BACKGROUND:Inappropriate therapy (IAT) is an undesirable side effect of implantable cardiac defibrillator (ICD) therapy. Early studies with the subcutaneous ICD (S-ICD) showed relatively high inappropriate shock (IAS) rates. The PRAETORIAN (Prospective Randomized Comparison of Subcutaneous and Transvenous Implantable Cardioverter Defibrillator Therapy) trial demonstrated that the S-ICD is noninferior to the transvenous ICD (TV-ICD) with regard to the combined end point of IAS and complications. This secondary analyses evaluates all IAT in the PRAETORIAN trial. METHODS:This international, multicenter trial randomized 849 patients with an indication for ICD therapy between S-ICD (n=426) and TV-ICD therapy (n=423). ICD programming was mandated by protocol. All analysis were performed in the modified intention-to-treat population. RESULTS:In both groups 42 patients experienced IAT (48-month Kaplan-Meier estimated cumulative incidence, 9.9% and 10.1%, respectively; hazard ratio (HR), 0.99 [95% CI, 0.65-1.52]; P=0.97). There was no significant difference in patients experiencing IAS between both groups (P=0.14). In the S-ICD group, 81 IAT episodes with 124 IAS and 1 inappropriate antitachycardia pacing occurred versus 89 IAT episodes with 130 IAS and 124 inappropriate antitachycardia pacing in the TV-ICD group. IAT episodes were most frequently caused by supraventricular tachycardias in the TV-ICD group (n=83/89) versus cardiac oversensing in the S-ICD group (n=40/81). In the TV-ICD group, a baseline heart rate >80 bpm (HR, 1.99 [95% CI, 1.05-3.76]; P=0.03), a history of atrial fibrillation (HR, 2.66 [95% CI, 1.41-5.02]; P=0.003), and smoking (HR, 2.46 [95% CI, 1.31-4.09]; P=0.005) were independent predictors for IAT. A QRS duration >120 ms was an independent predictor for IAT caused by cardiac oversensing in the S-ICD group (HR, 3.13 [95% CI, 1.34-7.31]; P=0.008). Post-IAS interventions significantly reduced IAS recurrence in both groups (P=0.046). CONCLUSIONS:There was no significant difference in IAT and IAS rates between the S-ICD and TV-ICD in a conventional ICD population, but causes and predictors for IAT differed between the devices. After the first IAS, an intervention significantly reduced the recurrence rate of IAS. REGISTRATION:URL: https://www.clinicaltrials.gov; Unique identifier: NCT01296022.

BACKGROUND:The PRAETORIAN trial (A Prospective, Randomized Comparison of Subcutaneous and Transvenous Implantable Cardioverter Defibrillator Therapy) showed noninferiority of subcutaneous implantable cardioverter defibrillator (S-ICD) compared with transvenous implantable cardioverter defibrillator (TV-ICD) with regard to inappropriate shocks and complications. In contrast to TV-ICD, S-ICD cannot provide antitachycardia pacing for monomorphic ventricular tachycardia. This prespecified secondary analysis evaluates appropriate therapy and whether antitachycardia pacing reduces the number of appropriate shocks. METHODS:The PRAETORIAN trial was an international, investigator-initiated randomized trial that included patients with an indication for implantable cardioverter defibrillator (ICD) therapy. Patients with previous ventricular tachycardia <170 bpm or refractory recurrent monomorphic ventricular tachycardia were excluded. In 39 centers, 849 patients were randomized to receive an S-ICD (n=426) or TV-ICD (n=423) and were followed for a median of 49.1 months. ICD programming was mandated by protocol. Appropriate ICD therapy was defined as therapy for ventricular arrhythmias. Arrhythmias were classified as discrete episodes and storm episodes (≥3 episodes within 24 hours). Analyses were performed in the modified intention-to-treat population. RESULTS:In the S-ICD group, 86 of 426 patients received appropriate therapy, versus 78 of 423 patients in the TV-ICD group, during a median follow-up of 52 months (48-month Kaplan-Meier estimates 19.4% and 17.5%; P=0.45). In the S-ICD group, 83 patients received at least 1 shock, versus 57 patients in the TV-ICD group (48-month Kaplan-Meier estimates 19.2% and 11.5%; P=0.02). Patients in the S-ICD group had a total of 254 shocks, compared with 228 shocks in the TV-ICD group (P=0.68). First shock efficacy was 93.8% in the S-ICD group and 91.6% in the TV-ICD group (P=0.40). The first antitachycardia pacing attempt successfully terminated 46% of all monomorphic ventricular tachycardias, but accelerated the arrhythmia in 9.4%. Ten patients with S-ICD experienced 13 electrical storms, versus 18 patients with TV-ICD with 19 electrical storms. Patients with appropriate therapy had an almost 2-fold increased relative risk of electrical storms in the TV-ICD group compared with the S-ICD group (P=0.05). CONCLUSIONS:In this trial, no difference was observed in shock efficacy of S-ICD compared with TV-ICD. Although patients in the S-ICD group were more likely to receive an ICD shock, the total number of appropriate shocks was not different between the 2 groups. Registration: URL: https://www.clinicaltrials.gov; Unique identifier: NCT01296022.

Background The subcutaneous implantable cardioverter-defibrillator (S-ICD) is developed to overcome lead-related complications and systemic infections, inherent to transvenous ICD (TV-ICD) therapy. The PRAETORIAN trial demonstrated that the S-ICD is non-inferior to the TV-ICD with regard to the combined primary endpoint of inappropriate shocks and complications. This prespecified secondary analysis evaluates all complications in the PRAETORIAN trial. Methods and results The PRAETORIAN trial is an international, multicentre, randomized trial in which 849 patients with an indication for ICD therapy were randomized to receive an S- ICD (N = 426) or TV-ICD (N = 423) and followed for a median of 49 months. Endpoints were device-related complications, lead-related complications, systemic infections, and the need for invasive interventions. Thirty-six device-related complications occurred in 31 patients in the S-ICD group of which bleedings were the most frequent. In the TV-ICD group, 49 complications occurred in 44 patients of which lead dysfunction was most frequent (HR: 0.69; P = 0.11). In both groups, half of all complications were within 30 days after implantation. Lead-related complications and systemic infections occurred significantly less in the S-ICD group compared with the TV-ICD group (P < 0.001, P = 0.03, respectively). Significantly more complications required invasive interventions in the TV-ICD group compared with the S-ICD group (8.3% vs. 4.3%, HR: 0.59; P = 0.047). Conclusion This secondary analysis shows that lead-related complications and systemic infections are more prevalent in the TV-ICD group compared with the S-ICD group. In addition, complications in the TV-ICD group were more severe as they required significantly more invasive interventions. This data contributes to shared decision-making in clinical practice.

Introduction: The randomized PRAETORIAN trial demonstrated non-inferiority of the subcutaneous implantable cardioverter-defibrillator (S-ICD) compared to the transvenous ICD (TV-ICD) with regard to inappropriate shocks and complications. Due to its extrathoracic position, the S-ICD lacks the possibility to provide antitachycardia pacing (ATP) which might result in more appropriate shock therapy. In this pre-specified secondary analysis, we aim to compare first occurrence of appropriate therapy in the S-ICD and TV-ICD. Methods: The PRAETORIAN trial is an international, multicenter, randomized trial (NCT01296022) in which 849 patients with a class I or IIa indication for ICD therapy and without the need for pacing were randomized in a 1:1 ratio to receive either an S-ICD (n = 426) or a TV-ICD (n = 423). Analyses were performed in the modified intention-to-treat population, which included patients according to the group to which they had been randomly assigned regardless of the device they received, but excluded patients who did not receive any ICD. Results: At a median follow-up of 49.1 months, 164 patients received appropriate therapy, of whom 86 in the S-ICD group and 78 in the TV-ICD group (48-month Kaplan-Meier estimated cumulative incidence 19.4% and 17.5%, respectively; hazard ratio 1.12; 95%CI, 0.83 to 1.53; p=0.45). In 83 patients (97%) in the S-ICD group the first arrhythmia was treated with a shock and in 3 patients (3%) with ATP. In 25 patients (32%) in the TV-ICD group the first arrhythmia was treated with a shock, in 31 patients (40%) solely with ATP and in 22 patients (28%) with ATP followed by a shock. Conclusions: In this secondary analysis of the PRAETORIAN trial, we found no statistical difference in first occurrence of appropriate therapy in the S-ICD group and TV-ICD group. Due to ATP, patients were less often treated with shocks in the TV-ICD group. A further analysis of all appropriate therapy in the PRAETORIAN trial could reveal the true benefit of ATP.

The high recurrence rate of persistent AF after PVI has led to interest in the underlying substrate maintaining AF. Rotational activity, slow conduction, and automatic activity have been proposed. No methods to identify critical sites have been validated through convincing clinical trials, and no gold standard exists to evaluate the commercially available mapping systems applicable to this purpose.

BACKGROUND:Medtronic implantable cardioverter defibrillators (ICDs; Medtronic Inc., Mounds View, MN, USA) are equipped with Patient Alert™, a feature in which the ICD generator emits a series of audible tones to notify patients of possible system malfunction. A prior study of this issue revealed that only 50% of patients with older Medtronic devices were able to hear alerts. More recently, Medtronic has incorporated modifications to the alert. Therefore, we studied how frequently alert tones emitted by the current generation of Medtronic ICDs are audible by patients. METHODS:A series of patients were evaluated in an outpatient ICD clinic. Alert tones were demonstrated using a device programmer in a quiet room and in the presence of low-level background noise. Patients reported whether they heard the tones, and they completed questionnaires regarding the tones. RESULTS:The total sample size was 100 patients, 81 male, who ranged from 29 years to 94 years of age (mean age 72.1 ± 11.8). Among the study subjects, 46% were older than 75 years, 41% were between 55 years and 75 years, and 13% were younger than 55 years. In the absence of background noise, 94% of patients were able to hear both alerts, 1% heard only one alert, and 5% heard neither. In the presence of background noise, 88% of patients heard both the alerts, 7% heard only one alert, and 5% heard neither alerts. CONCLUSIONS:Our results demonstrate that alert tones in recent generation Medtronic ICDs have improved audibility, compared to prior published data, among a large outpatient ICD population.

Radiofrequency catheter ablation of atrial fibrillation carries a risk of thermal damage to extracardiac structures, including the esophagus and the phrenic nerves [(1–3)][1]; however, aortic complications have not been described previously. We report a case of aortic intramural hematoma in a 68-

Methods: During visits to an outpatient device clinic, patients with Medtronic ICDs were evaluated for their ability to hear ICD tones.Results: The patient group consisted of 102 patients. Patients older than 70 years comprised 68% of the sample, with 16% between 60 and 70, and 17% younger than 60 years. Of the 102 patients, 59% (56% of males and 70% of females) were able to hear at least one tone. Ability to hear ICD tones decreased with advancing age. Among patients over 60 and 70 years, 52% and 43%, respectively (P < 0.001 vs. patients below 60 and 70 years), could hear at least one tone.Conclusions: The Patient Alert (TM) feature is not useful among a large proportion of ICD patients. Patients with Sprint Fidelis leads should be evaluated for their ability to hear audible ICD tones. For patients who cannot hear the Patient Alert (TM) feature, a wireless remote monitoring and/or daily application of a magnet by a caregiver should be considered. Device manufacturers should include nonauditory alert technologies such as wireless remote monitoring and vibratory stimulation in future devices.(PACE 2009; 1272-1275).

BACKGROUND:The autonomic nervous system is thought to be involved in the initiation of atrial fibrillation (AF). However, there is a distinct entity of vagal AF characterized by episodes occurring at rest, postprandially, or during sleep. The purpose of this study was to compare intraatrial conduction in patients with vagally mediated AF to those with nonvagal AF, using the signal-averaged electrocardiogram (SAECG) of P wave.METHODS:SAECG of P wave was performed in 58 patients with AF using the Marquette Medical System, and the mean filtered P-wave duration (SAPW) was measured. Nine patients were categorized as having pure vagal AF (Group I), and 42 patients as having nonvagal AF (Group II); the remaining seven patients were excluded from analysis because of incomplete data.RESULTS:The patients in Group I were significantly younger and more likely to have paroxysmal lone AF, as compared to those in Group II. There was no significant difference in left atrial size and left ventricular function in the two groups. The mean SAPW was significantly shorter in Group I when compared to Group II (118 +/- 5 ms vs 149 +/- 39 ms, P < 0.001). Whereas all patients in Group I had a normal SAPW, 79% of patients in Group II had an abnormal SAPW (P < 0.001). A normal SAPW was significantly predictive of vagal AF independent of other co-variables.CONCLUSIONS:(1) Patients with vagal AF are younger, and invariably have paroxysmal lone AF. (2) SAPW is normal and significantly shorter in vagal AF when compared to patients with nonvagal AF. (3) This suggests that those in the vagal AF population have normal intraatrial conduction, which has implications for AF ablation in these patients.

Background: Brief atrial high rate episodes (AHREs) of even 5 minutes duration, as detected by pacemaker (PPM) diagnostics, are a reliable surrogate for atrial fibrillation (AF) and potentially identify patients at increased risk for stroke and death. However, the incidence and predictors of de novo AF following dual chamber PPM implantation are unknown. Methods : We retrospectively evaluated 127 patients (71 male; 76 ± 11 years) without documented AF who underwent PPM implantation for management of sinus node dysfunction. Information regarding patient demographics, cardiovascular diseases, and medication history was obtained. The cumulative percentage of right ventricular pacing (Cum VP) was determined. Results : During a mean follow-up of 599 ± 353 days, 33 (26%) patients had an AHRE ≥ 5 minutes. Age, gender, ejection fraction, co-morbid medical conditions, use of medications, and burden of atrial pacing were similar between patients with and without AHREs during the follow-up period. The only significant predictor of an AHRE was ≥ 50% Cum VP (RR 2.2; CI [1.1–4.8]; p = 0.03, Figure). The 1- and 2-year incidence of an AHRE Conclusions: Cumulative right ventricular pacing ≥ 50% was the sole significant predictor of de novo AF (defined as an AHRE ≥ 5 minutes) in patients with sinus node dysfunction following dual chamber PPM implantation and is associated with a more than two-fold increased risk of AF. The routine use of novel pacing strategies that minimize right ventricular pacing merits prospective investigation as a means of reducing the incidence of de novo AF in this population.

Introduction : Multiple randomized clinical trials have shown that an ICD improves survival in patients (pts) with an ischemic cardiomyopathy. Although a life expectancy ≤ 1 year is considered a contraindication to ICD implantation, the incidence and predictors of early mortality remain undefined. Methods : We evaluated consecutive pts with ischemic heart disease and depressed left ventricular ejection fraction (LVEF ≤ 35%) who underwent prophylactic ICD implantation between February 2002 and December 2004. No pt underwent pre-implant electrophysiologic testing. Predictors of mortality within one year of ICD implantation were determined using Cox-regression analysis. Results : The study population consisted of 123 pts (103 male, age 70 ± 11 years) with a mean EF of 25 ± 6 %. The mean QRS duration was 149 ± 29 msec and 75 (61%) pts had class III CHF. Sixty-two (50%) pts received a LV lead. During a follow-up of 2.1 ± 1.1 years, 34 (28%) pts died. Overall, 22 (65%) of these 34 pts died ≤ 1 year post-ICD implantation. Pts who died within a year were less likely to be taking a β-blocker (73 vs 93%, p=0.005) and more likely to have unrevascularized coronary artery disease (32 vs 15%, p=0.06). No other predictor of early mortality was identified. In multivariate analysis, lack of β-blocker use was the only predictor of early mortality (RR 3.6, 95% CI: 1.4–9.3, p=0.007). The 1-year mortality in pts not taking a β-blocker was 43%. Conclusions : In a real world population of pts with an ischemic cardiomyopathy, overall mortality is high in the first year after ICD implantation. Lack of β-blocker use significantly increases the likelihood of early mortality in these pts.

Background: Vagal atrial fibrillation is characterized by paroxysms occurring at rest or during sleep and generally terminating with exercise or in the morning. The electroanatomic substrate of patients with vagal atrial fibrillation has not been well studied. Our aim was to determine whether there is a difference in intra-atrial conduction time, as measured by the signal-averaged electrocardiogram of the P wave, between patients with vagal and non-vagal atrial fibrillation.