A simple algorithm for defining the mechanism and the chamber of origin in atrial tachycardias

INTRODUCTION

Although macroreentrant atrial tachycardia (MRAT) and focal atrial tachycardia (FAT) can be successfully cured by catheter ablation, the proper diagnosis and treatment of these arrhythmias can still be challenging.

AIM

The objective of this study is to develop an algorithm allowing rapid diagnosis of the mechanism and the chamber of origin of atrial tachycardia based on intracardiac catheter recordings from the right atrium and the coronary sinus (CS).

METHODS

A 2-stepped algorithm was designed: (1) The time of biatrial activation expressed as a percentage of the tachycardia cycle length served to discriminate FAT from MRAT. (2) In FAT, the direction of activation of the CS catheter and the earliest atrial activation were used to define the chamber of origin. In MRAT, the time of right atrium activation was determined or entrainment was used at different sites. Thirty-two intracardiac recordings were reviewed off-line after the algorithm by 4 electrophysiologists blinded to the mechanism and the chamber of origin. The results of their analysis were compared with the intraoperative diagnosis.

RESULTS

The algorithm correctly identified 11 (100%) of 11 FATs and 19 (90.4%) of 21 MRATs. The site of origin was correctly identified in 8 (72.7%) of 11 FATs and in 20 of 21 (95.2%) MRATs. The site of origin was misidentified in 3 FATs, all arising from the CS ostium.

CONCLUSIONS

This algorithm allows rapid discrimination between FAT and MRAT. The chamber of origin is detected with a high accuracy in MRAT. However, the earliest atrial activation taken as an isolated event is not a good predictor for the chamber of origin in FAT arising from the ostium of the CS.

Atrial tachycardia: mechanisms, diagnosis, and management

Atrial tachycardia is an uncommon arrhythmia and may be focal or macroreentrant. This review concentrates on focal atrial tachycardia. Over the last decade there have been a number of advances in delineating the mechanism and anatomic locations of focal atrial tachycardia. The lack of efficacy of antiarrhythmic therapy and the advent of radiofrequency ablation have altered our primary approach to the treatment of focal atrial tachycardia. This review discusses the clinical features, diagnosis, and treatment of focal atrial tachycardia. There is particular focus on the mechanisms, anatomic locations, and P wave morphology, as well as the techniques of mapping and radiofrequency ablation.

Characterization of sustained atrial tachycardia in dogs with rapid ventricular pacing-induced heart failure

INTRODUCTION

Atrial arrhythmias often complicate congestive heart failure (CHF). We characterized inducible atrial tachyarrhythmias and electrophysiologic alterations in dogs with CHF and atrial enlargement produced by rapid ventricular pacing.

METHODS AND RESULTS

Endocardial pacing leads were implanted in the right ventricle, right atrium, and coronary sinus in 18 dogs. The right ventricular lead was connected to an implanted pacemaker capable of rapid ventricular pacing. The atrial leads were used to perform electrophysiologic studies in conscious animals at baseline in all dogs, during CHF induced by rapid ventricular pacing at 235 beats/min in 15 dogs, and during recovery from CHF in 6 dogs. After 20 +/- 7 days of rapid ventricular pacing, inducibility of sustained atrial tachycardia (cycle length 120 +/- 12 msec) was enhanced in dogs with CHF. Atrial tachycardia required a critical decrease in atrial burst pacing cycle length (< or = 130 msec) for induction and often could be terminated by overdrive pacing. Calcium antagonists (verapamil, flunarizine, ryanodine) terminated atrial tachycardia and suppressed inducibility. Effective refractory periods at 400- and 300-msec cycle lengths in the right atrium and coronary sinus were prolonged in dogs with CHF. Atrial cells from dogs with CHF had prolonged action potential durations and reduced resting potentials and delayed afterdepolarizations (DADs). Mitochondria from atrial tissue from dogs with CHF were enlarged and had internal cristae disorganization.

CONCLUSIONS

CHF promotes inducibility of sustained atrial tachycardia. Based on the mode of tachycardia induction, responses to pacing and calcium antagonists, and presence of DADs, atrial tachycardia in this CHF model has a mechanism most consistent with DAD-induced triggered activity resulting from intracellular calcium overload.

[Ectopic atrial tachycardia complicating a congenital left atrial aneurysm: value of an electro-anatomical mapping system]

The authors report the case of a patient with a congenital left atrial aneurysm complicated by ectopic atrial tachycardia treated successfully by surgery. Transoesophageal echocardiography and magnetic resonance imaging provided accurate measurements of the aneurysm and its anatomical relationships. Three-dimensional electro-anatomical mapping with the CARTO, system (Biosense) confirmed the shape and dimensions of the aneurysm. The system showed the electrically mute zones and the ectopic focus situated just beyond the aneurysmal neck. Surgical ablation confirmed the morphological and functional data of the imaging techniques and the patient was definitely cured.

First postpacing interval variability during right ventricular stimulation: a single algorithm for the differential diagnosis of regular tachycardias

BACKGROUND

Failure to differentiate supraventricular from ventricular arrhythmias is the most frequent cause of inappropriate implantable cardioverter-defibrillator therapies. Although a sudden-onset criterion is available to differentiate sustained monomorphic ventricular tachycardias (SMVTs) and sinus tachycardias (STs), SMVTs arising during ST and SMVTs gradually accelerating above the cutoff rate can remain undetected. Regular paroxysmal atrial tachycardias (ATs) also can be undetected by onset and stability algorithms. We hypothesized that the first postpacing interval (FPPI) variability after overdrive right ventricular pacing may differentiate SMVTs from STs and ATs.

METHODS AND RESULTS

FPPI variability was measured in 23 SMVTs (cycle length [CL] 366+/-50 ms [VT group]), 27 supraventricular tachycardias, 15 episodes of induced or simulated ATs (CL 376+/-29 ms [AT group]), and 12 exercise-related STs (CL 381+/-24 [ST group]). Sequences of trains of 5, 10, and 15 beats were delivered with a CL 40 ms shorter than the tachycardia CL. An FPPI absolute mean difference between consecutive trains of 5 and 10 beats (deltaFPPI) < or =25 ms identified all VTs (mean difference 5+/-7 ms). In the AT group, the deltaFPPI was >25 ms in all sequences (mean difference 129+/-60 ms, P<0.01). In the ST group, the deltaFPPI was >50 ms in all STs (mean difference 118+/-47 ms, P<0.01).

CONCLUSIONS

FPPI variability may differentiate SMVT from AT and ST. This criterion is potentially useful in implantable devices that use a single ventricular lead.

[Atrial tachycardia and nodal ventricular fibers]

The paper presents the results of direct operations for nodal tachycardias. Electrophysiological studies and open heart operations revealed that extranodal formations were implicated in the tachycardias. In particular it was found that some of them were located in front of the atrioventricular node closer to the fibrous angle (Type A) in some cases or closer to the base of the coronary sinus (Type B) in the others. From 1983 to 1989 the author performed 107 operations for nodal, the so-called borderline tachycardias (Type A) and 7 operations for Type B, as well as 4 for mixed tachycardia. No patient died, the negative results amounted to 8%. The incidence of complete transversal block was 3%. The long-term results indicated recurrent tachycardias in 13% of the cases, all the cases being noted in Type A.