Materiały źródłowe

• #1 Atrial Tachycardia – StatPearls – NCBI Bookshelf

  https://www.ncbi.nlm.nih.gov/books/NBK542235/

  A focal atrial tachycardia is an arrhythmia with electrical impulses originating and confined within the atria. Focal atrial tachycardia requires differentiation from other atrial arrhythmias, like atrial fibrillation and atrial flutter. Appropriate diagnosis of focal atrial tachycardia must be made to guide proper management. Atrial tachycardia can be a result of one or a combination of the mechanisms leading to arrhythmia: automatic, triggered activity, or reentry. Focal atrial tachycardias can arise from any or a combination of the three mechanisms causing tachyarrhythmias: enhanced automaticity, triggered, or reentry. Reentry is typically the underlying mechanism in macro-reentrant atrial tachycardias like atrial flutter. If a reentrant mechanism is involved in a focal atrial tachycardia, it involves a micro-reentrant circuit which can be difficult to distinguish from an automatic focus on surface ECG. Abnormal automaticity occurs as a result of accelerated phase 4 upslope, leading to spontaneously depolarizing cells. The triggered activity has features seen with enhanced automaticity, though are felt to primarily involve calcium channels.

• #1 Atrial Tachycardia: Practice Essentials, Background, Anatomy

  https://emedicine.medscape.com/article/151456-overview

  Atrial tachycardia is a supraventricular tachycardia (SVT) that does not require the atrioventricular (AV) junction, accessory pathways, or ventricular tissue for its initiation and maintenance. […] In clinical practice, three major types of atrial tachycardia are seen: focal atrial tachycardia, multifocal atrial tachycardia (MAT), and re-entrant atrial tachycardia. These arrhythmias have unique arrhythmic substrates and characteristics. […] Focal atrial tachycardia arises from a localized atrial site and is characterized by regular, organized atrial activity with discrete P waves and, typically, an isoelectric segment between P waves. […] MAT is an irregular supraventricular tachycardia characterized by three distinct P-wave morphologies and/or patterns of atrial activation at different rates.

• #1 Atrial Tachycardia: Symptoms, Causes & Treatment

  https://my.clevelandclinic.org/health/diseases/21800-atrial-tachycardia

  Atrial tachycardia is a type of arrhythmia an irregular heart rhythm that causes the upper chambers (atria) of your heart to beat faster than normal. They can beat 100 to 250 beats per minute. A faulty electrical signal or malfunctioning cell can cause this. There are three ways that this usually happens: […] Automaticity: Another group of cells or a single cell in your heart can become dominant over your normal cells that set the pace of your heart rhythm. This can happen because of an imbalance of sodium, potassium and calcium. […] Triggered activity: Sometimes, a chemical imbalance in heart muscle cells may make them fire when they arent supposed to. […] Reentry: Because of a redirection of electricity, cells can form a circuit and propagate this wave of electricity leading to abnormal beats. This typically happens after surgery or with scar tissue in your heart.

• #1 Clinical Approach to Atrial Tachycardia and Atrial Flutter From an Understanding of the Mechanisms. Electrophysiology Based on Anatomy – Revista Española de Cardiología (English Edition)

  https://www.revespcardiol.org/en-clinical-approach-atrial-tachycardia-atrial-articulo-S1885585712000138

  FAT is characterized by radial and centrifugal atrial activation from the point of origin, which can be located anywhere in the atria, pulmonary veins, superior vena cava or coronary sinus. […] This definition does not address the issue of whether the focal discharge mechanism is a rapid depolarization of action potential during phase 4, afterdepolarizations (oscillations of the membrane), or a very small diameter reentry circuit (microreentrant). […] In some cases the electrophysiological mechanism can be deduced from the response to stimulation or drugs, but in practical terms defining the discharge mechanism of the initiating focus has become almost irrelevant. […] In MAT, atrial activation occurs in a continuous, uninterrupted manner because of a wavefront rotating around an obstacle formed by anatomical structures (venous or valvular orifices), scars, or areas of functional (anisotropic) block.

• #1 Atrial tachycardias – AF-ABLATION

  https://af-ablation.org/en/arrhythmological-disorders/supraventricular-tachycardia/atrial-tachycardia/

  Automatic atrial tachycardia is found both in patients with a structurally healthy heart and in patients with underlying heart disease. […] Triggered atrial tachycardias are due to late post-depolarizations, which are made up of low voltage oscillations at the end of the action potential. […] Intra-atrial re-entry tachycardias can be due to both macro-reenteries and micro-indentations. […] Because a re-entry circuit is possible, three conditions are indispensable: 1) at least two pathways of propagation of the impulse must be present, whether anatomical or functional, which must join proximally and distally to form a closed circuit; 2) In one of these ways there must be a one-way block; 3) the conduction along the unblocked way must be slowed down allowing the blocked way to restore its excitability.

• #1 Atrial Tachycardias and Atypical Atrial Flutters: Mechanisms and Approaches to Ablation | AER Journal

  https://www.aerjournal.com/articles/atrial-tachycardias-and-atypical-atrial-flutters-mechanisms-and-approaches-ablation?language_content_entity=en

  Localised reentry occurs in the setting of diseased atrial myocardium that supports very slow conduction. A characteristic feature of localised reentry is highly fractionated, low-amplitude electrograms that encompass most of the tachycardia cycle length over a small diameter. […] Advances in understanding the mechanisms of ATs and their signature electrogram characteristics have improved the efficacy and efficiency of catheter ablation. […] Focal ATs are defined as arrhythmias that arise from a circumscribed site of early activation and propagate to the atria in a centrifugal pattern. […] The mechanisms that give rise to focal ATs are triggered activity and automaticity. A consistent feature of focal ATs is sensitivity to adenosine, which terminates tachycardias due to triggered activity and transiently suppresses tachycardias related to enhanced automaticity but does not affect reentrant ATs.

• #1 Atrial Tachycardias and Atypical Atrial Flutters: Mechanisms and Approaches to Ablation | AER Journal

  https://www.aerjournal.com/articles/atrial-tachycardias-and-atypical-atrial-flutters-mechanisms-and-approaches-ablation?language_content_entity=en

  Atrial tachycardias (ATs) may be classified into three broad categories: focal ATs, macroreentry and localised reentry also known as microreentry. Features that distinguish these AT mechanisms include electrogram characteristics, responses to entrainment and pharmacological sensitivities. […] Focal ATs may occur in structurally normal hearts but can also occur in patients with structural heart disease. These typically arise from preferential sites such as the valve annuli, crista terminalis and pulmonary veins. […] Macro-reentrant ATs occur in the setting of atrial fibrosis, often after prior catheter ablation or post atriotomy, but also de novo in patients with atrial myopathy. High-resolution mapping techniques have defined details of macro-reentrant circuits, including zones of conduction block, scar and slow conduction.

• #1 Atrial Tachycardia: Diagnosis – The Cardiology Advisor

  https://www.thecardiologyadvisor.com/ddi/atrial-tachycardia-diagnosis/

  In multifocal atrial tachycardia (MAT), the ECG shows an irregular rhythm with at least 3 different P-wave morphologies, and the average atrial rate is 100 beats/min. This rhythm most often occurs in the setting of severe pulmonary disease or hypomagnesemia. […] Atrial tachycardia commonly occurs after ablation for atrial fibrillation which is a chaotic rhythm with an atrial rate so rapid that P-waves cannot be distinguished on the ECG. […] Prognosis depends on the underlying cause. Unifocal atrial tachycardia is usually benign in adults and may not require treatment if it is not sustained. On the other hand, incessant atrial tachycardia can contribute directly to tachycardic cardiomyopathy and reversible heart failure.

• #1 Multifocal Atrial Tachycardia: Overview of Multifocal Atrial Tachycardia, Pathophysiology of MAT, Etiology of MAT

  https://emedicine.medscape.com/article/155825-overview

  Multifocal atrial tachycardia (MAT) is a cardiac arrhythmia caused by multiple sites of competing atrial activity. It is characterized by an irregular atrial rate greater than 100 beats per minute (bpm). Atrial activity is well organized, with at least 3 morphologically distinct P waves, irregular P-P intervals, and an isoelectric baseline between the P waves. […] The mechanism of the arrhythmia has not been well defined. Delayed afterdepolarizations leading to triggered automaticity are postulated to result in the development of multifocal atrial tachycardia (MAT). The evidence that implicates this mechanism is mainly indirect and points to intracellular calcium overload by various mechanisms (eg, catecholamine excess, phosphodiesterase inhibition, acidosis, hypoxemia). […] MAT most often is found in the elderly patient with decompensated chronic lung disease and should be thought of as a hypoxic complication of underlying heart conduction pathology. However, other underlying causes may be present, such as heart failure, sepsis, or methylxanthine toxicity. The effect of MAT on the hearts conduction system may or may not lead to hemodynamic instability.

• #1 Atrial Tachycardia: Practice Essentials, Background, Anatomy

  https://emedicine.medscape.com/article/151456-overview

  Re-entrant atrial tachycardia is usually seen after cardiac surgery or catheter ablation with linear lesions that result in islets of scars. […] Several pathophysiologic mechanisms have been ascribed to atrial tachycardia. These mechanisms can be differentiated on the basis of the pattern of onset and termination and the response to drugs and atrial pacing. […] Automatic atrial tachycardia arises due to enhanced tissue automaticity and is observed in patients with structurally normal hearts and in those with organic heart disease. […] Atrial tachycardia caused by triggered activity is due to delayed after-depolarizations, which are low-amplitude oscillations occurring at the end of the action potential. […] Intra-atrial reentry tachycardias may have either a macroreentrant or a microreentrant circuit.

• #1 Atrial Tachycardias and Atypical Atrial Flutters: Mechanisms and Approaches to Ablation | AER Journal

  https://www.aerjournal.com/articles/atrial-tachycardias-and-atypical-atrial-flutters-mechanisms-and-approaches-ablation?language_content_entity=en

  Macro-reentrant ATs other than typical CTI-dependent atrial flutter often occur in patients with atrial disease, such as those with cardiomyopathies, prior atrial ablation or prior cardiac surgery. […] A hallmark of macroreentry is the ability to entrain the tachycardia with fusion; this property is inconsistent with a truly focal source. […] Another feature of macroreentry is identification of activation throughout the tachycardia cycle length with adjacent zones of early and late activation relative to a fiducial point. […] An interesting subset of ATs is best described as micro-reentry or localised reentry. This mechanism occurs in patients with prior catheter ablation, prior atrial surgery and sometimes de novo in patients with atrial myopathy. […] Localised reentry is arbitrarily defined as a circuit with a diameter 23 cm.

• #1 Atrial Tachycardias and Atypical Atrial Flutters: Mechanisms and Approaches to Ablation

  https://pmc.ncbi.nlm.nih.gov/articles/PMC6528065/

  A hallmark of macroreentry is the ability to entrain the tachycardia with fusion; this property is inconsistent with a truly focal source. Another feature of macroreentry is identification of activation throughout the tachycardia cycle length with adjacent zones of early and late activation relative to a fiducial point. Macro-reentrant tachycardias are consistently insensitive to adenosine, which results in AV block but does not interrupt the tachycardia. […] An interesting subset of ATs is best described as micro-reentry or localised reentry. This mechanism occurs in patients with prior catheter ablation, prior atrial surgery and sometimes de novo in patients with atrial myopathy. Localised reentry is arbitrarily defined as a circuit with a diameter 23 cm. The circuits often occur adjacent to prior ablation lesions or near patchy areas of scar that are identified with electroanatomical mapping. These tachycardias characteristically demonstrate low-amplitude continuous electrograms encompassing 85% of the tachycardia cycle length. Recent studies with ultra-high-density mapping show that localised atrial reentrant circuits may have multiple sequential zones of very slow conduction and occur in low-voltage areas of the atria. A notable feature of localised reentry is insensitivity to adenosine, a property which is common with macro-reentrant tachycardias. […] High-resolution mapping, in addition to entrainment responses, define the mechanisms of AT and identify sites of origin and critical isthmuses that are targets for ablation.

• #1 Atrial tachycardias – AF-ABLATION

  https://af-ablation.org/en/arrhythmological-disorders/supraventricular-tachycardia/atrial-tachycardia/

  Atrial tachycardia (AT) is a heart rhythm disorder that originates in the atria, defined as a supraventricular tachycardia that does not require the participation of the atrioventricular junction, accessory pathways, or ventricular tissue for its onset or maintenance. […] Atrial tachycardias can be classified based on endocardial activation data, pathophysiological mechanisms, or anatomy. […] Based on the pathophysiological mechanism, atrial tachycardias can be classified into: tachycardia due to increased automatism, triggered activity, and re-entry. […] Many atrial structures can represent a substrate for arrhythmia. The orifices of the vena cava, the pulmonary veins, the coronary sinus, the atrial septum, the tricuspid, and the mitral annulus are potential anatomical barriers that can favor the re-entry circuits.

• #1 Atrial Tachycardia – Clinical Tree

  https://clinicalpub.com/atrial-tachycardia/

  Recent studies with ultra-high-density mapping have shown that localized atrial reentrant (microreentrant) circuits may have multiple sequential zones of very slow conduction and occur in low-voltage areas of the atria. […] The predominant areas of origin of focal AT include the crista terminalis, near or inside the pulmonary veins (PVs; superior veins more commonly), around the AV annuli, around or inside the coronary sinus, and in the para-Hisian region (atrial septum and Kochs triangle). […] Characterization of the mechanism of AT based on electrocardiographic findings is fraught with limitations. […] The limitations of the ECG for deducing the origin of focal AT are caused by several factors. […] Advances in electrocardiographic imaging (ECGI) using body surface electrograms or a combination of body surface electrograms with chest imaging (computed tomography [CT] or magnetic resonance imaging [MRI]) provide new hope for enhancing the accuracy of noninvasive localization of the site of origin of focal ATs.

• #1 Atrial tachycardia – Wikipedia

  https://en.wikipedia.org/wiki/Atrial_tachycardia

  Atrial tachycardia is a type of heart rhythm problem in which the heart’s electrical impulse comes from an ectopic pacemaker (that is, an abnormally located cardiac pacemaker) in the upper chambers (atria) of the heart, rather than from the sinoatrial node, the normal origin of the heart’s electrical activity. As with any other form of tachycardia (rapid heart beat), the underlying mechanism can be either the rapid discharge of an abnormal focus, the presence of a ring of cardiac tissue that gives rise to a circle movement (reentry), or a triggered rapid rhythm due to other pathological circumstances (as would be the case with some drug toxicities, such as digoxin toxicity). […] Atrial tachycardia tends to occur in individuals with structural heart disease, with or without heart failure, and ischemic coronary artery disease. However, focal atrial tachycardia often occurs in healthy individuals without structural heart disease. Other possible etiologies are listed below:

• #1 Atrial Flutter with Alternating Cycle Lengths: Mechanism and Mapping

  https://www.innovationsincrm.com/cardiac-rhythm-management/2012/april/260-alternating-cycle-lengths-mechanism

  Atrial tachycardia after ablation for persistent atrial fibrillation can occur in over 50% of patients depending on the center and technique used. Macrore-entrant tachycardias account for approximately 75% of atrial tachycardias, and the remaining 25% are due to microre-entry and automaticity. Atrial tachycardias with varying cycle lengths are more commonly associated with focal mechanisms of tachycardia due to automaticity or localized re-entry, although perimitral annular flutter with two cycle lengths has been described. […] There are multiple possible mechanisms for atrial tachycardias with variable cycle lengths, including re-entry with variable conduction through a single or multiple gaps or automaticity from two separate foci. In this case the varying cycle lengths of the atrial flutter appeared to be due to alternating conduction times through a single gap located on the roof of the left atrium near the right superior pulmonary vein. This is supported by the observation of split potentials on either side of the gap, the presence of constant and progressive fusion with pacing, and the termination of tachycardia within 10 s with a single lesion. Dofetilide may have enhanced the likelihood of conduction delay through the gap and facilitated development of such an alternating conduction. […] The varying cycle length was dependent on conduction changes in a small area of atrial tissue and the critical isthmus was identified by locating the site characterized with the earliest change in atrial electrogram cycle length.

• #1 Second-generation atrial tachycardias: adverse repercussions of a

  https://www.openaccessjournals.com/articles/secondgeneration-atrial-tachycardias-adverse-repercussions-of-ablation-or-a-step-in-the-right-direction-9238.html

  As the AF of longer durations are ablated and lesion sets become more extensive and complex, the mechanisms of subsequent ATs shift from predominantly macro-re-entry to focal ATs and localized (small-circuit) re-entrant tachycardias. […] The presence of subsequent AT over recurrences of AF probably represents a step closer to sustained sinus rhythm and an atrium incapable of maintaining a fibrillatory process.

• #1 Incomplete ablation as a mechanism of atrial fibrillation recurrence and atrial tachycardia development after maze procedure – JTCVS Open

  https://www.jtcvsopen.org/article/S2666-2736(24)00375-9/fulltext

  Atrial tachyarrhythmias are the most frequent complication after the maze procedure. […] We examined the mechanism of atrial tachyarrhythmias in association with the ablation energy and technique used at each lesion and by the findings of postoperative electrophysiological study. […] Incomplete ablation is a cause of AF recurrence and AT development after the maze procedure. […] Intraoperative PV pacing prevents AF recurrence and additional epicardial CS ablation prevents AT development. […] Two-thirds of the patients with postoperative AT development had a conduction gap as the result of incomplete ablation, and two-thirds of these patients had an incomplete ablation at the CS. […] Creation of a complete conduction block at the CS by encircling ablation is essential to prevent the reentrant AT.

• #1 Atrial Tachycardias and Atypical Atrial Flutters: Mechanisms and Approaches to Ablation

  https://pmc.ncbi.nlm.nih.gov/articles/PMC6528065/

  Atrial tachycardias (ATs) may be classified into three broad categories: focal ATs, macroreentry and localised reentry also known as microreentry. Features that distinguish these AT mechanisms include electrogram characteristics, responses to entrainment and pharmacological sensitivities. […] Macro-reentrant ATs occur in the setting of atrial fibrosis, often after prior catheter ablation or post atriotomy, but also de novo in patients with atrial myopathy. High-resolution mapping techniques have defined details of macro-reentrant circuits, including zones of conduction block, scar and slow conduction. Localised reentry occurs in the setting of diseased atrial myocardium that supports very slow conduction. A characteristic feature of localised reentry is highly fractionated, low-amplitude electrograms that encompass most of the tachycardia cycle length over a small diameter.

• #1 Electrocardiogram Recognition and Ablation of Atrial Tachycardia | ECR Journal

  https://www.ecrjournal.com/articles/electrocardiogram-recognition-and-ablation-atrial-tachycardia?language_content_entity=en

  Studies evaluating mechanism of focal AT have demonstrated electrophysiological characteristics reflecting abnormal automaticity, triggered activity and micro-re-entry in different patients. […] The introduction of 3-D mapping systems has greatly facilitated the mapping and ablation of focal AT. The electroanatomical mapping system is based on sequential mapping technology and permits a detailed reconstruction of the chamber geometry and the activation sequence. However, this approach still requires regular ectopics or sustained tachycardia, and, as a consequence, electroanatomical maps cannot be constructed in up to 12% of patients. […] The presence of poor local cell-to-cell coupling is suggested by the recording of an early and fractionated signal at the site of successful ablation in 93% of cases. […] The mechanism of focal AT arising from PVs is most consistent with abnormal automaticity or triggered automaticity and these foci are rarely, if ever, inducible with programmed electrical stimulation.

• #1 Atrial Tachycardias and Atypical Atrial Flutters: Mechanisms and Approaches to Ablation | AER Journal

  https://www.aerjournal.com/articles/atrial-tachycardias-and-atypical-atrial-flutters-mechanisms-and-approaches-ablation?language_content_entity=en

  Recent studies with ultra-high-density mapping show that localised atrial reentrant circuits may have multiple sequential zones of very slow conduction and occur in low-voltage areas of the atria. […] A notable feature of localised reentry is insensitivity to adenosine, a property which is common with macro-reentrant tachycardias. […] Effective ablation of microreentrant ATs usually occurs at sites with highly fractionated, low-amplitude electrograms.

• #1 Atrial Tachycardia With Fluctuating Cycle Length Post Multiple Atrial Fibrillation Ablations

  https://www.acc.org/education-and-meetings/patient-case-quizzes/atrial-tachycardia-with-fluctuating-cycle-length-post-multiple-atrial-fibrillation-ablations

  Similarly, pacing did not result in acceleration of the tachycardia, indicating that triggered activity is unlikely. […] Variable fusion occurring at different pacing cycle lengths on the available intracardiac electrograms indicates reentry rather than another mechanism. In tachycardia with fluctuating cycle lengths, if the post-pacing interval consistently matches one of the several original cycle lengths (usually the shorter cycle length) after multiple repetitions, the consistency of those post-pacing intervals also supports reentry. […] The identical atrial activation sequence of the recorded electrograms of both cycle lengths of the tachycardia suggests that the difference in cycle lengths is attributable to the protected zone within the central isthmus. Two different paths with differential conduction/ repolarization properties within the central isthmus likely cause the two different cycle lengths. […] Radiofrequency ablation at this site changed the cycle length of the tachycardia to a fixed cycle length (elimination of the path with the shorter cycle length) prior to the termination of the tachycardia (block of the path with the longer cycle length).

• #1

  https://link.springer.com/article/10.1007/s10840-024-01817-8

  High-resolution mapping offers superior accuracy in delineating conduction features; however, certain characteristics are still linked to elevated recurrence rates of atrial tachycardia (AT), suggesting the influence of additional mechanisms. This study systematically assessed the substrate of functional conduction block (FCB) regions in relation to the mechanisms of multiple ATs. […] The participation of FCB regions in the mechanism of ATs showed three different kinds of performance. The dynamic nature of this substrate may provide insight into the reasons for the high recurrence of related ATs. […] In multiple ATs, FCB regions may not be uncommon. The FCB area serves as the main obstacle for maintaining the circular reentry pathway, and this phenomenon occurred in 3 out of 7 patients.

• #1

  https://link.springer.com/article/10.1007/s10840-024-01817-8

  The FCB area plays the role of an obstacle line in the reentry pathway, significantly prolonging the total reentry path. […] The FCB area acts as a bystander and does not affect the main reentry circuit path, which may be unrelated to the mechanism of AT. […] The FCB is a manifestation of anisotropic conduction in local tissues, and this anisotropic conduction is often related to different directions of excitation sources and different input frequencies. […] The FCB phenomenon may be a common electrophysiological feature, especially for scar-related ATs. According to the results of excitation mapping, FCB regions can describe three manifestations in the maintenance mechanism of multiple ATs. First, the FCB region acts as a central block, maintaining the reentry circuit. Second, the FCB region acts as a barrier line, which may reorganize the propagation of reentry. Third, the FCB region acts as a bystander and may be unrelated to the mechanism of AT. FCB is a manifestation of local block conduction anisotropy, and this dynamic property of the substrate may be one of the most important reasons for the high recurrence rate of related ATs.

• #1 Atrial Tachycardia | Thoracic Key

  https://thoracickey.com/atrial-tachycardia-3/

  A new technique has been proposed to differentiate between focal and macroreentrant ATs based on the surface electrocardiogram (ECG). […] The autonomic nervous system likely has a critical role in initiating or triggering some ATs. […] Atrial tachycardias can be located all along the CT, which has been described as a ring of fire because it is a common location for ATs in patients without structural heart disease, accounting for two thirds of right ATs in one study. […] The tricuspid annulus probably represents the second most common location of right-sided ATs. […] The SVC is an uncommon site of origin for focal ATs (2%).

• #1 Tachycardia pathophysiology – wikidoc

  https://www.wikidoc.org/index.php/Tachycardia_pathophysiology

  When an electrical impulse begins in any part of the heart, it will spread throughout the myocardium and cause a contraction; see Electrical conduction system of the heart. Abnormal impulses can begin by one of two mechanisms: automaticity or reentry. […] Automaticity refers to a cardiac muscle cell firing off an impulse on its own. […] Any part of the heart that initiates an impulse without waiting for the sinoatrial node is called an ectopic focus, and is by definition a pathological phenomenon. […] Conditions that increase automaticity include sympathetic nervous system stimulation and hypoxia. The resulting heart rhythm depends on where the first signal begins: if it is the sinoatrial node, the rhythm remains normal but rapid; if it is an ectopic focus, many types of dysrhythmia can result.

• #1 Atrial Tachycardia (AT) – Supraventricular Tachycardias – Supraventricular Arrhythmias – Cardiac Arrhythmias – Cardiovascular Diseases – Diseases – McMaster Textbook of Internal Medicine

  https://empendium.com/mcmtextbook/chapter/B31.II.2.6.4.

  Atrial tachycardia (AT) is a paroxysmal or sustained tachycardia originating in the atrium outside the sinus node. AT may be divided into 2 types: […] Focal AT: An accelerated (100-250 beats/min) regular rhythm originating in the atrium with a stable P wave morphology. It can occur in patients with or without heart disease. […] Multifocal AT: An irregular rhythm with 3 varying morphologies of the P waves. It is commonly seen in patients with cardiac or lung disease and metabolic or electrolytic disturbances. […] AT sustained over a long period may lead to tachycardia-induced cardiomyopathy. AT does not cause thromboembolic complications but it may trigger atrial fibrillation (AF). […] In patients with focal AT, P waves are identical and their shape depends on the location of the anatomical focus (they can also resemble sinus rhythm if coming from a close-by location). In multifocal AT the rhythm is grossly irregular and several morphologies of P waves are seen. […] In multifocal AT catheter ablation is less effective. Oral verapamil or diltiazem are recommended in this case.

• #1 Atrial Fibrillation, Atrial Tachycardia: What’s the Difference?

  https://www.acc.org/Education-and-Meetings/Patient-Case-Quizzes/Atrial-Fibrillation-Atrial-Tachycardia-Whats-the-Difference

  A focal atrial tachycardia as the sole mechanism for supraventricular tachycardia is relatively rare accounting for 10-15% of cases referred for catheter ablation. […] The posterior wall of the left atrium is hypothesized to be a territory rich in triggers for the formation of atrial fibrillation. […] Although relatively rare, sustained episodes of focal atrial tachycardia may lead to a rate related cardiomyopathy. […] Pulmonary vein associated tachycardia is a rare entity. […] In this series, focal ablation of either the earliest activation site at the os of the vein, or circumferential ablation of the culprit vein resulted in favorable long term freedom from recurrent atrial tachycardia, and atrial fibrillation. […] Pulmonary vein arrhythmias have been associated with the development of atrial fibrillation.

• #1 Atrial Fibrillation, Atrial Tachycardia: What’s the Difference?

  https://www.acc.org/Education-and-Meetings/Patient-Case-Quizzes/Atrial-Fibrillation-Atrial-Tachycardia-Whats-the-Difference

  In three large series of patients undergoing ablation for focal pulmonary vein tachycardia, the reported development of atrial fibrillation post ablation is low. […] While our patient has had improvement of his LVEF, and is free from arrhythmias, his future risk of the development of atrial fibrillation is unknown.

• #1 Clinical Approach to Atrial Tachycardia and Atrial Flutter From an Understanding of the Mechanisms. Electrophysiology Based on Anatomy – Revista Española de Cardiología (English Edition)

  https://www.revespcardiol.org/en-clinical-approach-atrial-tachycardia-atrial-articulo-S1885585712000138

  In patients who have episodes of AF and atrial fibrillation, the risk of embolism is the same as in patients with atrial fibrillation alone, whereas patient with AF alone have a lower risk. […] The effectiveness and few complications of CTI catheter ablation make it the treatment of choice for typical AF, especially if it is recurrent.

• #1 Atrial Tachycardia: Symptoms, Causes & Treatment

  https://my.clevelandclinic.org/health/diseases/21800-atrial-tachycardia

  Depending on the type, atrial tachycardia is often curable. When a chronic disease is the cause, treating that disease can often make atrial tachycardia stop. […] Focal atrial tachycardia: This type has a very high cure rate, especially with catheter-based techniques. […] Micro-reentrant atrial tachycardia: Its often possible to cure this using catheter-based techniques. In rarer cases, you may need a surgical approach. […] Ablation treats certain areas of your heart to stop them from improperly conducting electricity. This is very helpful in stopping focal atrial tachycardia. It also can stop reentry problems by blocking part of a faulty electrical circuit.

• #2 Focal atrial tachycardia – UpToDate

  https://www.uptodate.com/contents/focal-atrial-tachycardia

  Focal atrial tachycardia (AT) is a regular atrial rhythm at a constant rate of >100 beats per minute originating outside of the sinus node. Focal ATs arise from a single site within the left or right atrium, in contrast to macroreentrant atrial arrhythmias (eg, atrial flutter) and atrial fibrillation, which involve multiple sites or larger circuits. […] Focal ATs are usually paroxysmal and self-limited, although in some patients, focal AT may be present nearly continuously (ie, incessant AT). Incessant AT is important as it may be associated with left ventricular dysfunction. […] In 2001, the Joint Expert Group from the Working Group of Arrhythmias of the European Society of Cardiology and the North American Society of Pacing and Electrophysiology classified regular ATs according to electrophysiologic mechanisms and anatomy. The Joint Expert Group defined focal AT as „being characterized by atrial activation starting rhythmically at a small area (focus) from where it spreads centrifugally.” This definition indicates that the arrhythmia arises from an area that is smaller than would be required for classical macroreentry, which conventionally is considered to be a circuit greater than 2 cm in diameter.

• #2 Atrial Tachycardia: Practice Essentials, Background, Anatomy

  https://emedicine.medscape.com/article/151456-overview

  Re-entrant atrial tachycardia is usually seen after cardiac surgery or catheter ablation with linear lesions that result in islets of scars. […] Several pathophysiologic mechanisms have been ascribed to atrial tachycardia. These mechanisms can be differentiated on the basis of the pattern of onset and termination and the response to drugs and atrial pacing. […] Automatic atrial tachycardia arises due to enhanced tissue automaticity and is observed in patients with structurally normal hearts and in those with organic heart disease. […] Atrial tachycardia caused by triggered activity is due to delayed after-depolarizations, which are low-amplitude oscillations occurring at the end of the action potential. […] Intra-atrial reentry tachycardias may have either a macroreentrant or a microreentrant circuit.

• #2 Atrial tachycardias – AF-ABLATION

  https://af-ablation.org/en/arrhythmological-disorders/supraventricular-tachycardia/atrial-tachycardia/

  Automatic atrial tachycardia is found both in patients with a structurally healthy heart and in patients with underlying heart disease. […] Triggered atrial tachycardias are due to late post-depolarizations, which are made up of low voltage oscillations at the end of the action potential. […] Intra-atrial re-entry tachycardias can be due to both macro-reenteries and micro-indentations. […] Because a re-entry circuit is possible, three conditions are indispensable: 1) at least two pathways of propagation of the impulse must be present, whether anatomical or functional, which must join proximally and distally to form a closed circuit; 2) In one of these ways there must be a one-way block; 3) the conduction along the unblocked way must be slowed down allowing the blocked way to restore its excitability.

• #2 Atrial Tachycardias and Atypical Atrial Flutters: Mechanisms and Approaches to Ablation | AER Journal

  https://www.aerjournal.com/articles/atrial-tachycardias-and-atypical-atrial-flutters-mechanisms-and-approaches-ablation?language_content_entity=en

  Localised reentry occurs in the setting of diseased atrial myocardium that supports very slow conduction. A characteristic feature of localised reentry is highly fractionated, low-amplitude electrograms that encompass most of the tachycardia cycle length over a small diameter. […] Advances in understanding the mechanisms of ATs and their signature electrogram characteristics have improved the efficacy and efficiency of catheter ablation. […] Focal ATs are defined as arrhythmias that arise from a circumscribed site of early activation and propagate to the atria in a centrifugal pattern. […] The mechanisms that give rise to focal ATs are triggered activity and automaticity. A consistent feature of focal ATs is sensitivity to adenosine, which terminates tachycardias due to triggered activity and transiently suppresses tachycardias related to enhanced automaticity but does not affect reentrant ATs.

• #2

  https://link.springer.com/article/10.1007/s10840-024-01817-8

  The FCB area plays the role of an obstacle line in the reentry pathway, significantly prolonging the total reentry path. […] The FCB area acts as a bystander and does not affect the main reentry circuit path, which may be unrelated to the mechanism of AT. […] The FCB is a manifestation of anisotropic conduction in local tissues, and this anisotropic conduction is often related to different directions of excitation sources and different input frequencies. […] The FCB phenomenon may be a common electrophysiological feature, especially for scar-related ATs. According to the results of excitation mapping, FCB regions can describe three manifestations in the maintenance mechanism of multiple ATs. First, the FCB region acts as a central block, maintaining the reentry circuit. Second, the FCB region acts as a barrier line, which may reorganize the propagation of reentry. Third, the FCB region acts as a bystander and may be unrelated to the mechanism of AT. FCB is a manifestation of local block conduction anisotropy, and this dynamic property of the substrate may be one of the most important reasons for the high recurrence rate of related ATs.

• #2 Atrial Tachycardia With Fluctuating Cycle Length Post Multiple Atrial Fibrillation Ablations

  https://www.acc.org/education-and-meetings/patient-case-quizzes/atrial-tachycardia-with-fluctuating-cycle-length-post-multiple-atrial-fibrillation-ablations

  Similarly, pacing did not result in acceleration of the tachycardia, indicating that triggered activity is unlikely. […] Variable fusion occurring at different pacing cycle lengths on the available intracardiac electrograms indicates reentry rather than another mechanism. In tachycardia with fluctuating cycle lengths, if the post-pacing interval consistently matches one of the several original cycle lengths (usually the shorter cycle length) after multiple repetitions, the consistency of those post-pacing intervals also supports reentry. […] The identical atrial activation sequence of the recorded electrograms of both cycle lengths of the tachycardia suggests that the difference in cycle lengths is attributable to the protected zone within the central isthmus. Two different paths with differential conduction/ repolarization properties within the central isthmus likely cause the two different cycle lengths. […] Radiofrequency ablation at this site changed the cycle length of the tachycardia to a fixed cycle length (elimination of the path with the shorter cycle length) prior to the termination of the tachycardia (block of the path with the longer cycle length).

• #2 Atrial Tachycardia: Symptoms, Causes & Treatment

  https://my.clevelandclinic.org/health/diseases/21800-atrial-tachycardia

  Depending on the type, atrial tachycardia is often curable. When a chronic disease is the cause, treating that disease can often make atrial tachycardia stop. […] Focal atrial tachycardia: This type has a very high cure rate, especially with catheter-based techniques. […] Micro-reentrant atrial tachycardia: Its often possible to cure this using catheter-based techniques. In rarer cases, you may need a surgical approach. […] Ablation treats certain areas of your heart to stop them from improperly conducting electricity. This is very helpful in stopping focal atrial tachycardia. It also can stop reentry problems by blocking part of a faulty electrical circuit.

• #2 Atrial Tachycardias and Atypical Atrial Flutters: Mechanisms and Approaches to Ablation

  https://pmc.ncbi.nlm.nih.gov/articles/PMC6528065/

  A hallmark of macroreentry is the ability to entrain the tachycardia with fusion; this property is inconsistent with a truly focal source. Another feature of macroreentry is identification of activation throughout the tachycardia cycle length with adjacent zones of early and late activation relative to a fiducial point. Macro-reentrant tachycardias are consistently insensitive to adenosine, which results in AV block but does not interrupt the tachycardia. […] An interesting subset of ATs is best described as micro-reentry or localised reentry. This mechanism occurs in patients with prior catheter ablation, prior atrial surgery and sometimes de novo in patients with atrial myopathy. Localised reentry is arbitrarily defined as a circuit with a diameter 23 cm. The circuits often occur adjacent to prior ablation lesions or near patchy areas of scar that are identified with electroanatomical mapping. These tachycardias characteristically demonstrate low-amplitude continuous electrograms encompassing 85% of the tachycardia cycle length. Recent studies with ultra-high-density mapping show that localised atrial reentrant circuits may have multiple sequential zones of very slow conduction and occur in low-voltage areas of the atria. A notable feature of localised reentry is insensitivity to adenosine, a property which is common with macro-reentrant tachycardias. […] High-resolution mapping, in addition to entrainment responses, define the mechanisms of AT and identify sites of origin and critical isthmuses that are targets for ablation.

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