Kenichiro Otomo

Characterization of Reentrant Circuit in Macroreentrant Right Atrial Tachycardia After Surgical Repair of Congenital Heart Disease Isolated Channels Between Scars Allow “Focal” Ablation

Background —The purpose of this study was to characterize the circuit of macroreentrant right atrial tachycardia (MacroAT) in patients after surgical repair of congenital heart disease (SR-CHD). Methods and Results —Sixteen patients with atrial tachycardia (AT) after SR-CHD were studied (atrial septal defect in 6, tetralogy of Fallot in 4, and Fontan procedure in 6). Electroanatomic right atrial maps were obtained during 15 MacroATs in 13 patients, focal AT in 1 patient, and atrial pacing in 2 patients without stable AT. A large area of low bipolar voltage (≤0.5 mV) involved most of the free wall in all patients and contained 2 to 7 dense scars or lines of double potentials, forming 29 narrow channels (width ≤2.7 cm) between scars in all but 1 patient, who had a single scar and only focal AT. All 15 MacroATs were propagated through narrow channels. Ablation within the channel eliminated all 15 MacroATs with 1 to 3 (median 1) radiofrequency applications. Ablation was performed in 9 other channels identified during MacroAT (5 patients) and in 5 channels identified during atrial pacing (2 patients). Conduction block was obtained across 28 of 29 channels. After ablation, reproducible sustained right AT was not induced in any patient. During follow-up (median 13.5 months), new MacroATs, atrial fibrillation, or palpitations occurred in 3 of 16 patients. Conclusions —MacroAT after SR-CHD requires a large area of low voltage containing ≥2 scars forming narrow channels. Ablation within the channels eliminates MacroAT.

Characterization of Reentrant Circuit in Macroreentrant Right Atrial Tachycardia After Surgical Repair of Congenital Heart Disease

Background—The purpose of this study was to characterize the circuit of macroreentrant right atrial tachycardia (MacroAT) in patients after surgical repair of congenital heart disease (SR-CHD). Methods and Results—Sixteen patients with atrial tachycardia (AT) after SR-CHD were studied (atrial septal defect in 6, tetralogy of Fallot in 4, and Fontan procedure in 6). Electroanatomic right atrial maps were obtained during 15 MacroATs in 13 patients, focal AT in 1 patient, and atrial pacing in 2 patients without stable AT. A large area of low bipolar voltage (≤0.5 mV) involved most of the free wall in all patients and contained 2 to 7 dense scars or lines of double potentials, forming 29 narrow channels (width ≤2.7 cm) between scars in all but 1 patient, who had a single scar and only focal AT. All 15 MacroATs were propagated through narrow channels. Ablation within the channel eliminated all 15 MacroATs with 1 to 3 (median 1) radiofrequency applications. Ablation was performed in 9 other channels identified ...

Para-Hisian Pacing A New Method for Differentiating Retrograde Conduction Over an Accessory AV Pathway From Conduction Over the AV Node

BACKGROUND Differentiation between ventriculoatrial (VA) conduction over an accessory AV pathway (AP) and the AV node (AVN) may be difficult, especially in patients with a septal AP. METHODS AND RESULTS A new pacing method, para-Hisian pacing, was tested in 149 patients with AP and 53 patients without AP who had AV nodal reentrant tachycardia (AVNRT). Ventricular pacing was performed adjacent to the His bundle and proximal right bundle branch (HB-RB), initially at high output to capture both RV and HB-RB. The output was then decreased to lose HB-RB capture. The change in timing and sequence of retrograde atrial activation between HB-RB capture and noncapture was examined. Loss of HB-RB capture without change in stimulus-atrial (S-A) interval or atrial activation sequence indicated exclusive retrograde AP conduction. An increase in S-A interval without change in His bundle-atrial interval or atrial activation sequence indicated exclusive retrograde AVN conduction. A change in atrial activation sequence indicated the presence of both retrograde AP and AVN conduction. Para-Hisian pacing correctly identified retrograde AP conduction in 132 of 147 AP patients, including all septal and right free wall APs. Retrograde AVN conduction masked AP conduction in 9 of 34 patients with a left free wall AP and 6 of 9 patients with the permanent form of junctional reciprocating tachycardia. Para-Hisian pacing correctly excluded AP conduction in all 53 patients with AVNRT. CONCLUSIONS Para-Hisian pacing reliably identifies retrograde conduction over septal and right free wall APs, but AVN conduction may mask APs located far from the pacing site or with a long retrograde conduction time.

Coronary Sinus-Ventricular Accessory Connections Producing Posteroseptal and Left Posterior Accessory Pathways Incidence and Electrophysiological Identification

Background—The coronary sinus (CS) has a myocardial coat (CSMC) with extensive connections to the left and right atria. We postulated that some posteroseptal and left posterior accessory pathways (CSAPs) result from connections between a cuff of CSMC extending along the middle cardiac vein (MCV) or posterior coronary vein (PCV) and the ventricle. The purpose of the present study was to use CS angiography and mapping to define and determine the incidence of CSAPs and determine the relationship to CS anatomy. Methods and Results—CSAP was defined by accessory pathway (AP) potential or earliest activation in the MCV or PCV and late activation at anular endocardial sites. A CSAP was identified in 171 of 480 patients undergoing ablation of a posteroseptal or left posterior AP. CS angiography revealed a CS diverticulum in 36 (21%) and fusiform or bulbous enlargement of the small cardiac vein, MCV, or CS in 15 (9%) patients. The remaining 120 (70%) patients had an angiographically normal CS. A CSMC extension potential (CSE), like an AP potential, was recorded in the MCV in 98 (82%), in the PCV in 13 (11%), in both the MCV and PCV in 6 (5%), and in the CS in 3 (2%) of 120 patients. CSMC potentials were recorded between the timing of atrial and CSE potentials. Conclusions—CSAPs result from a connection between a CSMC extension (along the MCV or PCV) and the ventricle. The CS is angiographically normal in most patients.

Chapter 59 – Electrophysiologic Characteristics of Atrioventricular Nodal Reentrant Tachycardia: Implications for the Reentrant Circuits

Atrioventricular nodal reentrant tachycardia (AVNRT), the most common form of paroxysmal supraventricular tachycardia, 1 is a fascinating complex of arrhythmias. AVNRT was originally proposed to result from reentry totally confined within the compact atrioventricular (AV) node. 2 3 However, the typical form of AVNRT (slow/fast) is now thought to involve the AV node, a component of atrial myocardium, and at least two atrionodal connections. 4 5 6 7 8 9 10 11 12 13 14 15 16 Much of the current understanding about the components of the reentrant circuit has evolved from the development of ablation procedures, in which one of the atrionodal connections, remote from the compact AV node, is destroyed, eliminating AVNRT without producing AV block. 4 5 6 7 8 9 10 11 12 16 17 18

Electrophysiology of the Atrio-AV Nodal Inputs and Exits in the Normal Dog Heart.: Radiofrequency Ablation Using an Epicardial Approach

Ablation of Atrionodal Connections. Introduction: We studied the effects of selective and combined ablation of the fast (FP) and slow pathway (SP) on AV and VA conduction in the normal dog heart using a novel epicardial ablation technique.

Critical Atrial Site for Ablation of Pacing‐Induced Atrial Fibrillation in the Normal Dog Heart

Site for Ablation of AF in Dogs. Introduction: Radiofrequency catheter ablation (RFA) has been used recently to treat atrial fibrillation (AF). The purpose of this study was to investigate a new approach to preventing AF by RFA.

Utility of gallium-67 scintigraphy for evaluation of cardiac sarcoidosis with ventricular tachycardia.

BackgroundThe outcome of cardiac sarcoidosis is sometimes very poor. Ventricular tachycardia (VT) associated with cardiac sarcoidosis is the most common cause of sudden death among most patients. However, there is no established method for potential VT in patients with cardiac sarcoidosis. Thus, we investigated the utility of evaluation of gallium-67 scintigraphy for potential VT in patients with cardiac sarcoidosis.Methods and ResultsCardiac sarcoidosis was diagnosed in 25 patients at ours or collaborating hospitals during the period 1982 through 2004. Twenty-one of these patients were treated with corticosteroid, and these patients were divided into two groups, depending on whether VT was present: a non-VT group (n=7) and a VT group (n=14). Laboratory and gallium-67 scintigraphy findings were examined in both groups. During the follow-up period, initial and maintenance dosages of corticosteroid did not differ significantly between the groups. Accumulation of gallium-67 in the heart at the time of diagnosis was detected more frequently in the VT group than in the non-VT group (14.3 vs. 71.4%, p<0.05). Six of the seven VT patients who underwent follow-up examination showed improvement on the scintigram obtained after treatment. Five of the six showed no VT recurrence in terms of Holter electrocardiogram, electrophysiologic study, or delivery of implantable cardioverter defibrillator shock. Serum angiotensin-converting enzyme and lysozyme concentrations were within normal limits in most patients in both groups.ConclusionsActivity of sarcoid granulomas may be associated with the occurrence of VT. Gallium-67 scintigraphy reflects the activity of sarcoid granulomas and thus is useful for evaluation of cardiac sarcoidosis in patients with potential VT.

A Technique for Stable His-Bundle Recording and Pacing: Electrophysiological and Hemodynamic Correlates

His‐bundle electrograms recorded from intracardiac electrode catheters have been a mainstay of basic and clinical electrophysiology. However, consistent His‐bundle pacing has not been as readily achieved. In 13 dogs anesthetized with sodium pentobarbital (30 mg/kg), we recorded leads II and aVR as well as the His‐bundle electrogram from the aortic root. A deflectable tip multipolar catheter (4 rings, 5 mm apart) was introduced via the right jugular vein into the right ventricle (RV). In 7 dogs, using fluoroscopy, the tip was placed under the tricuspid septal leaflet. In the other 6, after thoracotomy, the same placement was made by palpation through the right atrial wall. Stable His‐bundle and right bundle (Rb) branch recordings were made from distal and proximal electrode pairs, respectively. H‐V intervals measured 35 ± 6 ms from the aortic root and 33 ± 5 ms from under the tricuspid leaflet (P = NS). Rb‐V measured 25 ± 4 ms. Consistent His‐bundle pacing was accomplished from the aortic root with an average stimulus intensity of 6 ± 10 mA and from the tricuspid leaflet at 16 ± 8 mA (P < 0.05). In 7 anesthetized dogs we compared the hemodynamic effects of A‐V sequential pacing at the same heart rates using the His‐bundle recording site under the septal leaflet of the tricuspid valve (A‐H pacing) or pacing from the RV apex (A‐RV pacing). Under normal conditions there was a significant depression of mean blood pressure when A‐RV pacing was compared with atrial pacing (AOO); but no difference was found between AOO and A‐H pacing. These same differences were found after hemodynamic depression with propranolol (1 mg/kg; 4 dogs) or combining the beta blocker and verapamil (0.5 mg/kg; 1 dog). Thus, this catheter positioning provides both stable recordings of the His‐bundle electrogram and consistent pacing from the common bundle.

Radiofrequency catheter ablation with the split-tip electrode in the temperature-controlled mode.

ANTZ, M., et al.: Radiofrequency Catheter Ablation with the Split‐Tip Electrode in the Temperature‐Controlled Mode. The 7 Fr “split‐tip electrode” (2.5‐mm tip electrode divided longitudinally into four electrodes with an adjacent 2‐mm ring electrode) improves mapping resolution due to its small recording electrodes and narrow interelectrode distances (0.1 mm). The purpose of this study was to examine the temperature‐controlled ablation properties of this electrode. In seven anesthetized dogs, the thigh muscles were exposed and superfused with canine blood. A split‐tip catheter electrode (with a thermocouple in each of the five electrodes) and a conventional 4‐mm catheter electrode were positioned at constant pressure perpendicular or parallel to the surface of the thigh muscle. Impedance measured between each split electrode and a skin patch correlated with the degree of contact with blood and tissue. In the parallel catheter to tissue orientation, split electrodes not in contact with tissue had a low impedance (mean 210–224 Ω), and the split electrode almost entirely in contact with tissue had the highest impedance (380 ± 56 Ω). In the perpendicular catheter to tissue orientation all split electrodes had a similar impedance (mean 279–286 Ω). A total of 75 radiofrequency (RF) lesions were produced in the temperature‐controlled mode with the 4‐mm electrode (target 60°C) or the split‐tip electrode (power limited by the hottest electrode reaching 70°C) with current delivered to all five electrodes simultaneously, or only to electrodes in contact with tissue. Lesion depth was not significantly different between electrodes in the parallel orientation (5.2 ± 0.9 vs 5.1 ± 1.4 vs 5.3 ± 1.1 mm), but significantly deeper with the conventional 4‐mm tip electrode in the perpendicular orientation (6.7 ± 1.2 vs 5.3 ± 1.3 vs 5.6 ± 0.9 mm, P < 0.05). This was due to higher power delivered to the conventional 4‐mm electrode (27 ± 9 vs 17 ± 7 vs 15 ± 7 W, P < 0.05) because convective cooling by the blood flow was less effective for the split‐tip electrode due to a reduced heat conduction across the interelectrode space from the hottest electrode to cooler areas of the group of five electrodes (mean temperature difference between the hottest split electrodes and the ring electrode: 24°C). Electrode cooling or heat conduction was not effected by the elimination of current delivery to noncontact electrodes. Steam pops occurred in 36% of applications with the conventional 4‐mm electrode in the perpendicular orientation but never with the split‐tip electrode in spite of the higher target temperature. Measurement of impedance from the split electrodes allow the determination of electrode tissue contact and RF lesions produced with the split‐tip electrode in the temperature‐controlled mode using a target of 70°C were of reasonable size and not associated with steam pops.