Cha, Y

Abstract Background and introduction Cardioversion is commonly used to terminate cardiac arrhythmias. Some previous reports have suggested that cardioversion results in myocardial injury as evidenced by increased levels of cardiac troponin. However, many of these studies were done years ago with less sensitive troponin assays and monophasic waveform defibrillators. Purpose To determine if external direct current (DC) cardioversion with biphasic rectilinear waveform shocks results in myocardial injury as assessed by high sensitivity cardiac troponin T (hs-cTnT) and I (hs-cTnI). Methods Patients scheduled for elective DC cardioversion for atrial fibrillation or atrial flutter were recruited. Plasma samples for measurement of hs-cTnT and hs-cTnI were obtained pre-cardioversion and as late as feasible but at least 6 hours post-cardioversion [median of 9 (7–11) hours]. Results A total of 96 patients were recruited. One patient was excluded because the pre-cardioversion sample was hemolysed. Median (25th–75th interquartile range) cumulative energy delivered was 121.6J (62.4–277.4J) and median highest energy individual shock was 121.0J (62.1–146.2J). A total of 39 (41.1%) patients received more than 1 shock, 23 (24.2%) patients received a cumulative energy of 300J or higher and 5 (5.3%) patients received a cumulative energy of 1,000J or more. The median pre-cardioversion hs-cTnT value was 11.48 (7.19–18.38) ng/L and the median hs-cTnI value was 5.1 (2.0–9.4) ng/L. Median post-cardioversion hs-cTnT value were 12.46 (7.98–20.28) ng/L and hs-cTnI value were 6.3 (3.5–10.0) ng/L. Wilcoxon-Signed ranks test showed a statistically significant change between the pre-and-post cardioversion hs-cTnT values (Z=−4.237, p<0.001) and hs-cTnI values (Z=−4.822, p<0.001). In only 5 (hs-cTnT) and 4 patients (hs-cTnI) was there an increase of >5 ng/L. There were 5 cases where the post-cardioversion values of both hs-cTnT and hs-cTnI were above the 50% reference change value. There was no relation between the change in hs-cTn values and sex, number of shocks, total energy delivered (even in those who received more than 1,000J), highest energy per shock, total current delivered, highest current delivered per shock or transthoracic impedance. Conclusion(s) There is a statistically significant but very small change in median hs-cTnT and hs-cTnI values (1 ng/L and 1.2 ng/L respectively) after DC cardioversion. The results were similar even in patients where high energy shocks were delivered and did not vary based on the pre cardioversion baseline value. Patients who have marked troponin elevations after cardioversion should be assessed for other causes of myocardial injury. It should not be assumed that they have myocardial injury from the cardioversion alone. Figure 1 Funding Acknowledgement Type of funding source: Other. Main funding source(s): Dr. Allan Jaffe has substantial research funds from both grants and private industry. Funds were used to pay for blood sample collection and analysis of high sensitivity cardiac troponin T at Mayo Clinic. Abbott Laboratories donated reagents for the high sensitivity cardiac troponin I analysis.

Abstract Background His bundle pacing aims to mimic the activation pattern of normal conduction to maintain ventricular synchrony. However, selective His capture can be challenging, and the activation sequence during His pacing may not replicate normal conduction. Purpose Compare the right ventricular (RV) and left ventricular (LV) activation pattern in sinus rhythm and His bundle pacing. Methods Baseline LV and RV map was created in sinus rhythm using Rhythmia mapping system (Boston Scientific Corporation) in canine animal model. Medtronic 3830 lead was placed near the bundle of His under fluoroscopic, intracardiac echocardiogram, and electroanatomic guidance. Conduction system capture was confirmed by observing a QRS duration <120ms and an isoelectric segment between pacing artifact and QRS on surface ECG. Repeat LV and RV activation map was obtained during His pacing. Average QRS, HV and pacing to V intervals were calculated with standard deviation. Results Mapping was performed successfully in four animals. At baseline, the average QRS duration was 44±2.6ms and HV interval was 32±4.2ms. Earliest site of myocardial activation was in the mid-septal LV region. The earliest RV myocardial activation was also at the septum closer to the apex, but later than the LV (Figure1A). With His pacing, the average QRS duration was 70±17.0ms and the average stim to V interval was 31±8.7ms. During His pacing, the earliest site of activation was in the RV septum, with an activation pattern from base to apex in both the RV and LV. Conclusion Unlike normal physiology, the activation pattern during conduction system pacing is from base to apex with earliest site in the RV. Funding Acknowledgement Type of funding source: Public hospital(s). Main funding source(s): Mayo Clinic

Abstract Introduction Chronic right ventricular pacing (RVP) has been associated with dyssynchrony, leading to increased mortality. However, there have been discrepancies in previous reports in the effect of RVP levels. Objective To sub-stratify mortality risk by age for different RVP level groups within a large real-world ICD cohort. Methods Optum® de-identified electronic health records were linked to the Medtronic Carelink data to identify dual chamber ICD recipients (2007–2017). RVP level was based on median daily pacing during the first 90 days post-implant and categorized either into groups with a cutoff of 40%, or with groups of 0–9%, 10–19%, 20–29%, 30–39%, 40–49%, and 50–100%. The endpoint was death more than 90 days post-implant. Kaplan-Meier survival curves, log-rank tests, and Cox regression were used to analyze the relationship between RVP and risk of death. Results Among 14,832 ICD patients (median age 67; 74.0% male), there were 2,602 deaths within 10 years after implant. In unadjusted comparisons, high RVP (>40%) increased the risk of death relative to low RVP (≤40%) (p<0.001). This effect remained significant in older cohort (≥67 years old at implant) (p<0.001), but not in younger cohort (<67 years old) (p=0.955) (Figure). After controlling for age, gender, pacing mode, MI, SCA, HF hospitalization, diabetes, and renal dysfunction, similar or increased risk was associated with higher pacing groups relative to the 0–9% pacing group in the older cohort, but not in the younger cohort. Conclusions Our data from a large contemporaneous real-world source suggests that older age or characteristics associated with age make patients more sensitive to chronic RVP effects. These results help reconcile differences observed in prior studies. Funding Acknowledgement Type of funding source: Private company. Main funding source(s): Medtronic, Inc.

Abstract Background Venous stenosis is a well-recognized complication of transvenous leads when patients require lead revisions or device upgrade. In these cases, balloon venoplasty or alternative venous access with subcutaneous tunneling can be performed. Purpose Compare the outcomes of venoplasty vs. tunneling in patients requiring additional transvenous lead implantation. Methods A single center retrospective cohort study of all patients undergoing lead implantation/revision requiring venoplasty or tunneling from 2005–2017. Chi-squared and Wilcoxon Rank-Sum tests were used to compare categorical and continuous variables. Results Ninety five patients met our inclusion criteria (60 venoplasty & 35 tunneling). There was no difference in procedure success rates (p-value=0.98). Tunneling was associated with less fluoroscopy time but higher incidence of acute complications (0% vs. 23%, p-value=0.002) most requiring invasive intervention and/or blood product transfusion. Long term outcomes were comparable and related to lead failure or infection. Outcomes for tunneling vs. venoplasty Variable Tunneling (n=35) Venoplasty (n=60) p-value Age Y 67 (23–84) 70 (29–91) 0.25 Male (%) 24 (69%) 41 (68%) 0.98 Number of existing leads 2.1 (1–4) 2.4 (0–4) 0.1 Age of oldest lead 7.0 (0–21) 7.2 (0–33) 0.73 Number of new leads 1.2 (1–3) 1.4 (1–3) 0.26 Fluoroscopy time (SD) min 29.2 (21.3) 39.7 (21.5) 0.012 Procedure success (%) 35 (100%) 55 (92%) 0.9 Acute complications (%) 8 (23%)1 0 (0%) 0.0002 Pocket hematoma/bleed 4 (11%)2 Hemothorax 2 (6%)3 Pericarditis 1 (3%) Lead compromise 1 (3%) Follow up M 18 (0–76) 28 (0–98) N/A Long term lead issues (%) 6 (17%) 10 (17%) 0.95 Long term complication requiring intervention 4 (11%) 8 (13%) N/A Procedure success: functional lead placed as a result of venoplasty or tunneling. 1Two patients required blood products. 2Two patients required invasive intervention. 3One patient required chest tube and the other ICU admission. Conclusions Balloon venoplasty is associated with similar rates of success and a less incidence of acute complications when compared subcutaneous tunneling. Acknowledgement/Funding NIH T32 Training Grant HL07111-40

Abstract Recent guideline statements approve the performance of magnetic resonance imaging (MRI) in patients with non-conditional cardiac implantable electronic devices (CIEDs) under certain closely monitored conditions. Data from current registries may have lower power to discern changes that may occur in the CIED after the MRI. Objective We aimed to systematically review the literature to identify the adverse events and significance of changes in device function associated with performing MRI in patients with CIEDs Methods A comprehensive literature search of the databases was performed between 1980- 2017. Two independent reviewers selected studies and extracted data. A random-effects model was used for meta-analysis. Results A total of 7,422 patients underwent 8,865 MRI studies. No death occurred post MRI. Clinical adverse events were extremely rare (mostly less than 1%) and are summarized in Table 1. No significant changes in the pooled mean effect size estimate was noted for the changes in the lead parameters (pacing threshold, sensing and impedance) Binary outcomes post magnetic resonance imaging in patients with non-conditional cardiac implantable electronic devices Outcome Sample size Number of patients Rate SE LL of CI UL of CI Death 7401 0 0 0 0 0 Atrial arrhythmia 7173 10 0.001 0.0004 0.0007 0.0024 Ventricular arrhythmia 7371 9 0.0012 0.0004 0.0006 0.0022 Oversensing 4981 17 0.0034 0.0008 0.0020 0.0053 Inhibition of pacing 7371 6 0.0008 0.0003 0.0003 0.0016 Lead Failure/Generator Failure 7475/7475 2/8 0.0002/0.0011 0.0001/0.0004 0.0001/0.0005 0.0009/0.002 Power on Reset 1388 105 0.0131 0.0014 0.0107 0.0161 Did not complete scan 6851 13 0.0019 0.0005 0.0011 0.0031 Chest pain 7080 11 0.0021 0.0004 0.0008 0.0027. Lead threshold rise (>0.5v/>50%-A/V) 5076/6246 12/16 0.0024/0.0026 0.0007/0.0006 0.0013/0.0015 0.0040/0.0041 Change in Battery voltage >0.04V 7132 42 0.0061 0.0009 0.0043 0.0079 Sensing decrease >50%-A/V 5087/5834 17/9 0.0033/0.0015 0.0008/0.0005 0.0020/0.0008 0.0052/0.0028 Impedance changes >50ohms/>50% 5810 22 0.0038 0.0008 0.0024 0.0057 Rise in cardiac enzymes 1703 26 0.0152 0.0030 0.0102 0.0219 A, atrial; V, ventricular; SE, standard Error; LL, lower limit; UL, upper limit; CI, Confidence intervals. Conclusions MRI in patients with non-conditional CIEDs can be performed with high degree of safety and low rate of clinical events when performed under standardized protocols Acknowledgement/Funding None