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There are now more adults living with a history of congenital heart disease than there are children. Modern electrophysiologists must familiarize themselves with the most common congenital lesions requiring electrophysiologic care as adults. Advancements in this field have been made most notably with high-resolution 3D imaging and electroanatomic mapping, left ventricular cannulation techniques, alternative pacing strategies, intracardiac echo, and transeptal access tools.

BackgroundRepolarization alternans, defined as period-2 oscillation in the repolarization phase of the action potentials, is one of the cornerstones of cardiac electrophysiology as it provides a mechanistic link between cellular dynamics and ventricular fibrillation (VF). Theoretically, higher-order periodicities (e.g., period-4, period-8,…) are expected but have very limited experimental evidence.MethodsWe studied explanted human hearts, obtained from the recipients of heart transplantation at the time of surgery, using optical mapping technique with transmembrane voltage-sensitive fluorescent dyes. The hearts were stimulated at an increasing rate until VF was induced. The signals recorded from the right ventricle endocardial surface just before the induction of VF and in the presence of 1:1 conduction were processed using the Principal Component Analysis and a combinatorial algorithm to detect and quantify higher-order dynamics.ResultsA prominent and statistically significant 1:4 peak (corresponding to period-4 dynamics) was seen in three of the six studied hearts. Local analysis revealed the spatiotemporal distribution of higher-order periods. Period-4 was localized to temporally stable islands. Higher-order oscillations (period-5, 6, and 8) were transient and primarily occurred in arcs parallel to the activation isochrones.DiscussionWe present evidence of higher-order periodicities and the co-existence of such regions with stable non-chaotic areas in ex-vivo human hearts before VF induction. This result is consistent with the period-doubling route to chaos as a possible mechanism of VF initiation, which complements the concordant to discordant alternans mechanism. The presence of higher-order regions may act as niduses of instability that can degenerate into chaotic fibrillation.

Objective. Current segmentation practice for thoracic cancer RT considers the whole heart as a single organ despite increased risks of cardiac toxicities from irradiation of specific cardiac substructures. Segmenting up to 15 different cardiac substructures can be a very time-intensive process, especially due to their different volume sizes and anatomical variations amongst different patients. In this work, a new deep learning (DL)-based mutual enhancing strategy is introduced for accurate and automatic segmentation, especially of smaller substructures such as coronary arteries. Approach. Our proposed method consists of three subnetworks: retina U-net, classification module, and segmentation module. Retina U-net is used as a backbone network architecture that aims to learn deep features from the whole heart. Whole heart feature maps from retina U-net are then transferred to four different sets of classification modules to generate classification localization maps of coronary arteries, great vessels, chambers of the heart, and valves of the heart. Each classification module is in sync with its corresponding subsequent segmentation module in a bootstrapping manner, allowing them to share their encoding paths to generate a mutual enhancing strategy. We evaluated our method on three different datasets: institutional CT datasets (55 subjects) 2) publicly available Multi-Modality Whole Heart Segmentation (MM-WHS) challenge datasets (120 subjects), and Automated Cardiac Diagnosis Challenge (ACDC) datasets (100 subjects). For institutional datasets, we performed five-fold cross-validation on training data (45 subjects) and performed inference on separate hold-out data (10 subjects). For each subject, 15 cardiac substructures were manually contoured by a resident physician and evaluated by an attending radiation oncologist. For the MM-WHS dataset, we trained the network on 100 datasets and performed an inference on a separate hold-out dataset with 20 subjects, each with 7 cardiac substructures. For ACDC datasets, we performed five-fold cross-validation on 100 datasets, each with 3 cardiac substructures. We compared the proposed method against four different network architectures: 3D U-net, mask R-CNN, mask scoring R-CNN, and proposed network without classification module. Segmentation accuracies were statistically compared through dice similarity coefficient, Jaccard, 95% Hausdorff distance, mean surface distance, root mean square distance, center of mass distance, and volume difference. Main results. The proposed method generated cardiac substructure segmentations with significantly higher accuracy (P P Significance. A new DL-based mutual enhancing strategy was introduced for automatic segmentation of cardiac substructures. Overall results of this work demonstrate the ability of the proposed method to improve segmentation accuracies of smaller substructures such as coronary arteries without largely compromising the segmentation accuracies of larger substructures. Fast and accurate segmentations of up to 15 substructures can possibly be used as a tool to rapidly generate substructure segmentations followed by physicians’ reviews to improve clinical workflow.

BACKGROUND Little is known about health status and quality of life (QoL) after implantable cardioverter-defibrillator (ICD) generator exchange (GE). METHODS We prospectively followed patients undergoing first-time ICD GE. Serial assessments of health status were performed by administering the 36-Item Short Form Survey (SF-36). RESULTS Mean age was 67.5 ± 14.3 years, left ventricle ejection fraction (LVEF) was 36.5% ± 15.0% and over 40% of the cohort had improved LVEF to > 35% at the time of GE. SF-36 scores were significantly worse in physical/general health domains compared to domains of emotional/social well-being ( P < 0.001 for each comparison). Physical health scores were significantly worse among those with medical comorbidities including diabetes, chronic obstructive pulmonary disease and atrial fibrillation. Mean follow-up was 1.6 ± 0.5 years after GE. Overall SF-36 scores remained stable across all domains during follow-up. Survival at 3 years post-GE was estimated at 80%. Five patients died during follow-up and most deaths were adjudicated as non-arrhythmic in origin. Four patients experienced appropriate ICD shocks after GE, three of whom had LVEF which remains impaired LVEF (i.e., < 35%) at the time of GE. CONCLUSION Patients undergoing ICD GE have significantly worse physical health compared to emotional/social well-being, which is associated with the presence of medical comorbidities. In terms of clinical outcomes, the incidence of appropriate shocks after GE among those with improvement in LVEF is very low, and most deaths post-procedure appear to be non-arrhythmic in origin. These data represent an attempt to more fully characterize the spectrum of QoL and clinical outcomes after GE.

Direct oral anticoagulants (DOACs) are not recommended in adult Fontan patients (Level of Evidence C). We hypothesized that DOACs are comparable to warfarin and do not increase thrombotic and embolic complications (TEs) or clinically significant bleeds.We reviewed the medical records of adult Fontan patients on DOACs or warfarin at three major medical centers. We identified 130 patients: 48 on DOACs and 107 on warfarin. In total, they were treated for 810 months on DOACs and 5637 months on warfarin.The incidence of TEs in patients on DOACs compared to those on warfarin was not increased in a statistically significant way (hazard ratio [HR] 1.7 and p value 0.431). Similarly, the incidence of nonmajor and major bleeds in patients on DOACs compared to those on warfarin was also not increased in a statistically significant way (HR for nonmajor bleeds in DOAC patients was 2.8 with a p value of 0.167 and the HR for major bleeds was 2.0 with a p value 0.267). In multivariate analysis, congestive heart failure (CHF) was a risk factor for TEs across both groups (odds ratio [OR] = 4.8, 95% confidence interval [CI] = 1.3-17.6) and bleed history was a risk factor for clinically significant bleeds (OR = 6.8, 95% CI = 2.7-17.2).In this small, retrospective multicenter study, the use of DOACs did not increase the risk of TEs or clinically significant bleeds compared to warfarin in a statistically significant way.

Hands-on defibrillation (HOD) could theoretically improve the efficacy of cardiopulmonary resuscitation (CPR) though a few mechanisms. Polyethylene drapes could potentially facilitate safe HOD, but questions remain about the effects of CPR on polyethylene's conductance and the magnitude of current looping through rescuers' arms in contact with patients.This study measured the leakage current through 2 mil (0.002 in.) polyethylene through two different current pathways before and after 30 min of continuous compressions on a CPR mannequin. The two pathways analyzed were the standardized IEC (International Electrotechnical Commission) leakage current analysis and a setup analyzing a current pathway looping through a rescuer's arms and returning to the patient. First, ten measurements involving the two pathways were obtained on a single polyethylene drape. 30 min of continuous compressions were applied to the drape on a CPR mannequin after which the ten measurements were repeated.Twenty patients undergoing elective cardioversion for atrial fibrillation (18/20) or atrial flutter (2/20) at Emory University Hospital underwent analysis all receiving 200 J shocks (age 38-101, 35% female). Through the IEC measurement method the peak leakage current mean was 0.70 +/- 0.02 mA before compressions and 0.59 +/- 0.19 mA after compressions. Only three of the ten measurements assessing current passing through a rescuer's arms had detectable current and each was of low magnitude. All measurements were well below the maximum IEC recommendations of 3.5 mA RMS and 5.0 mA peak.Polyethylene may facilitate safe HOD even after long durations of compressions. Current looping through a rescuer's arms is likely of insignificant magnitude.

Background Little data exist on long-term outcomes following extraction of implantable cardioverter defibrillator (ICD) leads, particularly for noninfectious indications. We sought to identify predictors of long-term survival after ICD lead extraction. Methods We retrospectively reviewed ICD lead extractions at our institution (n = 508). Procedural outcomes and long-term survival were ascertained by medical records review. Results Indication for lead extraction was infection in 32.5% and lead failure in 61.8%. Mean dwell time of the oldest extracted lead was 5.1 ± 5.9 years. Complete procedural success was achieved in 96.5% of cases. Major procedure-related complications occurred in 1.6% with six periprocedural deaths. During a mean follow-up of 866 ± 798 days, survival was significantly worse among patients with infection as the indication for extraction. At 1 year after extraction, survival among those with infection was 88.2%, compared to 95.0% in the lead failure cohort (P < 0.001). Procedural failure was a significant predictor of long-term mortality, even after excluding periprocedural deaths. In multivariate models, the presence of chronic kidney disease, increased number of leads requiring extraction, lower ejection fraction, and procedural failure were predictors of mortality. Conclusion Despite high rates of procedural success, infectious indication for ICD lead extraction is associated with increased long-term mortality. In contrast, among patients undergoing extraction for lead failure, long-term survival was excellent. The presence of procedural failure was a significant predictor of long-term mortality. Further studies will be necessary to better understand the mechanisms by which procedural failure may adversely impact long-term outcomes.

Background Sudden cardiac death is a major cause of late mortality in adults with congenital heart disease (ACHD). While data exist for adults with repaired Tetralogy of Fallot (TOF), little is known about those with non-TOF lesions. We examined the relative rates in implantable cardioverter defibrillator (ICD) therapy according to congenital lesion type in a large-volume adult congenital heart center. Methods A cohort of 59 individuals (median follow up time, 3.2 years range 0–10) with ACHD and ICDs was stratified according to underlying congenital lesion and implant indication. Appropriate therapies were defined as any therapy for a physician-adjudicated ventricular arrhythmia. Rates of inappropriate and appropriate ICD therapies were analyzed according to several relevant clinical variables. Results Thirty-three (56%) TOF, 15 (25.4%) L- or D-transposition of great arteries, and 11 (18.6%) with other lesions were included in the analysis. Approximately half (52.5%) were implanted for primary prevention indications. During follow-up, 12 (20.3%) patients received appropriate ICD therapies and 13 (22%) patients received inappropriate therapies. The incidence of appropriate shocks among patients with TOF was 27.3% (9/33) compared to 11.5% (3/26) among non-TOF diagnoses during the follow-up time (p = 0.043). Conclusions ACHD patients with non-TOF congenital lesions are significantly less likely to receive appropriate ICD therapy than those with TOF. Our analysis calls into question the validity of traditional ICD implantation guidelines in this growing and diverse patient population.

This study compared risks associated with magnetic resonance imaging (MRI) in patients with non-MRI conditional and MRI conditional pacing and defibrillator systems with particular attention to clinically actionable outcomes.While recipients of new MRI conditional pacemaker and defibrillator systems may undergo MRI scanning with very low risk, safety and regulatory concerns persist regarding such scanning in recipients of non-MRI conditional systems.Patients with any cardiac device who were referred for MRI were prospectively enrolled at a single center and underwent scanning at 1.5 Tesla. Pre- and postscan lead characteristic changes, system integrity, and symptoms were analyzed. A comparison was made between non-MRI conditional and MRI conditional devices.105 patients were evaluated allowing for comparison of 97 scans with non-MRI conditional devices and 16 scans with MRI conditional devices. The cohort included those with pacemaker dependency, defibrillator, and cardiac resynchronization devices. Small, nonsignificant changes were observed in lead characteristics following scanning, and there was no significant difference when comparing non-MRI and MRI conditional devices. Lead parameter changes did not require lead revision or programming changes. No device reset, failures, or premature scan termination was observed.1.5 T MRI scanning in patients with MRI conditional and non-MRI conditional cardiac devices was performed with similar, low clinical risk.

Intracardiac electrogram voltage remains an important metric for radiofrequency lesion application. Embedded micro-electrodes within ablation catheters are now approved for use in humans.This study examined electrogram characteristics of miniaturized electrode bipoles (iEGMmini ) compared to distal ablation tip bipoles (iEGMstandard ) in the setting of typical atrial flutter in humans.This was a single-center prospective trial involving 21 patients. A total of 54 non-ablated and 56 ablated sites were analyzed offline by separate blinded observers for iEGM voltage after a clinically successful radiofrequency (RF) ablation for typical atrial flutter. Ablation sites were defined as sites that were localized anatomically within the RF lesion set and did not have atrial capture at 10 mA and 2 milliseconds. Non-ablated sites were defined as sites adjacent to or remote from the ablation lesion set with capture at 10 mA and 2 milliseconds.iEGMmini had greater voltages at non-ablated sites and lower voltages at ablated sites than iEGMstandard (non-ablated sites iEGMstandard 0.64 mV vs. iEGMmini 1.0 mV; ablated sites iEGMstandard 0.15 mV, iEGMmini 0.08 mV, P0.001). The difference for each patient between ablated and non-ablated sites was greater for iEGMmini compared to iEGMstandard (0.94 mV ± 0.57 iEGMmini vs. 0.52 mV ± 0.35 iEGMstandard , P0.001). Inter-observer agreement was good among all non-ablated sites and iEGMmini ablated sites, but was less robust for ablated sites using iEGMstandard .Imbedded mini-electrode iEGM bipoles had higher voltages in non-ablated tissue, lower voltages in ablated tissue, and significantly greater intra-patient differences between ablated and non-ablated sites. These data suggest a potential role for miniaturized electrode bipole use in RF lesion monitoring.

Little data exist on long-term outcomes following extraction of implantable cardioverter defibrillator (ICD) leads, particularly for noninfectious indications. We sought to identify predictors of long-term survival after ICD lead extraction.We retrospectively reviewed ICD lead extractions at our institution (n = 508). Procedural outcomes and long-term survival were ascertained by medical records review.Indication for lead extraction was infection in 32.5% and lead failure in 61.8%. Mean dwell time of the oldest extracted lead was 5.1 ± 5.9 years. Complete procedural success was achieved in 96.5% of cases. Major procedure-related complications occurred in 1.6% with six periprocedural deaths. During a mean follow-up of 866 ± 798 days, survival was significantly worse among patients with infection as the indication for extraction. At 1 year after extraction, survival among those with infection was 88.2%, compared to 95.0% in the lead failure cohort (P0.001). Procedural failure was a significant predictor of long-term mortality, even after excluding periprocedural deaths. In multivariate models, the presence of chronic kidney disease, increased number of leads requiring extraction, lower ejection fraction, and procedural failure were predictors of mortality.Despite high rates of procedural success, infectious indication for ICD lead extraction is associated with increased long-term mortality. In contrast, among patients undergoing extraction for lead failure, long-term survival was excellent. The presence of procedural failure was a significant predictor of long-term mortality. Further studies will be necessary to better understand the mechanisms by which procedural failure may adversely impact long-term outcomes.

Although the subcutaneous ICD (S-ICD®) is an attractive alternative in patients with end-stage renal disease (ESRD), data on S-ICD outcomes in dialysis patients are lacking.Patients with cardiomyopathy undergoing S-ICD implantation in our center were stratified by need for chronic dialysis at the time of implant. The primary endpoint was incidence of death, heart failure hospitalization or appropriate S-ICD shocks, and secondary endpoints were incidence of inappropriate shocks or implant related complications requiring surgical re-intervention. Mean follow-up was longer in the nondialysis cohort (514 ± 495 vs. 227 ± 233 days, P = 0.006), so all endpoints were analyzed using time-dependent comparisons and reported as annual event rates.Out of 79 S-ICD implants included in this analysis, 27 patients were on dialysis. Dialysis patients were older and more likely to be diabetic. Mean ejection fraction across the entire cohort was 26.9% without significant difference between dialysis and nondialysis groups. Although not significant, the incidence of the primary endpoint was higher in the dialysis cohort (23.8%/year vs. 10.9%/year, P = 0.317), driven primarily by a higher rate of appropriate shocks. The rate of inappropriate shocks was similar between groups (dialysis 6.0%/year vs. nondialysis 6.8%/year, P = 0.509). No patients in the dialysis cohort had complications requiring surgical re-intervention versus 6 patients in the nondialysis cohort (P = 0.086).Our data suggest that S-ICD implantation in dialysis patients is not associated with an excess risk of implant related complications or inappropriate shocks.

St. Jude Riata/Riata ST defibrillator leads (St. Jude Medical, Sylmar, CA, USA) were recalled by the Food and Drug Administration in 2011 for an increased rate of failure. More than 227,000 leads were implanted and at least 79,000 patients still have active Riata leads. Studies have examined clinical predictors of lead failure in Riata leads, but none have addressed the effect of implantable cardioverter defibrillator (ICD) generator exchange on lead failure. The purpose of this study is to assess the effect of ICD generator exchange on the rate of electrical failure in the Riata lead at 1 year.A retrospective chart review was conducted in patients who underwent implantation of a Riata/Riata ST lead at one center. Patients with a functioning Riata lead (with/without externalized conductor) at the time of ICD exchange were compared to controls with Riata leads implanted for a comparable amount of time who did not undergo generator replacement.Riata leads were implanted in 1,042 patients prior to the recall and 153 of these patients underwent generator exchange without lead replacement. Conductor externalization was noted in 21.5% of Riata leads in the ICD exchange cohort, which was not different from the control group (19.2%; P = 0.32). Two leads failed in the first year after generator replacement (1.5%) which did not significantly differ from the control group (2.0%; P = 0.57). At change-out, 54% received a commanded shock (18.6 ± 0.9 J) that did not result in any change in the high-voltage lead impedance (46.1 ± 1.1 ohms).Conductor externalization was seen frequently in our cohort of patients. ICD generator exchange did not accelerate the rate of Riata lead failure at 1 year. Although both the control and the change-out cohorts failed at a rate much greater than nonrecalled leads, generator exchange did not appear to add to the problem.

Sudden cardiac death is a major cause of late mortality in adults with congenital heart disease (ACHD). While data exist for adults with repaired Tetralogy of Fallot (TOF), little is known about those with non-TOF lesions. We examined the relative rates in implantable cardioverter defibrillator (ICD) therapy according to congenital lesion type in a large-volume adult congenital heart center.A cohort of 59 individuals (median follow up time, 3.2 years range 0-10) with ACHD and ICDs was stratified according to underlying congenital lesion and implant indication. Appropriate therapies were defined as any therapy for a physician-adjudicated ventricular arrhythmia. Rates of inappropriate and appropriate ICD therapies were analyzed according to several relevant clinical variables.Thirty-three (56%) TOF, 15 (25.4%) L- or D-transposition of great arteries, and 11 (18.6%) with other lesions were included in the analysis. Approximately half (52.5%) were implanted for primary prevention indications. During follow-up, 12 (20.3%) patients received appropriate ICD therapies and 13 (22%) patients received inappropriate therapies. The incidence of appropriate shocks among patients with TOF was 27.3% (9/33) compared to 11.5% (3/26) among non-TOF diagnoses during the follow-up time (p = 0.043).ACHD patients with non-TOF congenital lesions are significantly less likely to receive appropriate ICD therapy than those with TOF. Our analysis calls into question the validity of traditional ICD implantation guidelines in this growing and diverse patient population.

Although left ventricular (LV) systolic dysfunction is known to occur in adults with repaired Tetralogy of Fallot (TOF), the effects of cardiac resynchronization therapy (CRT) are not well characterized.We retrospectively divided all patients with repaired TOF and impaired LV ejection fraction (LVEF ≤ 40%) undergoing CRT at our institution (n = 10) into two groups: de novo CRT (group A, n = 6) or upgrade from existing device (group B, n = 4). Echocardiograms were reviewed at baseline, medium-term (6 months post-CRT), and long-term follow-up. CRT response was defined as reduction in LV end-systolic volume (LVESV) ≥15% at medium term.Age at surgical repair was 13.1 ± 16.0 years, age at CRT was 44.4 ± 12.5 years, and baseline LVEF was 24.0 ± 10.5%. Group A demonstrated a preponderance of right ventricular (RV) conduction delay, whereas all patients in group B demonstrated RV pacing at baseline. At medium-term follow-up, patients in group A showed significant improvements in LVEF, LV end-diastolic volume (LVEDV), and LVESV. Group B also demonstrated a significant improvement in LVEF with favorable trends in LV volumes. Of nine patients with complete data at medium term, eight showed evidence of CRT response. Average long-term follow-up was 53.4 ± 29.3 months. At long-term follow-up, LVEF, LVEDV, and LVESV remained numerically better than baseline, although the results were no longer significant.Adult patients with repaired TOF and LV systolic dysfunction demonstrate significant medium-term response to CRT, even among those with RV conduction delay. The long-term impact of CRT in this population requires further characterization.

To develop a robust method to assess regional mechanical dyssynchrony from cine short-axis MR images. Cardiac resynchronization therapy (CRT) is an effective treatment for patients with heart failure and evidence of left-ventricular (LV) dyssynchrony. Patient response to CRT is greatest when the LV pacing lead is placed in the most dyssynchronous segment. Existing techniques for assessing regional dyssynchrony require difficult acquisition and/or postprocessing. Our goal was to develop a widely applicable and robust method to assess regional mechanical dyssynchrony.Using the endocardial boundary, radial displacement curves (RDCs) were generated throughout the LV. Cross-correlation was used to determine the delay time between each RDC and a patient-specific reference. Delay times were projected onto the American Heart Association 17-segment model creating a regional dyssynchrony map. Our method was tested in 10 normal individuals and 10 patients enrolled for CRT (QRS120 ms, NYHA III-IV, EF35%).Delay times over the LV were 23.9 ± 33.8 ms and 93.1 ± 99.9 ms (P0.001) in normal subjects and patients, respectively. Interobserver reproducibility for segment averages was 6.8 ± 39.3 ms and there was 70% agreement in identifying the latest contracting segment.We have developed a method that can reliably calculate regional delay times from cine steady-state free-precession (SSFP) images. Maps of regional dyssynchrony could be used to identify the latest-contracting segment to assist in CRT lead implantation.

Dofetilide, a class III antiarrhythmic, is one of the few alternatives to amiodarone in patients with atrial fibrillation (AF) and heart failure or coronary artery disease (CAD). While amiodarone has been extensively studied, little is known about predictors of response to dofetilide. We sought to identify clinical parameters associated with dofetilide success in a large cohort of patients with AF.A total of 287 patients with AF started on dofetilide between 2001 and 2008 were included. Dofetilide was deemed "completely effective" if the patient remained on dofetilide at follow-up and had no recurrences of AF clinically or by electrocardiogram. Dofetilide efficacy was analyzed in relation to clinical variables relevant to AF and AF recurrence. After a follow-up of 10.2 ± 7.7 months, 54.7% of the patients remained on dofetilide and it was completely effective in 26.8%. The discontinuation rate during initial hospitalization was 13.3% from excessive QT prolongation and one patient with torsades de pointes (successfully treated). A history of CAD was the only univariate predictor of efficacy (odds ratio [OR] 2.27, 95% confidence interval [CI] 1.29-4.01, P0.05). CAD remained the only significant factor associated with efficacy of dofetilide in a multivariate regression model (OR 2.01, 95% CI 1.11-3.70, P0.05, n = 270). The overall efficacy of dofetilide in patients with CAD was 41.1%, compared to 23.5% in those without CAD (P0.05).In this large cohort of patients with AF, underlying coronary disease was significantly associated with dofetilide success. This finding may have utility for clinical decisions regarding initiation of dofetilide.

Left ventricular (LV) response to cardiac resynchronization therapy (CRT) has typically been studied over 3- to 12-month periods. Longer-term data are unclear and response of strain parameters has not been reported. The authors evaluated long-term response with standard and strain echocardiography in 57 patients (52±15 years; 40 male; 30 white; 15 with ischemic etiology) who received a CRT-defibrillator between January 2004 and December 2005. Median ejection fraction (EF) at baseline was 22% (17%-25%). Global longitudinal, radial, and circumferential strain were -6.5% (-5.0% to -8.4%), 10.4% (6.9%-15.1%), and -7.6% (-5.5% to -10.8%), respectively. After a median of 42 months, EF increased by 5% (-1% to 15%; P.001), with improvements in circumferential (-3.2% [-5.2% to 1.5%]; P=.001), longitudinal (-0.5% [-3.4% to 1.2%]; P=.035), and radial (1.4% [-1.1% to 9.2%]; P=.035) strain. Changes in volumes were nonsignificant. EF improvement ≥5% was observed in 29 patients (50.9%). Relative improvement ≥15% in longitudinal, radial, and circumferential strain was observed in 26 (45.6%), 29 (50.9%), and 37 (64.9%) patients, respectively. Improvement in longitudinal strain and EF was strongly associated with lower rates of heart failure-related and all-cause readmissions. A wide range of long-term LV responses to CRT was observed, with approximately 50% of patients showing favorable responses.

Background: During cardiopulmonary resuscitation, the need for rescuers to stand clear before a shock is delivered invariably interrupts chest compressions. Brief interruptions like these reduce the efficacy of defibrillation in animal models. Current flow through a rescuer in contact with a patient being shocked with modern biphasic waveforms and adhesive patch electrodes has not been investigated. We hypothesized that leakage current is low through a rescuer performing chest compressions at the time of shock delivery. Methods: During 18 elective cardioversions using truncated exponential biphasic waveforms (median energy 200 joules, range 100 –360 joules), an investigator serving as the rescuer placed a gloved hand on the patient’s anterior chest immediately adjacent to the defibrillating patch with approximately 20lbs of pressure to simulate chest compressions. Skin electrodes were used to connect the rescuer’s thigh to the patient’s posterior shoulder, simulating a worst-case return current pathway. During shock delivery, voltage and current through the rescuer (hand to thigh) were recorded using a digital storage oscilloscope during the shock delivery. Results: In no cases were shocks perceptible to the rescuer. Mean patient transthoracic impedance was 57 +/− 14 ohms (range 36 –79 ohms). Potential differences in volts (V) between the rescuer’s wrist and thigh ranged from 1.7 to 14 V (mean 6.7 +/− 2.7 V). Calculated impedances through rescuers ranged from 8,190 to 100,400 ohms (mean 30,100 +/− 20,400 ohms). The average leakage current flowing through the rescuer’s body for each phase of the shock waveform was 273 +/−191 microamperes (range 1 to 910 microamperes). All measured values in our series were well below 2,500 microamperes, an accepted safety standard for earth-leakage current in medical devices. Conclusions: Even in a simulated worst-case scenario, a rescuer performing chest compressions during biphasic external defibrillation is exposed to low levels of leakage current. Our findings demonstrate the safety and feasibility of uninterrupted chest compressions during shock delivery, which may enhance the efficacy of defibrillation and cardiocerebral perfusion.

Background: Myocardial depolarization can be achieved with currents of either anodal or cathodal polarity. In contrast to conventional cathodal pacing, anodal pacing initially hyperpolarizes tissue and improves myocardial contractility in animal models. Methods and Results: In 13 patients undergoing cardiac resynchronization therapy (CRT) device implantation, we compared the mean left ventricular outflow velocity-time integral (LV-VTI) for anodal and cathodal polarities in three different pacing configurations. Intraoperative continuous-wave Doppler measurements were taken at a fixed interrogation angle, while polarities were switched during unipolar left ventricular, unipolar biventricular, and shared-coil biventricular pacing. Comparisons used identical pacing rates, intervals, and stimulus strengths. Patients had a mean ejection fraction of 0.18 ± 0.08 and a mean QRS duration of 140 ± 34 ms. All capture thresholds were less than 4.5 volts at a pulse width of 0.4 ms. Data were suitable for analysis in 37 of the 39 pairs of Doppler measurements. Anodal polarity significantly increased average LV-VTI in 36 of these 37 comparisons. The mean increase in LV-VTI for each configuration with anodal versus cathodal polarity was 2.8 ± 2.6 cm (P < 0.001). The combined mean LV-VTI for all configurations was similarly higher for anodal polarity (24.4 ± 11.7 cm) versus cathodal polarity (21.7 ± 10.9 cm; P < 0.001). Conclusion: Anodal pacing polarity significantly improves a measure of LV function compared to traditional cathodal currents. Anodal pacing, which can be achieved by a simple reversal of pacing circuit polarity, may represent an important therapeutic addition to future resynchronization devices.