Clinical and electrophysiologic characteristics of left septal atrial tachycardia

A novel endocardial activation-derived predictor for focal paraseptal atrial tachycardias: Evidence from a multicenter cohort study

BACKGROUND

The electrocardiogram-based algorithm for predicting paraseptal atrial tachycardia (PSAT) is limited by the significant overlaps in P-wave morphology originating from various paraseptal sites.

OBJECTIVES

The goals of this study were to investigate the endocardial activation characteristics of PSAT and to seek an endocardial activation-derived predictor for the ablation site.

METHODS

Forty-four patients [11 men (25%); mean age 62.6 ± 14.7 years] with PSAT ablation in 4 tertiary medical centers were assigned to 3 groups according to the ablation site: right atrial (RA) para-Hisian region (group 1, n = 10), noncoronary cusp (NCC) (group 2, n = 13), and left atrial (LA) paraseptal area (group 3, n = 21). Multiple-chamber activation mapping was performed guided by a 3-dimensional navigation system. The discrepancies in the earliest activation time between 2 of 3 chambers (ΔRA-LA, ΔRA-NCC, and ΔLA-NCC) were calculated in each group and used for pairwise comparisons.

RESULTS

There was a significant difference in ΔRA-LA, ΔRA-NCC, and ΔLA-NCC among the 3 groups. ΔRA-LA was the only parameter that could consistently predict the ablation site of PSAT with good accuracy (area under the curve 1.000, sensitivity 100% and specificity 100%, and cutoff value 7 ms for predicting right para-Hisian or NCC ablation; area under the curve 0.974, sensitivity 92.3% and specificity 95.2%, and cutoff value -4 ms for predicting NCC or left paraseptal ablation). Based on 2 cutoff values, a 2-step algorithm was developed to predict the ablation site of PSAT with a positive predictive value of 95.4% and a negative predictive value of 97.0%.

CONCLUSION

ΔRA-LA is a useful endocardial activation-derived parameter for predicting the successful ablation site of PSAT.

Focal Atrial Tachycardia Arising From the Posterior Wall of the Left Atrium

Potential foci for atrial tachycardia have been previously described in various locations including crista terminalis, tricuspid annulus, coronary sinus ostium, pulmonary vein ostia. In this report, we present a case of a focal atrial tachycardia arising from the posterior wall of the left atrium which has not been described before. (Level of Difficulty: Advanced.)

P-Wave Morphology in Focal Atrial Tachycardia: An Updated Algorithm to Predict Site of Origin

OBJECTIVES

This study sought to report P-wave morphology (PWM) from a series of paraseptal (PS) atrial tachycardia (AT), revise then prospectively evaluate a simplified PWM algorithm against a contemporary consecutive cohort with focal AT.

BACKGROUND

The 2006 PWM algorithm was useful in predicting the origin of focal AT. An updated algorithm was developed given advances in multipolar 3-dimensional mapping, potential limitations of PWM in separating PS sites, and a renewed interest in the P-wave in mapping non-pulmonary vein triggers.

METHODS

The PWM from a consecutive series of 67 patients with PS AT were analyzed. PS sites included were coronary sinus ostium, perinodal, left and right septum, septal tricuspid annulus, superior mitral annulus, and noncoronary cusp. Next the P-wave algorithm was revised and prospectively evaluated by 3 blinded assessors.

RESULTS

The P-wave for PS sites was neg/pos (n = 50), iso/pos (n = 10), or isoelectric (n = 4) in lead V₁ (96%). The P-wave algorithm was modified and prospectively applied to 30 consecutive patients with focal AT who underwent successful ablation. Foci (n = 30) originated from the right atrium (33.3%), left atrium (30%), and PS (36.7%). Using the PW algorithm, the correct anatomic location was identified in 93%. Incorrect interpretation of the terminal positive P-wave component (n = 3) and initial negative P-wave deflection (n = 1) in lead V₁ misidentified 4 paraseptal cases.

CONCLUSIONS

The revised PWM algorithm offers a simplified and accurate method of localizing the responsible site for focal AT. The P-wave remains an important first step in mapping atrial arrhythmias.

Cellular and Molecular Mechanisms of Functional Hierarchy of Pacemaker Clusters in the Sinoatrial Node: New Insights into Sick Sinus Syndrome

The sinoatrial node (SAN), the primary pacemaker of the heart, consists of a heterogeneous population of specialized cardiac myocytes that can spontaneously produce action potentials, generating the rhythm of the heart and coordinating heart contractions. Spontaneous beating can be observed from very early embryonic stage and under a series of genetic programing, the complex heterogeneous SAN cells are formed with specific biomarker proteins and generate robust automaticity. The SAN is capable to adjust its pacemaking rate in response to environmental and autonomic changes to regulate the heart's performance and maintain physiological needs of the body. Importantly, the origin of the action potential in the SAN is not static, but rather dynamically changes according to the prevailing conditions. Changes in the heart rate are associated with a shift of the leading pacemaker location within the SAN and accompanied by alterations in P wave morphology and PQ interval on ECG. Pacemaker shift occurs in response to different interventions: neurohormonal modulation, cardiac glycosides, pharmacological agents, mechanical stretch, a change in temperature, and a change in extracellular electrolyte concentrations. It was linked with the presence of distinct anatomically and functionally defined intranodal pacemaker clusters that are responsible for the generation of the heart rhythm at different rates. Recent studies indicate that on the cellular level, different pacemaker clusters rely on a complex interplay between the calcium (referred to local subsarcolemmal Ca²⁺ releases generated by the sarcoplasmic reticulum via ryanodine receptors) and voltage (referred to sarcolemmal electrogenic proteins) components of so-called "coupled clock pacemaker system" that is used to describe a complex mechanism of SAN pacemaking. In this review, we examine the structural, functional, and molecular evidence for hierarchical pacemaker clustering within the SAN. We also demonstrate the unique molecular signatures of intranodal pacemaker clusters, highlighting their importance for physiological rhythm regulation as well as their role in the development of SAN dysfunction, also known as sick sinus syndrome.

Catheter Ablation of Paroxysmal Atrial Fibrillation Originating from Non-pulmonary Vein Areas

Pulmonary veins (PVs) are a major source of ectopic beats that initiate AF. PV isolation from the left atrium is an effective therapy for the majority of paroxysmal AF. However, investigators have reported that ectopy originating from non-PV areas can also initiate AF. Patients with recurrent AF after persistent PV isolation highlight the need to identify non-PV ectopy. Furthermore, adding non-PV ablation after multiple AF ablation procedures leads to lower AF recurrence and a higher AF cure rate. These findings suggest that non-PV ectopy is important in both the initiation and recurrence of AF. This article summarises current knowledge about the electrophysiological characteristics of non-PV AF, suitable mapping and ablation strategies, and the safety and efficacy of catheter ablation of AF initiated by ectopic foci originating from non-PV areas.

Atrial tachycardias arising from the atrial appendages and aortic sinus of valsalva

Focal atrial tachycardias arising from the atrial appendages and the aortic sinuses of Valsalva are less frequently encountered in clinical practice. This review article describes the clinical presentation, surface P wave morphology, electrophysiologic characteristics and treatment of these arrhythmias. Catheter ablation of these focal tachycardias has a high success rate. It is however important to be aware of specific anatomic considerations in these locations for optimal treatment outcomes with low complication rates.

Mapping strategies in focal atrial tachycardias demonstrating early septal activation: distinguishing left from right

Determining the chamber of origin of focal atrial tachycardias (FATs) arising at or close to the septum might require biatrial mapping. This review focuses on the available tools and methods used to distinguish right atrial from left atrial origin before left atrial access is obtained. These include analysis of P wave morphology, assessing the timing of right atrial septal activation, the sequence of right atrial and/or biatrial activation and analysis of earliest electrogram morphology. The electroanatomical properties of the interatrial septum and coronary sinus that provide the basis for the above mentioned tools have also been briefly described.

Electrocardiographic diagnosis of atrial tachycardia: classification, P-wave morphology, and differential diagnosis with other supraventricular tachycardias

Atrial tachycardia is defined as a regular atrial activation from atrial areas with centrifugal spread, caused by enhanced automaticity, triggered activity or microreentry. New ECG classification differentiates between focal and macroreentrant atrial tachycardia. Macroreentrant atrial tachycardias include typical atrial flutter and other well characterized macroreentrant circuits in right and left atrium. Typical atrial flutter has been described as counterclockwise reentry within right atrial and it presents a characteristic ECG "sawtooth" pattern on the inferior leads. The foci responsible for focal atrial tachycardia do not occur randomly throughout the atria but tend to cluster at characteristic anatomical locations. The surface ECG is a very helpful tool in directing mapping to particular areas of interest. Atrial tachycardia should be differentiated from other supraventricular tachycardias. We propose a diagnostic algorithm in order to help the physician to discriminate among those. Holter analysis could offer further details to differentiate between atrial tachycardia and another supraventricular tachycardia. However, if the diagnosis is uncertain, it is possible to utilize vagal maneuvers or adenosine administration. In conclusion, in spite of well-known limits, a good interpretation of ECG is very important and it could help the physician to manage and to treat correctly patients with atrial tachycardia.

Evidence of specialized tissue in human interatrial septum: histological, immunohistochemical and ultrastructural findings

Background

There is a paucity of information on structural organization of muscular bundles in the interatrial septum (IAS). The aim was to investigate histologic and ultrastructural organization of muscular bundles in human IAS, including fossa ovalis (FO) and flap valve.

Methods

Macroscopic and light microscopy evaluations of IAS were performed from postmortem studies of 40 patients. Twenty three IAS specimens underwent serial transverse sectioning, and 17 - longitudinal sectioning. The transverse sections from 10 patients were immunolabeled for HCN4, Caveolin3 and Connexin43. IAS specimens from 6 other patients underwent electron microscopy.

Results

In all IAS specimens sections the FO, its rims and the flap valve had muscle fibers consisting of working cardiac myocytes. Besides the typical cardiomyocytes there were unusual cells: tortuous and horseshoe-shaped intertangled myocytes, small and large rounded myocytes with pale cytoplasm. The cells were aggregated in a definite structure in 38 (95%) cases, which was surrounded by fibro-fatty tissue. The height of the structure on transverse sections positively correlated with age (P = 0.03) and AF history (P = 0.045). Immunohistochemistry showed positive staining of the cells for HCN4 and Caveolin3. Electron microscopy identified cells with characteristics similar to electrical conduction cells.

Conclusions

Specialized conduction cells in human IAS have been identified, specifically in the FO and its flap valve. The cells are aggregated in a structure, which is surrounded by fibrous and fatty tissue. Further investigations are warranted to explore electrophysiological characteristics of this structure.

Atrial tachycardia originating from the aortomitral junction

Atrial tachycardia (AT) originating from the aortomitral junction is a very rare and challenging disease. Its arrhythmic characteristics have not been described in detail compared with the descriptions of the arrhythmic characteristics of AT originating from the other locations. Only a few case reports have documented successful ablation of this type of AT using transaortic or transseptal approaches. We describe a case with AT that was resistant to right-sided ablation near the His bundle failed and transaortic ablation at the aortomitral junction successfully eliminated.

Left septal atrial tachycardias: electrocardiographic and electrophysiologic characterization of a paraseptal focus

OBJECTIVE

The objective was to characterize the electrocardiographic and electrophysiological features of focal atrial tachycardia (FAT) originating from the left septum (LS).

BACKGROUND

FAT is recognized to occur at predefined anatomic locations rather than randomly throughout the atria. We describe the ECG and EP features of ATs originating from the LS as an important site for apparent perinodal tachycardias.

METHODS

Nine patients presenting with LS FAT from a consecutive series of 384 underwent EP/RFA for symptomatic FAT.

RESULTS

The mean age was 56 ± 12 years; 7 female with symptoms for 36 ± 28 months. P wave morphology (PWM) was negative/positive in lead V1 and across the precordial leads and negative or negative/positive in inferior leads in all patients. Tachycardia was incessant in 6 out of 9 patients with a mean tachycardia cycle length 421 ± 56 milliseconds. His A was ahead of P wave in all patients (mean -15 ± 5 milliseconds) and earlier than CS proximal (mean 4 ± 9 milliseconds). Successful acute focal ablation achieved at a mean of 31 ± 12 milliseconds ahead of P wave with no recurrences at a mean follow-up of 30 ± 28 months.

CONCLUSION

Although the left septum is an uncommon site for focal AT an awareness of this location for harboring foci is particularly important when mapping apparently right-sided septal tachycardias.

Magnetic resonance imaging-confirmed ablative debulking of the left atrial posterior wall and septum for treatment of persistent atrial fibrillation: rationale and initial experience

INTRODUCTION

Though pulmonary vein (PV) isolation has been widely adopted for treatment of atrial fibrillation (AF), recurrence rates remain unacceptably high with persistent and longstanding AF. As evidence emerges for non-PV substrate changes in the pathogenesis of AF, more extensive ablation strategies need further study.

METHODS

We modified our PV antrum isolation procedure to include abatement of posterior and septal wall potentials. We also employed recently described image-processing techniques using delayed-enhancement (DE) MRI to characterize tissue injury patterns 3 months after ablation, to assess whether each PV was encircled with scar, and to assess the impact of these parameters on procedural success.

RESULTS

118 consecutive patients underwent debulking procedure and completed follow-up, of which 86 underwent DE-MRI. The total left atrial (LA) radiofrequency delivery correlated with percent LA scarring by DE-MRI (r = 0.6, P < 0.001). Based on DE patterns, complete encirclement was seen in only 131 of 335 PVs (39.1%). As expected, Cox regression analysis showed a significant relationship between the number of veins encircled by delayed enhancement and clinical success (hazard ratio of 0.62, P = 0.015). Also, progressive quartile increases in postablation posterior and septal wall scarring reduced recurrences rates with a HR of 0.65, P = 0.022 and 0.66, P = 0.026, respectively.

CONCLUSION

Pathologic remodeling in the septal and posterior walls of the LA helps form the pathogenic substrate for AF, and these early results suggest that more aggressive treatment of these regions appears to correlate with improved ablation outcomes. Noninvasive imaging to characterize tissue changes after ablation may prove essential to stratifying recurrence risk.

Focal atrial tachycardia arising from the right atrial appendage: electrophysiologic and electrocardiographic characteristics and catheter ablation

BACKGROUND

Focal atrial tachycardia (AT) arising from the crista terminalis, pulmonary veins, para-Hisian region, tricuspid annulus and coronary sinus ostium regions are well described. Less information exists regarding AT arising from the right atrial appendage (RAA).

OBJECTIVE

The study was done to characterise the electrocardiographic and electrophysiologic features and radiofrequency ablation (RFA) of focal AT arising from the RAA.

METHODS

Six patients of a consecutive series of 250 patients undergoing RFA for focal AT are reported. Mapping was performed during tachycardia or frequent atrial ectopy to identify the earliest activation in the atria. Atrial appendage angiography was performed to identify the origin in the RAA after RFA.

RESULTS

All the six (2.4%) patients (four women; mean age 26 +/- 11 years) had tachycardia originating from RAA. The tachycardia demonstrated a characteristic P-wave morphology and endocardial activation pattern. P-wave morphology was upright in I, II, III and aVF, inverted in aVR, inverted or isoelectric in aVL. Lead V1 showed a negative component and lead V4-V6 showed an upright component in all the patients. The earliest endocardial activity occurred at the high right atria in all the patients. The earliest endocardial activation at the successful RFA site occurred 48 +/- 18 ms before the onset of the P wave. RFA was highly successful in all the six patients. Long-term success was achieved in six of the six patients over a mean follow-up of 24 +/- 5 months.

CONCLUSIONS

The RAA is an uncommon site of origin for focal AT 2.4%. There is consistent P-wave morphology and endocardial activation associated with this type of AT. Using mapping targeted to anatomic structures achieved a high success rate for ablation. Irrigated-tip catheter may be helpful for patients who had a recurrence.

Focal Atrial Tachycardia Originating from the Left Atrial Appendage: Electrocardiographic and Electrophysiologic Characterization and Long-Term Outcomes of Radiofrequency Ablation

INTRODUCTION

This study sought to investigate electrophysiologic characteristics and radiofrequency ablation (RFA) in patients with focal atrial tachycardia (AT) arising from the left atrial appendage (LAA).

METHODS

This study included seven patients undergoing RFA with focal AT. Activation mapping was performed during tachycardia to identify an earlier activation in the left atria and the LAA. The atrial appendage angiography was performed to identify the origin in the LAA before and after RFA.

RESULTS

AT occurred spontaneously or was induced by isoproterenol infusion rather than programmed extrastimulation and burst atrial pacing in any patient. The tachycardia demonstrated a characteristic P-wave morphology and endocardial activation pattern. The P wave was highly positive in inferior leads in all patients. Lead V1 showed upright or biphasic (+/-) component in all patients. Lead V2-V6 showed an isoelectric component in five patients or an upright component with low amplitude (<0.1 mV) in two patients. Earliest endocardial activity occurred at the distal coronary sinus (CS) ahead of P wave in all seven patients. Mean tachycardia cycle length was 381 +/- 34 msec and the earliest endocardial activation at the successful RFA site occurred 42.3 +/- 9.6 msec before the onset of P wave. RFA was acutely successful in all seven patients. Long-term success was achieved in seven of the seven over a mean follow-up of 24 +/- 5 months.

CONCLUSIONS

The LAA is an uncommon site of origin for focal AT (3%). There were consistent P-wave morphology and endocardial activation associated with this type of AT. The LAA focal ablation is safe and effective. Long-term success was achieved with focal ablation in all patients.

Successful catheter ablation of focal left atrial tachycardia originating from the mitral annulus aorta junction

Focal left atrial tachycardias (AT) originating from the mitral annulus-aorta (MA-Ao) junction are rare and their mechanisms are unclear. We report a 35-year-old male with successful ablation of an exercise-induced focal AT due to triggered activity originating from the MA-Ao junction. The AT occurred spontaneously during treadmill exercise testing and was easily induced by an atrial extrastimulus and atrial burst pacing after intravenous administration of isoproterenol. The AT was terminated by an atrial extrastimulus as well as a bolus of 5 mg of adenosine 5'-triphosphate. The coupling intervals of the extrastimuli that induced the AT were positively correlated with the interval between the extrastimuli and the first beat of the AT, suggesting the triggered activity as a tachycardia mechanism. The AT was successfully eliminated by a focal ablation at the MA-Ao junction with the earliest atrial activation where fractionated atrial potentials were recorded. The MA-Ao junction should be recognized as an important arrhythmogenic region.

The 12-lead electrocardiogram in supraventricular tachycardia

The 12-lead electrocardiogram (ECG) is an invaluable tool for the diagnosis of supraventricular tachycardia (SVT). Most forms of SVT can be distinguished with a high degree of certainty based on specific ECG characteristics by using a systematic, stepwise approach. This article provides a general framework with which to approach an ECG during SVT by describing the salient characteristics, ECG findings, and underlying electroanatomical relationships of each specific type of SVT encountered in adults. It concludes by providing a systematic algorithm for diagnosing SVT based on the findings of the 12-lead ECG.

P-wave morphology in focal atrial tachycardia: development of an algorithm to predict the anatomic site of origin

OBJECTIVES

The purpose of this study was to perform a detailed analysis of the P-wave morphology (PWM) in focal atrial tachycardia (AT) and construct and prospectively evaluate an algorithm for identification of the anatomic site of origin.

BACKGROUND

Although smaller studies have described the PWM from particular anatomic locations, a detailed algorithm characterizing the likely location of a tachycardia associated with a P-wave of unknown origin has been lacking.

METHODS

The PWMs for 126 consecutive patients undergoing successful radiofrequency ablation of 130 ATs are reported. P waves were included only when the onset was preceded by a discernible isoelectric segment. P waves were classified as positive (+), negative (-), isoelectric, or biphasic. Sensitivity, specificity, and predictive values were calculated. On the basis of these results, an algorithm was constructed and prospectively evaluated in 30 new consecutive ATs.

RESULTS

The distribution of ATs was right atrial (RA) in 82 of 130 (63%) and left atrial (LA) in 48 of 130 (37%). Right atrial sites included crista (n = 28), tricuspid annulus (n = 29), coronary sinus (CS) ostium (n = 14), perinodal (n = 7), right septum (n = 1), and RA appendage (n= 3). Left atrial sites included pulmonary veins (n = 32), mitral annulus (n = 8), CS body (n= 3), left septum (n = 3), and LA appendage (n = 2). In electrocardiographic lead V1, a negative or +/- P-wave demonstrated a specificity of 100% for a RA focus, and a + or -/+ P-wave demonstrated a sensitivity of 100% for a LA focus. A characteristic PWM was associated with high sensitivity and specificity at common atrial sites for tachycardia foci. A P-wave algorithm correctly identified the focus in 93%.

CONCLUSIONS

Characteristic PWMs corresponding to known anatomic sites for focal AT are associated with high specificity and sensitivity. A P-wave algorithm correctly identified the site of tachycardia origin in 93%.

Atrial Tachycardia Originating from the Upper Left Atrial Septum: Demonstration of Transseptal Interatrial Conduction Using the Infolded Atrial Walls

We report a rare case of atrial tachycardia (AT) originating from the upper left atrial septum. Electroanatomic mapping of both atria demonstrated that the earliest atrial activation during AT occurred at the upper left atrial septum 26 msec before the onset of the P wave, followed by the mid-right atrial septum (10 msec before the onset of the P wave) and then the upper right atrial septum just adjacent to the left septal AT site (1 msec before the onset of the P wave), indicating detour pathway conduction from the upper left to the upper right atrium. Embryologically, it was suggested that the superior components of the secondary atrial septum are made by the infolded atrial walls and could develop a transseptal detour pathway involving the left-side atrial septal musculature, the superior rim of the oval fossa and the right-side atrial septal musculature. A single radiofrequency application targeting the upper left atrial septum successfully abolished the AT.

Focal Atrial Tachycardia II: Management

Over the last decade there have been significant changes in the treatment of focal atrial tachycardia (AT). This review concentrates on the different approaches to the treatment of focal AT. Initial therapies included antiarrhythmic medications and surgery. However, with the advent of radiofrequency ablation, and the poor efficacy of pharmacological therapy, there has been a shift toward a primary ablative approach. Several different mapping techniques have been proposed. The different techniques, including P-wave morphology and advanced three-dimensional mapping, are discussed in this review.

Focal Atrial Tachycardia I: Clinical Features, Diagnosis, Mechanisms, and Anatomic Location

Atrial tachycardia (AT) may be focal or macroreentrant. In this review we will concentrate on focal AT. The diagnosis of focal AT may be made from a standard electrocardiogram (ECG); however, in some cases differentiation from other forms of supraventricular tachycardia may be difficult. Focal AT may be due to several different mechanisms, including abnormal automaticity, triggered activity, and microreentry. Focal AT does not occur randomly throughout the atria but has a characteristic anatomic distribution. In this review, we particularly focus on the clinical features, diagnosis, mechanisms, and anatomic location of focal AT.

Characterization of Focal Atrial Tachycardia Using High-Density Mapping

OBJECTIVES

The goal of this study was to characterize the origin of focal atrial tachycardias (AT).

BACKGROUND

Focal ATs originate from a small area and spread centrifugally; however, activation at the AT origin has not been characterized.

METHODS

Twenty patients with AT having failed prior ablation or occurring after atrial fibrillation ablation were studied. After excluding macro-re-entry, AT was mapped using a 20-pole catheter (five radiating spines; diameter 3.5 cm), performing vector mapping to identify the earliest activity followed by high-density mapping at the AT origin. Localized re-entry was considered if >85% of the tachycardia cycle length (CL) was observed within the mapping field and was confirmed by entrainment.

RESULTS

A total of 27 ATs were mapped to the pulmonary vein ostia (n = 5), and left (n = 16) and right atria (n = 6). A localized focus was evidenced at the site of origin in 19 ATs (70%), whereas in 8 (30%), localized re-entry was evidenced by 95.2 +/- 4.5% of the tachycardia CL recorded within the mapping field and entrainment showed a post-pacing interval <20 ms longer than tachycardia CL (6 of 6 tested). Localized re-entry had a shorter CL (p = 0.009), slowed conduction at its origin (fractionated potential 115 +/- 19 ms vs. 64 +/- 22 ms, representing 49 +/- 10% and 20 +/- 10% of tachycardia CL, respectively; p < 0.0001), and were more often contiguous with regions of electrical silence or conduction abnormalities (88% vs. 32%; p = 0.01). In addition, mapping documented varying degrees of intra-atrial conduction block, preferential conduction (n = 5), and rapid bursts of myocardial activity (n = 1). At 11 +/- 7 months, none have had recurrence of AT.

CONCLUSIONS

High-density multielectrode mapping can be used to perform vector mapping to localize complex AT. It provides novel insight into the mechanisms of focal AT, distinguishing focal AT from localized re-entry.

Electrophysiologic characteristics of verapamil-sensitive atrial tachycardia originating from the atrioventricular annulus

We examined the electrophysiologic characteristics and mechanisms of verapamil-sensitive atrial tachycardia (AT) originating from the atrioventricular (AV) annulus in 18 patients. AT originated from the AV node vicinity (AV nodal AT, 10 patients) and the area distant from the AV node (non-AV nodal AT, 8 patients). There was no significant difference in the tachycardia cycle length between AV nodal and non-AV nodal AT. For both types of AT, tachycardia was inducible by atrial extrastimulation with an inverse relation between the coupling and the postpacing intervals. A single extrastimulus delivered from the earliest atrial activation site reset both ATs with an inverse relation between the coupling interval and return cycle. Also no significant difference was observed in the percentage of the excitable gap to tachycardia cycle length between AV nodal and non-AV nodal AT. Concealed entrainment was observed by rapid atrial pacing delivered from the earliest atrial activation site for both ATs. These findings suggest that these ATs are due to reentry. Intravenous administration of verapamil (2.5 to 5 mg) and adenosine triphosphate (5 mg) terminated AT in all patients. AT was successfully ablated at the earliest atrial activation site in all patients. It was shown that this form of AT in which a calcium channel-dependent substrate is involved arises not only from the vicinity of the AV node but also along the AV annulus with common electrophysiologic characteristics. These suggest the presence of a distinct entity of tachycardia more appropriately classified as verapamil-sensitive AV annular AT.

Focal Atrial Tachycardia From the Ostium of the Coronary Sinus

OBJECTIVES

The goal of this study was to characterize the electrocardiographic and electrophysiologic features and frequency of focal atrial tachycardia (AT) originating from the coronary sinus ostium (CS).

BACKGROUND

The ostium of the coronary sinus has been described as a site of origin of AT, but detailed characterization of these tachycardias is limited.

METHODS

Thirteen patients (6.7%) of 193 undergoing radiofrequency ablation (RFA) for focal AT are reported. Endocardial activation maps (EAM) were recorded from catheters at the CS (10 pole), crista terminalis (20 pole), and His positions. The P waves were classified negative, positive, isoelectric, or biphasic.

RESULTS

The mean age was 41 +/- 6 years, seven female patients, with symptoms for 8 +/- 3 years. Tachycardia was induced by programmed extra-stimuli in eight patients, was spontaneous in three patients, and in response to isoproterenol in two patients. These foci had a characteristic P-wave morphology. At the CS ostium, the P-wave was deeply negative in all inferior leads, negative or isoelectric becoming positive in lead V(1), then progressively negative across the precordium. Lead aVL was positive in all patients. Earliest EAM activity occurred at the proximal CS at 20 +/- 3 ms ahead of P-wave. Mean activation time at the successful RFA site = -36 +/- 8 ms; RFA was acutely successful in 11 of 13 patients. Long-term success was achieved in 11 of 11 over a median follow-up of 25 +/- 4 months.

CONCLUSIONS

The CS ostium is an uncommon site of origin for focal AT (6.7%). It can be suspected as a potential anatomic site of AT origin from the characteristic P-wave and activation timing. Long-term success was achieved with focal ablation in the majority of patients.

Left Atrial Tachycardia Originating From the Mitral Annulus–Aorta Junction

Background— At the mitral annulus–aorta (MA-Ao) junction, the left atrium is continuous through the subaortic curtain with the musculature of the anterior mitral leaflet. Under experimental conditions, this region can generate abnormal electrical activity. In patients with left atrial tachycardia, we investigated whether this region could be the source of this arrhythmia.

Methods and Results— In 10 (28%) of 35 consecutive patients with left atrial tachycardia, the arrhythmia originated from the MA-Ao junction. Sustained, self-limited episodes of atrial tachycardia (cycle length, 340±56 ms; duration, 125±69 seconds) were repeatedly induced. Prematurity of the extrastimulus and time to first atrial tachycardia complex were directly correlated ( R =0.66; P <0.001). During tachycardia, bipolar electrograms at the earliest site preceded onset of the P wave by 44±14 ms and were of longer duration and lower amplitude than those recorded from nearby left atrial sites (52±8 versus 24±4 ms, P <0.001; and 0.53±0.08 versus 3.45±0.96 mV, respectively; P <0.001). Ablation eliminated the tachycardia with no recurrence after a mean follow-up of 24±19 months. A comparative study in mouse embryos demonstrated the presence of the developing specialized conduction system in the MA-Ao region starting at embryonic age 11.5.

Conclusions— The MA-Ao junction can be a frequent source of left atrial tachycardia. This previously unrecognized site of origin may explain why catheter ablation has been less successful in eliminating left versus right atrial tachycardias. Remnants of the developing specialized conduction system could be the underlying substrate of this arrhythmia.

Focal atrial tachycardia arising from the mitral annulus: electrocardiographic and electrophysiologic characterization

OBJECTIVES

The study was done to characterize the electrocardiographic and electrophysiologic features of focal atrial tachycardia originating at the mitral annulus (MA).

BACKGROUND

Though the majority of left atrial tachycardias originate around the ostia of the pulmonary veins, only isolated reports have described focal tachycardia originating from the MA.

METHODS

Seven patients of a consecutive series of 172 patients undergoing radiofrequency ablation for focal atrial tachycardia are reported. Electrophysiologic study involved catheters positioned along the coronary sinus (CS), crista terminalis (CT), His bundle, and a mapping/ablation catheter.

RESULTS

All seven patients had tachycardia foci originating from the superior region of the MA in close proximity to the left fibrous trigone and mitral-aortic continuity. These foci demonstrated a characteristic P-wave morphology and endocardial activation pattern. The P-wave morphology in the precordial leads typically showed a biphasic pattern, with an inverted component followed by an upright component. The P-wave was consistently of low amplitude in the limb leads. Earliest endocardial activity occurred at the His bundle region in all seven patients. In general, CS activation was proximal to distal, and mid-CT activation was earlier than high or low CT. Ablation was successful at the superior aspect of the MA in all patients.

CONCLUSIONS

The MA is an unusual but important site of origin for focal atrial tachycardia, with a propensity to be localized to the superior aspect. It can be suspected as a potential anatomic site of tachycardia origin from analysis of P-wave morphology and the atrial endocardial activation sequence map. Using mapping targeted to anatomic structures achieved a high success rate for ablation.