Apoor Patel

Multidetector row computed tomography for identification of left atrial appendage filling defects in patients undergoing pulmonary vein isolation for treatment of atrial fibrillation: Comparison with transesophageal echocardiography

BACKGROUND Advances in multidetector computed tomography (MDCT) technology now permit three-dimensional cardiac imaging with high spatial and temporal resolution. Historically, transesophageal echocardiography (TEE) has been the gold standard for assessment of the left atrial appendage (LAA) in patients with atrial fibrillation and other atrial arrhythmias. Findings on TEE, including demonstration of LAA thrombus and dense nonclearing spontaneous echocardiographic contrast (SEC), predict future fatal and nonfatal thromboembolic events. OBJECTIVE The purpose of this study was to compare the diagnostic performance of 64-detector row MDCT in detecting LAA thrombus and dense nonclearing SEC as identified by TEE in patients undergoing pulmonary vein isolation for treatment of atrial fibrillation. METHODS A total of 72 consecutive patients (69.4% male; mean age 56.1 +/- 10.3 years) underwent both MDCT and TEE for evaluation of the LAA (median intertest interval 0 days, interquartile range 0-5 days). MDCT assessment of the LAA was performed by two methods: (1) comparison of Hounsfield unit (HU) densities in the LAA apex to the ascending aorta (AscAo) in the same axial plane and (2) nonquantitative visual identification of a filling defect in the LAA. TEE evaluation of the LAA included identification of echodense intracavitary masses in the LAA as well as pulsed-wave Doppler interrogation of the LAA ostium. RESULTS Patients with LAA thrombus or dense nonclearing SEC by TEE exhibited significantly lower LAA/AscAo HU ratios than patients who did not (0.82 +/- 0.22 vs 0.39 +/- 0.19, P <.001). LAA/AscAo HU cutoff ratios < or = 0.75 correlated to LAA thrombus or dense nonclearing SEC by TEE, with 100% sensitivity, 72.2% specificity, 28.6% positive predictive value, and 100% negative predictive value. HU ratios < or = 0.75 were associated with pulsed-wave Doppler velocities <50 cm/s of the LAA ostium (P <.001). In multivariable analysis, LAA/AscAo HU ratio < or = 0.75 remained a robust predictor of LAA thrombus or dense nonclearing SEC by TEE (P <.001). In contrast, MDCT identification of TEE-identified LAA thrombus or dense nonclearing SEC by visual detection of LAA filling defects resulted in lower sensitivity (50%) and negative predictive value (95.1%). CONCLUSION Current-generation MDCT successfully identifies LAA thrombus and dense nonclearing SEC with high sensitivity and moderate specificity. Importantly, LAA/AscAo HU ratios >0.75 demonstrate 100% negative predictive value for exclusion of LAA thrombus or dense nonclearing SEC. These results suggest that in patients undergoing pulmonary vein isolation procedures, MDCT examinations that demonstrate LAA/AscAo HU ratios >0.75 may preclude the need for preprocedural TEE.

Atrial tachycardia: mechanisms and management

Atrial tachycardias comprise a heterogeneous group of arrhythmias that include focal atrial tachycardia, typical atrial flutter and atypical atrial flutter. Focal atrial tachyardias arise from automatic, triggered or microreentrant mechanisms, while typical and atypical flutters are macroreentrant in nature. Typical flutter describes a reentrant circuit that is dependant on the cavotricuspid isthmus in the right atrium while atypical flutter includes various lesional and de novo macroreentrant circuits in the right and left atria. Electrocardiographic criteria have been proposed to distinguish these mechanisms of tachycardia, but they are not specific; whereas adenosine often aids in the diagnosis. Management of focal atrial tachyardias and macroreentry centers around rate control, antiarrhythmic therapy, ablation and anticoagulation. Success rates for ablation are highest for typical atrial flutter and higher than antiarrhythmic therapy for most atrial tachycardias.

Trends in Fidelis Lead Survival Transition From an Exponential to Linear Pattern of Lead Failure Over Time

Background—The Sprint Fidelis implantable cardioverter-defibrillator lead was recalled in 2007 because of an elevated risk of lead fracture. Several studies have demonstrated an accelerating risk of lead failure over time. We sought to identify predictors and characterize trends of Fidelis lead failure. Methods and Results—We evaluated 604 Fidelis leads with ≥90 days of follow-up implanted at our institution. Fidelis lead survival was analyzed by the Kaplan-Meier method. Analysis of log-log plots of cumulative hazard plots was performed to assess changes in lead failure rate over time. During follow-up of 3.3±1.7 years, 51 (8.4%) Fidelis lead failures were identified. The 3-year and 5-year Fidelis lead survival rates were 93.5% and 85.3%, respectively. Female sex was the only significant predictor of lead failure (heart rate, 2.1; 95% CI, 1.1–3.9; P<0.0001). The rate of lead failure initially increased exponentially with a power of 2.3 (95% CI, 2.22–2.43; P<0.0001). However, log-log analysis of cumulative hazard for leads functioning at 2 and 4 years revealed a stable rate of failure of 4.5%/year. Mathematical modeling of the Fidelis lead failure demonstrated a transition from an exponential to linear pattern of lead failure at 2.9 years. Conclusions—After 3 years, failure rates of Fidelis leads stabilize but at a significantly elevated rate. Female sex is associated with a doubling of the risk of Fidelis lead failure. These findings have implications for Fidelis lead management decisions that are based on the prediction of lead failure risk.Background— The Sprint Fidelis implantable cardioverter-defibrillator lead was recalled in 2007 because of an elevated risk of lead fracture. Several studies have demonstrated an accelerating risk of lead failure over time. We sought to identify predictors and characterize trends of Fidelis lead failure. Methods and Results— We evaluated 604 Fidelis leads with ≥90 days of follow-up implanted at our institution. Fidelis lead survival was analyzed by the Kaplan-Meier method. Analysis of log-log plots of cumulative hazard plots was performed to assess changes in lead failure rate over time. During follow-up of 3.3±1.7 years, 51 (8.4%) Fidelis lead failures were identified. The 3-year and 5-year Fidelis lead survival rates were 93.5% and 85.3%, respectively. Female sex was the only significant predictor of lead failure (heart rate, 2.1; 95% CI, 1.1–3.9; P <0.0001). The rate of lead failure initially increased exponentially with a power of 2.3 (95% CI, 2.22–2.43; P <0.0001). However, log-log analysis of cumulative hazard for leads functioning at 2 and 4 years revealed a stable rate of failure of 4.5%/year. Mathematical modeling of the Fidelis lead failure demonstrated a transition from an exponential to linear pattern of lead failure at 2.9 years. Conclusions— After 3 years, failure rates of Fidelis leads stabilize but at a significantly elevated rate. Female sex is associated with a doubling of the risk of Fidelis lead failure. These findings have implications for Fidelis lead management decisions that are based on the prediction of lead failure risk.

Recovery of atrioventricular conduction in patients with heart block after transcatheter aortic valve replacement

Recovery of conduction has been demonstrated in >50% of patients who receive pacemakers (PPMs) for high‐degree atrioventricular block (HD‐AVB) after transcatheter aortic valve replacement (TAVR). Little information is available about the time course of conduction recovery in these patients and if any features predict early recovery of conduction.

Techniques for Successful Early Retrieval of the Micra Transcatheter Pacing System: A Worldwide Experience

BACKGROUND Experience with retrieval of the Micra transcatheter pacing system (TPS) is limited because of its relatively newer technology. Although abandonment of the TPS at end of life is recommended, certain situations such as endovascular infection or device embolization warrant retrieval. OBJECTIVE The purpose of this study was to report the worldwide experience with successful retrieval of the Micra TPS. METHODS A list of all successful retrievals of the currently available leadless pacemakers (LPs) was obtained from the manufacturer of Micra TPS. Pertinent details of retrieval, such as indication, days postimplantation, equipment used, complications, and postretrieval management, were obtained from the database collected by the manufacturer. Other procedural details were obtained directly from the operators at each participating site. RESULTS Data from the manufacturer consisted of 40 successful retrievals of the Micra TPS. Operators for 29 retrievals (73%) provided the consent and procedural details. Of the 29 retrievals, 11 patients underwent retrieval during the initial procedure (immediate retrieval); the other 18 patients underwent retrieval during a separate procedure (delayed retrieval). Median duration before delayed retrieval was 46 days (range 1-95 days). The most common reason for immediate retrieval was elevated pacing threshold after tether removal. The most common reasons for delayed retrieval included elevated pacing threshold at follow-up, endovascular infection, and need for transvenous device. Mean procedure duration was 63.11 ± 56 minutes. All retrievals involved snaring via a Micra TPS delivery catheter or steerable sheath. No serious complications occurred during the reported retrievals. CONCLUSION Early retrieval of the Micra TPS is feasible and safe.

Inappropriate Implantable Cardioverter-Defibrillator Shocks Attributed to Alternating-Current Leak in a Swimming Pool

Implantable cardioverter-defibrillators (ICDs) are the standard of care for preventing sudden cardiac death in patients who are predisposed to malignant ventricular arrhythmias. Causes of inappropriate ICD shock include equipment malfunction, improper arrhythmia evaluation, misinterpretation of myopotentials, and electromagnetic interference. As the number of implanted ICDs has increased, other contributors to inappropriate therapy have become known, such as minimal electrical current leaks that mimic ventricular fibrillation. We present the case of a 63-year-old man with a biventricular ICD who received 2 inappropriate shocks, probably attributable to alternating-current leaks in a swimming pool. In addition, we discuss ICD sensitivity and offer recommendations to avoid similar occurrences.

Charge circuit timeout: a sequence of events leading to failure of an implantable cardioverter-defibrillator to deliver therapy.

Since the advent of the implantable cardioverter-defibrillator (ICD) for primary prevention of sudden cardiac death, much attention has been given to the possibility of ICD or lead hardware failures resulting in inappropriate ICD function. Less attention has been given to the potential for software programming errors resulting in inappropriate device behavior. We report a case of a software programming error that led to a premature “end of service” alert that triggered a “lock-up” of the device antitachycardia therapies. Typically, the capacitor charge time for the Medtronic Secura ICD in anticipation of a full energy shock is about 7.7 to 9.2 seconds, depending on how close the device is to the elective replacement time and other factors.1 A charge circuit timeout indicates that at least 1 charging period exceeded 30 seconds. When 3 consecutive charging periods each exceed 30 seconds, the ICD charge circuit becomes inactive, and all automatic therapy functions and manual system tests become disabled except for emergency VVI pacing, all for the purpose of conserving battery voltage for pacemaker dependent patients when the generator reaches end of service.1 An alert is displayed to indicate that the time allotted to reach the programmed output energy (30 seconds) has been exceeded. A charge circuit timeout usually occurs when the battery voltage is depleted below the “elective replacement indicator.” In this specific instance, the charge circuit timeout occurred because of a glitch in the software. Three events occurred almost simultaneously, exposing the software programming error.2 These events occurred during an episode of tachycardia in the brief time span between the end of charging the capacitors and redetection/confirmation before delivery of a shock. The 3 events are:

Ventricular Arrhythmia Originating from the Left Ventricular Papillary Muscles: Clinical Features and Technical Aspects

The discovery, characterization, and ablation of the papillary muscles have evolved rapidly since the initial description in 2008. New innovations in pacemapping, intracardiac imaging, ablation catheters, and ablation methodologies have dramatically impacted the approach to the treatment of papillary muscle ventricular arrhythmias. This review provides an up-to-date summary of these methods, as well as guidance on how to integrate them into clinical practice.

Subcutaneous defibrillator lead management in a patient undergoing a sternotomy: GABRIELS et al.

Subcutaneous implantable cardioverter-defibrillators (S-ICDs) are currently approved for use in the primary prevention of sudden cardiac death. The single S-ICD lead is tunneled in subcutaneous tissue in closeproximity to the sternum.Whenapatientwith aS-ICDundergoes a subsequent surgery that requires amedian sternotomy there arises a possibility of damage to the lead intraoperatively and contact between the lead and the sternotomy wires in the postoperative period. This may result in S-ICD malfunction. The optimal way to manage the lead during a surgery involving a median sternotomy in a patient with a S-ICD is not well defined. Implantation of a left ventricular assist device (LVAD) in a patient with an existing S-ICD raises another level of complexity given the potential for electromagnetic interference (EMI) from the LVAD, which may lead to inappropriate sensing and defibrillation.

Venous Obstruction in Cardiac Rhythm Device Therapy

Purpose of reviewA variety of complex vascular pathologies arise following the implantation of electronic cardiac devices. Pacemaker and defibrillator lead insertion may cause proximal venous obstruction, resulting in symptomatic venous congestion and the compromise of potential future access sites for cardiac rhythm lead management.Recent findingsVarious innovative techniques to recanalize the vein and establish alternate venous access have been pioneered over the past few years.SummaryA collaborative team of electrophysiologists and vascular specialists strategically integrate the patient’s vascular disease into the planning of electrophysiology procedures. When vascular complications occur after device implantation, the same team effectively manages both the resulting vascular sequelae and related cardiac rhythm device challenges. This review will outline the various vascular challenges related to device therapy and offer an effective strategy for their management.