Clinical Validation and Comparison of Alternative Methods for Evaluation of Entrainment Mapping

Introduction: Measuring the postpacing interval (PPI) and correcting for the tachycardia cycle length (TCL) is an important entrainment response (ER). However, it may be impossible to measure PPI due to electrical noise on the mapping catheter. To overcome this problem, 2 alternative methods for the assessment of ER have been proposed: N+1 difference (N+1 DIFF) and PPIR method. PPI-TCL difference (PPI − TCL) correlates very well with ER assessed by new methods, but the agreement with PPI − TCL was established only in relation to PPIR method. Moreover, it is not known which of these methods is superior in the assessment of ER.
Methods: We analyzed 155 episodes of ER in 21 patients with heterogeneous reentrant arrhythmias. ER was estimated by PPI − TCL and by both alternative methods. Agreement between methods was assessed by means of the Bland-Altman test, kappa coefficient (κ), and correlation coefficient (r). Finally, a mathematical comparison of the alternative methods was performed.
Results: The agreement between PPI − TCL and alternative methods was very good. For N+1 DIFF the mean difference was −1.86 ± 7.31 ms; kappa = 0.9; r = 0.98; for PPIR method the mean difference was −1.46 ± 7.65 ms; kapa = 0.92; r = 0.99. Agreement between both alternative methods was also very high: the mean difference of 0.5 ± 6.6 ms; kappa = 0.89; r = 0.99. The analysis of the equations used for calculation of ER by these methods revealed that essentially they were mathematically equivalent.
Conclusion: Each of the alternative methods may be used for evaluation of ER when PPI − TCL cannot be assessed directly. Results obtained by both alternative methods are comparable.     

Prolonged PR interval despite a programmed short sensed AV delay: the role of intra-atrial conduction time.

Intracavitary electrogram (IEGM) is a useful tool in the interpretation of difficult pacemaker electrograms. A case of 320 ms P-V spike interval on the surface ECG despite a 110 ms programmed sensed AV delay is presented. Atrial IEGM revealed atrial tachycardia with a significant atrial conduction delay.     

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

A special form of macroreentrant atrial tachycardia (MRAT), due to reentrant activation around surgical scars, can occur in patients after cardiac surgery. Scar MRAT occurs usually after correction of congenital defects, such as atrial or ventricular septal defects, and especially after Mustard, Senning or Fontan procedures, but it can occur also after myxoma, valvular or coronary bypass surgery. The simplest form of scar MRAT is reentry around a lateral right atrial surgical scar. A basic mapping array with multiple simultaneous recordings from the anterior and septal right atrium is very useful to make the electrophysiological diagnosis. A line of double electrograms can be mapped in the centre of the circuit and a fragmented electrogram usually marks the pivoting point between the inferior end of the scar and the inferior vena cava (IVC). Extension of the scar toward the closest fixed obstacle, usually the IVC, by means of radiofrequency ablation, can interrupt the tachycardia and make it non-inducible. Typical atrial flutter usually coexists with scar MRAT and flutter isthmus ablation is probably indicated in all cases. In patients having undergone baffle atrial surgery it can be impossible to map the whole circuit and entrainment-mapping is helpful to localize critical isthmuses in the circuit. After the Fontan operation the right atrium can be severely dilated and scarred, and multiple, complex reentry circuits can be found. Left atrial MRAT based on large areas of scar has been described, but there is still too little experience with these to propose general rules for diagnosis and management.     

Sustained intra-atrial reentrant tachycardia. Electrophysiologic study of 20 cases

Twenty cases of sustained tachycardia due to intra-atrial reentry were investigated in patients aged 17 to 80 years (mean 47). The average frequency of the tachycardia was 128.6/min (extremes 95 and 180). Three modes of onset of the tachycardia were observed: atrial extra-stimulus (19 times), progressively accelerated atrial pacing (9 times) and atrial escape beat (10 times). The tachycardia was stopped in all cases by a premature stimulation. When spontaneous, the termination was either sudden (10 times) or preceded by a progressive slowing (9 times) or an alternating phenomenon of long-short cycle (13 times). Precise atrial mapping allowed to localize the first atrial depolarization less frequently in the sinus node area (1 case) than in the mean right atrium (21 cases), the low right atrium (2 cases), the interatrial septum (2 cases), and the left atrium (4 cases). The macroscopic size of the reentry circuit was demonstrated in only 3 cases. A junctional reentry was accurately ruled out in all cases thanks to the existence of a second or third-degree AV or VA black, or by studying the sequence of retrograde atrial activation. A true junctional reciprocating tachycardia was associated with the intra-atrial reentry in 2 cases.     

Accuracy of the Unipolar Electrogram for Identification of the Site of Origin of Ventricular Activation

Unipolar Electrogram. Introduction: The purpose of this study was to determine the accuracy of the unipolar electrogram for identifying the earliest site of ventricular activation. The earliest site of ventricular activation may be identified with the unipolar electrogram by the absence of an R wave. However, the accuracy of this technique is unknown.
Methods and Results: A single ventricular premature complex was induced mechanically at the tip of an electrode catheter to simulate a ventricular premature depolarization site of origin. Unipolar electrograms were recorded from the right ventricular septum at the tip electrode and at 2, 5, 8, and 11 mm from the electrode tip in 20 patients. No R waves were detected at the ventricular premature depolarization site of origin. R waves were detected in 4 of 20 patients (20%) at 2 mm from the tip electrode and 7 of 20 patients (35%) at 5, 8, and 11 mm from the tip electrode. An R wave was not observed at distances ≤ 11 mm from the site of tachycardia origin in 13 of 20 patients (65%).
Conclusions: While an R wave in the unipolar electrogram can he seen as close as 2 mm from the site of impulse origin, the absence of an R wave as an indicator of the site of impulse origin in the right ventricle is highly inaccurate. Therefore, the absence of an R wave in the unipolar electrogram is unlikely to be an adequate guide for identification of an effective target site for ablation of right ventricular tachycardia.     

P‐P Cycle Alternans During Atrial Tachycardia:

Background: A‐63 year‐old man complaining of palpitations underwent a 24‐hour ambulatory ECG monitoring that revealed the presence of recurrent episodes of nonsustained supraventricular tachycardia. Analysis of the tracings suggests an atrial origin of the arrhythmia. Tachycardias, quite regular at the beginning, suddenly showed a P‐P cycle alternans, namely, P‐P intervals alternately short and long. The evidence of two separate cycle ranges can be explained by the presence of a longitudinal dissociation within a discrete zone of the atrial circuit.     

Atypical Atrioventricular Nodal Reentry Tachycardia with Atrioventricular Block Mimicking Atrial Tachycardia:

AVNRT Mimicking Atrial Tachycardia, Introduction : Fast-intermediate form AV nodal reentry tachycardia (AVNRT) sometimes may mimic atrial tachycardia or atrial flutter and render the diagnosis difficult when the tachycardia rate is fast and AV block occurs during tachycardia.
Methods and Results : A 45-year-old woman with paroxysmal supraventricular tachycardia was referred to this institution. Initially, the tachycardia was thought to be an atrial tachycardia because of: (1) a short cycle length of the tachycardia with 2:1 and Wenckebach AV block; (2) a difference in the atrial activation sequence during tachycardia and during ventricular pacing; and (3) failure of burst ventricular pacing to affect the atrial rate and the atrial activation sequence during tachycardia. An accurate diagnosis of fast-intermediate form AVNRT was subsequently made based on the finding that the tachycardia was induced following delivery of a third ventricular extrastimulus, which showed a sequence of V-A-H and a change on atrial activation sequence of the induced beat. Successful radiofrequency ablation was achieved only after accurate diagnosis of the tachycardia was made.
Conclusion : Fast-intermediate form AVNRT sometimes may masquerade as atrial tachycardia. Accurate diagnosis is mandatory for successful ablation therapy.     

Successful radiofrequency catheter ablation of atrial muscle reentry tachycardia in a young adult

Atrial muscle reentry as a mechanism of tachycardia has been well illustrated in isolated animal atrial muscle. It has infrequently been reported as an etiology of supraventricular tachycardia in young patients. A case of atrial muscle reentry tachycardia and its successful elimination using radiofrequency catheter and its successful elimination using radiofrequency catheter ablation is reported.     

Characterization of Atrial Activation (A‐A) Intervals During Atrial Fibrillation Due to a Single Driver: Do They Reflect Atrial Effective Refractory Periods?

Characterization of Atrial Activation Intervals During AF . Background: The mean, median, and minimum local atrial activation (A‐A) intervals have been used to determine the local atrial effective refractory period (AERP) during atrial fibrillation (AF), the underlying assumption being that AF is due to multiple reentrant wavelets. Objective: We tested the hypothesis that when AF is due to a single, rapid, stable reentrant circuit (driver), the minimum and mean local A‐A intervals will be similar at sites in the reentrant circuit, but will vary widely at sites with fibrillatory conduction, making these latter intervals unreliable indicators of AERP. Methods: During sustained AF due to a left atrial (LA) driver in 6 sterile pericarditis dogs, electrograms were recorded from 186 bipolar electrodes from both atria. A‐A intervals were measured from each recording site during 1.2 seconds of AF. Minimum A‐A intervals as well as temporal (within site) and spatial (between sites) variability were determined from all sites. Results: A‐A intervals from each site during AF demonstrated that (1) 90–100% of right atrial (RA) sites and 18–39% of LA sites showed considerable (SD > 6 ms) temporal variability; (2) RA and LA sites with fibrillatory conduction (SD > 6 ms) showed considerable (a) spatial variability (RA: 9–36 ms; LA: 5–27 ms) and (b) variability of the minimum A‐A intervals (RA: 14–35 ms; LA 11–28 ms). Conclusion: During AF due to a driver, areas with fibrillatory conduction manifested considerable variability in the mean and the minimum A‐A intervals. Therefore, it is unlikely that any of the A‐A intervals reflect AERP. (J Cardiovasc Electrophysiol, Vol. 22, pp. 310‐315, March 2011)