Richard K. Shepard

Delayed complications following pacemaker implantation.

ELLENBOGEN, K.A., et al.: Delayed Complications Following Pacemaker Implantation. Acute complications resulting from permanent pacemaker implantation are well known and include perforation of the right atrium or right ventricle. Recently, several reports have described the occurrence of perforation and pericarditis as late complications following pacemaker implantation. These complications may occur days to weeks following uncomplicated pacemaker implantation and may lead to death if they are not recognized early. Five patients with late complications caused by active‐fixation leads are reported and the clinical features of their presentation and management are reviewed. Late perforation of the right atrium or right ventricle is an uncommon complication after pacemaker implantation but should be suspected by the general cardiologist in a patient who has a device implanted within a week to several months prior to the development of chest pain.

Results of a Minimally Invasive Surgical Pulmonary Vein Isolation and Ganglionic Plexi Ablation for Atrial Fibrillation Single-Center Experience With 12-Month Follow-Up

Background—The Cox Maze procedure for treatment of medically refractory atrial fibrillation (AF) is limited by its complexity and requirement for cardiopulmonary bypass. Long-term follow-up and success using criteria established by the Heart Rhythm Society/European Heart Rhythm Association/European Cardiac Arrhythmia Society consensus statement have not been reported for surgical AF ablation. We describe the results of using a thorascopic approach and radiofrequency energy to perform bilateral pulmonary vein isolation and left atrial ganglionic plexi ablation for treatment of AF. Methods and Results—Forty-five (33 paroxysmal; 12 persistent) consecutive patients underwent thorascopic bilateral radiofrequency pulmonary vein isolation, ganglionic plexi ablation, ligament of Marshall ablation, and left atrial appendage exclusion by a single surgeon. Forty-three patients were prospectively followed without antiarrhythmic drugs for a minimum of 1 year with a 30-day continuous event monitor or pacemaker interrogation at 6 and 12 months. Failure was defined as any atrial tachyarrhythmia of >30 seconds’ duration occurring >90 days after surgery. Mean follow-up was 516±181 days (202 to 858 days). Twenty-eight (65%) patients had no atrial tachyarrhythmia >30 seconds by 1 year, and 15 (35%) patients had atrial tachyarrhythmia recurrences by 1 year. Eight of 15 patients with recurrent AF had catheter ablation resulting in elimination and/or reduction of AF episodes in 7 of 8 patients. Four of 15 patients had AF elimination or reduction with antiarrhythmic drugs alone. Three patients did not benefit from surgery and received rate control only. There were no deaths; 1 phrenic nerve injury and 2 pleural effusions were the only major complications. Conclusions—The single procedure success at 1-year follow-up for surgical pulmonary vein isolation and ganglionic plexi ablation is 65%. Atrial tachyarrhythmia recurrences after surgery are usually responsive to catheter ablation and/or antiarrhythmic drugs.

Benefit of Primary Prevention Implantable Cardioverter-Defibrillators in the Setting of Chronic Kidney Disease: A Decision Model Analysis

Introduction: Primary prevention ICD trials have excluded patients with CKD. Comorbidities and lower life expectancy in patients with CKD make the benefit of primary prevention ICD implantation uncertain.

Phased-array intracardiac echocardiography during pulmonary vein isolation and linear ablation for atrial fibrillation.

Phased‐Array Intracardiac Echocardiography for AF Ablation. Introduction: Fluoroscopic imaging provides limited anatomic guidance for left atrial structures. The aim of this study was to determine the utility of real‐time, phased‐array intracardiac echocardiography during radiofrequency ablation for atrial fibrillation.

Sensing Failure Associated with the Medtronic Sprint Fidelis Defibrillator Lead

Introduction: The diameter of implantable cardioverter‐defibrillator (ICD) leads has become progressively smaller over time. However, the long‐term performance characteristics of these smaller ICD leads are unknown.

Characteristics of Ventricular Tachycardia Ablation in Patients With Continuous Flow Left Ventricular Assist Devices

Background—Left ventricular assist devices (LVADs) are increasingly used as a bridge to cardiac transplantation or as destination therapy. Patients with LVADs are at high risk for ventricular arrhythmias. This study describes ventricular arrhythmia characteristics and ablation in patients implanted with a Heart Mate II device. Methods and Results—All patients with a Heart Mate II device who underwent ventricular arrhythmia catheter ablation at 9 tertiary centers were included. Thirty-four patients (30 male, age 58±10 years) underwent 39 ablation procedures. The underlying cardiomyopathy pathogenesis was ischemic in 21 and nonischemic in 13 patients with a mean left ventricular ejection fraction of 17%±5% before LVAD implantation. One hundred and ten ventricular tachycardias (VTs; cycle lengths, 230–740 ms, arrhythmic storm n=28) and 2 ventricular fibrillation triggers were targeted (25 transseptal, 14 retrograde aortic approaches). Nine patients required VT ablation <1 month after LVAD implantation because of intractable VT. Only 10/110 (9%) of the targeted VTs were related to the Heart Mate II cannula. During follow-up, 7 patients were transplanted and 10 died. Of the remaining 17 patients, 13 were arrhythmia-free at 25±15 months. In 1 patient with VT recurrence, change of turbine speed from 9400 to 9000 rpm extinguished VT. Conclusions—Catheter ablation of VT among LVAD recipients is feasible and reasonably safe even soon after LVAD implantation. Intrinsic myocardial scar, rather than the apical cannula, seems to be the dominant substrate.

The Acute Effects of Biatrial Pacing on Atrial Depolarization and Repolarization

Permanent biatrial and/or multisite atrial pacing may prevent atrial fibrillation (AF), but the effects on atrial electrophysiology remain incompletely understood. Acute biatrial pacing was studied in 20 patients with and 28 without (controls) a history of atrial fibrillation and/or flutter. Twelve‐lead electrocardiograms were recorded during pacing from the high right atrium (RA), from the distal coronary sinus (LA), and biatrial pacing. P wave duration was measured in each lead and the difference between maximum and minimum P duration was termed P wave dispersion. Effective refractory periods (ERPs) were measured during each pacing mode. The dispersion of P wave duration was 35 ± 14 ms in controls and 40 ± 29 ms in AF patients (P = 0.17). Compared to RA pacing, LA pacing shortened P duration in controls (127 ± 18 to 107 ± 16 ms, P < 0.05) and biatrial pacing markedly shortened P duration in controls (127 ± 18 to 93 ± 14 ms, P < 0.05) and AF patients (114 ±43 to 97 ± 21 ms, P < 0.05). P wave dispersion was unaffected. In controls, the LA ERP was longer than the RA ERP. This phenomenon was not present in AF patients, whose LA ERP was shorter than that of controls. Biatrial pacing had no effect on atrial ERPs or the dispersion of atrial refractoriness. In conclusion, acute biatrial pacing does not affect atrial repolarization but it does cause a marked shortening of global biatrial depolarization. Distal coronary sinus pacing produces a shorter P wave than RA pacing. There is substantial dispersion in the surface P wave of the electrocardiogram, the significance of which awaits further study.

Leads and longevity: how long will your pacemaker last?

Prolonging pacemaker system longevity and time between pulse generator changes remains an important goal of device therapy for several reasons. There is a small but finite risk of infection and other complications each time a generator change is performed. If patients have one less generator change during their lifetime, the relative risk of complications is reduced. A 10% increase in generator longevity will result in large savings for healthcare costs each year. Therefore, interest in maximizing pacemaker longevity continues. Modern pacemakers use current not only for pacing but also for other functions such as obtaining measurements of diagnostic data, measurements made by rate response sensors, and implementation of algorithms, such as for mode switching. Pacemaker battery life therefore depends on a variety of variables, including baseline battery self-discharge, current drain for device housekeeping functions, current used to pace the heart, and current to sense the underlying heart rhythm. An average pacemaker battery has about 0.5–2Ah of battery life. Factors controlling current drain with a pacing stimulus include pacing rate, per cent pacing, programmed voltage, pulse width (PW), and lead impedance. Energy use is proportional to PW and to the square of the voltage. By Ohms law, I = V / R , where R is the impedance, current is inversely proportional to impedance. For a given voltage ( V ) and PW, current will be less for a high-impedance lead. For an electrical circuit, a voltage drop occurs and energy is dissipated across a load or impedance. The area of high impedance in a lead should … *Corresponding author. Tel: +1 804 828 7565, Fax: +1 804 828 6082. Email: rshepard{at}mcvh-vcu.edu

Use of a Non-Fluoroscopic Catheter Navigation System for Pulmonary Vein Isolation

AbstractIntroduction: Pulmonary vein (PV) isolation is commonly performed by using separate mapping and ablating catheters. Steering the ablation catheter to the target electrodes on the mapping catheter can be difficult and time consuming under fluoroscopic guidance. We investigated the use of a non-fluoroscopic catheter navigation system to facilitate radiofrequency pulmonary vein isolation. Methods: The LocaLisa non-fluoroscopic catheter navigation system was used during PV isolation in 21 patients. Eleven control patients underwent the procedure under fluoroscopic guidance alone. PV isolation was performed by mapping the veins with a 10 or 20 pole circular mapping catheter and ablating at targeted mapping bipoles with a separate ablation catheter. Results: The electrodes of both catheters were visualized in 3 dimensional virtual space by LocaLisa. There were no clinical differences between the LocaLisa and control patients. During mapping, electrical artifacts were produced on specific mapping electrodes by contact with the ablation catheter. A blinded observer using LocaLisa correctly identified the mapping electrodes being contacted by the ablation catheter in 368 of 398 (92%) of cases. Total fluoroscopic time was reduced in the LocaLisa group (72 ± 29 minutes) compared to the control group (102 ± 37 minutes, p = 0.02). There were no differences between the groups in total procedure times, number of lesions given, complications or long term procedural success (all p > 0.45). Conclusions: The LocaLisa catheter navigation system accurately identifies the position of an ablation catheter relative to the target electrodes on a circular mapping catheter. The system also significantly reduces total fluoroscopic time for PV isolation.

Prospective randomized comparison of 65%/65% versus 42%/42% tilt biphasic waveform on defibrillation thresholds in humans.

AbstractBackground: The waveform tilt of biphasic shocks yielding the lowest defibrillation threshold (DFT) is not well defined. Some evidence indicates that tilts less than 65% may improve DFTs. Methods: In 57 patients undergoing ICD implantation, DFTs were determined with truncated exponential biphasic waveform tilts at 65%/65% and at 42%/42%. An external defibrillator with custom software was used for testing. The effective capacitance of the defibrillator was 132-μF for both waveforms. DFTs were determined using a binary search method starting with 12 Joules (J). Patients were randomly assigned to initial testing with either one of the two tilts. Thirty patients (Group 1) were tested with a two electrode (active can to RV coil, or SVC coil to RV coil) and 27 patients (Group 2) were tested with a three electrode system (subcutaneous patch or active can + SVC coil to RV coil). Results: Groups 1 and 2 did not differ in age, ejection fraction or antiarrhythmic medications. Group 1 delivered energy DFTs were 10.1 ± 5.5 J with the 65%/65% tilt and 10.1 ± 5.9 J for the 42%/42% tilt (p = 0.92). In group 2 the average DFT for the 65%/65% tilt was 8.4 ± 5.7 J and for the 42%/42% tilt was 8.1 ± 5.3 J (p = 0.70). There were no significant differences in DFTs for either group. The system impedance for Group 1 was 64 ± 12 ohms and for Group 2 was 39 ± 6 ohms (p < 0.0001). Conclusions: We found no differences in DFTs between 65%/65% tilt and 42%/42% tilt using either 2- or 3-electrode defibrillation systems. Further research is needed to optimize waveforms in order to minimize DFTs, which will result in smaller ICDs and/or greater safety margins for defibrillation.