The best way of preventing device-device interactions may be avoiding implanting 2 devices in the first place.

Extensive testing during the second device implantation was required to best program the devices in order to decrease these negative interactions. Unfortunately, these programming changes were not always successful at preventing device-device interactions during clinical follow-up.

Remaining longevity and evidence of failure of cardiac implantable electrophysiology devices recovered from funeral homes.

BACKGROUND: Given the prohibitive cost of pacemakers and defibrillators for medically underserved patients in low-income countries, these devices are sometimes recovered from funeral homes for charitable reimplantation. Many devices are implanted near the end of the patients' lives, meaning that recovered devices from funeral homes have the potential for significant remaining longevity. METHODS: After sending letters asking funeral directors in the Philadelphia area to donate explanted pacemakers and defibrillators, 78 devices were recovered. Sixty-seven of these devices were successfully interrogated, and 64 devices reported estimates of remaining battery life in years. Twenty-one defibrillators were also interrogated for evidence of failure. RESULTS: Twenty-two percent of the 64 devices had greater than 4 years of longevity. Fourteen percent of the devices had between 1 and 4 years of longevity, and the remaining 64% had less than 1 year of remaining battery life. We found no evidence from 21 recovered defibrillators that the patient's cause of death was because of defibrillator failure. In almost half (10/21) of the defibrillators, however, the arrhythmia logs were nondecipherable given the entire log was replaced by episodes of signal noise likely occurring after death. CONCLUSIONS: A significant percentage of devices explanted in funeral homes have suitable remaining battery life for reuse. While no evidence of defibrillator device failure could be found, the analysis was limited by postmortem signal artifact, which may preclude accurate assessment of rates of failure in devices explanted postmortem.

Electrocardiogram voltage discordance: Interpretation of low QRS voltage only in the precordial leads.

OBJECTIVES: To define clinical correlates of low voltage isolated to precordial leads on the surface electrocardiogram (ECG). INTRODUCTION: Low voltage (V) on the ECG is defined as QRS V<5mm in all limb leads and <10mm in all precordial leads. The diagnostic use of ECGs with low voltage isolated to the precordial leads with normal limb lead voltages is unclear. METHODS: Twelve-lead ECGs with QRS V>5mm in one or more limb leads and <10mm in all precordial leads were collected. Associated clinical conditions were determined from clinical data, echocardiograms, and chest radiographs. RESULTS: Low precordial voltage was found in 256 of 150,000 ECGs (~0.2%). 50.4% of patients had discordant ECGs that correlated with classic etiologies, with a higher incidence of LV dilation in those with classic etiologies than those without. CONCLUSION: Low precordial voltage is associated with classic etiologies and LV dilation.

The ethics of unilateral implantable cardioverter defibrillators and cardiac resynchronization therapy with defibrillator deactivation: patient perspectives.

AIMS: Decisions about deactivation of implantable cardioverter defibrillators (ICDs) are complicated. Unilateral do-not-resuscitate (DNR) orders (against patient/family wishes) have been ethically justified in cases of medical futility. Unilateral deactivation of ICDs may be seen as a logical extension of a unilateral DNR order. However, the ethical implications of unilateral ICD deactivation have not been explored. METHODS AND RESULTS: Sixty patients who had an ICD or cardiac resynchronization therapy with defibrillator (CRT-D) were interviewed at a quaternary medical centre outpatient electrophysiology practice. Survey questions addressed whether deactivation of defibrillator function was included in advanced directives, whether deactivation constitutes physician-assisted suicide, and whether unilateral deactivation can be ethically justified. Responses were elicited to scenarios in which defibrillation function was deactivated in different contexts (including patient request to deactivate, existing DNR, and unilateral deactivation). Only 15% of respondents had thought about device deactivation if they were to develop a serious illness from which they were not expected to recover. A majority (53%) had advance directives, but only one mentioned what to do with the device. However, a majority (78%) did not consider deactivation of an ICD shocking function against patients' wishes to be ethical or moral. CONCLUSION: Management of ICDs and CRT-Ds as patients near the end of their lives creates ethical dilemmas. Few patients consider device deactivation at end-of-life, although a large majority believes that unilateral deactivation is not ethical/moral, even in the setting of medical futility. Advance care planning for these patients should address device deactivation.

Relation of Body Mass Index to Long-Term Survival After Cardiac Resynchronization Therapy.

Obesity confers a paradoxical survival benefit in patients with heart failure, but this obesity paradox has not been well established in those who have undergone cardiac resynchronization therapy with a defibrillator (CRT-D). We sought to determine the impact of body mass index (BMI) on long-term survival in patients with heart failure after CRT-D. We identified 113 patients implanted with CRT-D at our institution from May 2002 to November 2003. Patients were divided into 3 categories by pre-implant BMI (kg/m2): normal weight (BMI <25), overweight (BMI 25-29), and obese (BMI ≥30). Ten-year survival free from orthotopic heart transplant or ventricular assist device implantation was analyzed with Kaplan-Meier plots, the log-rank test, and Cox proportional hazards modeling. Thirty-three patients (29%) were normal weight, 47 (42%) were overweight, and 33 were obese (29%). Median follow-up time was 4.5 years (interquartile range 1.9 to 8.7 years). Obese patients were younger and had a higher proportion of women (both p <0.05). Ten-year survival free of orthotopic heart transplant or ventricular assist device was highest in obese patients (36.3%) followed by overweight (19.2%) and then normal-weight patients (12.1%), log-rank p trend = 0.004. After adjustment for clinical risk factors, every 1 kg/m2 increase in BMI was associated with a 8% reduction in the risk of the primary end point (adjusted hazard ratio 0.92, 95% confidence interval 0.88 to 0.97, p = 0.002). In conclusion, higher BMI is associated with improved long-term survival after CRT-D.

Optimal QT interval correction formula in sinus tachycardia for identifying cardiovascular and mortality risk: Findings from the Penn Atrial Fibrillation Free study.

BACKGROUND: The QT interval measures cardiac repolarization, and prolongation is associated with adverse cardiovascular outcomes and death. The exponential Bazett correction formula overestimates the QT interval during tachycardia. OBJECTIVE: We evaluated 4 formulas of QT interval correction in individuals with sinus tachycardia for the identification of coronary artery disease, heart failure, and mortality. METHODS: The Penn Atrial Fibrillation Free study is a large cohort study of patients without atrial fibrillation. The present study examined 6723 Penn Atrial Fibrillation Free study patients without a history of heart failure and with baseline sinus rate ≥100 beats/min. Medical records were queried for index clinical parameters, incident cardiovascular events, and all-cause mortality. The QT interval was corrected by using Bazett (QT/RR(0.5)), Fridericia (QT/RR(0.33)), Framingham [QT + 0.154 * (1000 - RR)], and Hodges (QT + 105 * (1/RR - 1)) formulas. RESULTS: In 6723 patients with a median follow-up of 4.5 years (interquartile range 1.9-6.4 years), the annualized cardiovascular event rate was 2.3% and the annualized mortality rate was 2.2%. QT prolongation was diagnosed in 39% of the cohort using the Bazett formula, 6.2% using the Fridericia formula, 3.7% using the Framingham formula, and 8.7% using the Hodges formula. Only the Hodges formula was an independent risk marker for death across the range of QT values (highest tertile: hazard ratio 1.26; 95% confidence interval 1.03-1.55). CONCLUSION: Although all correction formulas demonstrated an association between QTc values and cardiovascular events, only the Hodges formula identified one-third of individuals with tachycardia that are at higher risk of all-cause mortality. Furthermore, the Bazett correction formula overestimates the number of patients with a prolonged QT interval and was not associated with mortality. Future work may validate these findings and result in changes to automated algorithms for QT interval assessment.

Defibrillator Deactivation against a Patient's Wishes: Perspectives of Electrophysiology Practitioners.

BACKGROUND: Unilateral do-not-resuscitate (DNR) orders (against patient/family wishes) have been ethically justified in cases of medical futility. We investigated whether electrophysiology practitioners believe medical futility justifies unilateral implantable cardioverter defibrillator (ICD) deactivation. METHODS AND RESULTS: Email invitations to take an online survey were sent to 1,894 electrophysiology practitioners. A total of 384 responses were collected (response rate 20.6%). Though the sample included respondents from Europe, Asia, Australia, South America, and Africa, the majority were from North America (78%), were academically affiliated (64%), and practiced in an urban setting (67.8%). Deactivation of ICD shock function in agreement with patient wishes and a preexisting DNR were not considered physician-assisted suicide (93.2%, 358/384). However, a majority of the sample responded that it was not ethical/moral for doctors to deactivate ICDs against patients' wishes (77.1%, 296/384) or against family/surrogates' wishes (72.4%, 278/384), even in the context of medical futility. A majority indicated that deactivating ICD shock function is not ethically/morally different than withholding cardiopulmonary resuscitation or external defibrillation in a code (72.7%, 277/381), but was different than deactivating pacing in a pacemaker-dependent patient (82.8%, 318/384). In the classification of interventions, a plurality (43.0%, 165/383) regarded ICDs to be unlike any other intervention. Concerning pacemakers, 50% (191/382) considered them to be like dialysis (a therapy that keeps patients alive). CONCLUSIONS: This international sample of electrophysiology practitioners considered ICD and pacemaker deactivation to be ethically distinct. While ICD deactivation was considered appropriate in the setting of patient/family agreement, unilateral deactivation was not.

Untreated atrial fibrillation in the United States of America: Understanding the barriers and treatment options.

Atrial fibrillation is the most commonly treated arrhythmia in the United States of America. Stroke is the most devastating consequence of atrial fibrillation. For decades, warfarin has been the most recommended treatment for patients with atrial fibrillation at risk for stroke and systemic emboli. However, many patients at risk are not treated with anticoagulants. Several reasons exist, including physician underestimation of patient stroke risk, physician overestimation of bleeding risk, and patients' reluctance to take chronic warfarin due to the difficulties of this medication in relation to its pharmacokinetics and interactions with food and other medications. Risk scores have helped to better define patient risks and benefits from chronic anticoagulation. Novel anticoagulants (NOACs) have improved the ability for patients to be compliant with anticoagulation.

Management of Atrial Fibrillation.

Atrial fibrillation remains the most prevalent cardiac arrhythmia, and its incidence is increasing as the population ages. Common conditions associated with an increased incidence include advanced age, hypertension, heart failure, and valvular heart disease. Patients with atrial fibrillation may complain of palpitations, fatigue, and decreased exercise tolerance or may be completely asymptomatic. Options for treating patients who experience atrial fibrillation include rate-controlling drugs such as digoxin, ß-blockers, and calcium channel blockers or a rhythm-controlling strategy with agents such as sodium channel blockers and potassium channel blockers. Atrial fibrillation increases the risk of stroke due to atrial thrombus formation and embolization. Anticoagulation with the vitamin K antagonist, warfarin, remains the most widely prescribed treatment option to decrease stroke risk. Several other antithrombotic agents have recently become available and offer excellent alternatives to warfarin. Catheter ablation can be undertaken as a nonpharmacologic rhythm control option with varying degrees of success depending on duration of atrial fibrillation and follow-up time from the procedure. This review article further describes the management options for patients presenting with atrial fibrillation.

Incidence and predictors of right ventricular pacing-induced cardiomyopathy.

BACKGROUND: Frequent right ventricular (RV) pacing can lead to a decline in left ventricular ejection fraction (LVEF). OBJECTIVE: This study aimed to identify incidence and predictors of RV pacing-induced cardiomyopathy (PICM). METHODS: We retrospectively studied 1750 consecutive patients undergoing pacemaker implantation between 2003 and 2012. Patients were included if baseline LVEF was normal, single-chamber ventricular or dual-chamber pacemaker (but not implantable cardioverter-defibrillator or biventricular pacemaker) was implanted, frequent (≥20%) RV pacing was present, and repeat echocardiogram was available ≥1 year after implantation. PICM was defined as ≥10% decrease in LVEF, resulting in LVEF <50%. Patients with alternative causes of cardiomyopathy were excluded. Predictors of the development of PICM were identified using multivariate Cox proportional hazards modeling. RESULTS: Of 257 patients meeting study criteria, 50 (19.5%) developed PICM, with a decrease in mean LVEF from 62.1% to 36.2% over a mean follow-up period of 3.3 years. Those who developed PICM were more likely to be men, with lower baseline LVEF and wider native QRS duration (bundle branch blocks excluded; P = .005, P = .03, and P = .001, respectively). In multivariate analysis, male gender (hazard ratio 2.15; 95% confidence interval 1.17-3.94; P = .01) and wider native QRS duration (hazard ratio 1.03 per 1 ms increase; 95% confidence interval 1.01-1.05; P < .001) were independently associated with the development of PICM. Native QRS duration >115 ms was 90% specific for the development of PICM. CONCLUSION: PICM may be more common than previously reported, and risk for its occurrence begins below the commonly accepted threshold of 40% pacing burden. Men with wider native QRS duration (particularly >115 ms) are at increased risk. These patients warrant closer follow-up with a lower threshold for biventricular pacing.

Risk of stroke or transient ischemic attack after atrial fibrillation ablation with oral anticoagulant use guided by ECG monitoring and pulse assessment.

INTRODUCTION: We sought to gain insight into stroke risk after atrial fibrillation (AF) ablation. METHODS AND RESULTS: We followed 1,990 patients for >1 year (49 ± 29 months) who underwent AF ablation. Prior to stopping oral anticoagulants (OAC), we performed 3-week transtelephonic ECG monitoring (TTM) and taught patients heart rate and pulse assessment. Documented AF or inability to do monitoring or assess pulse precluded stopping OAC in CHADS2 ≥1 patients. OAC was stopped in 546/840 (65%) with CHADS2  = 0; 384/796 (48%) with CHADS2  = 1 and 101/354 (40%) with CHADS2 ≥ 2. Sixteen strokes or TIAs occurred (0.2%/patient-year); 5 in CHADS2  = 0 patients (all off OAC); 5 in CHADS2  = 1 (1 off and 4 on OAC); and 6 in CHADS2 ≥2 (2 off and 4 on OAC). Twelve of 16 patients (75%) with stroke or TIA had documented AF. In patients "off " OAC, stroke rate/year stratified by the CHADS2 score was similar (CHADS2  = 0: 0.28%; CHADS2  = 1: 0.07%; CHADS2 ≥2: 0.50%; P = NS). There was no difference in stroke risk "on" versus "off " OAC in CHADS2  = 1 (0.48% vs. 0.07%) or CHADS2 ≥2 (0.39% vs. 0.50%). Risk of major bleeding per patient year "on" OAC was > "off " OAC (13/1,138 (1.14%) versus 1/832 (0.1%); P<0.016). CONCLUSIONS: Post-AF ablation with OAC guided by TTM and pulse assessment: (1) Overall stroke or TIA rate risk is low and risk is due to recurrent AF and (2) OAC can be stopped in 40% of CHADS2 ≥2 patients with low stroke and hemorrhagic risk.

Usefulness of QRS axis change to predict mortality in patients with left bundle branch block.

QRS duration correlates with poor prognosis in patients with left bundle branch block (LBBB), but the importance of left-axis deviation (LAD) is not well established. To determine if LAD confers a mortality risk in patients with LBBB, a single-center, retrospective, population-based cohort study was conducted. Included were all patients at 1 hospital with LBBB on electrocardiography from 1995 to 2005 over a 17-year follow-up period (n = 2,794, median follow-up duration 20 months, interquartile range 6 to 64). Half of all patients with LBBB had LAD. The all-cause mortality rate in the entire cohort was 15%. LAD was not associated with mortality, either as a single outcome (odds ratio [OR] 1.1, 95% confidence interval [CI] 0.88 to 1.3, p = 0.50) or in time-to-event analysis (p = 0.40). Significant risk factors for mortality included high creatinine (OR 1.2, 95% CI 1.1 to 1.3), low hemoglobin (OR 1.2, 95% CI 1.1 to 1.3), history of atrial fibrillation (OR 1.6, 95% CI 1.3 to 2.1), electrocardiographic evidence of previous infarct (OR 1.5, 95% CI 1.2 to 1.9), and history of ventricular tachycardia (OR 1.4, 95% CI 1.0 to 1.9). On bivariate analysis, LAD was associated with atrial fibrillation, ventricular tachycardia, age, and congestive heart failure. Patients with LBBB who converted from normal axis to LAD had significantly higher mortality in time-to-event analysis (p = 0.02). In conclusion, in patients with LBBB, LAD does not confer significant mortality risk. However, those with normal axis who developed LAD during the study period had significantly higher mortality. Perhaps when LBBB and LAD develop concurrently, there is no increased risk over baseline LBBB development, but it may herald a worse prognosis if LAD develops against the background of previous LBBB, from an unknown mechanism.

Assessing arrhythmia burden after catheter ablation of atrial fibrillation using an implantable loop recorder: the ABACUS study.

INTRODUCTION: Arrhythmia monitoring in patients undergoing atrial fibrillation (AF) ablation is challenging. Transtelephonic monitors (TTMs) are cumbersome to use and provide limited temporal assessment. Implantable loop recorders (ILRs) may overcome these limitations. We sought to evaluate the utility of ILRs versus conventional monitoring (CM) in patients undergoing AF ablation. METHODS AND RESULTS: Forty-four patients undergoing AF ablation received ILRs and CM (30-day TTM at discharge and months 5 and 11 postablation). Over the initial 6 months, clinical decisions were made based on CM. Subjects were then randomized for the remaining 6 months to arrhythmia assessment and management by ILR versus CM. The primary endpoint was arrhythmia recurrence. The secondary endpoint was actionable clinical events (change of antiarrhythmic drugs [AADs], anticoagulation, non-AF arrhythmia events, etc.) due to either monitoring strategy. Over the study period, 6 patients withdrew. In the first 6 months, AF recurred in 18 patients (7 noted by CM, 18 by ILR; P = 0.002). Five patients in the CM (28%) and 5 in the ILR arm (25%; P = NS) had AF recurrence during the latter 6 months. AF was falsely diagnosed frequently by ILR (730 of 1,421 episodes; 51%). In more patients in the ILR compared with the CM arm, rate control agents (60% vs 39%, P = 0.02) and AADs (71% vs 44%, P = 0.04) were discontinued. CONCLUSION: In AF ablation patients, ILR can detect more arrhythmias than CM. However, false detection remains a challenge. With adequate oversight, ILRs may be useful in monitoring these patients after ablation.

Innovative P-wave detection for discrimination between ventricular and supraventricular tachycardia in single-chamber ICDs: is the P-wave invisible during tachycardia?

AIMS: Differentiation between supraventricular tachycardia (SVT) and ventricular tachycardia (VT) remains a substantial clinical challenge in patients with single-chamber implantable cardioverter-defibrillators (ICDs) due to absence of visible P waves. Innovative optimization of intrathoracic electrogram (EGM) configuration will facilitate P-wave detection and rhythm differentiation during tachycardia. METHODS AND RESULTS: Innovative optimization of EGM configuration was originally performed to improve patient care. In this retrospective cohort study, we examined our database for records of 140 consecutive patients undergoing single-chamber ICD implantation. During the follow-ups of 61 included patients with optimized EGM configuration, 27 patients were identified to have VT and/or SVT. EGMs in the Can (generator) to superior vena cava (Can-SVC) configuration were compared with those conventionally from the Can to right ventricular coil (Can-RV coil) source in the same patients. In Can-SVC EGMs, the ratio of P/QRS amplitude was 14-fold higher (0.57 ± 0.08 vs. 0.04 ± 0.00, P < 0.001) compared with those in Can-RV coil EGMs during sinus rhythm. With Can-SVC configuration, the odds of atrioventricular dissociation detection in patients with VT was increased 15-fold (61.9% vs. 9.5% with Can-RV coil; odds ratio, 15.4; 95% confidence interval, 2.8 to 84.7; P = 0.0009). In patients with SVT, P-waves or retrograde P-waves were markedly more identifiable in Can-SVC configuration compared with Can-RV coil (odds ratio, 40; 95% confidence interval, 3.6 to 447.1; P = 0.0010). CONCLUSION: P-wave recognition by optimizing EGM configuration provides a novel diagnostic tool for differentiation between VT and SVT in single-chamber ICDs. A potential discrimination algorithm would provide a cost-effective approach to improving the qualitative outcomes.

Longevity of implantable electrophysiology devices explanted from patients having autopsy in hospitals.

The cost of cardiac implantable electrophysiologic devices (CIEDs) remains prohibitively high for many patients in low- and middle-income countries. Recent efforts have focused on obtaining CIEDs for donation and reuse in low- and middle-income countries from funeral homes and after device upgrades. Most patients in the United States die in health care facilities, yet few data exist on the acceptability for reuse of devices from hospital morgues. Three hundred thirty-four autopsies were performed at the University of Pennsylvania morgue from February 2009 to July 2011, during which CIEDs were routinely removed and collected. Devices were interrogated to ascertain remaining longevity. When a longevity estimate was not provided by the device, the manufacturer was contacted to obtain an estimate. Date of death was obtained from the electronic medical record. Twenty-seven patients (8% of autopsies performed) had CIEDs, of which 17 (63%) were pacemakers and 10 (37%) were implantable cardioverter-defibrillators. Two of the defibrillators were part of cardiac resynchronization therapy systems. CIEDs were interrogated 1.7 ± 0.7 years after death. The mean time between implantation and death was 2.5 ± 2.3 years, but 13 (48%) devices were implanted within 1 year of death. Nine devices (33%) had <1 year of battery life remaining, 10 devices (37%) had an estimated longevity of 1 to 4 years, and 8 devices (30%) had longevity estimates of ≥4 years. In conclusion, a significant percentage of patients who underwent autopsy had CIEDs implanted <1 year before death. Hospital morgues may serve as a source for devices in reuse programs, provided patients or their next of kin authorize donation.

Noninvasive programmed ventricular stimulation early after ventricular tachycardia ablation to predict risk of late recurrence.

OBJECTIVES: The goal of this study was to evaluate the ability of noninvasive programmed stimulation (NIPS) after ventricular tachycardia (VT) ablation to identify patients at high risk of recurrence. BACKGROUND: Optimal endpoints for VT ablation are not well defined. METHODS: Of 200 consecutive patients with VT and structural heart disease undergoing ablation, 11 had clinical VT inducible at the end of ablation and 11 recurred spontaneously. Of the remaining 178 patients, 132 underwent NIPS through their implantable cardioverter-defibrillator 3.1 ± 2.1 days after ablation. At 2 drive cycle lengths, single, double, and triple right ventricular extrastimuli were delivered to refractoriness. Clinical VT was defined by comparison with 12-lead electrocardiograms and stored implantable cardioverter-defibrillator electrograms from spontaneous VT episodes. Patients were followed for 1 year. RESULTS: Fifty-nine patients (44.7%) had no VT inducible at NIPS; 49 (37.1%) had inducible nonclinical VT only; and 24 (18.2%) had inducible clinical VT. Patients with inducible clinical VT at NIPS had markedly decreased 1-year VT-free survival compared to those in whom no VT was inducible (<30% vs. >80%; p = 0.001), including 33% recurring with VT storm. Patients with inducible nonclinical VT only, had intermediate 1-year VT-free survival (65%). CONCLUSIONS: When patients with VT and structural heart disease have no VT or nonclinical VT only inducible at the end of ablation or their condition is too unstable to undergo final programmed stimulation, NIPS should be considered in the following days to further define risk of recurrence. If clinical VT is inducible at NIPS, repeat ablation may be considered because recurrence over the following year is high.