Outcomes using a single tapered dilator for Micra leadless pacemaker implant.

OBJECTIVES: Comparison of outcomes, device deployment time (DT), and total time (TT) using a single tapered Coons dilator versus sequential serial dilation for implantation of the Micra leadless pacemaker. BACKGROUND: Micra leadless pacemaker placement requires a 23 French Micra introducer sheath (MIS) for percutaneous delivery. We sought to evaluate outcomes with use of a single tapered Coons dilator (CD) versus sequential serial dilatation (SD) method to facilitate insertion of the Micra introducer sheath. METHODS: 35 patients were included in the SD arm and 49 in the CD arm. DT and TT were recorded in minutes and cost in dollars. Analysis was performed using independent t-test between two groups and one-way ANOVA to evaluate inter-operator variability in the CD arm. RESULTS: Both DT and TT were significantly lower for the CD arm (15.1 ± 5.1 vs 23.5 ± 9.3, p < 0.0005 and 29.9 ± 14 vs 39.3 ± 13.5 min, p = 0.000374; respectively). The cost was also significantly lower using a CD versus SD. There was no inter-operator variability in the CD arm between 6 operators (p = 0.177 for DT and p = 0.304 for TT). No complications occurred in the SD arm. There were 3 vascular access site complications in the CD arm, all of which occurred early in the operator's experience. CONCLUSION: Coons dilator is an efficient and cost-effective method for vascular dilatation to facilitate Micra leadless pacemaker insertion. Rate of complications is low and expected to improve with greater experience.

The Registry Evaluating Functional Outcomes of Resynchronization Management (REFORM): quality of life and psychological functioning in patients receiving cardiac resynchronization therapy.

BACKGROUND: Cardiac resynchronization therapy (CRT) is a treatment for heart failure (HF) that improves cardiac, functional, and quality of life (QoL) outcomes. This study was designed to examine the effect of the addition of CRT (CRTD) to the implantable cardioverter defibrillator (ICD) on psychological functioning. METHODS AND RESULTS: Overall, 99 participants completed batteries before and 9 months after ICD or CRTD implantation in a registry of HF patients receiving device treatment in 3 US centers. Measures included validated indices of mental health (State Trait Anxiety Inventory, Patient Health Questionnaire: Depression) and generic and disease/device-specific QoL (Medical Outcomes Study-Short Form-12, Kansas City Cardiomyopathy Questionnaire, Florida Patient Acceptance Survey, Florida Shock Anxiety Scale). Mixed between-within analyses of covariance were employed to compare device groups on each outcome controlling for cardiac and demographic covariates. Clinically significant anxiety was elevated in both groups at both time points (57% CRTD at baseline, 29% CRTD 9 months, 44% ICD at baseline, 45% ICD 9 months). Clinically significant depressive symptoms were high at baseline (38% CRTD, 31% ICD), but dropped at follow-up (16% CRTD, 7% ICD; P = 0.01). Participants with CRTD had improved mental component and disease-specific QoL following CRT; however, CRTD patients had worse QoL, worse mental component QoL at baseline, and worse device acceptance at 9-month follow-up than patients with ICDs (all P < 0.05). CONCLUSIONS: Evidence of low QoL, psychological functioning, and device acceptance provides the impetus to increase research on well-being of HF patients being implanted with CRTD in research and clinical work.

Global LEADR pivotal trial results.

BACKGROUND: Implantable cardioverter-defibrillators last longer, and interest in reliable leads with targeted lead placement is growing. The OmniaSecure™ defibrillation lead is a novel small-diameter, catheter-delivered lead designed for targeted placement, based on the established SelectSecure SureScan MRI Model 3830 lumenless pacing lead platform. OBJECTIVE: This trial assessed safety and efficacy of the OmniaSecure defibrillation lead. METHODS: The worldwide LEADR pivotal clinical trial enrolled patients indicated for de novo implantation of a primary or secondary prevention implantable cardioverter-defibrillator/cardiac resynchronization therapy defibrillator, all of whom received the study lead. The primary efficacy end point was successful defibrillation at implantation per protocol. The primary safety end point was freedom from study lead-related major complications at 6 months. The primary efficacy and safety objectives were met if the lower bound of the 2-sided 95% credible interval was >88% and >90%, respectively. RESULTS: In total, 643 patients successfully received the study lead, and 505 patients have completed 12-month follow-up. The lead was placed in the desired right ventricular location in 99.5% of patients. Defibrillation testing at implantation was completed in 119 patients, with success in 97.5%. The Kaplan-Meier estimated freedom from study lead-related major complications was 97.1% at 6 and 12 months. The trial exceeded the primary efficacy and safety objective thresholds. There were zero study lead fractures and electrical performance was stable throughout the mean follow-up of 12.7 ± 4.8 months (mean ± SD). CONCLUSION: The OmniaSecure lead exceeded prespecified primary end point performance goals for safety and efficacy, demonstrating high defibrillation success and a low occurrence of lead-related major complications with zero lead fractures.

Occurrence of phrenic nerve stimulation in cardiac resynchronization therapy patients: the role of left ventricular lead type and placement site.

AIMS: Unwanted phrenic nerve stimulation (PNS) has been reported in ∼1 in 4 patients undergoing left ventricular (LV) pacing. The occurrence of PNS over mid-term follow-up and the significance of PNS are less certain. METHODS AND RESULTS: Data from 1307 patients enrolled in pre-market studies of LV leads manufactured by Medtronic (models 4193 and 4195 unipolar, 4194, 4196, 4296, and 4396 bipolar) were pooled. Left ventricular lead location was recorded at implant using a common classification scheme. Phrenic nerve stimulation symptoms were either spontaneously reported or identified at scheduled follow-up visits. A PNS-related complication was defined as PNS resulting in invasive intervention or the termination of LV pacing. Average follow-up was 14.9 months (range 0.0-46.6). Phrenic nerve stimulation symptoms occurred in 169 patients (12.9%). Phrenic nerve stimulation-related complications occurred in 21 of 1307 patients (1.6%); 16 of 738 (2.2%) in the unipolar lead studies, and 5 of 569 (0.9%) in the bipolar lead studies (P = 0.08). Phrenic nerve stimulation was more frequent at middle-lateral/posterior, and apical LV sites (139/1010) vs. basal-posterior/lateral/anterior, and middle-anterior sites (20/297; P= 0.01). As compared with an anterior LV lead position, a lateral LV pacing site was associated with over a four-fold higher risk of PNS (P= 0.005) and an apical LV pacing site was associated with over six-fold higher risk of PNS (P= 0.001). CONCLUSION: Phrenic nerve stimulation occurred in 13% of patients undergoing LV lead placement and was more common at mid-lateral/posterior, and LV apical sites. Most cases (123/139; 88%) of PNS were mitigated via electrical reprogramming, without the need for invasive intervention.

Electrocardiogram Belt guidance for left ventricular lead placement and biventricular pacing optimization.

BACKGROUND: Patients with ischemic cardiomyopathy, non-left bundle branch block, or QRS duration <150 ms have a lower response rate to cardiac resynchronization therapy (CRT) than did other indicated patients. The ECG Belt system (EBS) is a novel surface mapping system designed to measure electrical dyssynchrony via the standard deviation of the activation times of the left ventricle. OBJECTIVES: The objectives of this study were to evaluate the efficacy of the EBS in patients less likely to respond to CRT and to determine whether EBS use in lead placement guidance and device programming was superior to standard CRT care. METHODS: This was a prospective randomized trial of patients with heart failure and EBS-guided CRT implantation and programming vs standard CRT care. The primary end point was relative change in left ventricular end-systolic volume from baseline to 6 months postimplantation. RESULTS: A total of 408 patients from centers in Europe and North America were randomized. Although both patients with EBS and control patients had a mean improvement in left ventricular end-systolic volume, there was no significant difference in relative change from baseline (P = .26). While patients with a higher baseline standard deviation of the activation times derived greater left ventricular reverse remodeling, improvement in electrical dyssynchrony did not correlate with the extent of reverse remodeling. CONCLUSION: The findings of the present study do not support EBS-guided therapy for CRT management of heart failure with reduced ejection fraction.

An Analysis of Telehealth in the Outpatient Management of Atrial Fibrillation During the COVID-19 Pandemic.

The COVID-19 pandemic accelerated adaption of a telehealth care model. We studied the impact of telehealth on the management of atrial fibrillation (AF) by electrophysiology providers in a large, multisite clinic. Clinical outcomes, quality metrics, and indicators of clinical activity for patients with AF during the 10-week period of March 22, 2020 to May 30, 2020 were compared with those from the 10-week period of March 24, 2019 to June 1, 2019. There were 1946 unique patient visits for AF (1,040 in 2020 and 906 in 2019). During 120 days after each encounter, there was no difference in hospital admissions (11.7% vs 13.5%, p = 0.25) or emergency department visits (10.4% vs 12.5%, p = 0.15) in 2020 compared with 2019. There was a total of 31 deaths within 120 days, with similar rates in 2020 and 2019 (1.8% vs 1.3%, p = 0.38). There was no significant difference in quality metrics. The following clinical activities occurred less frequently in 2020 than in 2019: offering escalation of rhythm control (16.3% vs 23.3%, p <0.001), ambulatory monitoring (29.7% vs 51.7%, p <0.001), and electrocardiogram review for patients on antiarrhythmic drug therapy (22.1% vs 90.2%, p <0.001). Discussions about risk factor modification were more frequent in 2020 compared with 2019 (87.9% vs 74.8%, p <0.001). In conclusion, the use of telehealth in the outpatient management of AF was associated with similar clinical outcomes and quality metrics but differences in clinical activity compared with traditional ambulatory encounters. Longer-term outcomes warrant further investigation.

Comparative outcomes of vascular access closure methods following atrial fibrillation/flutter catheter ablation: insights from VAscular Closure for Cardiac Ablation Registry.

PURPOSE: This registry compared the safety and efficacy of vascular closure device Perclose (PC) with figure-of-eight stitch (Fo8) and manual compression (MC) following catheter ablation of atrial fibrillation/flutter. METHODS: VAscular Closure for Cardiac Ablation Registry (VACCAR) is a prospective, observational registry that assessed the time to hemostasis (TTH), time to ambulation (TTA), length of stay (LOS), complications, patient-reported outcomes, and pain medication use. RESULTS: A total of 434 patients (mean age 64.0±11.0 years; 38% female; 94.9% white) were enrolled between October 2017 and May 2019: 156 in MC, 203 in Fo8, and 75 in the PC group. Median TTH was significantly reduced in the PC and Fo8 group at 7 and 9 min respectively vs. the MC group at 20 min (p<0.001). Median TTA was significantly reduced in both the PC and Fo8 group at 2.2 h vs. the MC group at 6.5 h (p<0.001 for both). Median LOS for the PC group was significantly reduced at 27.5 h compared to the MC and Fo8 group at 29 h (p<0.01). A higher proportion of same-day discharges were noted in the PC and Fo8 groups at 14 (18.7%) and 25 (12.3%), respectively, compared to 5 (3.2%) in the MC group (p<0.01 for all). There was no significant difference in complications between the three groups. CONCLUSIONS: Both PC and Fo8 are safe with improved TTH, TTA, LOS, and a higher number of same-day discharges compared to MC.

Prospective evaluation of the effect of smartphone electrocardiogram usage on anticoagulant medication compliance.

PURPOSE: Compliance with anticoagulation treatment for atrial fibrillation is highly variable. Smartphone electrocardiograms that allow patients to have greater insight into their arrhythmia burden may improve anticoagulant compliance. METHODS: Patients were enrolled if they had atrial fibrillation with a CHA2DS2-VASc score of 2 or more, were eligible for anticoagulation and had a smartphone. Participants were randomly assigned to receive a smartphone electrocardiogram (AliveCor Kardia) to record their electrocardiograms 5 times/week or to the control group. All patients received 6 months of anticoagulant (apixaban) dispensed as 1-month pre-loaded pill boxes. RESULTS: A total of 100 patients were enrolled from July 2017 to August 2019, but 5 patients in the monitor arm and 1 in the control arm withdrew prematurely. The monitor and control groups did not differ in age, gender, CHA2DS2-VASc score, or comorbidities. Median medication compliance was 99.7%, with nonsignificantly greater compliance in the monitor group (100%) than in the control group (99.7%) (p-value = 0.247). There was also no significant difference between missing any dose and use/nonuse of the smartphone monitor (48.9% vs. 55.1%; p-value = 0.692). Mean monitor compliance was 86.8% ± 14.0% with an average of 4.34 recorded electrocardiograms per week. Monitor group patients with perfect medication compliance had significantly higher monitor compliance than those patients who missed doses (median 95.3% vs 86.7%; p-value = 0.02). CONCLUSIONS: In a study population with higher-than-expected medication compliance, the use of smartphone electrocardiogram did not demonstrate an improvement in medication compliance as compared to usual care. Greater monitor compliance was associated with greater medication compliance. CLINICAL TRIAL REGISTRATION: BOAT-OAR ClinicalTrials.gov number, NCT03515083.

Real-World Evaluation of Magnetic Resonance Imaging in Patients With a Magnetic Resonance Imaging Conditional Pacemaker System: Results of 4-Year Prospective Follow-Up in 2,629 Patients.

OBJECTIVES: This global, multicenter, prospective study, initiated to meet U.S. Food and Drug Administration condition-of-approval requirements, evaluated the safety and efficacy of the Medtronic magnetic resonance imaging (MRI)-conditional pacing system when used in an MRI environment in routine clinical practice. The primary endpoint was MRI-related complications. The secondary endpoint was the cumulative change in pacing capture threshold (PCT) for patients undergoing multiple MRI scans. BACKGROUND: Large-scale, real-world evaluation of MRI in patients implanted with an MRI-conditional pacing system remains limited, with few published data for patients who undergo multiple MRI scans. METHODS: Patients were enrolled and followed up prospectively from the time of implantation. Evaluation of the pacemaker function was performed before and after MRI. The MRI-related complication-free rate was evaluated. Changes in electrical performance after each scan and cumulative changes over multiple scans were analyzed. RESULTS: In 81 centers, 2,629 patients were implanted with a complete SureScan pacing system (41.8% women, age 70.2 ± 12.5 years). A total of 526 patients (28.5%) received 872 clinically indicated MRI scans, including 58 thoracic scans. No MRI-related complications occurred during or after MRI, meeting the primary objective. Six (1%) MRI-related observations (atrial fibrillation, PCT increase, and chest symptoms) were reported. A total of 171 patients (32.5%) underwent 2 or more scans with no cumulative increase in PCT. CONCLUSIONS: This report constitutes the largest longitudinal MRI experience in patients implanted with an MRI-conditional pacing system. Results support the safety profile of the SureScan system and demonstrate for the first time that patients may safely undergo multiple MRI scans. (SureScan Post-Approval Study; NCT01299675).

Body surface mapping using an ECG belt to characterize electrical heterogeneity for different left ventricular pacing sites during cardiac resynchronization: Relationship with acute hemodynamic improvement.

BACKGROUND: Electrical heterogeneity (EH) during cardiac resynchronization therapy may vary with different left ventricular (LV) pacing sites. OBJECTIVE: The purpose of this study was to evaluate the relationship between such changes and acute hemodynamic response (AHR). METHODS: Two EH metrics-standard deviation of activation times and mean left thorax activation times-were computed from isochronal maps based on 53-electrode body surface mapping during baseline AAI pacing and biventricular (BiV) pacing from different pacing sites in coronary veins in 40 cardiac resynchronization therapy-indicated patients. AHR at different sites was evaluated by invasive measurement of LV-dp/dtmax at baseline and BiV pacing, along with right ventricular (RV)-LV sensing delays and QRS duration. RESULTS: The site with the greatest combined reduction in standard deviation of activation times and left thorax activation times from baseline to BiV pacing was hemodynamically optimal (defined by AHR equal to, or within 5% of, the largest dp/dt response) in 35 of 40 patients (88%). Sites with the longest RV-LV and narrowest paced QRS were hemodynamically optimal in 26 of 40 patients (65%) and 28 of 40 patients (70%), respectively. EH metrics from isochronal maps had much better accuracy (sensitivity 90%, specificity 80%) for identifying hemodynamically responsive sites (∆LV dp/dtmax ≥10%) compared with RV-LV delay (69%, 85%) or paced QRS reduction (52%, 76%). Multivariate prediction model based on EH metrics showed significant correlation (R2 = 0.53, P <.001) between predicted and measured AHR. CONCLUSION: Changes in EH from baseline to BiV pacing more accurately identified hemodynamically optimal sites than RV-LV delays or paced QRS shortening. Optimization of LV lead location by minimizing EH during BiV pacing, based on body surface mapping, may improve CRT response.

Impact of magnetic resonance imaging on ventricular tachyarrhythmia sensing: Results of the Evera MRI Study.

BACKGROUND: Studies have shown that magnetic resonance imaging (MRI) conditional pacemakers experience no significant effect from MRI on device function, sensing, or pacing. More recently, similar safety outcomes were demonstrated with MRI conditional defibrillators (implantable cardioverter-defibrillator [ICD]), but the impact on ventricular arrhythmias has not been assessed. OBJECTIVE: The purpose of this study was to assess the effect of MRI on ICD sensing and treatment of ventricular tachyarrhythmias. METHODS: The Evera MRI Study was a worldwide trial of 156 patients implanted with an ICD designed to be MRI conditional. Device-detected spontaneous and induced ventricular tachycardia/ventricular fibrillation (VT/VF) episodes occurring before and after whole body MRI were evaluated by a blinded episode review committee. Detection delay was computed as the sum of RR intervals of undersensed beats. A ≥5-second delay in detection due to undersensing was prospectively defined as clinically significant. RESULTS: Post-MRI, there were 22 polymorphic VT/VF episodes in 21 patients, with 16 of these patients having 17 VT/VF episodes pre-MRI. Therapy was successful for all episodes, with no failures to treat or terminate arrhythmias. The mean detection delay due to undersensing pre- and post-MRI was 0.60 ± 0.59 and 0.33 ± 0.63 seconds, respectively (P = .17). The maximum detection delay was 2.19 seconds pre-MRI and 2.87 seconds post-MRI. Of the 17 pre-MRI episodes, 14 (82%) had some detection delay as compared with 11 of 22 (50%) post-MRI episodes (P = .03); no detection delay was clinically significant. CONCLUSION: Detection and treatment of VT/VF was excellent, with no detection delays or significant impact of MRI observed.

Effect of chronic right ventricular apical pacing on left ventricular function.

The determinants of change in left ventricular (LV) ejection fraction (EF) over time in patients with impaired LV function at baseline have not been clearly established. Using a nuclear database to assess changes in LV function over time, we included patients with a baseline LVEF of 25% to 40% on a gated single-photon emission computed tomographic study at rest and only if second-gated photon emission computed tomography performed approximately 18 months after the initial study showed an improvement in LVEF at rest of > or =10 points or a decrease in LVEF at rest of > or =7 points. In all, 148 patients qualified for the EF increase group and 59 patients for the EF decrease group. LVEF on average increased from 33 +/- 4% to 51 +/- 8% in the EF increase group and decreased from 35 +/- 4% to 25 +/- 5% in the EF decrease group. The strongest multivariable predictor of improvement of LVEF was beta-blocker therapy (odds ratio 3.9, p = 0.002). The strongest independent predictor of LVEF decrease was the presence of a permanent right ventricular apical pacemaker (odds ratio 6.6, p = 0.002). Thus, this study identified beta-blocker therapy as the major independent predictor for improvement in LVEF of > or =10 points, whereas a permanent pacemaker (right ventricular apical pacing) was the strongest predictor of a LVEF decrease of > or =7 points.

Effect of pre-procedural interrupted apixaban on heparin anticoagulation during catheter ablation for atrial fibrillation: a prospective observational study.

PURPOSE: Effective intraprocedural anticoagulation is considered essential to minimize the risk of thromboembolism in catheter ablation (CA) of atrial fibrillation (AF). The effect of interrupted apixaban on intraprocedural heparin dosing requirements and levels of achieved anticoagulation with heparin has not been well studied. The purpose of the present study was to compare heparin administration and activated clotted times (ACTs) for patients undergoing CA for AF treated with interrupted apixaban before the procedure with patients on uninterrupted warfarin. METHODS: Consecutive patients undergoing CA for AF treated with interrupted apixaban or uninterrupted warfarin were prospectively enrolled. Heparin administration determined by a standard protocol and normalized to patient weight and procedure duration, as well as rapidity, and degree of anticoagulation with heparin (as measured by mean ACT, peak ACT, time to ACT ≥300 s, and time to ACT ≥350 s) were compared between the groups. RESULTS: Forty-eight patients were enrolled (25 apixaban and 23 warfarin). Heparin administered by bolus (51.3 ± 21.5 vs 27.8 ± 9.6 units/kg/h; p < 0.001) and mean heparin drip rate (25.3 ± 3.6 vs 20.7 ± 2.4 units/kg/h; p < 0.001) were significantly higher in the apixaban group compared to the warfarin group. Despite greater heparin administration, apixaban patients achieved a significantly lower mean ACT (332.3 ± 17.0 vs 384.5 ± 53.9; p < 0.001) and peak ACT (369.5 ± 22.6 vs 432.3 ± 75.8, p < 0.001) compared to the warfarin group. The time to ACT ≥350 s (66.7 ± 35.8 vs 26.9 ± 34.0; p < 0.001) was significantly longer for apixaban-treated patients. Outcome differences persisted after analysis using linear models and Cox proportional hazard regression with adjustment for propensity scores. CONCLUSIONS: A standard intraprocedural heparin protocol results in delayed and lower levels of anticoagulation as measured by the ACT for interrupted apixaban-treated patients in comparison to those on uninterrupted warfarin during CA of AF.

Short- and long-term electrical performance of the 5086MRI pacing lead.

BACKGROUND: Owing to potential patient harm, magnetic resonance imaging (MRI) in patients with cardiac implantable electronic devices has traditionally been contraindicated. Following the EnRhythm MRI SureScan Study, an MR conditional pacemaker with modified leads was approved by the Food and Drug Administration. Electrical and handling characteristics of MR conditional pacing leads compared with those of traditional leads have not been established. OBJECTIVE: To compare short- and long-term performance of the Medtronic 5086MRI lead with that of the Medtronic 5076 lead. METHODS: Patients (n = 466) implanted with 2 5086MRI leads (EnRhythm MRI Study) and 316 patients implanted with 2 5076 leads in 2 prospective clinical investigations were analyzed. RESULTS: Electrical characteristics were stable in both groups at implant and at 12 months and were clinically acceptable throughout. Ventricular capture thresholds were slightly higher at 12 months for the 5086MRI lead than for the 5076 lead (0.93 ± 0.47 V vs 0.74 ± 0.42 V; P < .001). Ventricular sensing amplitudes for the 5086MRI lead were lower at implant (9.0 ± 4.7 mV vs 13.9 ± 6.9 mV; P < .001) and 12 months (9.8 ± 4.8 mV vs 15.4 ± 7.5 mV; P < .001) than for the 5076 lead. There was no statistical difference in lead handling. At 12 months, the estimated right atrial lead-related complication-free survival rate was 99.3% for the 5086MRI lead and 99.6% for the 5076 lead (log-rank P = .65), and the estimated right ventricular lead-related complication-free survival rates were 98.5% and 100% (log-rank P = .03). Acute lead dislodgments occurred in 12 patients with the 5086MRI leads (2.6%) compared with 2 patients with 5076 leads (0.6%) (p = .05) than in 0.6% of the patients with the 5076 lead (P = .05). CONCLUSIONS: The 5086MRI lead demonstrates clinically acceptable electrical characteristics while providing safe access to MR-guided diagnostics. However, compared with the 5076 lead, the 5086MRI lead exhibits lower ventricular sensing, slightly higher ventricular capture thresholds, and higher acute lead dislodgement rate.

Differences in intraprocedural ACTs with standardized heparin dosing during catheter ablation for atrial fibrillation in patients treated with dabigatran vs. patients on uninterrupted warfarin.

PURPOSE: Effective intraprocedural anticoagulation for catheter ablation for atrial fibrillation is critical to minimize the risk of cerebral thromboembolism. The effect of dabigatran on anticoagulation with heparin during the procedure is unknown. This study compares heparin anticoagulation in patients treated with dabigatran vs. patients on uninterrupted warfarin. METHODS: Seventy-six consecutive patients (24 dabigatran and 52 warfarin) subjected to a standard intraprocedural heparin protocol were included. Heparin administration and rapidity and degree of anticoagulation were compared between the groups. RESULTS: Despite greater administration of heparin (52.5 ± 22.0 vs. 33.2 ± 10.1 units kg(-1) h(-1); p < 0.001), the mean (320.3 ± 19.5 s) and peak (358.8 ± 28.6 s) activated clotting time (ACT) for the dabigatran group were significantly lower than for the warfarin group (mean, 362.9 ± 35.9 and peak, 410.4 ± 49.7; p < 0.001). The time from initial heparin bolus to first ACT of ≥300 s in the dabigatran group was more than twice that observed in the warfarin group (45.0 ± 30.4 vs. 20.9 ± 14.5 min; p < 0.001). The time to first ACT of ≥350 s was similarly prolonged (109.1 ± 60.0 vs. 55.2 ± 51.1 min; p < 0.001) in the dabigatran group, with eight patients (33 %) failing to reach this target. Outcome differences persisted following analysis using linear models and Cox proportional hazard regression with adjustment for propensity scores. CONCLUSION: A standard intraprocedural heparin protocol results in delayed and lower levels of anticoagulation as measured by the ACT for patients treated with dabigatran compared with those on uninterrupted warfarin.

Genome-wide association of implantable cardioverter-defibrillator activation with life-threatening arrhythmias.

OBJECTIVES: To identify genetic factors that would be predictive of individuals who require an implantable cardioverter-defibrillator (ICD), we conducted a genome-wide association study among individuals with an ICD who experienced a life-threatening arrhythmia (LTA; cases) vs. those who did not over at least a 3-year period (controls). BACKGROUND: Most individuals that receive implantable cardioverter-defibrillators never experience a life-threatening arrhythmia. Genetic factors may help identify who is most at risk. METHODS: Patients with an ICD and extended follow-up were recruited from 34 clinical sites with the goal of oversampling those who had experienced LTA, with a cumulative 607 cases and 297 controls included in the analysis. A total of 1,006 Caucasian patients were enrolled during a time period of 13 months. Arrhythmia status of 904 patients could be confirmed and their genomic data were included in the analysis. In this cohort, there were 704 males, 200 females, and the average age was 73.3 years. We genotyped DNA samples using the Illumina Human660 W Genotyping BeadChip and tested for association between genotype at common variants and the phenotype of having an LTA. RESULTS AND CONCLUSIONS: We did not find any associations reaching genome-wide significance, with the strongest association at chromosome 13, rs11856574 at P = 5×10⁻6. Loci previously implicated in phenotypes such as QT interval (measure of the time between the start of the Q wave and the end of the T wave as measured by electrocardiogram) were not found to be significantly associated with having an LTA. Although powered to detect such associations, we did not find common genetic variants of large effect associated with having a LTA in those of European descent. This indicates that common gene variants cannot be used at this time to guide ICD risk-stratification. TRIAL REGISTRATION: ClinicalTrials.gov NCT00664807.

Cardiovascular screening with electrocardiography and echocardiography in collegiate athletes.

BACKGROUND: Current guidelines for preparticipation screening of competitive athletes in the US include a comprehensive history and physical examination. The objective of this study was to determine the incremental value of electrocardiography and echocardiography added to a screening program consisting of history and physical examination in college athletes. METHODS: Competitive collegiate athletes at a single university underwent prospective collection of medical history, physical examination, 12-lead electrocardiography, and 2-dimensional echocardiography. Electrocardiograms (ECGs) were classified as normal, mildly abnormal, or distinctly abnormal according to previously published criteria. Eligibility for competition was determined using criteria from the 36(th) Bethesda Conference on Eligibility Recommendations for Competitive Athletes with Cardiovascular Abnormalities. RESULTS: In 964 consecutive athletes, ECGs were classified as abnormal in 334 (35%), of which 95 (10%) were distinctly abnormal. Distinct ECG abnormalities were more common in men than women (15% vs 6%, P<.001) as well as black compared with white athletes (18% vs 8%, P<.001). Echocardiographic and electrocardiographic findings initially resulted in exclusion of 9 athletes from competition, including 1 for long QT syndrome and 1 for aortic root dilatation; 7 athletes with Wolff-Parkinson-White patterns were ultimately cleared for participation. (Four received further evaluation and treatment, and 3 were determined to not need treatment.) After multivariable adjustment, black race was a statistically significant predictor of distinctly abnormal ECGs (relative risk 1.82, 95% confidence interval, 1.22-2.73; P=.01). CONCLUSIONS: Distinctly abnormal ECGs were found in 10% of athletes and were most common in black men. Noninvasive screening using both electrocardiography and echocardiography resulted in identification of 9 athletes with important cardiovascular conditions, 2 of whom were excluded from competition. These findings offer a framework for performing preparticipation screening for competitive collegiate athletes.

Magnetic resonance imaging in patients with a pacemaker system designed for the magnetic resonance environment.

BACKGROUND: Magnetic resonance imaging (MRI) of pacemaker patients is contraindicated due to documented potential risks to the patient from hazardous interactions between the MRI and pacemaker system. OBJECTIVE: The purpose of this prospective, randomized, controlled, worldwide clinical trial was to evaluate the safety and effectiveness of a pacemaker system designed for safe use in MRI for any bradycardia indicated patient. METHODS: Patients (n = 464) were randomized to undergo an MRI scan between 9 and 12 weeks postimplant (MRI group, n = 258) or not to undergo MRI (control group, n = 206) after successful implantation of the specially designed dual-chamber pacemaker and leads. Patients were monitored for arrhythmias, symptoms, and pacemaker system function during 14 nonclinically indicated relevant brain and lumbar MRI sequences. Sequences were performed at 1.5 T and included scans with high radiofrequency power deposition and/or high gradient dB/dt exposure. Clinical evaluation of the pacemaker system function occurred immediately before and after MRI, 1 week and 1 month post-MRI, and at corresponding times for the control group. Primary endpoints for safety analyzed the MRI procedure complication-free rate and for effectiveness compared capture and sensing performance between MRI and control groups. RESULTS: No MRI-related complications occurred during or after MRI, including sustained ventricular arrhythmias, pacemaker inhibition or output failures, electrical resets, or other pacemaker malfunctions. Pacing capture threshold and sensed electrogram amplitude changes were minimal and similar between study groups. CONCLUSION: This trial documented the ability of this pacemaker system to be exposed in a controlled fashion to MRI in a 1.5 T scanner without adverse impact on patient outcomes or pacemaker system function.

Automated left ventricular capture management.

BACKGROUND: The stimulation thresholds of left ventricular (LV) leads tend to be less reliable than conventional leads. Cardiac resynchronization therapy (CRT) requires continuous capture of both ventricles. OBJECTIVE: The purpose of this study is to evaluate a novel algorithm for the automatic measurement of the stimulation threshold of LV leads in cardiac resynchronization systems. METHODS: We enrolled 134 patients from 18 centers who had existing CRT-D systems. Software capable of automatically executing LV threshold measurements was downloaded into the random access memory (RAM) of the device. The threshold was measured by pacing in the left ventricle and analyzing the interventricular conduction sensed in the right ventricle. Automatic LV threshold measurements were collected and compared with manual LV threshold tests at each follow-up visit and using a Holter monitor system that recorded both the surface electrocardiograph (ECG) and continuous telemetry from the device. RESULTS: The proportion of Left Ventricular Capture Management (LVCM) in-office threshold tests within one programming step of the manual threshold test was 99.7% (306/307) with a two-sided 95% confidence interval of (98.2%, 100.0%). The algorithm measured the threshold successfully in 96% and 97% of patients after 1 and 3 months respectively. Holter monitor analysis in a subset of patients revealed accurate performance of the algorithm. CONCLUSION: This study demonstrated that the LVCM algorithm is safe, accurate, and highly reliable. LVCM worked with different types of leads and different lead locations. LVCM was demonstrated to be clinically equivalent to the manual LV threshold test. LVCM offers automatic measurement, output adaptation, and trends of the LV threshold and should result in improved ability to maintain LV capture without sacrificing device longevity.