How to map and ablate atrial scar macroreentrant tachycardia of the right atrium

Arrhythmias (IV). Clinical approach to atrial tachycardia and atrial flutter from an understanding of the mechanisms. Electrophysiology based on anatomy

In 2009, 2343 catheter ablation procedures were performed in Spain for focal atrial tachycardia or atrial flutter (typical and atypical), with a yearly growth rate of 8%, indicating the clinical importance of these arrhythmias. The classic categorization of atrial tachycardia and atrial flutter based on rate and morphological criteria has become almost irrelevant at a time when clinical electrophysiology may lead to curative intervention based on a definition of the mechanism, making it necessary to bring laboratory experience closer to clinical practice. In this review we outline our present understanding of atrial tachycardia mechanisms, both focal and macroreentrant, and attempt to establish the conceptual links with classic concepts that may help the clinician to make a differential diagnosis and establish therapeutic indications, including that of an electrophysiologic study. Some of the concepts may seem complex, but we thought it important to provide an overview of the electrophysiological methods that may eventually lead to the description of the anatomic bases of the arrhythmias; currently, these are easier to understand thanks to the virtual anatomic casts built using computerized navigation systems.

Atrial macroreentry tachycardia in patients without obvious structural heart disease or previous cardiac surgical or catheter intervention: characterization of arrhythmogenic substrates, reentry circuits, and results of catheter ablation

INTRODUCTION

Atrial macroreentry tachycardia (AMRT) in patients without obvious structural heart disease or previous surgical or catheter intervention has not been characterized in detail.

METHODS AND RESULTS

Electroanatomical mapping and ablation of right or left AMRT were performed in 33 patients. Right atrial central conduction obstacle was formed by an electrically silent area (ESA) in 15 (68%) patients and by a line of double potentials (DPs) in seven (32%) patients. Left atrial ESAs were found in all 11 patients with the left AMRT. Reentry circuit was reconstructed in 19 (86%) patients with right AMRT and seven (64%) patients with left AMRT. Of the ESA-related right AMRT, eight (50%) were double-loop reentry circuits utilizing a narrow critical isthmus within the ESA and eight (50%) were single-loop reentry circuits with a critical isthmus bounded by ESA and either ostium of the vena cava. Single-loop DP-related AMRTs had the critical isthmus between the DP line and the ostium of the inferior vena cava (IVC). Left AMRTs included a variety of single-, double-, or triple-loop reentry circuits and their critical isthmuses. During the 37 +/- 15 month follow-up, atrial tachyarrhythmia-free clinical outcome was achieved in 21 (95%) patients (18 patients, 82%, without antiarrhythmic drugs) with the right AMRT and in nine (82%) patients (six patients, 55%, without antiarrhythmic drugs) with the left AMRT.

CONCLUSION

The majority of right and left AMRTs were related to the presence of ESA. Ablation can be successful with a favorable risk of atrial tachyarrhythmia recurrence.

Fusion of Electroanatomical Activation Maps and Multislice Computed Tomography to Guide Ablation of a Focal Atrial Tachycardia in a Fontan Patient

INTRODUCTION

Ablation of atrial tachycardia (AT) occurring late after cardiac surgery for congenital heart disease can be challenging due to the complexity of the arrhythmogenic substrate.

METHODS AND RESULTS

We performed an ablation procedure in a Fontan patient with an AT using a new approach combining 3D electroanatomical mapping with multislice computed tomography (MSCT). This technique visualizes the position of the catheter in relation to the endocardium, thereby improving delineation of scar tissue. The AT had a focal origin located between areas of scar tissue and was successfully ablated at the earliest activated site.

CONCLUSION

Ablation of complex arrhythmias can be facilitated by fusion of electroanatomical map and MSCT.

Catheter Ablation of Tachycardias After Undergoing a Surgical Atriotomy Using a Multipolar Electrode Catheter

BACKGROUND

A variety of supraventricular tachyarrhythmias may occur in patients after undergoing a surgical atriotomy. The purpose of this study was to characterize them and determine the role of conventional mapping.

METHODS AND RESULTS

In 45 patients after a surgical atriotomy, 68 atrial tachyarrhythmias were observed. A conventional mapping system with a 20-pole electrode catheter used in the electrophysiological study detected 39 atrial tachycardias (ATs). Type 1 atrial flutter (AFL) was observed in 23 and reverse type 1 AFL in 4. AT was classified into 3 subgroups, namely, incisional macroreentrant AT (n=31), incisional focal AT (n=1) and non-incisional AT (n=7). In the patients with incisional macroreentrant AT after the standard right atriotomy, the 20-pole electrode catheter placed on the incision could easily record the entire sequence of the atrial activation. Successful catheter ablation was achieved in all patients with incisional reentrant AT. The ablation site of incisional reentrant AT was the isthmus between the incision and the superior vena cava cannulation scar in 4, between the incision and the inferior vena cava cannulation scar in 22, and the area at the septal incision in 3. The remaining 2 incisional ATs were left atrial AT and right atrial transincisional AT.

CONCLUSIONS

The conventional mapping system is still very useful for making an electrophysiological diagnosis in patients after a standard right atriotomy.

Atypical flutter: a review

Understanding of typical flutter circuits led the way to the study of other forms of macroreentrant tachycardias of the atria, and to their treatment by catheter ablation. It has become evident that the ECG classification of atrial flutter and atrial tachycardia by a rate cutoff and the presence or absence of isoelectric baselines between atrial deflections is not a valid indicator of tachycardia mechanism. Macroreentrant circuits where activation rotates around large obstacles are the most common arrhythmias found in patients with atypical forms of flutter or atrial tachycardia, especially after surgery for congenital heart disease, however, focal mechanisms can also be found. Large areas of low voltage electrograms, suggestive of severe myocardial damage (fibrosis or infiltration) can be found in many atypical macroreentrant tachycardias at the center of the circuit. Many of these circuits can be mapped precisely, critical isthmuses can be defined, and effective catheter ablation can be performed. The need to match activation maps with anatomy precisely, makes computer assisted, anatomically precise mapping a useful tool. Entrainment techniques have to be used sparingly to avoid tachycardia interruption. In complex cases, ablation can be done in sinus rhythm, after definition of conducting channels between low voltage areas and scars or anatomic obstacles. Long-term prognosis is uncertain and depends on the underlying pathology.

Atrial tachycardia with recipient-to-donor atrioatrial conduction and isthmus-dependent donor atrial flutter in a patient after orthotopic heart transplantation. Successful treatment by radiofrequency catheter ablation

Atrial arrhythmias are common after orthotopic heart transplantation. We report an unusual case of a patient after heart transplantation with 2 types of atrial arrhythmias: one was a macro-reentrant, incisional, recipient-atrial tachycardia conducted to the donor atrium, and the other was a common-type, isthmus-dependent atrial flutter in the donor atrium. These 2 arrhythmias were successfully treated with selective radiofrequency catheter ablation.