James D. Allred

Transmural recording of shock potential gradient fields, early postshock activations, and refibrillation episodes associated with external defibrillation of long-duration ventricular fibrillation in swine.

BACKGROUND Knowledge of the shock potential gradient (nablaV) and postshock activation is limited to internal defibrillation of short-duration ventricular fibrillation (SDVF). OBJECTIVE The purpose of this study was to determine these variables after external defibrillation of long-duration VF (LDVF). METHODS In six pigs, 115-20 plunge needles with three to six electrodes each were inserted to record throughout both ventricles. After the chest was closed, the biphasic defibrillation threshold (DFT) was determined after 20 seconds of SDVF with external defibrillation pads. After 7 minutes of LDVF, defibrillation shocks that were less than or equal to the SDVF DFT strength were given. RESULTS For DFT shocks (1632 +/- 429 V), the maximum minus minimum ventricular voltage (160 +/- 100 V) was 9.8% of the shock voltage. Maximum cardiac nablaV (28.7 +/- 17 V/cm) was 4.7 +/- 2.0 times the minimum nablaV (6.2 +/- 3.5 V/cm). Although LDVF did not increase the DFT in five of the six pigs, it significantly lengthened the time to earliest postshock activation following defibrillation (1.6 +/- 2.2 seconds for SDVF and 4.9 +/- 4.3 seconds for LDVF). After LDVF, 1.3 +/- 0.8 episodes of spontaneous refibrillation occurred per animal, but there was no refibrillation after SDVF. CONCLUSION Compared with previous studies of internal defibrillation, during external defibrillation much less of the shock voltage appears across the heart and the shock field is much more even; however, the minimum nablaV is similar. Compared with external defibrillation of SDVF, the biphasic external DFT for LDVF is not increased; however, time to earliest postshock activation triples. Refibrillation is common after LDVF but not after SDVF in these normal hearts, indicating that LDVF by itself can cause refibrillation without requiring preexisting heart disease.

Ventricular fibrillation induced by a radiofrequency energy delivery for idiopathic premature ventricular contractions arising from the left ventricular anterior papillary muscle

A 73-year-old man with idiopathic premature ventricular contractions (PVCs) underwent electrophysiological testing. Left ventricular activation mapping revealed a focal mechanism of the PVCs with the earliest activation on the anterior papillary muscle (APM). Irrigated radiofrequency (RF) current delivered at that site induced a cluster of non-sustained ventricular tachycardia episodes with the same QRS morphology as the PVCs, followed by ventricular fibrillation (VF). The APM might have served as an abnormal automatic trigger and driver for the VF occurrence. Ventricular fibrillation may occur as a complication during RF catheter ablation of papillary muscle ventricular arrhythmias even if the clinical arrhythmia is limited to PVCs.

Idiopathic ventricular tachycardia originating from the left ventricle near the His bundle.

A 62‐year‐old man with idiopathic ventricular tachycardia (VT) exhibiting left bundle branch block and left inferior axis QRS morphology with a Qr in lead III underwent electrophysiological testing. Successful ablation was achieved in the left ventricle (LV) at a site with an excellent pace map, adjacent to the His bundle electrogram recording site. At that site, the sequence of the ventricular electrogram and late potential recorded during sinus rhythm reversed during spontaneous premature ventricular contractions with the same QRS morphology as the VT. This case shows that VT can arise from the LV ostium adjacent to the membranous septum. (PACE 2010; 33:e114–e118)

Guidelines for Plunge Needle Recording for Effective Detection of Purkinje Activation

Direct recording of Purkinje fiber activity may lead to a better understanding of the role of the specialized conduction system in pathological cardiac conditions. Two studies were conducted in pigs to determine guidelines for effective plunge needle recording techniques. In the first experiment, Purkinje fiber activations were recorded at 16 KHz with 3 bipolar electrodes (2 mm spacing) on epoxy plunge needles, and were later lowpass filtered and downsampled to determine the rate required for effective identification of Purkinje activation. Purkinje spikes were identifiable at sampling rates of 4 KHz and greater, but were not easily distinguished at sampling rates of 2 KHz or less. In the second experiment, 4 plunge needles with 15 electrodes (1 mm spacing) were inserted 8 times into different locations around the left ventricle. Unipolar (15 per needle) and bipolar (14 per needle) signals were recorded simultaneously at a sampling rate of 8 KHz. Purkinje activations were identified in 13/32 plunge needle sites. Of the 13 sites with identified Purkinje activations, 10 were within 2 mm of the endocardium. Bipolar recordings demonstrated Purkinje potentials that were 13% of the amplitude of the following myocardial activation, while unipolar recordings from the same electrodes recorded Purkinje potentials that were only 5% of the amplitude of the following myocardial activations. Three guidelines were developed for effective Purkinje fiber recording: 1) use a minimum sampling rate of 4 KHz., 2) record near the endocardium, and 3) use bipolar rather than unipolar recording electrodes

Printed Circuit Board Electrodes for Transmural Cardiac Mapping

Plunge needle recording techniques have provided valuable insights into transmural activation in cardiac tissue. Construction of plunge needles has been a costly and time intensive endeavor. Plunge needles constructed with standard printed circuit board (PCB) technology and methods are outlined. PCB plunge needles are less expensive in terms of raw materials and time required for construction than hypodermic stock or epoxy plunge needles. Tested PCB plunge needles recorded signals comparable to signals recorded by other plunge needles. PCB plunge needles provide an economical and rapid alternative to previously published techniques for plunge needle design

USE OF A DEDICATED EMERGENCY ROOM ALGORITHM FOR EARLY DISCHARGE OF ATRIAL FIBRILLATION PATIENTS

Atrial fibrillation (AF) is the most commonly diagnosed arrhythmia in the US and can result in Emergency Room (ER) visits. We describe an ER pathway for patients with AF to facilitate early discharge rather than admission. An AF treatment algorithm was implemented in a hospital ER. This pathway

INCIDENCE OF IMPLANTABLE LOOP RECORDERS UPGRADED TO PACEMAKERS/IMPLANTED CARDIAC DEFIBRILLATORS

Background: Implantable loop recorders (ILR) are implanted for arrhythmia diagnosis and management in a variety of patient populations. ILRs may potentially lead to the need for pacemakers (PM) or implanted cardiac defibrillators (ICD). We evaluated the incidence of upgrade of ILRs to therapy