An 83-year-old man underwent electrophysiological testing for focal atrial tachycardia (AT) exhibiting narrow P waves with negative deflections in the inferior leads. Catheter ablation at the cavo-tricuspid isthmus (CTI) successfully eliminated the AT. The propagation map during AT and pacing study from the successful ablation site demonstrated that the atrial activation throughout the CTI did not produce significant P wave deflections. Consequently, during AT, the left atrial activation time determined the P wave duration. This case demonstrates that AT originating from the CTI may exhibit narrow P waves which can be misinterpreted as AT originating from the inter-atrial septum.

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)

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.

This chapter contains sections titled: Clinical vignette Electrophysiology study and ablation

BACKGROUND Knowledge of the shock potential gradient (W) 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 del V (28.7 +/- 17 V/cm) was 4.7 +/- 2.0 times the minimum del V (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 del V 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.

A 32‐year‐old woman with a history of nonischemic dilated cardiomyopathy, left bundle branch block, left ventricular ejection fraction of 0.15, and New York Heart Association Class III congestive heart failure, despite optimal medical treatment, was referred for cardiac resynchronization therapy with implantation of an implantable cardioverter defibrillator. The patient had prior chemotherapy for non‐Hodgkin's lymphoma and was shown to have chronic total occlusion of the superior vena cava (SVC) by magnetic resonance imaging. Cardiac resynchronization was accomplished with an iliofemoral approach without complications resulting in marked clinical improvement. We conclude that the iliofemoral approach allows transvenous implantation of cardiac resynchronization therapy in patients with superior vena cava occlusion.

This chapter contains sections titled: Clinical vignette Electrophysiology study and ablation

Background: Following successful defibrillation of the long duration ventricular fibrillation (LDVF) associated with sudden cardiac arrest (SCA), refibrillation occurs in over half of resuscitation attempts. In experimental animals with normal hearts, refibrillation almost never occurs following short duration VF lasting < 1 min (SDVF). It is not known if refibrillation following LDVF is due to the cardiac disease that caused the initial LDVF of SCA or if the LDVF itself causes abnormalities that can initiate VF. Further, the mechanism of refibrillation initiation is unknown. We tested the hypothesis that refibrillation occurs frequently following LDVF in previously normal hearts and propagates from a common area within the heart. Methods : In 6 pigs, 115–120 plunge needles containing 3– 6 electrodes each were inserted throughout the heart. With the chest closed, external defibrillation pads were placed in a left lateral to right lateral configuration. Following successful defibrillation of 20 s of SDVF, the animal was observed for spontaneous VF for at least 4 min. After termination of 7 min of LDVF, the animal was placed on cardiopulmonary bypass and observed for 15 min for spontaneous VF. Results: Following LDVF, 1.33 ±0.8 episodes of spontaneous VF occurred in each animal. The mean time to VF was 71 s (range 5 – 139 s) following defibrillation of LDVF. Three animals had a second episode of VF within 3 min of termination of LDVF. Earliest sites of origin of spontaneous VF occurred equally in the LV (3), RV (3), and septum (2) and arose equally from the endocardium (3), epicardium (2), and myocardium (3). Refibrillation originated in the posterior half of the ventricles 75% of the time. The first refibrillation cycle appeared focal in 75% of cases and reentrant in 25%. Premature ventricular beats arising out of the posterior RV base immediately preceded 75% of VF episodes. Conclusions: Spontaneous VF is common after defibrillation of LDVF but not SDVF in previously health swine, indicating that refibrillation does not require preexisting cardiac disease but can be caused by the detrimental effects of LDVF. Most episodes of refibrillation begin as focal activity within the posterior half of the ventricles.

BACKGROUND Earliest recorded postshock myocardial activations in pigs originate in the subepicardium of the apex and lateral free wall of the left ventricle (LV) 30-90 ms after the shock.OBJECTIVE The purpose of this study was to determine whether the Purkinje system is a candidate for the source of postshock activations by performing endocardial and transmural postshock activation mapping.METHODS In five pigs, 32 plunge needles with 12 electrodes (1-mm spacing) were inserted into the LV apex and Lateral free wall. Up to 70 plunge needles with six electrodes (2-mm spacing) were spread throughout the remainder of the LV, while 9-12 plunge needles with four electrodes (2-mm spacing) were inserted into the right ventricle. A basket catheter with 32 bipolar recording sites was inserted into the LV. Defibrittation-threshold (DFT)-level shocks were delivered during 10 episodes of electrically induced ventricular fibrillation. Electrograms of postshock activation cycles were analyzed for Purkinje and myocardial activations.RESULTS Purkinje activations were recorded before Local myocardial activation in 9% of basket electrograms and in 15% of plunge needles during the first postshock activation cycle. Purkinje activations were identified during the first and subsequent several postshock activation cycles in at least one basket and one needle electrogram in 96% and 98% of defibrillation episodes, respectively.CONCLUSIONS The Purkinje system is active during the early postshock activation cycles after DFT-level shocks. Further studies are required to determine whether activation initiates in the Purkinje system or whether it is activated by the myocardium or by Purkinje-myocardial junctional cells.

Transmural Activation Sequence in Ventricular Fibrillation. Background: Humans are more similar in transmural Purkinje and cardiac ion channel distributions to dogs than pigs. The Purkinje network in pigs is transmural but confined to the endocardium in dogs. Little is known about intramural activation during long-duration ventricular fibrillation (LDVF) given these differences. We tested the hypothesis that the transmural activation sequence is similar in sinus rhythm (SR) and LDVF in dogs as well as pigs, but different between species.Methods and Results: In six pigs and seven dogs, 50-60 plunge needles (six electrodes, 2-mm spacing) were placed throughout the left ventricle. Unipolar recordings were made for >10 minutes of LDVF. SR and LDVF activation times were grouped into waves by linking activations along each needle. Origin (earliest activation) and propagation direction were determined for each wave. The mean wave origin was significantly more endocardial in dogs than pigs for SR and 1 through 10 minutes of LDVF. Predominant propagation direction in LDVF and SR was endocardial to epicardial in dogs, but the opposite or equal in both directions in pigs. Fastest activation rate was epicardial in pigs, but endocardial in dogs with an increasing endocardial-to-epicardial activation rate gradient as LDVF progressed in dogs but not pigs.Conclusions: The transmural activation sequence in SR and LDVF is markedly different between pigs and dogs. These differences may be related to differences in Purkinje fiber and ion channel distributions and suggest that dogs are a better model for investigating activation sequences during LDVF, given the similarities with humans.

Clinical CardiologyVolume 32, Issue 7 p. E49-E49 Images in CardiologyFree Access Mediastinal Mass with Blood Supply from the Coronary Arteries James D. Allred M.D., James D. Allred M.D. Department of Cardiovascular Disease, University of Alabama at Birmingham, Birmingham, Alabama, USASearch for more papers by this authorDeval Mehta M.D., Deval Mehta M.D. Department of Cardiovascular Disease, University of Alabama at Birmingham, Birmingham, Alabama, USASearch for more papers by this authorKevin A. Courville M.D., Kevin A. Courville M.D. Department of Cardiovascular Disease, University of Alabama at Birmingham, Birmingham, Alabama, USASearch for more papers by this authorRaed Aqel M.D., F.A.C.C., Corresponding Author Raed Aqel M.D., F.A.C.C. raed.aqel@va.gov Department of Cardiovascular Disease, University of Alabama at Birmingham, Birmingham, Alabama, USABoshell Building 383 1530 3rd Avenue South Birmingham, AL 35 294-0012, USASearch for more papers by this author James D. Allred M.D., James D. Allred M.D. Department of Cardiovascular Disease, University of Alabama at Birmingham, Birmingham, Alabama, USASearch for more papers by this authorDeval Mehta M.D., Deval Mehta M.D. Department of Cardiovascular Disease, University of Alabama at Birmingham, Birmingham, Alabama, USASearch for more papers by this authorKevin A. Courville M.D., Kevin A. Courville M.D. Department of Cardiovascular Disease, University of Alabama at Birmingham, Birmingham, Alabama, USASearch for more papers by this authorRaed Aqel M.D., F.A.C.C., Corresponding Author Raed Aqel M.D., F.A.C.C. raed.aqel@va.gov Department of Cardiovascular Disease, University of Alabama at Birmingham, Birmingham, Alabama, USABoshell Building 383 1530 3rd Avenue South Birmingham, AL 35 294-0012, USASearch for more papers by this author First published: 05 September 2007 https://doi.org/10.1002/clc.20180Citations: 1AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinked InRedditWechat No abstract is available for this article.Citing Literature Volume32, Issue7July 2009Pages E49-E49 ReferencesRelatedInformation

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

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

In most detective stories, the sleuth attempts to identify the incriminating evidence that proves the criminal is guilty. Sherlock Holmes frequently took the opposite approach and searched for evidence that would eliminate a possible explanation of the crime. In the Sign of Four, he states, “Eliminate all other factors, and the one which remains must be the truth.” Similarly, most investigators have attempted to identify risk factors that identify individuals at increased risk for sudden cardiac death (SCD). In this issue of Heart Rhythm, Rashba et al, 1 Rashba E.J. Estes N.A.M. Wang P. Schaechter A. Howard A. Zareba W. Couderc J.-P. Perkiomaki J. Levine J. Kadish A. Defibrillators in Non-Ischemic Cardiomyopathy Treatment Evaluation (DEFINITE) InvestigatorsPreserved heart rate variability identifies low-risk patients with nonischemic dilated cardiomyopathy results from the DEFINITE trial. Heart Rhythm. 2006; 3: 281-286 Abstract Full Text Full Text PDF PubMed Scopus (55) Google Scholar like Sherlock Holmes, take an opposite approach and attempt to identify individuals in a high-risk group who are not likely to have SCD. Specifically, among patients with nonischemic dilated cardiomyopathy (NIDCM) and left ventricular ejection fraction (LVEF) <36%, they found that none of the one in three patients (top tertile) with the highest standard deviation of normal RR intervals (SDNN) in a Holter recording had SCD.