Randomized Trial of Pacemaker and Lead System for Safe Scanning at 1.5 Tesla

BackgroundMagnetic resonance imaging (MRI) of pacemakers is a relative contraindication because of the risks to the patient from potentially hazardous interactions between the MRI and the pacemaker system. Chest scans (ie, cardiac magnetic resonance scans) are of particular importance and higher risk. The previously Food and Drug Administration-approved magnetic resonance conditional system includes positioning restrictions, limiting the powerful utility of MRI.ObjectiveTo confirm the safety and effectiveness of a pacemaker system designed for safe whole body MRI without MRI scan positioning restrictions.MethodsPrimary eligibility criteria included standard dual-chamber pacing indications. Patients (n = 263) were randomized in a 2:1 ratio to undergo 16 chest and head scans at 1.5 T between 9 and 12 weeks postimplant (n = 177) or to not undergo MRI (n = 86) post-implant. Evaluation of the pacemaker system occurred immediately before, during (monitoring), and after MRI, 1-week post-MRI, and 1-month post-MRI, and similarly for controls. Primary end points measured the MRI-related complication-free rate for safety and compared pacing capture threshold between MRI and control subjects for effectiveness.ResultsThere were no MRI-related complications during or after MRI in subjects undergoing MRI (n = 148). Differences in pacing capture threshold values from pre-MRI to 1-month post-MRI were minimal and similar between the MRI and control groups.ConclusionsThis randomized trial demonstrates that the Advisa MRI pulse generator and CapSureFix MRI 5086MRI lead system is safe and effective in the 1.5 T MRI environment without positioning restrictions for MRI scans or limitations of body parts scanned

Defibrillator Shocks and Their Impact on Objective and Subjective Patient Outcomes: Results from the Painfree SST Clinical Trial

BACKGROUND: The impact of ICD shock on device-measured activity and patient reported outcomes is unknown. OBJECTIVE: The purpose of this study was to analyze the acute and long-term effects of ICD shock on objective behavioral data (i.e., device-based physical activity) and subjective patient reported outcomes (e.g., quality of life and shock anxiety). METHODS: The PainFree SST clinical trial included 2,770 patients with a single or dual-chamber ICD, or cardiac resynchronization defibrillator (CRT-D) who were followed for 22 ± 9 months. Participants completed measures of quality of life (EuroQol 5-D [EQ5D]) and shock anxiety (Florida Shock Anxiety Scale [FSAS]) at baseline, bi-annual visits, and monthly for 6 months following an ICD shock. Daily physical activity data were obtained from a built-in device accelerometer. RESULTS: Average daily activity was 185.3 ± 119.4 minutes/day. Activity was significantly reduced after an ICD shock (p<0.0001) and recovered to a normal level after approximately 90 days. ICD shock was also associated with decreased quality of life (EQ5D Health Score) and increased EQ5D anxiety scores, but it did not impact mobility, self-care, activity, or pain. Similarly, shock anxiety (FSAS) increased in shocked patients and remained significantly elevated at 24 months, regardless of appropriate or inappropriate shock delivery. CONCLUSIONS: ICD shocks have a long-lasting, adverse impact on both objective, device-measured physical activity and subjective patient reported outcomes of quality of life and shock anxiety. Successful management of ICD patients requires attention to clinically relevant behavioral and psychological outcomes to expedite recovery and return to activities of daily living

Inappropriate shocks in single-chamber and subcutaneous implantable cardioverter-defibrillators: a systematic review and meta-analysis

Aims: Single-chamber (VR-ICD) and subcutaneous (S-ICD) implantable cardioverter-defibrillators are effective to protect patients against sudden death but expose them to higher risk of inappropriate shock (IS). We sought to quantify the annual rate and influencing factors of ISs in VR- and S-ICDs from the literature. Methods and results: PubMed, Embase, and Cochrane Library were searched for full text articles with IS rates. Poisson distribution estimated proportion of patients with ISs; rates were annualized based on follow-up duration. Random effects meta-analysis accounted for study-to-study variation. Out of 3264 articles, 16 qualified for the meta-analysis. Across studies, 6.4% [95% confidence interval (CI) 5.1-7.9%] of patients received an IS per year. Meta-regression analyses demonstrated that IS rates were lower in more recent studies [rate ratio (RR) per year: 0.93, 95% CI: 0.87-0.98; P = 0.01] and trended lower in studies with longer follow-up (RR per year: 0.78, 95% CI: 0.60-1.01; P = 0.06). Use of S-ICDs (RR: 1.81, 95% CI: 0.86-3.81; P = 0.12) and ventricular tachycardia zone programmed on (RR: 1.13, 95% CI: 0.65-1.97; P = 0.66) were not associated with a significantly increased change in risk. The IS rate observed in one of the more recent studies was significantly lower than predicted after accounting for covariates (RR: 0.29, 95% CI: 0.14-0.60; P < 0.001). Conclusions: A comprehensive review of the literature shows that 6.4% of patients with ICDs experienced their first IS annually. One of the 16 studies was better than predicted with the lowest reported rate (1.9%) and could not be explained by timing of the study or other covariates

Estimating the incidence of atrial fibrillation in single-chamber implantable cardioverter defibrillator patients

BACKGROUND Atrial arrhythmias are associated with major adverse cardiovascular events. Recent reports among implantable cardioverter defibrillator (ICD) patients have demonstrated a high prevalence of atrial fibrillation (AF), predominantly in dual-chamber recipients. AF incidence among patients with single-chamber systems (approximately 50% of all ICDs) is currently unknown. The objective was to estimate the prevalence of new-onset AF among single-chamber ICD patients by observing the rates of new atrial tachycardia (AT)/AF among a propensity scoring matched cohort of dual-chamber ICD patients from the PainFree SST study, to better inform screening initiatives. METHODS Among 2,770 patients enrolled, 1,862 single-chamber, dual-chamber, and cardiac resynchronization therapy (CRT) subjects with no prior history of atrial tachyarrhythmias were included. Daily AT/AF burden was estimated using a propensity score weighted model against data from dual-chamber ICDs. RESULTS Over 22 ± 9 months of follow-up, the estimated incidence of AT/AF - lasting at least 6 minutes, 6 hours and 24 hours per day - in the single-chamber cohort was 22.0%, 9.8% and 6.3%, whereas among dual-chamber patients, the prevalence was 26.6%, 13.1%, and 7.1%, respectively. Initiation of oral anticoagulation (OAC) was estimated to occur in 9.8% of the propensity matched single-chamber cohort, which was higher than the actual observed rate of 6.0%. Stroke and transient ischemic attack (TIA) occurred at low rates in all device subgroups. CONCLUSIONS Atrial arrhythmias occur frequently, and significant underutilization of anticoagulation is suggested in single-chamber ICD recipients. Routine screening for AF should be considered among single-chamber ICD recipients. This article is protected by copyright. All rights reserved

SVT discrimination algorithms significantly reduce the rate of inappropriate therapy in the setting of modern day delayed high-rate detection programming

BACKGROUND Contemporary ICD programming involving delayed high-rate detection and use of SVT discriminators has significantly reduced the rate of inappropriate shocks. The extent to which SVT algorithms alone reduce inappropriate therapies is poorly understood. METHODS AND RESULTS PainFree SST enrolled 2,770 patients with a single or dual-chamber ICD or cardiac resynchronization defibrillator. Patients were followed for 22±9 months with SVT discriminators on in 96% of patients. Sustained ventricular tachyarrhythmias and SVT episodes were adjudicated by an independent physician committee. For this analysis, all episodes were subjected to post-processing computer simulation with SVT discriminators off with and without delayed high-rate detection criteria (VF zone only, 30/40@320ms). There were 3,282 adjudicated SVT episodes of which 115 resulted in an ICD shock and 113 received only ATP (2-year inappropriate shock and therapy rates of 3.1% and 4.1%). Therapy was appropriately withheld for the remaining 3,054 SVT episodes. With both SVT discriminators and delayed high-rate detection simulated off, the 2-year inappropriate therapy rate would have been 22.9% (Hazard Ratio [HR]=6.24, 95% confidence interval [CI]: 5.20-7.49). With SVT discriminators simulated off and delayed high-rate detection simulated on in all patients, the 2-year rate would have been 6.4% (HR=1.63, CI: 1.44-1.85). CONCLUSIONS Use of SVT discriminators has a significant role in reducing the rate of inappropriate ICD therapy even in the setting of delayed high-rate detection settings. Deactivating SVT discriminators would have resulted in an overall increase in the inappropriate ICD therapy rate by 63% and 524% with and without delayed high-rate detection programming, respectively. This article is protected by copyright. All rights reserved

Low inappropriate shock rates in patients with single- and dual/triple-chamber implantable cardioverter-defibrillators using a novel suite of detection algorithms: PainFree SST trial primary results

BACKGROUND: The benefits of implantable cardioverter-defibrillators (ICDs) have been well demonstrated in many clinical trials, and ICD shocks for ventricular tachyarrhythmias save lives. However, inappropriate and unnecessary shock delivery remains a significant clinical issue with considerable consequences for patients and the healthcare system. OBJECTIVE: The purpose of the PainFree SmartShock Technology (SST) study was to investigate new-generation ICDs to reduce inappropriate and unnecessary shocks through novel discrimination algorithms with modern programming strategies. METHODS: This prospective, multicenter clinical trial enrolled 2790 patients with approved indication for ICD implantation (79% male, mean age 65 years; 69% primary prevention indication, 27% single-chamber ICD, 33% replacement or upgrade). Patients were followed for a minimum of 12 months, and mean follow-up was 22 months. The primary end-point of the study was the percentage of patients remaining free of inappropriate shocks at 1 year postimplant, analyzed separately for dual/triple-chamber ICDs (N = 2019) and single-chamber ICDs (N = 751). RESULTS: The inappropriate shock rate at 1 year was 1.5% for patients with dual/triple-chamber ICDs and 2.5% for patients with single-chamber devices. Two years postimplant, the inappropriate shock rate was 2.8% for patients with dual-/triple chamber ICDs and 3.7% for those with single-chamber ICDs. The most common cause of an inappropriate shock in both groups was atrial fibrillation or flutter. CONCLUSION: In a large patient cohort receiving ICDs for primary or secondary prevention, the adoption of novel enhanced detection algorithms in conjunction with routine implementation of modern programming strategies led to a very low inappropriate shock rate