Endocardial Mapping Research Articles

Cryoablation of Accessory Pathways in the Coronary Sinus in Young Patients: A Multicenter Study from the Pediatric and Congenital Electrophysiology Society's Working Group on Cryoablation

This is a multicenter retrospective study evaluating the immediate- and mid-term outcomes of cryoablation of accessory pathways in the coronary sinus in children or in patients with congenital heart disease. Twenty-one patients (median age 13.0 years, range 2-40) from six institutions were included. The accessory pathways were concealed in 11 and manifest in 10. Of 12 patients who had coronary sinus angiography, two had large coronary sinus diverticula, one had a dilated coronary sinus due to a left superior vena cava to coronary sinus, and one had a "pouch" at the mouth of the coronary sinus. Six patients underwent ablation procedures with cryoablation alone, while in the remaining 15 patients, both cryoablation and radiofrequency ablation were utilized. The ablation procedure included left-sided endocardial mapping via a retrograde or transseptal approach in 13 (62%). Procedural success was achieved with cryoablation in the coronary sinus in 15/21 (71%). Four patients (19%) had successful radiofrequency ablation at the right or left posterior septum. Two patients (10%) had unsuccessful procedures. Of the 15 patients with initially successful cryoablation procedures, six (40%) had arrhythmia recurrences at a median of 17 days (range 1-120). Recurrences could not be explained by differences in patient or procedural variables. Cryoablation in the coronary venous system in young patients is feasible but associated with a high arrhythmia recurrence rate. Cryoablation techniques and/or equipment need to be improved in order to safely create more permanent lesions in this arrhythmia substrate.

Mechanisms responsible for the initiation and maintenance of atrial fibrillation assessed by non-contact mapping system

Background This study is aimed to assess the initiation and maintenance mechanisms of atrial fibrillation (AF) and their relationships with the anatomical structures of the left atrium (LA) and pulmonary veins (PVs). Methods Thirty-seven patients (pts; 33 men, mean age 50 ± 12, range 25–68 years) with paroxysmal AF ( n = 29) and persistent AF ( n = 8) who underwent mapping of the LA and PV using 3D non-contact endocardial mapping system (EnSite 3000) were included. Atrial premature complexes (APCs) which triggered the initiation of AF lasted longer than 1 min were mapped and the activation sequence on isopotential color maps was analyzed. Results Wave front dynamics and the relationship with the underlying anatomical structures were assessed. APCs from PV were related to the initiation of AF, but not to the maintenance of AF in 59.5% of the pts (focally triggered type) whereas APCs from PV not only initiated AF but also maintained AF without continuous triggering in 27% (focally driven type). Mixed type and indeterminate type of AF was in 4.5% and 13.5%, respectively. During AF, the mean number of wavelet was 1.45 (maximum 3 in 76.5%). Anatomical structures showing frequent wave break and slow conduction were mostly located at the septopulmonary bundle (86.5%) and the posterior LA roof between left superior PV and right superior PV (54.1%). Conclusion Focal repetitive activity from PV played an important role in both initiation and maintenance of AF using NCM study. Specific anatomical structures such as septopulmonary bundle or posterior LA roof were associated with the spontaneous wave break and heterogeneous conduction delay, which was also appears to be important in the maintenance of AF.

Catheter ablation of haemodynamically unstable or non-sustained ventricular tachycardia

Background — Ventricular tachycardia (VT) may be haemodynamically unstable or non-sustained, interfering with detailed activation mapping. Non-contact mapping permits beat-by-beat analysis of VT, projected upon a 3-dimensional reconstructed geometry of the cardiac chamber.Objective —The aim of the present study is to determine the utility of non-contact endocardial mapping to guide ablation of haemodynamically unstable VT or non-sustained VT.Methods and results — Eighteen VTs in 17 patients were induced (cycle length 336±58ms) and mapped. Three patients were mapped during premature ventricular complexes (PVCs) because sustained VT could not be induced. Analysis of the archived non-contact activation maps was performed to identify the exit point and/or the diastolic pathway of the VT reentry circuit.The endocardial exit points (10±16ms before QRS) were defined in 17/18 VTs (94%). A diastolic pathway was identified in 5/6 ischaemic VTs.The earliest activation sites were identified in all 3patients with PVCs. Radiofrequency current was applied around the exit point or to create a line of block across the diastolic pathway. Catheter ablation was performed in 17/18 VTs, including 3patients mapped using only PVCs. Ablation was successful in 16/18 VTs (89%) and in 15/17patients (82%). Catheter ablation was not performed in one patient (peri-hisian VT) and was unsuccessful in one patient (mapped during PVCs).Conclusions — Non-contact endocardial mapping is useful to guide radiofrequency catheter ablation of untolerated or non-sustained VTs.

Endoscopic fluorescence mapping of the left atrium: A novel experimental approach for high resolution endocardial mapping in the intact heart

Despite the availability of several mapping technologies for investigating the electrophysiologic mechanisms of atrial fibrillation (AF), an experimental tool enabling high-resolution mapping of electrical impulses on the endocardial surface of the intact left atrium is lacking. The purpose of this report is to present a new optical mapping approach implementing a steerable cardio-endoscope in isolated hearts. The system consists of a direct or side-view endoscope coupled to a 532-nm excitation laser for illumination and a CCD camera for imaging of potentiometric dye fluorescence (di-4-ANEPPS, 80 x 80 pixels, 200-800 frames/s). The cardio-endoscope was aimed successively at diverse posterior left atrial locations to obtain high-resolution movies of electrical wave propagation and detailed endocardial anatomic features in the presence and absence of atrial stretch. We present several examples of high-resolution endoscopic posterior left atrial recordings of wave propagation patterns during both sinus rhythm and AF with signal-to-noise ratio similar to conventional optical mapping systems. We demonstrate the endoscope's ability to visualize highly organized AF sources (rotors) at specific locations on the posterior left atrium and posterior left atrium-pulmonary vein junctions. We present video images of waves emanating from such sources as they propagate into pectinate muscles in the left atrial appendage. In particular, we demonstrate this approach is ideally suited for studying the effects of atrial stretch on AF dynamics. In isolated hearts, cardio-endoscopic optical mapping of electrical activity should enable comprehensive evaluation of AF activity in the posterior left atrium, the role of local anatomy on AF dynamics, and the efficacy of pharmacologic and ablative interventions.

Intra-coronary guidewire mapping–A novel technique to guide ablation of human ventricular tachycardia

Endocardial catheter ablation of ventricular tachycardia (VT) may fail if originating from epicardial or intramural locations. We hypothesized that mapping could be achieved using an angioplasty guidewire in the coronary circulation, to guide trans-coronary ablation. Six patients (2 male), 64 +/- 14 years and previously unsuccessful endocardial VT ablation were studied. Using ECG and existing endocardial mapping data, a coronary artery supplying the predicted VT origin was selected. A 0.014-in angioplasty guidewire was advanced into branches of the artery and connected to an amplifier to record unipolar signals against an indifferent electrode within the inferior vena cava. An uninflated angioplasty balloon was advanced over the wire such that only the distal 5 mm was used for mapping. One VT per patient was mapped (CL 348 +/- 102.1 ms). Diastolic potentials were recorded from all (77.7 +/- 43.8 ms pre-QRS onset) and concealed entrainment demonstrated in 3. Pacemapping during sinus rhythm was used in the remainder due to failure of entrainment (n = 2) or degeneration to VF (n = 1). Following branch identification, cold saline injection causing VT termination was used for further confirmation. Five VTs were ablated using intra-coronary ethanol injection via the central lumen of the inflated over the wire balloon. The other was ablated using radiofrequency energy in a coronary vein adjacent to the target artery, which was too small for an angioplasty balloon. No complications or recurrence of ablated VT was seen over 19 +/- 17 months of follow up. Intracoronary guidewire mapping is a novel method of electrophysiological epicardial mapping to help guide trans-coronary VT ablation.

Normal Atrial Activation and Voltage During Sinus Rhythm in the Human Heart: An Endocardial and Epicardial Mapping Study in Patients with a History of Atrial Fibrillation

The three-dimensional contributions to human atrial activation in sinus rhythm have not been specifically characterized. We evaluated the sequence of endocardial and epicardial activation and voltage of the atria during normal sinus rhythm. The study group includes 35 patients with history of symptomatic atrial fibrillation. Prior to catheter ablation of atrial fibrillation, we performed multielectrode electroanatomic mapping during sinus rhythm, endocardially of the RA, LA, and coronary sinus (CS) and, in 10 patients, epicardially of the transverse sinus and oblique sinus. Following activation of the atrial region of the sinus node, the epicardial transverse sinus was activated 11 +/- 18 msec later, while the earliest endocardial LA activation occurred in the region of Bachmann's bundle at 31 +/- 13 msec, significantly earlier than the earliest epicardial LA activation of the oblique sinus at 54 +/- 10 msec (P < 0.002). The posterior LA revealed complex types of activation in 66% of patients analyzed, due to the convergence of wavefront propagation from the CS, oblique sinus, and endocardial LA. Bipolar voltage measurements revealed significantly higher values for the epicardium (mean 3.05 +/- 1.31 mv) than for the endocardium (mean 1.65 +/- 0.75 mv), P < 0.0001 between both groups. In sinus rhythm, we have characterized endocardial and epicardial atrial activation and voltage, and provide an analysis and understanding of the genesis of the P wave complex in humans.

Transmural and endocardial Purkinje activation in pigs before local myocardial activation after defibrillation shocks

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. 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. 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. Defibrillation-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. 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. 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.

Focus, reentry, or “focal” reentry?

the question whether tachyarrhythmias are caused by enhanced impulse formation (“focus”) or by reentrant excitation (“reentry”) has been the subject of debate for more than a century. In 1887 McWilliam ([12][1]) was the first to suggest that disturbances in impulse propagation could be

Remote Magnetic Navigation to Guide Endocardial and Epicardial Catheter Mapping of Scar-Related Ventricular Tachycardia

The present study examines the safety and feasibility of using a remote magnetic navigation system to perform endocardial and epicardial substrate-based mapping and radiofrequency ablation in patients with scar-related ventricular tachycardia (VT). Using the magnetic navigation system, we performed 27 procedures on 24 consecutive patients with a history of VT related to myocardial infarction, dilated cardiomyopathy, arrhythmogenic right ventricular cardiomyopathy, hypertrophic cardiomyopathy, or sarcoidosis. Electroanatomic mapping of the left ventricular, right ventricular, and ventricular epicardial surfaces was constructed in 24, 10, and 12 patients, respectively. Complete-chamber VT activation maps were created in 4 patients. A total of 77 VTs were inducible, of which 21 were targeted during VT with the remotely navigated radiofrequency ablation catheter alone. With a combination of entrainment and activation mapping, 17 of 21 VTs (81%) were successfully terminated in a mean of 8.4+/-8.2 seconds; for the remainder, irrigated radiofrequency ablation was necessary. The mean fluoroscopy times for endocardial and epicardial mapping were 27+/-23 seconds (range, 0 to 105 seconds) and 18+/-18 seconds (range, 0 to 49 seconds), respectively. In concert with a manually navigated irrigated ablation catheter, 75 of 77 VTs (97%) were ultimately ablated. Four patients underwent a second procedure for recurrent VT, 3 with the magnetic navigation system. After 1.2 procedures per patient, VT did not recur during a mean follow-up of 7+/-3 months (range, 2 to 12 months). The present study demonstrates the safety and feasibility of remote catheter navigation to perform substrate mapping of scar-related VT in a wide range of disease states with a minimal amount of fluoroscopy exposure.

Focal Atrial Tachycardias Arising from the Right Atrial Appendage: Electrocardiographic and Electrophysiologic Characteristics and Radiofrequency Ablation

To characterize the electrocardiographic and electrophysiological features and frequency of focal atrial tachycardia (AT) originating from the right atrial appendage (RAA). The RAA has been described as a site of origin of AT, but detailed characterization of these tachycardias is limited. Ten patients (3.8%) of 261 undergoing radiofrequency ablation (RFA) for focal AT are reported. Endocardial activation maps (EAM) were recorded from catheters at the CS (10 pole), tricuspid annulus (20 pole Halo catheter), and His positions. P waves were classified as negative, positive, isoelectric, or biphasic. The mean age was 39 +/- 20 years, nine males, with symptoms for 4.1 +/- 5.1 years. Tachycardia was incessant in seven patients, spontaneous in one patient, and induced by programmed extrastimuli in two patients. These foci had a characteristic P wave morphology. The P wave was negative in lead V(1) in all patients, becoming progressively positive across the precordial leads. The P waves in the inferior leads were low amplitude positive in the majority of patients. Earliest EAM activity occurred on the Halo catheter in all patients. Mean activation time at the successful RFA site =-38 +/- 15 msec. Irrigated catheters were used in six patients, due to difficulty achieving adequate power. RFA was acutely successful in all patients. Long-term success was achieved in all patients over a mean follow up of 8 +/- 7 months. The RAA is an uncommon site of origin for focal AT (3.8%). It can be suspected as a potential anatomic site of AT origin from the characteristic P wave and activation timing. Irrigated ablation catheters are often required for successful ablation. Long-term success was achieved with focal ablation in all patients.

Ventricular fibrillation in myopathic human hearts: mechanistic insights from in vivo global endocardial and epicardial mapping

Ventricular fibrillation (VF) is an important cause of sudden cardiac death and cardiovascular mortality in patients with cardiomyopathy. Although it was generally believed that chaotic reentrant wavefronts underlie VF in humans, there is emerging evidence of spatiotemporal organization during early VF. The mechanism of this organization of electrical activity in early VF is unknown in myopathic hearts. We studied early VF in vivo, intraoperatively in five cardiomyopathic patients. Simultaneous electrograms were obtained from the epicardium and endocardium in left ventricular cardiomyopathy and from the endocardium in right ventricular myopathy. The Hilbert transform was used to derive the phase of the electrograms. Rotors were identified by isolating phase singularity points. Rotors were present in all of the myopathic hearts studied during VF and cumulatively lasted a mean of 3.2 +/- 2.0 s of the 7.0 +/- 4.0 s of the VF segments analyzed. For each surface mapped, 3.6 +/- 2.9 rotors were identified for the duration mapped. The average number of cycles completed by these rotors was 4.9 +/- 4.9. The longest rotor lasted 10.2 +/- 6.2 rotations and lasted 2.0 +/- 1.2 s. The rotors on the endocardium had a cycle length of 192 +/- 33 ms compared with 220 +/- 15 ms on the epicardium (P=0.08). There is centrifugal activation of electrical activity from these rotors, and they give rise to domains that activate at faster rates with evidence of conduction block at the border with slower domains. These rotors frequently localized to border regions of myocardium with bipolar electrogram amplitude of <0.5 mV. The organization of electrical activity during early VF in myopathic human hearts is characterized by wavefronts emanating from a few rotors.

Atrial flutter: from ECG to electroanatomical 3D mapping

Atrial flutter is a common arrhythmia that may cause significant symptoms, including palpitations, dyspnea, chest pain and even syncope. Frequently it’s possible to diagnose atrial flutter with a 12-lead surface ECG, looking for distinctive waves in leads II, III, aVF, aVL, V1,V2. Puech and Waldo developed the first classification of atrial flutter in the 1970s. These authors divided the arrhythmia into type I and type II. Therefore, in 2001 the European Society of Cardiology and the North American Society of Pacing and Electrophysiology developed a new classification of atrial flutter, based not only on the ECG, but also on the electrophysiological mechanism. New developments in endocardial mapping, including the electroanatomical 3D mapping system, have greatly expanded our understanding of the mechanism of arrhythmias. More recently, Scheinman et al, provided an updated classification and nomenclature. The terms like common, uncommon, typical, reverse typical or atypical flutter are abandoned because they may generate confusion. The authors worked out a new terminology, which differentiates atrial flutter only on the basis of electrophysiological mechanism.

Stepwise Catheter Ablation of Chronic Atrial Fibrillation:Importance of Discrete Anatomic Sites for Termination

Background: Chronic atrial fibrillation (CAF) can be acutely terminated using a combination of approaches targeting thoracic veins, left atrial areas showing rapid/heterogeneous electrical activity, and by linear ablation. This observational study emphasizes the crucial role for conventional endocardial mapping to identify discrete anatomical sites, ablation of which is indispensable for the achievement of atrial fibrillation (AF) termination. Methods: Eighty consecutive patients with CAF underwent catheter ablation using the stepwise approach. Pulmonary vein isolation and roof‐line ablation were performed as the initial two steps in all patients. In the presence of locally rapid or heterogeneous activity, ablation was then performed at all sites within the left atrium and coronary sinus (CS) region with the endpoint of local organization or slowing. If AF persisted, the mitral isthmus was targeted. Patients in whom AF terminated during one of these five ablation steps were differentiated from those in whom AF was terminated by radiofrequency ablation at a single discrete anatomic site within 1 minute. Electrograms at discrete anatomic sites of termination were classified according to morphology. Results: Termination of AF was achieved in 69 (86%) patients by ablation alone. In 50 patients (72%), this occurred while following the predetermined ablation schema. In the remaining 19 patients (28%), ablation targeting a discrete site (preferentially located at the CS, the base of left atrial appendage, and the interatrial septum) terminated AF. Such sites were identified by (1) continuous electrical activity and fractionation and (2) bursts of short cycle activity (130–160 msec), centrifugal activation or local activation gradients, indicating sources perpetuating AF. Conclusion: In 28% of patients with termination of CAF, the final successful ablation site is anatomically discrete and displays electrophysiological characteristics that can be effectively identified by point and activation mapping. Failure to identify these sites may significantly reduce the likelihood of termination of CAF by catheter ablation.

Abstract 191: Analysis Of Conduction Block During Ventricular Fibrillation In Langendorff Perfused Explanted Human Hearts.

Purpose Rotors in Ventricular Fibrillation (VF) are known to occur in distinct domains identified by dominant frequency (DF). It has been postulated that VF is driven by these domains of excitation with fibrillatory propagation to adjacent domains with conduction blocks. If the dominant domain hypothesis is applicable to human VF, we postulated that minimally during VF, areas blocks in a DF map should localize at boundaries of DF domains. Methods Explanted hearts from 4 patients undergoing cardiac transplant were perfused with Krebs-Henseilet solution. The epicardial and endocardial mapping was constructed with 112 electrodes disposed on an extensible sock and balloon array. The electrodes were organized in 14 rows of 8 electrodes disposed radially around the apex. 12 episodes of VF from the 4 hearts were analyzed. Fast Fourier Transformation (FFT) analysis was performed with a resolution of 0.25 Hz. DF domain was defined as a region on the DF map with uniform DF. Double peak (DP) an estimate of conduction block, was identified at a time point if a secondary peak was present in the power spectrum of an FFT that was within a maximum separation of 80% of the dominant (highest) peak frequency and that had an amplitude of at least 20% of the amplitude of the dominant peak. Results The average DF was 4.64±1.20 Hz. The mean percentage of blocks was 26.13±12.19 %. The average number of domains per DF map were 9.25±3.77. The mean percent block per domain was 2.95±1.27.The number of domains per map correlated significantly to areas with blocks. (r = 0.49, p=0.014). When the hearts were individually analyzed, the correlation was greater than when analyzed together. Higher occurrence of block is seen with increasing number of DF domains. Conclusions During human VF, areas of blocks in a DF map localize at boundaries of DF domains.

Percutaneous Endocardial and Epicardial Ablation of Hypotensive Ventricular Tachycardia with Percutaneous Left Ventricular Assist in the Electrophysiology Laboratory

Ventricular tachycardia (VT) in the setting of structural heart disease is challenging to treat with percutaneous catheter ablation due to the presence of complex substrate, multiple morphologies, hemodynamic instability, and epicardial circuits. When substrate-based approaches fail, however, it may be impossible to map and ablate hemodynamically unstable arrhythmias. We describe a novel approach to endocardial and epicardial mapping and ablation of hypotensive VT using a percutaneous left ventricular assist device in the electrophysiology laboratory, permitting near-surgical access to cardiac structures.

Modalities to assess myocardial viability in the modern cardiology era

Detection of viable myocardium in patients with left ventricular dysfunction has become an increasingly important guide to prognosis and treatment. This article reviews the current status and future potential for the application of modalities to assess myocardial viability. Imaging and other techniques that are reviewed are myocardial perfusion imaging by single-photon-emission computed tomography, positron-emission tomography, echocardiography, cardiac magnetic resonance technology, computed tomography and catheter-based endocardial mapping.

Intraoperative Electro-Anatomical Mapping and Beating Heart Ablation of Ventricular Tachycardia

In most cases ventricular tachycardia is responsive to antiarrhythmic drug therapy. If antiarrhythmic drugs fail, then percutaneous, endocardial ablation guided by electro-anatomical mapping is usually curative. Occasionally neither of these therapies is successful and surgical ablation is required. Challenges encountered in surgical ablation include application of reliable intraoperative real-time electro-anatomical mapping to identify the focus of ventricular tachycardia and the need for technology that enables ablation on the beating heart. We present a case demonstrating the feasibility of surgical cryoablation of ventricular tachycardia arising from the right ventricle using intraoperative real-time epicardial and endocardial electro-anatomical mapping and argon-based cryoablation.

Selective Atrial Vagal Denervation Guided by Evoked Vagal Reflex to Treat Patients With Paroxysmal Atrial Fibrillation

The aim of this study was to evaluate whether selective radiofrequency (RF) catheter ablation of the atrial sites in which high-frequency stimulation induces vagal reflexes prevents paroxysmal atrial fibrillation (AF). Ten patients with episodes suggestive of vagal-induced paroxysmal AF and no heart disease were selected for percutaneous epicardial and endocardial mapping of the atria to search for sites in which high-frequency transcatheter stimulation (20 Hz,) induced vagal reflexes. A vagal response defined as AV block of > 2 seconds was elicited in 7 of 10 patients (70%) with an average of 5 +/- 2.4 (range, 2 to 9) sites per patient, and RF pulses (21.0 +/- 12.0 per patient) were applied at those sites to eliminate all evoked vagal reflexes. The 3 patients in whom evoked vagal reflexes were not obtained underwent circumferential pulmonary vein ablation with an average of 58.0 +/- 13.9 RF pulses per patient (P = 0.022). Autonomic evaluation was performed before and 48 hours and 3 months after the procedure and was consistent with vagal withdrawal in all patients. Two of the 7 patients who underwent denervation remained asymptomatic without the use of antiarrhythmic medication at a mean follow-up of 8.3 +/- 2.8 months (range, 5 to 15 months); 4 had frequent recurrences and were referred for circumferential pulmonary vein ablation; and 1 had few AF episodes without antiarrhythmic medication. The 3 patients without evoked vagal reflexes who underwent circumferential pulmonary vein ablation remained asymptomatic without antiarrhythmic medication. One patient had acute delayed gastric emptying after atrial vagal denervation. RF catheter ablation of selected atrial sites in which high-frequency stimulation induced vagal reflexes may prevent AF recurrences in selected patients with apparently vagal-induced paroxysmal AF.

Epicardial Radiofrequency Catheter Ablation of Ventricular Tachycardia in the Vicinity of Coronary Arteries Is Facilitated by Fusion of 3-Dimensional Electroanatomical Mapping With Multislice Computed Tomography

A 65-year-old male patient was referred for radiofrequency catheter ablation of a ventricular tachycardia (VT). The patient had a history of an anterior non–Q-wave infarction. Angiography revealed no significant lesions and normal left ventricular (LV) function. Before ablation, a contrast-enhanced 64-slice computed tomography (CT) scan was acquired. CT data were loaded into an electroanatomical (EA) mapping system (Biosense Webster, Inc, Diamond Bar, Calif) to provide 3-dimensional (3D) CT surface reconstruction of the coronary arteries and LV. Endocardial voltage mapping of the LV was performed during sinus rhythm and the 3D EA mapping data were merged with the 3D surface reconstruction data, allowing real-time visualization of the catheter tip in relation to the surface reconstruction (Figure 1). The clinical VT (cycle length 314 ms) was induced (Figure 2A). Endocardial …

Role of the Posterior Papillary Muscle and Purkinje Potentials in the Mechanism of Ventricular Fibrillation in Open Chest Dogs and Swine: Effects of Catheter Ablation

Papillary muscle (PM) ablation may terminate ventricular fibrillation (VF) in rabbit hearts. Whether or not PM ablation prevents ventricular fibrillation (VF) induction in large animals is unknown. We performed noncontact endocardial mapping and/or high-density epicardial mapping during VF in 12 dogs and 16 swine and tested the effects of posterior PM (PPM) ablation on VF inducibility. During VF in progressive global ischemia (3 swine and 2 dogs), the highest dominant frequency (DF) was near PPM. The majority of the reentrant wavefronts during a propranolol infusion (swine) were anchored to the PPM. Purkinje potentials onset were recorded on the PPM both during sinus rhythm and during VF. Radiofrequency (RF) ablation of the endocardium on the PPM with a linear extension of the ablation line from the PPM to the mitral valve annulus and then the left ventricular apex in 7 dogs reduced the VF inducibility from 100% at baseline to 22% after ablation (P < 0.0001). RF applications to the anterolateral wall of dogs (n = 3) did not prevent VF induction. The application of RF energy near the PPM frequently initiated VF in swine (n = 7), preventing subsequent testing of VF inducibility. In dogs and swine, the highest DF and majority of reentrant wavefronts during VF with acute global ischemia or during a propranolol infusion were located on the PPM. RF ablation targeted at the PPM reduced the inducibility of VF in normal dogs. However, the same ablation provoked incessant VF in swine, preventing subsequent testing of VF inducibility.