Infection in patients with subcutaneous implantable cardioverter-defibrillator: Results of the S-ICD Post Approval Study.

BACKGROUND: Early subcutaneous implantable cardioverter-defibrillator (S-ICD) studies included atypical cohorts of patients who were younger with fewer comorbidities. Recent S-ICD studies included patient populations with more comorbidities. OBJECTIVES: The goals of this study were to determine the incidence and predictors of S-ICD-related infection over a 3-year follow-up period and to use these results to develop an infection risk score. METHODS: The S-ICD Post Approval Study is a US prospective registry of 1637 patients. Baseline demographic characteristics and outcomes with 3-year postimplantation follow-up were compared between patients with and without device-related infection. A risk score was derived from multivariable proportional hazards analysis of 22 variables. RESULTS: Infection was observed in 55 patients (3.3%), with 69% of infections occurring within 90 days and a vast majority (92.7%) within 1 year of implantation. Late infections more likely involved device erosion; no infections occurred after year 2. The annual mortality rate postinfection was 0.6%/y. No lead extraction complications or bacteremia related to infection were observed. An infection risk score was created with diabetes, age, prior transvenous ICD implant, and ejection fraction as predictors. Patients with a risk score of ≥3 had an 8.8 hazard ratio (95% confidence interval 2.8-16.3) of infection compared with a 0 risk score. CONCLUSION: Infection rates in the S-ICD Post Approval Study were similar to other S-ICD populations and not associated with systemic blood-borne infections. Late infection (>1 year) is uncommon and associated with system erosion. A high-risk infection cohort can be identified that may facilitate preventive measures.

Assessment of primary prevention patients receiving an ICD - Systematic evaluation of ATP: APPRAISE ATP.

BACKGROUND: The value of antitachycardia pacing (ATP) in the overall cohort of primary prevention patients who receive implantable cardioverter-defibrillators (ICDs) remains uncertain. ATP success reported in prior trials potentially included a large number of patients receiving unnecessary ATP for arrhythmias that may have self-terminated owing to the prematurity of the intervention. Although some patients derive benefit from initial ATP in terminating rapid ventricular arrhythmias and thereby preventing shocks, there are limited data allowing us to identify those patients a priori. OBJECTIVE: The purpose of APPRAISE ATP is to understand the role of ATP in primary prevention patients currently indicated for ICD therapy in a large prospective randomized controlled trial with modern programming parameters. METHODS: The study is a global, prospective, randomized, multicenter clinical trial conducted at up to 150 sites globally, enrolling approximately 2600 subjects The primary endpoint of the trial is time to first all-cause shock in a 2-arm study with an equivalent study design in which the incidence of all-cause shocks will be compared between primary prevention subjects programmed with shocks only vs subjects programmed to standard therapy (ATP and shock). RESULTS: An Electrogram and Device Interrogation Core Laboratory will review interrogation data to determine primary endpoints that occur in APPRAISE ATP. Their decisions are based on independent physician review of the data from device interrogation. CONCLUSION: The ultimate purpose of the study is to aid clinicians in the selection of ICD technologies based on hard endpoint evidence across the spectrum of indications for primary prevention implantation.

An unusual ECG deflection: Fact or artifact?

Peculiar electrocardiographic findings are not unusual and upon careful review can often be clarified. We present a case of an 85year-old woman with no previous cardiac history, incidentally discovered high grade atrioventricular block, and a puzzling electrocardiographic complex of unclear etiology which defies reasonable physiological explanations. The finding resembled a tiny QRS in a perfectly regular R-R interval following only non-conducted P-waves. The patient declined further work-up, so a definite cause could not be determined, but based on history, complex morphology, and inability to reproduce or explain the findings, we were compelled to accept the finding as an artifact.

Heart failure severity, inappropriate ICD therapy, and novel ICD programming: a MADIT-RIT substudy.

BACKGROUND: The effects of heart failure (HF) severity on risk of inappropriate implantable cardioverter-defibrillator (ICD) therapy have not been thoroughly investigated. We aimed to study the association between HF severity and inappropriate ICD therapy in MADIT-RIT. METHODS: MADIT-RIT randomized 1,500 patients to three ICD programming arms: conventional (Arm A), high-rate cut-off (Arm B: ≥200 beats/min), and delayed therapy (Arm C: 60-second delay for ≥170 beats/min). We evaluated the association between New York Heart Association (NYHA) class III (n = 256) versus class I-II (n = 251) and inappropriate ICD therapy in Arm A patients with ICD-only and cardiac resynchronization therapy with defibrillator (CRT-D). We additionally assessed benefit of novel ICD programming in Arms B and C versus Arm A by NYHA classification. RESULTS: In Arm A, the risk of inappropriate therapy was significantly higher in those with NYHA III versus NYHA I-II for both ICD (hazard ratio [HR] = 2.55, confidence interval [CI]: 1.51-4.30, P < 0.001) and CRT-D patients (HR = 3.73, CI: 1.14-12.23, P = 0.030). This was consistent for inappropriate ATP and inappropriate ICD therapy < 200 beats/min, but not for inappropriate shocks. Novel ICD programming significantly reduced inappropriate therapy in patients with both NYHA III (Arm B vs Arm A: HR = 0.08, P < 0.001; Arm C vs Arm A: HR = 0.17, P < 0.001) and NYHA I-II (Arm B vs Arm A: HR = 0.25, P < 0.001; Arm C vs Arm A: HR = 0.28, P < 0.001). CONCLUSION: Patients with more severe HF are at increased risk for inappropriate ICD therapy, particularly ATP due to arrhythmias < 200 beats/min. Novel programming with high-rate cut-off or delayed detection reduces inappropriate ICD therapies in both mild and moderate HF.

Long-Term Success of Irrigated Radiofrequency Catheter Ablation of Sustained Ventricular Tachycardia: Post-Approval THERMOCOOL VT Trial.

BACKGROUND: Radiofrequency catheter ablation is used to treat recurrent ventricular tachycardia (VT). OBJECTIVES: This study evaluated long-term safety and effectiveness of radiofrequency catheter ablation using an open-irrigated catheter. METHODS: Patients with sustained monomorphic ventricular tachycardia associated with coronary disease were analyzed for cardiovascular-specific adverse events within 7 days of treatment, hospitalization duration, 6-month sustained monomorphic ventricular tachycardia recurrence, quality of life measured by the Hospital Anxiety and Depression Scale, long-term (1-, 2-, and 3-year) survival, symptomatic VT control, and amiodarone use. RESULTS: Overall, 249 patients, mean age 67.4 years, were enrolled. The cardiovascular-specific adverse events rate was 3.9% (9 of 233) with no strokes. Noninducibility of targeted VT was achieved in 75.9% of patients. Post-ablation median hospitalization was 2 days. At 6 months, 62.0% (114 of 184) of patients had no sustained monomorphic ventricular tachycardia recurrence; the proportion of patients with implantable cardioverter-defibrillator shocks decreased from 81.2% to 26.8% (p < 0.0001); the frequency of VT in implantable cardioverter-defibrillator patients with recurrences was reduced by ≥50% in 63.8% of patients; and the proportion with normal Hospital Anxiety and Depression Scale scores increased from 48.8% to 69.1% (p < 0.001). Patient-reported VT remained steady for 1, 2, and 3 years at 22.7%, 29.8%, and 24.1%, respectively. Amiodarone use and hospitalization decreased from 55% and 77.2% pre-ablation to 23.3% and 30.7%, 18.5% and 36.7%, 17.7% and 31.3% at 1, 2, and 3 years, respectively. CONCLUSIONS: Radiofrequency catheter ablation reduced implantable cardioverter-defibrillator shocks and VT episodes and improved quality of life at 6 months. A steady 3-year nonrecurrence rate with reduced amiodarone use and hospitalizations indicate improved long-term outcomes. (NaviStar ThermoCool Catheter for Endocardial RF Ablation in Patients With Ventricular Tachycardia [THERMOCOOL VT]; NCT00412607).

Fluoroscopic investigation of Riata® transvenous defibrillator leads.

BACKGROUND: Implantable cardioverter-defibrillator leads from Riata® family (St. Jude Medical Inc., Sylmar, CA, USA) have been recently recalled by Food and Drug Administration for concerns of a unique type of "inside-out" insulation failure leading to conductor externalization. The objective of this study was to evaluate the prevalence and predictors of conductor externalization in patients implanted with Riata 8 French (Fr) and 7 Fr leads. METHODS: Patients implanted with Riata® and Riata ST® who were actively followed up in our institution were scheduled for high resolution 3 view fluoroscopy and device interrogation including high voltage (HV) lead impedance testing. Fluoroscopic images were graded as presence of externalization or no externalization. RESULTS: Of the 90 patients who underwent screening fluoroscopy, majority had dual coil leads (62.5%) and median duration from the implant time to screening was 79.5 months. Twenty four (26.7%) patients exhibited evidence of lead externalization with 10 (41.6%) of these showing electrical abnormalities at the time of screening. No externalization was seen in the 7 Fr leads. Pacing thresholds were significantly elevated in the externalized cohort compared to non-externalized group (1.42 ± 1.23 vs. 0.93 ± 0.53; p = 0.01). Time since lead implant and lead diameter emerged as significant predictors of lead externalization on univariate analysis with only lead diameter being significant on multivariate analysis (odds ratio 30.68; 4.95-∞, p = 0.001). CONCLUSIONS: Prevalence of insulation failure exhibiting as conductor externalization is high (26.7%) among the large diameter 8 Fr Riata® leads with a significant proportion of patients manifesting electrical failure. High resolution 3 view fluoroscopy is a reasonable approach to screen for this unique type of insulation failure.

Effect of defibrillation threshold testing on heart failure hospitalization or death in the Multicenter Automatic Defibrillator Implantation Trial-Cardiac Resynchronization Therapy (MADIT-CRT).

BACKGROUND: Defibrillation threshold (DFT) testing is commonly practiced at the time of implantable cardioverter-defibrillator (ICD) implant. The clinical consequence of ICD shocks delivered during DFT testing is unknown. OBJECTIVE: The purpose of this study was to determine the impact of ICD shocks and ICD shock energy level delivered during DFT testing in patients enrolled in the Multicenter Automatic Defibrillator Implantation Trial with Cardiac Resynchronization Therapy (MADIT-CRT) on clinical outcomes. METHODS: Patients who underwent DFT testing within 1 month of device implant were categorized by the number of ICD shocks delivered during DFT testing (0, 1, 2, ≥3 shocks) and according to high vs low (>20 J vs ≤20 J) energy ICD shocks. Clinical outcomes consisting of heart failure (HF) or death, death alone, HF alone, and ventricular tachycardia or ventricular fibrillation were analyzed in each group. RESULTS: DFT testing was performed in 1,659 patients within 1 month of device implant (1 shock in 365 patients, 2 shocks in 896 patients, 3+ shocks in 398 patients). High-energy ICD shocks were delivered in 609 patients. Increasing number of ICD shocks during DFT testing was not associated with an increase risk for the primary end-point of HF or death or for any of the secondary end-points of HF alone, VT/VF alone, or death. Delivery of high vs low-energy ICD shocks was not associated with adverse clinical outcomes. CONCLUSIONS: In patients with mild symptoms of HF, increasing number of ICD shocks and delivery of high energy ICD shocks during DFT testing was not associated with increased risk for HF or death or future VT/VF episodes.

Failure to deliver therapy by a Riata Lead with internal wire externalization and normal electrical parameters during routine interrogation.

We present a case of failure to deliver a shock by a St. Jude Medical defibrillator involving a Riata lead that was discovered incidentally while the device was attempting to deliver inappropriate therapy. Routine interrogation, including high voltage (HV) impedance, failed to reveal any abnormality. Failure to deliver therapy was confirmed during DFT testing, which revealed extremely low HV impedance only while attempting to deliver therapy. Fluoroscopy indicated moderate externalization of internal wires. This case highlights an under-recognized issue with St. Jude Medical systems, namely the possibility that therapy may not be delivered despite the presence of normal electrical parameters during routine surveillance.

Strategies for pacemaker programming in acute heart failure.

In the past decade, cardiac pacing devices (either permanent pacemakers or Implanted Cardioverter Defibrillators) have become increasingly common in patients with heart failure. The manner in which the device is programmed to pace the heart can have significant implications on cardiac hemodynamics, both positive and negative. As such, in patients hospitalized with acute heart failure who have cardiac pacing devices, the clinician should note whether the programming of the device could be contributing to the patient's symptoms, and whether further programming changes could be made to improve the patient's clinical status. As of this date, there are no consensus guidelines available for the management of pacemaker programming in acute heart failure. This review article will discuss the physiologic implications of several parameters of pacemaker programming on heart failure, including the degree of RV pacing, the programmed atrioventricular (AV) interval, and the programmed interventricular pacing delay in patients with cardiac resynchronization therapy (CRT) devices. Based on the available data on the above parameters, this article will then propose a general algorithmic approach to the evaluation and management of patients with pacing devices who are hospitalized with acute heart failure.

Effect of race on the frequency of postoperative atrial fibrillation following coronary artery bypass grafting.

Atrial fibrillation (AF) commonly complicates the postoperative course after coronary artery bypass grafting (CABG). Among the general population, African Americans have been shown to have a lower prevalence of AF than European Americans. Although many factors have been identified to predict risk for postoperative AF, race has not been examined. All patients aged ≥18 years who underwent CABG at Henry Ford Hospital during a 5-year period from January 1, 2004, to December 31, 2008, were included. Patients were excluded for any previous diagnosis of AF or if they had concomitant valve surgery at the time of CABG. The incidence of AF was determined by International Classification of Diseases, Ninth Revision, coding from postoperative hospitalization records. Overall, 1,001 patients were eligible for analysis. Of these, 731 (73%) were European American and 270 (27%) were African American. The African American group had a higher prevalence of hypertension (75.6% vs 58.8%, p <0.001) and heart failure (22.6% vs 15.7%, p = 0.01) and a trend toward a higher prevalence of diabetes mellitus (38.1% vs 33.4%, p = 0.159). Postoperative AF was diagnosed in 214 European Americans (29.3%) and 50 African Americans (18.5%) (p = 0.001). In multivariate analysis adjusting for age strata, gender, hypertension, diabetes, and heart failure, African Americans had less postoperative AF than European Americans, with an adjusted odds ratio of 0.539 (95% confidence interval 0.374 to 0.777, p = 0.001). In conclusion, African Americans have a significantly reduced incidence of AF compared to European Americans after CABG.

Vasovagal syncope misdiagnosed as epilepsy for 17 years: prime importance of clinical history.

Distinguishing epilepsy from syncope often can be challenging. We report a case of a 20-year-old patient with presumed refractory epilepsy since the age of 3 years. Although the clinical suspicion of syncope was raised at the age of 9 years, key historic features were not identified, cardiac work-up was not pursued and despite lack of electrographic evidence of epilepsy, he received anticonvulsant treatment. During his presurgical evaluation for "refractory epilepsy", one typical event was captured that was associated with asystole and normal electroencephalogram. The diagnosis of vasodepressor syncope was made and anticonvulsant medication was discontinued. With this case report, we would like to emphasize the importance of a meticulous history and the need to perform continuous video electroencephalographic with simultaneous electrocardiographic recordings in the evaluation of paroxysmal events with atypical presentation. [Published with video sequences].

Mechanisms of ventricular arrhythmias in heart failure.

Congestive heart failure continues to be a leading cause of mortality and morbidity worldwide. In approximately 50% of these patients, the mode of death is sudden. Ventricular tachycardia and fibrillation represent the majority of arrhythmias; the mechanisms responsible are heterogeneous and complex. Myocardial scar, a potent environment for reentry, is likely to contribute to many of the ventricular arrhythmias in ischemic heart failure. Altered calcium handling and changes in potassium currents may contribute to the increase in early and delayed afterdepolarizations seen in the failing heart. In addition, compensatory mechanisms may become deleterious and potentially arrhythmogenic via a variety of mechanisms. This article provides a general overview of the mechanisms thought to be responsible for ventricular arrhythmias in chronic heart failure.

Mechanism of atrial flutter occurring late after orthotopic heart transplantation with atrio-atrial anastomosis.

OBJECTIVE: We sought to better define the electrophysiologic mechanism of atrial flutter in patients after heart transplantation. BACKGROUND: Atrial flutter is a recognized problem in the post-cardiac transplant population. The electrophysiologic basis of atrial flutter in this patient population is not completely understood. METHODS: Six patients with cardiac allografts and symptoms related to recurrent atrial flutter underwent diagnostic electrophysiologic study with electroanatomic mapping and radiofrequency catheter ablation. Comparison was made with a control non-transplant population of 11 patients with typical counterclockwise right atrial flutter. RESULTS: In each case, mapping showed typical counterclockwise activation of the donor-derived portion of the right atrium, with concealed entrainment shown upon pacing in the cavotricuspid isthmus (CTI). The anastomotic suture line of the atrio-atrial anastomosis formed the posterior barrier of the reentrant circuit. Ablation of the electrically active, donor-derived portion of the CTI was sufficient to terminate atrial flutter and render it noninducible. Comparison with the control population showed that the electrically active portion of the CTI was significantly shorter in patients with transplant-associated flutter and that ablation was accomplished with the same or fewer radiofrequency lesions. CONCLUSIONS: Atrial flutter in cardiac transplant recipients is a form of typical counterclockwise, isthmus-dependent flutter in which the atrio-atrial anastomotic suture line forms the posterior barrier of the reentrant circuit. Ablation in the donor-derived portion of the CTI is sufficient to create bidirectional conduction block and eliminate this arrhythmia. Ablation or surgical division of the donor CTI at the time of transplantation could prevent this arrhythmia.

Amiodarone versus implantable cardioverter-defibrillator:randomized trial in patients with nonischemic dilated cardiomyopathy and asymptomatic nonsustained ventricular tachycardia--AMIOVIRT.

OBJECTIVES: The purpose of this multicenter randomized trial was to compare total mortality during therapy with amiodarone or an implantable cardioverter-defibrillator (ICD) in patients with nonischemic dilated cardiomyopathy (NIDCM) and nonsustained ventricular tachycardia (NSVT). BACKGROUND: Whether an ICD reduces mortality more than amiodarone in patients with NIDCM and NSVT is unknown. METHODS: One hundred three patients with NIDCM, left ventricular ejection fraction < or =0.35, and asymptomatic NSVT were randomized to receive either amiodarone or an ICD. The primary end point was total mortality. Secondary end points included arrhythmia-free survival, quality of life, and costs. RESULTS: The study was stopped when the prospective stopping rule for futility was reached. The percent of patients surviving at one year (90% vs. 96%) and three years (88% vs. 87%) in the amiodarone and ICD groups, respectively, were not statistically different (p = 0.8). Quality of life was also similar with each therapy (p = NS). There was a trend with amiodarone, as compared to the ICD, towards improved arrhythmia-free survival (p = 0.1) and lower costs during the first year of therapy ($8,879 US dollars vs. $22,039 US dollars, p = 0.1). CONCLUSIONS: Mortality and quality of life in patients with NIDCM and NSVT treated with amiodarone or an ICD are not statistically different. There is a trend towards a more beneficial cost profile and improved arrhythmia-free survival with amiodarone therapy.

La brecha excitable en la taquicardia auriculoventricular por reentrada nodal / The excitable gap in atrioventricular nodal reentrant tachycardia

La taquicardia auriculoventricular por reentrada nodal es una causa común de taquicardia con complejos angostos y es la arritmia supraventricular paroxística encontrada más frecuentemente en la práctica clínica. Los avances en las técnicas de ablación por catéter han descartado la importancia del conocimiento más completo del sustrato anatómico y electrofisiológico de esta taquiarritmia. El circuito más común resulta de la disociación longitudinal de la conducción en el nódulo AV, en un componente anterógrado "lento" y otro retrógrado "rápido". Cuando la taquicardia se debe a reentrada funcional o anatómica, una brecha excitable está presente comúnmente entre la cola de refractariedad del último impulso de la taquicardia y el nuevo frente de onda. Un extraestímulo debería ser capaz de penetrar el circuito de reentrada en un momento apropiado y activar el tejido excitable de un modo similar al del frente de onda reentrante. Este fenómeno se denomina reciclado (resetting). Cuando el circuito de la taquicardia es penetrado por un tren de extraestímulos, resultando en un reciclado repetitivo, el fenómeno se denomina entrecruzamiento (entrainment)