"Cristal tachycardias": origin of right atrial tachycardias from the crista terminalis identified by intracardiac echocardiography

Intracardiac phased-array imaging: methods and initial clinical experience with high resolution, under blood visualization: initial experience with intracardiac phased-array ultrasound

OBJECTIVES

This study was designed to test the feasibility of high-resolution phased-array intracardiac imaging.

BACKGROUND

Intracardiac echocardiographic imaging of the heart during interventional electrophysiologic (EP) procedures has been limited by inadequate ultrasound penetration and absence of Doppler hemodynamic and flow information produced by rotating mechanical ultrasound elements.

METHODS

A 10F (3.2 mm) phased-array, variable 5.5 to 10 MHz frequency imaging catheter with a four-way deflectable tip was applied in 24 patients undergoing EP studies. Sixteen prespecified cardiac targets were imaged from a right heart venue.

RESULTS

Fifteen patients had no underlying organic heart disease; nine had ischemic, cardiomyopathic, valvular or congenital heart disorders. Longitudinal and short-axis imaging readily disclosed each cardiac valve, support structures and chamber, as well as the pericardium, right and left atrial appendages, the junction of the right atrium and superior vena cava, crista terminalis, tricuspid valve isthmus, coronary sinus orifice, membranous fossa ovalis and pulmonary veins. The average target depth was 8.8+/-1.5 cm (range 0.5 to 15 cm), with adequate penetration at a 7.5 MHz imaging frequency. Color flow and Doppler utilities clearly characterized transaortic and pulmonic valve and pulmonary vein blood flow, including during low output states.

CONCLUSIONS

These first human studies with this technology demonstrate the methods, feasibility and utility of intracardiac phased-array vector and Doppler imaging for long-axis, apex-to-base global cardiac imaging. High resolution of endocardial structures and catheters suggests additional utility for visualizing interventional procedures from the right heart.

Electrophysiological characteristics and radiofrequency ablation of focal atrial tachycardia originating from the superior vena cava

The initiation of focal atrial tachycardia (AT) from the superior vena cava (SVC) remains unclear. In 3 patients (2 females, 1 male; aged 57, 66 and 50 years, respectively) with focal AT arising from different parts of the SVC, the AT occurred spontaneously, rather than being induced by electrical stimulation. The cycle length of the tachycardia was highly variable, ranging between 190 and 300 ms in patient 1, 180 and 320ms in patient 2, and 200 and 300ms in patient 3. The clinical or associated arrhythmias were atrial fibrillation (AF) (patients 1, 3) and atrial flutter (AFL) (patients 2, 3). A presumed SVC potential that was earlier than the activation of all the other mapping sites was recorded during AT at the lower anterior (15-mm above the atriocaval junction), the mid-anterior (25-mm above the atriocaval junction) and the lower posterior aspect of the SVC (17-mm above the atriocaval junction. Radiofrequency (RF) ablation targeting the SVC focus with the SVC potential promptly eliminated the focal AT in all 3 patients. The coexistent typical AFL was ablated, but the AF was not. The follow-up period was 6, 6, and 3 months, respectively, for each of the patients under no antiarrhythmic medication; there has not been a recurrence of symptomatic palpitation. In conclusion, focal electrical firing in the SVC can initiate AT and this type of focal AT is always associated with AFL or AF. RF ablation guided by the presumed SVC potential is safe and highly effective in eliminating the tachycardia.

Advances in cardiac electrophysiology and pacing

Significant advances have been made in the management of cardiac arrhythmias. New technology has enhanced the ability to understand and treat a variety of tachycardias. Excitement and caution surround ablative approaches for atrial fibrillation. The role of ICDs and class III antiarrhythmic drugs in the management of patients at risk for sudden cardiac death has been clarified. A new indication for cardiac pacing is evolving as a supplemental treatment for patients with refractory congestive heart failure. These and other advances provide numerous exciting options for management of cardiac patients.

Electrophysiologic findings of a patient with inappropriate sinus tachycardia cured by selective radiofrequency catheter ablation

Radiofrequency catheter ablation (RFCA) for inappropriate sinus tachycardia (IST) is associated with a high recurrence rate and sometimes requires pacemaker implantation, especially after extensive ablation. We report a patient with drug-refractory IST who was successfully treated by selective RFCA to the 2 earliest activation sites. During tachycardia, the earliest atrial activation preceded the surface P wave by 50 ms or more, whereas it was only 27 ms for the rest of the right atrium after ablation. Our patient had the longest activation period during tachycardia among the reported patients. In IST patients, a longer activation time at the site of the earliest atrial activation may imply that the abnormality is confined to a small area within the sinus node and may predict the efficacy of selective RFCA.

Atrial tachycardias originating from the atrial septum: electrophysiologic characteristics and radiofrequency ablation

INTRODUCTION

The characteristics of atrial tachycardia (AT) have varied widely among different reports. The anatomic locations of ATs may bias the results. We propose that septal ATs and free-wall ATs have different characteristics.

METHODS AND RESULTS

One hundred forty-one patients with AT underwent electropharmacologic study, endocardial mapping, and radiofrequency ablation. Forty-nine (34.7%) patients had septal AT originating from the anteroseptal, mid-septal, and posteroseptal areas. Tachycardia cycle length was similar between septal AT and free-wall AT (367 +/- 46 msec vs 366 +/- 58 msec, P > 0.05). More patients with septal AT required isoproterenol to facilitate induction (44.9% vs 31.5%, P <.0.05). Septal AT was more sensitive to adenosine than free-wall AT (84.4% vs 67.8%, P < 0.05). Only posteroseptal AT showed a positive P wave in lead V1 and negative P wave in all the inferior leads (II, III, aVF). Radiofrequency catheter ablation had a comparable success rate for septal AT and free-wall AT (96% vs 95%) without impairment of AV conduction. During follow-up of 49 +/- 13 months (range 17 to 85), the recurrence rate was similar for septal AT and free-wall AT (3.2% vs 4.6%, P = 0.08).

CONCLUSION

Septal AT has electrophysiologic characteristics that are distinct from those of free-wall AT. Catheter ablation of the septal AT is safe and effective.

The utility of intracardiac echocardiography in interventional electrophysiology

With the mounting of an ultrasound transducer on the end of a percutaneously placed catheter, intracardiac echocardiography is now possible. It has become clear that endocardial anatomy plays a critical role in a variety of cardiac arrhythmias. The ability to visualize this anatomy, and it's relationship to mapping and ablation catheters, may greatly enhance the safety and efficacy of catheter ablation procedures.

Focal ablation of chaotic atrial rhythm in an infant with cardiomyopathy

Chaotic atrial rhythm in infants has been defined similar to multifocal atrial tachycardia in adults, implying a multifocal etiology. However, its ECG appearance resembles atrial fibrillation, which sometimes has a unifocal ectopic mechanism amenable to catheter ablation. Curative focal radiofrequency ablation was performed in a 4-month-old infant with chaotic atrial rhythm and dilated cardiomyopathy. Left ventricular function subsequently returned to normal. Reversibility of associated cardiomyopathy supports aggressive rhythm management of chaotic atrial rhythm. In this patient, the unifocal origin allows insight into the pathophysiology of the rhythm and demonstrates the potential utility of catheter ablation for refractory cases.

Computer-assisted animation of atrial tachyarrhythmias recorded with a 64-electrode basket catheter

OBJECTIVES

The aim of this study was to assess the value of a new mapping technique based on computer-assisted animation of multielectrode basket catheter (BC) recordings in patients with atrial arrhythmias.

BACKGROUND

The three-dimensional activation patterns of cardiac arrhythmias are not completely understood owing to limitations of conventional mapping techniques.

METHODS

The study included 32 patients with atrial tachycardia (AT) and 38 patients with atrial flutter (AFL). A software program was developed to analyze the activation patterns based on 56 bipolar electrograms recorded with a 64-electrode BC deployed in the right atrium (RA).

RESULTS

The total time needed for the animation of activation patterns of atrial arrhythmias was 5 +/- 0.8 min. In 22 patients with right AT, the animated maps revealed that arrhythmia was unifocal in 15 patients, multifocal in 2 patients, polymorphic in 4 patients and reentrant in 1 patient. In 10 patients with left AT, breakthroughs on the right side of the septum (2 in 8 patients and 1 in 2 patients) and a left-to-right activation of the RA were demonstrated. In patients with typical AF, the reentrant excitation was a broad activation front with preferential propagation around the tricuspid annulus. In patients with atypical AFL, the reentry circuit involved one of the venae cavae and a line of block located in the posterior wall.

CONCLUSIONS

The computer-assisted animation of multiple electrograms recorded with a BC is a valuable mapping tool that delineates the three-dimensional activation patterns of various atrial arrhythmias. The technique is appropriate for complex, short-lived or unstable arrhythmias.

Relation between ligament of Marshall and adrenergic atrial tachyarrhythmia

BACKGROUND

The mechanism of the adrenergic atrial tachyarrhythmia is unclear. We hypothesize that the ligament of Marshall (LOM) is sensitive to adrenergic stimulation and may serve as a source of the adrenergic atrial tachyarrhythmia.

METHODS AND RESULTS

We performed computerized mapping studies in isolated-perfused canine left atrial tissues from normal dogs (n=9) and from dogs with chronic atrial fibrillation (AF) induced by 10 to 41 weeks of rapid pacing (n=3). Before isoproterenol, spontaneous activity occurred in only one normal tissue (cycle length, CL >1300 ms). During isoproterenol infusion, automatic rhythm was induced in both normal tissues (CL=578+/-172 ms) and AF tissues (CL=255+/-29 ms, P<0.05). The origin of spontaneous activity was mapped to the LOM. In the AF tissues, but not the normal tissues, we observed the transition from rapid automatic activity to multiple wavelet AF. Ablation of the LOM terminated the spontaneous activity and prevented AF. Immunocytochemical studies of the LOM revealed muscle tracts surrounded by tyrosine hydroxylase-positive (sympathetic) nerves.

CONCLUSIONS

We conclude that the LOM is richly innervated by sympathetic nerves and serves as a source of isoproterenol-sensitive focal automatic activity in normal canine atrium. The sensitivity to isoproterenol is upregulated after long-term rapid pacing and may contribute to the development of AF in this model.

Atrial Tachycardia

The available therapies for atrial tachycardia include the use of antiarrhythmic drugs, radiofrequency catheter ablation, and antiarrhythmic surgery. The growing realization that catheter ablation cures atrial tachycardia with high efficacy and safety has contributed to the increasing popularity of the procedure and makes it the therapy of choice in symptomatic patients. Antiarrhythmic drugs are thought to be effective acutely in 40% to 60% of patients, but their long-term efficacy remains poorly defined. Infrequently, atrioventricular nodal catheter ablation combined with pacing may be needed in patients whose arrhythmias are refractory to antiarrhythmic drugs and curative radiofrequency ablation. Antiarrhythmic surgery has a limited role as a therapy of last resort.

Clinical experience with a novel multielectrode basket catheter in right atrial tachycardias

BACKGROUND

The complexity of atrial tachycardias (ATs) makes the electroanatomic characterization of the arrhythmogenic substrate difficult with conventional mapping techniques. The aim of our study was to evaluate possible advantages of a novel multielectrode basket catheter (MBC) in patients with AT.

METHODS AND RESULTS

In 31 patients with AT, an MBC composed of 64 electrodes was deployed in the right atrium (RA). The possibility of deployment, spatial relations between MBC and RA, MBC recording and pacing capabilities, mapping performance, and MBC-guided ablation were assessed. MBC deployment was possible in all 31 patients. The MBC was left in the RA for 175+/-44 minutes. Stable bipolar electrograms were recorded in 88+/-4% of electrodes. Pacing from bipoles was possible in 64+/-5% of electrode pairs. The earliest activity intervals, in relation to P-wave onset, measured from the MBC and standard roving catheters were 41+/-9 and 46+/-6 ms, respectively (P=0.21). Radiofrequency ablation was successful in 15 (94%) of 16 patients in whom it was attempted, including 2 patients with polymorphic right atrial tachycardia (RAT), 2 with RAT-atrial flutter combination, 1 with macroreentrant AT, and 1 with focal origin of atrial fibrillation.

CONCLUSIONS

These data demonstrate that MBC can be used safely in patients with right atrial arrhythmias. The simultaneous multielectrode mapping aids in the rapid identification of sites of origin of the AT and facilitates radiofrequency ablation procedures. The technique is especially effective for complex atrial arrhythmias.

Narrowing of the superior vena cava-right atrium junction during radiofrequency catheter ablation for inappropriate sinus tachycardia: analysis with intracardiac echocardiography

OBJECTIVES

The study explored the potential for tissue swelling and venous occlusion during radiofrequency (RF) catheter ablation procedures using intracardiac echocardiography (ICE).

BACKGROUND

Transient superior vena cava occlusion has been reported following catheter ablation procedures for inappropriate sinus tachycardia (IST). Presumably, venous occlusion could occur owing to thrombus formation or tissue swelling with resultant narrowing of the superior vena cava-right atrial (SVC-RA) junction.

METHODS

Intracardiac echocardiography (9 MHz) was used to guide ablation catheter position and for continuous monitoring during RF application in 13 ablation procedures in 10 patients with IST. The SVC-RA junction was measured prior to and following ablation. Successful ablation was marked by abrupt reduction in the sinus rate and a change to a superiorly directed p-wave axis.

RESULTS

Eleven of 13 procedures were successful, requiring 29 +/- 20 RF lesions. Prior to the delivery of RF lesions, the SVC-RA junction measured 16.4 +/- 2.9 mm. With RF delivery, local and circumferential swelling was observed, causing progressive reduction in the diameter of the SVC-RA junction to 12.6 +/- 3.3 mm (24% reduction, p = 0.0001). A reduction in SVC-RA orifice diameter of > or = 30% compared to baseline was observed in five patients.

CONCLUSIONS

The delivery of multiple RF ablation lesions, often necessary for cure of IST, can cause considerable atrial swelling and resultant narrowing of the SVC-RA junction. Smaller venous structures, such as the coronary sinus and the pulmonary veins, would also be expected to be vulnerable to this complication. Thus, ICE imaging may be helpful in preventing excessive tissue swelling leading to venous occlusion during catheter ablation procedures.

Differential effects of adenosine on focal and macroreentrant atrial tachycardia

INTRODUCTION

The effects of adenosine on atrial tachycardia (AT) remain controversial, and the mechanistic implications of adenosine termination have not been fully established. The purpose of this study was to elucidate the differential effects of adenosine on focal and macroreentrant AT and describe the characteristics of adenosine-sensitive AT.

METHODS AND RESULTS

Thirty patients received adenosine during AT. Tachycardia origins were identified as focal or macroreentrant during invasive electrophysiologic studies. Responses to adenosine were analyzed and characterized as tachycardia termination, transient suppression, or no effect. Electrophysiologic studies demonstrated a focal origin of tachycardia in 17 patients. Adenosine terminated focal tachycardias in 14 patients (dose 7.3 +/- 4.0 mg) and transiently suppressed the arrhythmias in three others (dose 10.0 +/- 6.9 mg). A macroreentrant mechanism was demonstrated in 13 patients; adenosine terminated only one of these tachycardias and had no effect on the remaining 12 patients (dose 10.2 +/- 2.9 mg). Four classes of adenosine-sensitive AT were identified. Class I consisted of nine patients with tachycardia arising from the crista terminalis; these tachycardias also terminated with verapamil (4/4). Class II consisted of four patients with repetitive monomorphic AT arising from diverse sites in the right atrium; these either slowed or terminated in response to verapamil (2/2). Class III consisted of the three patients with transient suppression and demonstrated electropharmacologic characteristics consistent with an automatic mechanism, including insensitivity to verapamil (2/2). In the one patient with macroreentrant AT that was comprised of decremental atrial tissue, adenosine terminated tachycardia in a zone of decremental slow conduction (Class IV); this tachycardia slowed with verapamil.

CONCLUSIONS

Adenosine-sensitive AT is usually focal in origin and arises either from the region of the crista terminalis (inclusive of the sinus node) or from diverse atrial sites with an incessant nonsustained repetitive pattern. Although most forms of macroreentrant AT are insensitive to adenosine, rarely macroreentrant AT with zones of decremental slow conduction can demonstrate adenosine sensitivity.

Development of the cardiac conduction tissue in human embryos using HNK-1 antigen expression: possible relevance for understanding of abnormal atrial automaticity

BACKGROUND

Abnormal atrial automaticity in young patients with structurally normal hearts is often located around the pulmonary veins and in sinus venosus-related parts of the right atrium. We hypothesize that these ectopic pacemaker sites correspond to areas of embryonic myocardium with an early phenotypic differentiation, as indicated by differences in antigen expression during normal cardiac development.

METHODS AND RESULTS

In human embryos ranging in age from 42 to 54 days of gestation, the development of the cardiac conduction system was studied with the use of HNK-1 immunohistochemistry. HNK-1 stains the developing atrioventricular conduction system, ie, the bundle branches, His bundle, right atrioventricular ring, and retroaortic ring. In addition, the myocardium around the common pulmonary vein showed transient HNK-1 antigen expression. In the right atrium, 3 HNK-1-positive connections were demonstrated between the sinoatrial node and the right atrioventricular ring. An anterior tract through the septum spurium connects the sinoatrial node with the anterior right atrioventricular ring, and 2 posterior tracts connect the sinoatrial node with the posterior right atrioventricular ring through the right venous valve (future crista terminalis) and sinus septum, encircling the coronary sinus. The medioposterior part of the right atrioventricular ring connected to the His bundle and the medioanterior part form 2 node-like structures.

CONCLUSIONS

In patients with abnormal atrial automaticity, the distribution of left and right atrial pacemaker foci correspond to areas of the embryonic myocardium that temporarily express the HNK-1 antigen.

Electroanatomic imaging using magnetic catheter tracking in the diagnosis and treatment of atrial arrhythmias

Recent data emphasize the importance of structural factors in the pathophysiology of atrial arrhythmias. As a consequence, catheter ablation increasingly has become an anatomically oriented procedure. A recently developed magnetic catheter tracking system provides spatially precise and realistic three-dimensional reconstructions of endocardial geometry. A variety of electrophysiologic data can be superimposed on these reconstructions, including activation sequence, electrogram amplitude and morphologic features, response to pacing maneuvers, and sites of planned or delivered radiofrequency energy ablation. These features enhance the ability to analyze and visualize arrhythmia mechanisms, plan and execute appropriate ablation strategies, and provide new opportunities for physiologic research.

Ablation of right and left ectopic atrial tachycardias using a three-dimensional nonfluoroscopic mapping system

We report our experience with mapping and ablation of right and left atrial tachycardia using a 3-dimensional nonfluoroscopic mapping system. Twenty-nine ectopic atrial tachycardias were successfully ablated. This novel mapping system has the potential to increase a successful cure of this arrhythmia by catheter ablation.