Dennis W. X. Zhu

Continuing warfarin therapy is superior to interrupting warfarin with or without bridging anticoagulation therapy in patients undergoing pacemaker and defibrillator implantation

BACKGROUND Current guidelines recommend stopping oral anticoagulation and starting bridging anticoagulation with intravenous heparin or subcutaneous enoxaparin when implanting a pacemaker or defibrillator in patients at moderate or high risk for thromboembolic events. A limited body of literature suggests that device surgery without cessation of oral anticoagulation may be feasible. OBJECTIVE The purpose of this study was to evaluate the safety of device surgery in orally anticoagulated patients without interrupting warfarin therapy. METHODS We performed a retrospective study of 459 consecutive patients on chronic warfarin therapy who underwent device surgery from April 2004 to September 2008. Warfarin was continued in 222 patients during the perioperative period. Warfarin was temporarily held and bridging therapy administered in 123 patients. Warfarin was temporarily held without bridging therapy in 114 patients. RESULTS There were no significant differences with regard to age, sex, or risk factors for thromboembolism in the three groups. Patients who continued taking warfarin had a lower incidence of pocket hematoma (P = .004) and a shorter hospital stay (P <.0001) than did patients in the bridging group. Holding warfarin without bridging is associated with a higher incidence of transient ischemic attacks (P = .01). CONCLUSION Temporarily interrupting anticoagulation is associated with increased thromboembolic events, whereas cessation of warfarin with bridging anticoagulation is associated with a higher rate of pocket hematoma and a longer hospital stay. Continuing warfarin with a therapeutic international normalized ratio appears to be a safe and cost-effective approach when implanting a pacemaker or defibrillator in patients with moderate to high thromboembolic risk.

Normalization of Left Ventricular Ejection Fraction and Incidence of Appropriate Antitachycardia Therapy in Patients With Implantable Cardioverter Defibrillator for Primary Prevention of Sudden Death

BACKGROUND Patients with severely depressed left ventricular ejection fractions (LVEFs) receive implantable cardioverter-defibrillators (ICDs) for the primary prevention of sudden death. In some patients, however, LVEF may improve or even normalize over time. Limited data are available on the incidence of appropriate antitachycardia therapy, including pacing and shock, in these patients. METHODS AND RESULTS We retrospectively identified consecutive patients at our institution with an ICD for primary prevention who had LVEF measurement available at initial implantation and at the time of generator replacement. None of these patients had ever received appropriate antitachycardia therapy before generator replacement. The incidence of appropriate antitachycardia therapy after generator replacement was assessed. Of the 125 patients who received generator replacement, 53 (42%) received an ICD and 72 (58%) a cardiac resynchronization therapy-defibrillator (CRT-D). Among them, 30 (21%) had LVEF normalized to ≥50%, 25 (17%) had LVEF partially improved to 36%-49%, and 70 (63%) had LVEF that remained depressed at ≤35%. During an overall follow-up period of 25 ± 18 months, none of the individuals with normalized LVEF experienced appropriate antitachycardia therapy regardless of ICD or CRT-D. Meanwhile, 20% of patients with LVEF at 36%-49% and 14% of patients with LVEF at ≤35% received appropriate ICD therapy. The omnibus P value for any differences among the 3 LVEF groups was 0.046 for the entire cohort, 0.01 for ICD, and 0.15 for CRT-D patients. CONCLUSIONS These preliminary data suggest that patients with reduced LVEF and primary-prevention ICDs who normalize their LVEF over time may be at lower risk of appropriate antitachycardia therapy.

Race: Another risk factor for postoperative atrial fibrillation?

g m c t fi g w d g More than 400,000 coronary artery bypass graft (CABG) rocedures are performed each year in the United States. Up o 40% of patients undergoing the procedure experience trial fibrillation, making this arrhythmia one of the most ommon postoperative complications. Although comonly regarded as a self-limited problem, postoperative trial fibrillation (POAF) is associated with increased moridity and mortality and longer, more expensive hospital tays. Despite a general decline of operative mortality and orbidity associated with CABG over the last several deades, the incidence of POAF persists and actually appears o be increasing. Numerous attempts have been made to dentify risk factors for POAF in an effort to direct prevenive treatment at those patients most likely to benefit. mong the risk factors, older age has consistently predicted higher incidence of POAF; incidence increases by at least 0% per decade. In addition, the long list of other risk actors include hypertension, male gender, obesity, concomtant valvular disease, chronic obstructive lung disease, preious atrial fibrillation, digoxin use, congestive heart failre, prolonged P-wave duration, enlarged left atrium, educed left ventricular systolic function, elevated left venricular end-diastolic pressure before surgery, long aortic ross-clamp time, combined CABG–valve operations, proonged vasopressor use, intraaortic balloon pump placeent, postoperative respiratory compromise including neumonia, and prolonged ventilation. Some of these isk factors are not always identified in different studies, robably due to the variations in patient profile, type of urgery, definition of arrhythmia, and method of analysis. se of beta-blockers is associated with risk reduction. In this issue of Heart Rhythm, Nazeri et al, using the exas Heart Institute Research Database, report yet another isk factor predicting new-onset POAF after isolated ABG. In addition to obesity, congestive heart failure, and dvanced age, the authors found that Caucasians were at igher risk for POAF than persons of other races. This ariation was not explained by differences in traditional risk actors for POAF. Other studies have reported a higher

Predictors of appropriate therapy in patients with implantable cardioverter-defibrillator for primary prevention of sudden cardiac death.

The purpose of this study was to evaluate predictors of appropriate therapy in patients with implantable cardioverter-defibrillators (ICD) for primary prevention of sudden cardiac death. A retrospective cohort of 321 patients with systolic heart failure undergoing ICD placement for primary prevention of sudden cardiac death was queried with a mean follow-up period of 2.6 years. Appropriate ICD therapy was defined as therapy delivered for termination of a ventricular tachyarrhythmia. Appropriate ICD therapy was delivered in 142 (44%) of the patients. In a multivariate model, body mass index ≥28.8 kg/m2, chronic kidney disease, left ventricular ejection fraction ≤20% and metabolic syndrome were found to be independent predictors of appropriate ICD therapy. Appropriate ICD therapy was associated with higher cardiovascular mortality. These findings show the importance of identification of risk factors, especially metabolic syndrome, in patients following ICD implantation as aggressive treatment of these co-morbidities may decrease appropriate ICD therapy and cardiovascular mortality.

Management of functional Sprint Fidelis leads at cardiac resynchronization therapy-defibrillator generator replacement: a novel option for preventing inappropriate shocks from lead failure in fragile patients with high risk of sudden death

Aims In patients with a functional Sprint Fidelis lead at generator replacement, the manufacturer recommended to either continue to use the existing lead or replace it with a new lead. For those patients who continue to use a functional Fidelis lead, the risk of inappropriate shocks remains present if the lead fails in the future. We evaluated the feasibility of an alternative approach at the time of cardiac resynchronization therapy-defibrillator (CRT-D) generator replacement in patients with a functional bipolar left ventricular (LV) lead for prevention of inappropriate shocks from future Fidelis lead failure. Methods and results During the procedure, the pace/sense IS-1 connection pin of the functional Fidelis lead was intentionally inserted into the LV port of the new CRT-D generator, while the existing bipolar LV lead IS-1 connection pin was inserted into the right ventricular (RV) pace/sense port. After such switching, the existing bipolar LV lead was used for functional LV pacing/sensing, while the Fidelis lead was used for functional RV pacing and high voltage shock only and could no longer be used for the purpose of sensing and detecting. This approach precluded oversensing and inappropriate shocks should the functional Fidelis lead fail in the future. Six fragile patients, who were not considered suitable candidates for lead replacement, underwent the alternative approach. During a follow-up of 35 ± 23 months, the CRT-D system functioned normally in five patients. The Fidelis lead fractured in one patient 7 months after generator replacement. The malfunction was detected promptly and the defected lead was replaced. No inappropriate detections or shock was triggered. Conclusions In CRT-D patients with a functional Fidelis lead and a bipolar LV lead, switching of the Fidelis lead pace/sense IS-1 pin with the bipolar LV lead IS-1 pin at generator replacement did not affect normal system function. This novel approach may be valuable in fragile patients with high risk of sudden death for prevention of inappropriate shocks triggered by oversensing from a malfunctioning Fidelis lead.

Spontaneous scar-based reentrant atrial flutter: Electrophysiologic characteristics and ablation outcome in a retrospective analysis

The understanding of spontaneous scar‐based reentrant atrial arrhythmia is limited. We aim to characterize the electrophysiologic and mapping features of spontaneous scar‐based atrial flutter (AFL) and outcomes of catheter ablation.

A Simple Method to Differentiate Atrioventricular Node Reentrant Tachycardia from Orthodromic Reciprocating Tachycardia

Discrimination between atrioventricular node reentry tachycardia (AVNRT) and orthodromic reciprocating tachycardia (ORT) during an electrophysiological study is sometimes challenging. This study aimed to investigate if the difference in the local VA (ventricle-atrium) interval during ventricular entrainment pacing and during tachycardia (DVA, defined as the shortest local VA interval of coronary sinus [CS] during entrainment minus the shortest local VA interval of CS during tachycardia) was different in patients with AVNRT and patients with ORT.Diagnoses of AVNRT or ORT through a concealed accessory pathway (AP) were made according to conventional electrophysiological criteria and ablation results. Entrainment by right ventricular (RV) pacing was performed in each patient before ablation and patients with successful entrainment were included in the study. The DVA was compared between patients with AVNRT and patients with ORT. The DVA in patients with AVNRT was significantly longer than that in patients with ORT (120 ± 20 versus 5.7 ± 9; P < 0.001). In each patient with AVNRT of slow-fast type, fast-slow type, and slow-slow type, the DVA was more than 48 ms. In each patient with ORT using a left free wall accessory pathway (AP), right free wall AP, and septal AP, the DVA was less than 20 ms.DVA was found to be a rapid, useful test in distinguishing patients with AVNRT from those with ORT.

Clonal hematopoiesis of indeterminate potential (CHIP): A potential contributor to atherlosclerotic cardio/cerebro-vascular diseases?

At least 10% of the elderly population above the age of 70 carry a condition termed clonal hematopoiesis indeterminate potential (CHIP) due to oligoclonal expansion of mutated hematopoietic stem cells. Although CHIP is known to predispose patients to a higher risk of malignant blood disorders, the recent revelation of its association with higher morbidity and mortality of atherosclerotic cardiovascular disease and ischemic stroke is rather surprising. Two independent research groups published studies indicating that Tet2 mutated monocytes from mice modeling CHIP had a causal role in accelerating the growth of atherosclerotic lesions due to their pro-inflammation activities. This important discovery points to CHIP as a risk factor and raises the prospect of novel treatment to minimize the adverse cardio/cerebro-vascular events.

Feasibility of an Elective Cardioversion Service Led by Advanced Practice Providers without Direct Cardiologist Supervision

Background: Elective direct current cardioversion (DCCV) has traditionally been performed by physicians in the United States. A few recent reports from the United Kingdom suggested that a specialist nurse-led service for elective DCCV of persistent atrial fibrillation was feasible. This practice has not been reported in the United States previously. Several years ago, we introduced a program where specially trained advanced practice providers (APPs) (physician assistants and nurse practitioners) assisted by an anesthesiology team, performed elective DCCV in patients with atrial fibrillation and atrial flutter, without direct cardiologist supervision. Methods: Upon receiving approval from the Institutional Review Board, we conducted a retrospective analysis of 447 consecutive DCCVs electively performed by APPs, for atrial fibrillation or atrial flutter, at Regions Hospital between 12/2006 and 10/2010. Transient deep sedation was administered by an anesthesiology team. The cohort was evaluated for procedural success and safety. Results: The procedural success rate was 92% (412/447). The incidence of procedural related adverse events, requiring immediate intervention, was 0.2% (1/447). This patient required emergent temporary pacing catheter insertion followed by a permanent pacemaker implantation at a later date. There were no other procedure-related complications and no thromboembolic events. A comparison with fifty elective cardioversions performed by cardiologists during the same period found no statistical difference in procedural success rates or complications. Conclusion: Under deep sedation administered by anesthesiology service, elective DCCV of atrial fibrillation and atrial flutter performed by well-trained APPs, without direct cardiologist supervision, is feasible and does not compromise patient safety.

ATRIAL FLUTTER WITH 1:1 CONDUCTION IN UNDIAGNOSED WOLFF-PARKINSON-WHITE SYNDROME

BACKGROUND Atrial flutter with 1:1 atrioventricular conduction via an accessory pathway is an uncommon presentation of Wolff-Parkinson-White syndrome not previously reported in the emergency medicine literature. Wolff-Parkinson-White syndrome, a form of ventricular preexcitation sometimes initially seen and diagnosed in the emergency department (ED), can present with varied tachydysrhythmias for which certain treatments are contraindicated. For instance, atrial fibrillation with preexcited conduction needs specific consideration of medication choice to avoid potential degeneration into ventricular fibrillation. CASE REPORT We describe an adult female presenting with a very rapid, regular wide complex tachycardia successfully cardioverted in the ED followed by a normal electrocardiogram (ECG). Electrophysiology study confirmed atrial flutter with 1:1 conduction and revealed an accessory pathway consistent with Wolff-Parkinson-White syndrome, despite lack of ECG findings of preexcitation during sinus rhythm. Why should an emergency physician be aware of this? Ventricular tachycardia must be the first consideration in patients with regular wide complex tachycardia. However, clinicians should consider atrial flutter with 1:1 conduction related to an accessory pathway when treating patients with the triad of very rapid rate (>250 beats/min), wide QRS complex, and regular rhythm, especially when considering pharmacologic treatment. Emergency physicians also should be aware of electrocardiographically concealed accessory pathways, and that lack of delta waves does not rule out preexcitation syndromes such as Wolff-Parkinson-White syndrome.