantable cardioverter defibrillators (ICDs) and ICD shocks on psychological state have previously been studied. However, it is still unclear how health-related quality-of-life changes over time using standardized assessments. We sought to characterize the effects of ICDs and ICD shocks on psychological outcomes.
Methods: Three hundred-eight patients receiving ICDs were prospectively identified. Baseline QOL assessments including standardized psychological surveys [Hospital Anxiety and Depression Scale (HADS), Impact of Events Scale-Revised (IES-R), and Short Form 36 Health Survey (SF-36)] were obtained within 2 months of device implantation and at 6 and 12 months, respectively. Outcomes including ICD shocks were followed over the 12-month study period.
Results: The number of patients meeting criteria for anxiety or posttraumatic stress disorder (PTSD) at baseline (78/223, 35%) was higher than at 6 (34/223, 15%) or 12 (34/223, 15%) months (P < 0.01). There was a significant improvement over time in HADS (P < 0.001) and IES-R (PTSD) scores (P < 0.001). Amongst the 20 patients who received ICD shocks, no significant differences were observed in IES-R, SF-36, or HADS scores when compared with those who did not receive shocks at any time point. Patients who experienced electrical storms (N = 5) had significantly higher baseline PTSD scores (29.6 ± 11.4 vs 14.6 ± 11.6, P < 0.01).
Conclusions: Patients receiving ICDs have significant rates of baseline psychopathology after implantation. However, psychological assessment scores tend to improve with time. ICD shocks do not appear to significantly impact psychological state. These results suggest the importance of close screening and referral for possible psychopathology in patients receiving ICDs, especially in the peri-implant period.
(PACE 2010; 33:198-208)

Title: Differences in effects of electrical therapy type for ventricular arrhythmias on mortality in implantable cardioverter-defibrillator patients

BACKGROUND Implantable cardioverter-defibrillator (ICD) shocks have been associated with an increased risk of death. It is unknown whether this is due to the ventricular arrhythmia (VA) or shocks and whether antitachycardia pacing (ATP) termination can reduce this risk.
OBJECTIVE The purpose of this study was to determine whether mortality in ICD patients is influenced by the type of therapy (shocks of ATP) delivered.
METHODS Cox models evaluated effects of baseline characteristics, ventricular tachycardia (VT; _188 bpm), fast VT (FVT; 188-250 bpm), ventricular fibrillation (VF; _250 bpm), and therapy type (shocks or ATP) on mortality among 2135 patients in four trials of ATP to reduce shocks.
RESULTS Over 10.8 _ 3.3 months, 24.3% patients received appropriate shocks (50.6%) or ATP only (49.4%), and 6.6% died. Mortality predictors were age (hazard ratio 1.07, 95% confidence interval 1.04 -1.08, P _.0001), New York Heart Association class III/IV (3.50 [2.27-5.41]; P _.0001), coronary disease (3.08 [1.31-7.25]; P _ .01), and cumulative VA (VT _ FVT _ VF) episodes shocked (1.20 [1.13, 1.29]; P _.0001). Beta-blockers (0.65, 0.46-0.92; P _.0001) and remote myocardial infarction (0.53, [0.38-0.76] P _ .0004) predicted reduced risk. Since 92% of VT and all VF received a single therapy type (ATP and shocks, respectively), the effect of therapy on episode risk could not be established. For FVT (32% shocked, 68% ATP), episode and therapy effects could be uncoupled; ATP-terminated FVT did not increase episode mortality risk, whereas shocked FVT increased risk by 32%. Survival rates were highest among patients with no VA (93.8%) of ATP-only (94.7%) and lowest for shocked patients (88.4%). Monthly episode rates were 80% higher among shocked versus ATP-only patients.
CONCLUSIONS Shocked VA episodes are associated with increased mortality risk. Shocked patients have substantially higher VA episode burden and poorer survival compared with ATP-only treated patients.
 (Heart Rhythm 2010;7:353-360)

Title: Long-Term Prognosis of Patients Diagnosed With Brugada Syndrome

Background--Brugada syndrome is characterized by ST-segment elevation in the right precordial leads and an increased risk of sudden cardiac death (SCD). Fundamental questions remain on the best strategy for assessing the real disease-associated arrhythmic risk, especially in asymptomatic patients. The aim of the present study was to evaluate the prognosis and risk factors of SCD in Brugada syndrome patients in the FINGER (France, Italy, Netherlands, Germany) Brugada syndrome registry.
Methods and Results--Patients were recruited in 11 tertiary centers in 4 European countries. Inclusion criteria consisted of a type 1 ECG present either at baseline or after drug challenge, after exclusion of diseases that mimic Brugada syndrome. The registry included 1029 consecutive individuals (745 men; 72%) with a median age of 45 (35 to 55) years. Diagnosis was based on (1) aborted SCD (6%); (2) syncope, otherwise unexplained (30%); and (3) asymptomatic patients (64%). During a median follow-up of 31.9 (14 to 54.4) months, 51 cardiac events (5%) occurred (44 patients experienced appropriate implantable cardioverter-defibrillator shocks, and 7 died suddenly). The cardiac event rate per year was 7.7% in patients with aborted SCD, 1.9% in patients with syncope, and 0.5% in asymptomatic patients. Symptoms and spontaneous type 1 ECG were predictors of arrhythmic events, whereas gender, familial history of SCD, inducibility of ventricular tachyarrhythmias during electrophysiological study, and the presence of an SCN5A mutation were not predictive of arrhythmic events.
Conclusions--In the largest series of Brugada syndrome patients thus far, event rates in asymptomatic patients were low. Inducibility of ventricular tachyarrhythmia and family history of SCD were not predictors of cardiac events. (Circulation. 2010;121:635-643.)

Title: Chest compression fraction determines survival in patients with out-of-hospital ventricular fibrillation

Christenson et al (Circulation 2009;120:1241-1247, PMID 19752324) evaluated the influence of time spent performing chest compressions during cardiac arrest on survival to hospital discharge in patients with out-of-hospital ventricular fibrillation or pulseless ventricular tachycardia. In this prospective observational cohort study of 506 patients with no defibrillation before emergency medical services arrival, the mean age was 64 years, 80% were male, 71% were witnessed by a bystander, 51% received bystander cardiopulmonary resuscitation, 34% occurred in a public location, and 23% survived. After adjustment for age, gender, location, bystander cardiopulmonary resuscitation, bystander witness status, and response time, the odds ratios of surviving to hospital discharge in the two highest categories of chest compression fraction compared with the reference category were 3.01 and 2.33. The authors conclude that increased chest compression fraction is independently predictive of better survival in cardiac arrest patients

Title: Appropriate Evaluation and Treatment of Heart Failure Patients After Implantable Cardioverter-Defibrillator Discharge: Time to Go Beyond the Initial Shock

Multiple clinical trials support the use of implantable cardioverter-defibrillators (ICDs) for prevention of sudden cardiac death in patients with heart failure (HF). Unfortunately, several complicating issues have arisen from the universal use of ICDs in HF patients. An estimated 20% to 35% of HF patients who receive an ICD for primary prevention will experience an appropriate shock within 1 to 3 years of implant, and one-third of patients will experience an inappropriate shock. An ICD shock is associated with a 2- to 5-fold increase in mortality, with the most common cause being progressive HF. The median time from initial ICD shock to death ranges from 168 to 294 days depending on HF etiology and the appropriateness of the ICD therapy. Despite this prognosis, current guidelines do not provide a clear stepwise approach to managing these high-risk patients. An ICD shock increases HF event risk and should trigger a thorough evaluation to determine the etiology of the shock and guide subsequent therapeutic interventions. Several combinations of pharmacologic and device-based interventions such as adding amiodarone to baseline beta-blocker therapy, adjusting ICD sensitivity, and employing antitachycardia pacing may reduce future appropriate and inappropriate shocks. Aggressive HF surveillance and management is required after an ICD shock, as the risk of sudden cardiac death is transformed to an increased HF event risk.
Jacc nov 2009

Title: Outcomes of Early Risk Stratification and Targeted ICD Implantation After STEMI Treated With Primary PCI


Background--Methods to identify high-risk patients and timing of implantable cardioverter-defibrillator (ICD) therapy after ST-elevation myocardial infarction need further optimization.
Methods and Results--We evaluated outcomes of early ICD implantation in patients with inducible ventricular tachycardia. Consecutive patients treated with primary percutaneous coronary intervention for acute ST-elevation myocardial infarction underwent early left ventricular ejection fraction (LVEF) assessment. Patients with LVEF _40% were discharged (group 1); patients with LVEF _40% underwent risk stratification with electrophysiological study. If no ventricular tachycardia was induced, patients were discharged without an ICD (group 2). If sustained monomorphic ventricular tachycardia (_200-ms cycle length) was induced, an ICD was implanted before discharge (group 3). Follow-up was obtained up to 30 months in all patients and up to 48 months in a subgroup of patients with LVEF _30% without an ICD. The primary end point was total mortality. Group 1 (n_574) had a mean LVEF of 54_8%; group 2 (n_83), 32_6%; and group 3 (n_32), 29_7%. At a median follow-up of 12 months, there was no significant difference in survival between the 3 groups (P_0.879), with mortality rates of 3%, 3%, and 6% for groups 1 through 3, respectively. In the subgroup of group 2 patients with LVEF _30% and no ICD (n_25), there was 9% mortality at a median follow-up of 25 months. In group 3, 19% had spontaneous ICD activation resulting from ventricular tachycardia.
Conclusions--Early ICD implantation limited to patients with inducible ventricular tachycardia enables a low overall mortality in patients with impaired LVEF after primary percutaneous coronary intervention for ST-elevation myocardial infarction. (Circulation. 2009;120:194-200.)

Title: Outcomes of Early Risk Stratification and Targeted Implantable Cardioverter-Defibrillator Implantation After ST-Elevation Myocardial Infarction Treated With Primary Percutaneous Coronary Intervention

Background--Methods to identify high-risk patients and timing of implantable cardioverter-defibrillator (ICD) therapy after ST-elevation myocardial infarction need further optimization.
Methods and Results--We evaluated outcomes of early ICD implantation in patients with inducible ventricular tachycardia. Consecutive patients treated with primary percutaneous coronary intervention for acute ST-elevation myocardial infarction underwent early left ventricular ejection fraction (LVEF) assessment. Patients with LVEF _40% were discharged (group 1); patients with LVEF _40% underwent risk stratification with electrophysiological study. If no ventricular tachycardia was induced, patients were discharged without an ICD (group 2). If sustained monomorphic ventricular tachycardia (_200-ms cycle length) was induced, an ICD was implanted before discharge (group 3). Follow-up was obtained up to 30 months in all patients and up to 48 months in a subgroup of patients with LVEF _30% without an ICD. The primary end point was total mortality. Group 1 (n_574) had a mean LVEF of 54_8%; group 2 (n_83), 32_6%; and group 3 (n_32), 29_7%. At a median follow-up of 12 months, there was no significant difference in survival between the 3 groups (P_0.879), with mortality rates of 3%, 3%, and 6% for groups 1 through 3, respectively. In the subgroup of group 2 patients with LVEF _30% and no ICD (n_25), there was 9% mortality at a median follow-up of 25 months. In group 3, 19% had spontaneous ICD activation resulting from ventricular tachycardia.
Conclusions--Early ICD implantation limited to patients with inducible ventricular tachycardia enables a low overall mortality in patients with impaired LVEF after primary percutaneous coronary intervention for ST-elevation myocardial infarction. (Circulation. 2009;120:194-200.)

Title: Dofetilide effect on DFT

Introduction: High defibrillation threshold (DFT) with an inadequate defibrillation safety margin remains an infrequent but troubling problem associated with defibrillator implantation. Dofetilide is a selective class III antiarrhythmic drug that reduces DFTs in a canine model.We hypothesized that dofetilide would reduce DFTs in humans, obviating the need for complex lead systems.

Methods and Results: Sixteen consecutive patients with DFTs 20 J delivered energy at implantreceived dofetilide therapy and underwent follow-up DFT testing acutely following drug loading and/or chronically (128 ± 94 days). Amiodarone was discontinued in four patients at implantation. With dofetilide, DFTs decreased from 28 ± 4 J to 19 ± 7 J (P < 0.0001), resulting in a safety margin of 15 ± 8 J for the implanted devices. Five patients subsequently had spontaneous arrhythmias terminated successfully with shocks.

Conclusion: Dofetilide reduces DFTs sufficiently to prevent the need for more complex lead systems. This strategy should be considered when an inadequate defibrillation safety margin is present. (PACE 2009; 32:24-28)

Title: Leisure-Time Activities of Patients with ICDs: Findings of a Survey with Respect to Sports Activity, High Altitude Stays, and Driving Patterns

Background: Physicians who are caring for patients with implantable cardioverter-defibrillators (ICDs) are regularly confronted with questions concerning daily activities. This study evaluates the habits of ICD patients with respect to sports activities, stays at high-altitude, and driving patterns.

Methods: A survey was performed in 387 patients with ICDs who were followed at two hospitals in Switzerland. The special-designed questionnaire addressed lifestyle practices concerning sportshigh-altitude visits, and driving motor vehicles.

Results: Fifty-nine percent of ICD patients participated in some kind of sports activity; an ICD shock was experienced in 14% of these patients. Fifty-six percent of the patients reported a stay at high altitudes at least 2,000 m above the sea level; 11% of them stayed regularly above 2,500 m; 4% of these patients experienced an ICD shock during high altitude stay. Seventy-nine percent of the patients drove a motor vehicle; 2% of them experienced an ICD shock during driving, but none of them reported loss of consciousness or a traffic accident.

Conclusion: It is accepted that ICD patients disqualify for competitive sports. However, the patients may be encouraged to continue leisure-time physical activities at low-to-moderate intensity. Staying at high altitudes and driving motor vehicles are very rarely associated with ICD shocks. Therefore, these activities that are likely to contribute to a better quality of life should not be discouraged in most ICD recipients in the absence of other medical reasons. (PACE 2008; 31:845-849)

Title: Integration of Automatic Intrathoracic Fluid Content Measurement into Clinical Decision Making in Patients with Congestive Heart Failure

Background: Hospitalizations due to decompensation are a frequent problem in treating patients with congestive heart failure (CHF). Continuous impedance measurement via implantable devices may detect pulmonary fluid accumulation due to worsening CHF. An acoustic alert might allow an earlier treatment of impending decompensation. An algorithm that implemented impedance measurement into clinical decision making in treating CHF patients was evaluated.

Methods: Forty-two CHF patients (ejection fraction: 27 ± 6%; New York Heart Association 2.9 ± 0.6) with cardiac resynchronization therapy and automatic impedance measurements were included. Upon an alert, a stepped therapy was initiated: category (1) overt decompensation, hospitalization; category (2) worsened CHF, increase of diuretics; category (3) no CHF worsening, brain natriuretic peptide (BNP) measurement, elevated BNP: increase of diuretics, normal BNP: no specific treatment.

Results: During 18 ± 4 months, 45 alerts were treated according to the algorithm. Eleven category 1 alerts led to hospitalization; 21 category 2 and 11 category 3 patients (elevated BNP) were treated conservatively. Two category 3 alerts (normal BNP) received no treatment.

Conclusions: Automatic impedance measurement can be integrated into CHF management. BNP measurement restricted to patients with alert but without clinical signs of worsened CHF may prevent premature therapy escalation. (PACE 2008; 31:961-967)

Title: Association between statin therapy and reductions in atrial fibrillation or flutter and inappropriate shock therapy

Aims: In patients without implantable cardioverter defibrillators (ICDs), statins have been shown to reduce the incidence of atrial fibrillation and atrial flutter (AF/AFL). We sought to determine if statin therapy could reduce the occurrence of AF/AFL with rapid ventricular rates with and without inappropriate shock therapy among a large heterogeneous ICD cohort.

Methods and results: We prospectively followed 1445 consecutive patients receiving an ICD for the primary (n ¼ 833) or secondary (n ¼ 612) prevention from December 1997 through January 2007.Outcome measures include incidence of AF/AFL that initiated ICD therapy or was detected during ICD interrogation. Cox hazard regression analyses were conducted to determine the predictors of AF/AFL with and without inappropriate shock delivery and did not include inappropriate shocks resulting from lead dysfunction or other exogenous factors. Patients in this study (n ¼ 1445) were followed over a mean follow-up period of (mean+SD) 874+805 days. There were 563 episodes of AF/AFL detected, with 200 episodes resulting in inappropriate shock therapy. Overall, 745 patients received statin therapy and 700 did not. The use of statin therapy was associated with an adjusted hazard ratio of 0.472 [95% confidence interval (CI), 0.349-0.638, P , 0.001] for the development of AF/AFL with shock therapy and 0.613 (95% CI, 0.496-0.758, P , 0.001) without shock therapy when compared with the group without statin use.

Conclusion: Among a cohort with ICDs at high risk for cardiac arrhythmias, statin therapy was associated with a reduction in AF/AFL tachyarrhythmia detection and inappropriate shock therapy

Title: Mechanisms of Ventricular Fibrillation Initiation in MADIT II Patients with Implantable Cardioverter Defibrillators

Background: The availability of stored intracardiac electrograms from implantable defibrillators (ICDs) has facilitated the study of the mechanisms of ventricular tachyarrhythmia onset. This study aimed to determine the patterns of initiation of ventricular fibrillation (VF) in Multicenter Automatic Defibrillator Implantation Trial (MADIT) II patients along with associated electrocardiogram (ECG) parameters and clinical characteristics.

Methods: Examination of stored electrograms enabled us to evaluate the rhythm preceding each episode of VF and to calculate (intracardiac) ECG parameters including QT, QT peak (QTp), coupling interval, and prematurity index.

Results: Sixty episodes of VF among 29 patients (mean age 64.4±2.5 years) were identified.Asingle ventricular premature complex (VPC) initiated 46 (77%) episodes whereas a short-long-short (SLS) sequence accounted for 14 (23%) episodes. Of the 29 patients studied, 23 patients had VF episodes preceded by a VPC only, two patients with SLS only, and four patients with both VPC and SLS-initiated episodes. There were no significant differences between initiation patterns in regards to the measured ECG parameters; a faster heart rate with SLS initiation (mean RR prior to VF of 655 ± 104 ms for SLS and 744 ± 222 ms for VPC) approached significance (P = 0.06). The two patients with SLS only were not on β-blockers compared to 83% of the VPC patients.

Conclusion: Ventricular fibrillation is more commonly initiated by a VPC than by a SLS sequence among the MADIT II population. Current pacing modes designed to prevent bradycardia and pause-dependent arrhythmias are unlikely to decrease the incidence of VPC-initiated episodes of VF.

Title: Risk of Interference from Transcutaneous Electrical Nerve Stimulation on the Sensing Function of Implantable Defibrillators

Background: The use of transcutaneous electrical nerve stimulation (TENS) for pain relief is increasing.At the same time the implantable cardioverter defibrillator (ICD) is a routine treatment for malignant tachyarrhythmias. Today patients often need devices for more than one condition, and consideration must be given to the interaction between them. We studied the risk of interference between TENS and the ICD function.

Methods and Results: Thirty patients who had received an ICD underwent a test protocol including TENS at the mammilla and hip levels, at two energy levels, and at the highest comfortable stimulation level. The effects of TENS on the electrocardiogram lead II, intracardiac electrograms, and the ICD marker channels were analyzed. Disturbance from TENS on the sensing function was seen at all stimulation attempts. Interference between the systems was observed in 16 patients. In eight patients (27%) the interpretation was VT/VF and in 14 patients (47%) as ventricular premature extra beats. Other kinds of interactions were seen in five patients (16%). Each patient could have more than one kind of interference.

Conclusions: Noise reversion and undersensing might prevent the ICD from delivering shock when it should and the interpretation as VT/VF could result in inappropriate shocks. Because of the potentially serious consequences of interference we do not recommend the use of TENS in patients with ICD.