Baiyan Xie

Identification of Atrial Fibrillation Episodes in Ambulatory Electrocardiographic Recordings: Validation of a Method for Obtaining Labeled R-R Interval Files

MURGATROYD, F.D., et.al.: Identification of Atrial Fibrillation Episodes in Ambulatory Electrocardiographic Recordings: Validation of a Method for Obtaining Labeled R‐R Interval Files. Current systems for analyzing ambulatory electrocardiograms (ECGs) are unable to distinguish precisely between sinus rhythm and atrial fibrillation (AF) episodes, and are unable to produce RR interval listings that distinguish AF from sinus rhythm on a beat‐to‐beat basis. We describe a method for obtaining such a computerized listing (“Composite Rhythm” file) from ambulatory recordings containing episodes of AF. The file lists the rhythm of each beat, its real time, and the QRS complex morphology. A visual inspection is made of a full printout of the recording to identify the precise time of onset and termination of each episode of AF. These times are entered into a computer and identified with the corresponding beats on a conventional RR interval file generated by Holter analysis. The method was validated using 1‐hour segments from 20 ambulatory ECGs containing 145 episodes of AF. These were visually identified by four independent observers with a mean sensitivity of 99.1%. The first beat of AF was identified concordantly in 96% of episodes, with a discrepancy of ≤ 3 beats in the other episodes. The times of 200 selected QRS complexes were then entered into the computer by each observer; 91.1 % of these complexes were identified exactly and 100% were identified to within one beat. The Composite Rhythm files have several potential applications for testing AF detection algorithms and studying the mode of onset of AF.

Performance of Basic Ventricular Tachycardia Detection Algorithms in Implantable Cardioverter Defibrillators; Implications for Device Programming

Around 20% of patients with third generation implantable cardioverter defibrillators receive inappropriate therapy, usually triggered by atrial fibrillation. This is because the criteria used for ventricular tachycardia detection by current implantable cardioverter defibrillators are based on the analysis of a sequence of RR intervals and may be inappropriately satisfied by supraventricular tachyarrhythmias. Algorithms for ventricular tachycardia detection were challenged against the full RR interval sequences from 482 spontaneous episodes of atrial fibrillation and 260 spontaneous episodes of ventricular tachycardia to determine their ability to discriminate between the arrhythmias. The sensitivities and specificities of the algorithms were calculated over a wide range of programmable parameters. For a given window length and detection interval, the most stringent algorithms, that required all beats to be classified as “fast”, were more specific than those allowing a proportion of “normal” intervals, even after adjustment for differing sensitivity. These differences were less marked for faster tachycardias. Specificity increased with the detection window length to a limit of approximately 18 beats. We conclude that ventricular tachycardia is detected with the highest specificity if all beats in an analyzed sequence are required to be “fast” even after lengthening of the tachycardia detection interval to maintain sensitivity. Further improvement in algorithm performance may require the incorporation of criteria such as tachycardia onset and stability.

Radiofrequency catheter ablation of accessory atrioventricular pathways: primary failure and recurrence of conduction.

OBJECTIVE: To identify possible factors associated with primary failure of radiofrequency ablation of accessory pathways or recurrence of accessory pathway conduction. PATIENTS AND METHODS: Radiofrequency ablation of accessory pathways failed in 25 of 243 patients, and recurrence of accessory pathway conduction occurred in an additional 13 patients. Factors possibly related to primary failure and recurrence were analysed. RESULTS: Primary failure and recurrence were less frequent in patients with left sided pathways (7% v 19%; 4% v 24%; P = 0.04). The factors that might relate to primary failure included an unstable catheter position (seven patients), a possible epicardial pathway (six patients), or misdiagnosis of accessory pathway location (two patients). The major factors for recurrence included the stability of the local atrial electrogram < or = 0.5 together with the stability of the local ventricular electrogram < or = 0.8, and prolonged time to pathway conduction block > or = 12 seconds). Thirty one patients underwent repeat ablation which was successful in 28. CONCLUSIONS: Primary failure and recurrence were more frequent in patients with right sided pathways. An unstable catheter position and a possible epicardial pathway location are the main contributing factors for primary failure, while unstable local electrograms and prolonged time to block are independent predictors for recurrence.

Radiofrequency catheter ablation of septal accessory atrioventricular pathways.

OBJECTIVE--Septal accessory atrioventricular pathways are recognised as being more difficult to ablate than pathways in other locations. This paper describes an experience of 48 consecutive patients with septal accessory pathways who had catheter ablation with radiofrequency current. PATIENTS AND METHODS--There were 28 male and 20 female patients, mean (SD) age 35 (17). 43 patients had a single accessory pathway and 5 patients had multiple accessory pathways. Pre-excitation was present in 37 patients, and 11 patients had concealed accessory pathways. 21 patients had had a previous electrophysiological study. Catheter ablation was undertaken with radiofrequency current delivered by a standard unipolar technique or by delivery of current across the septum (the bipolar technique). RESULTS--The median total procedure time was 167 (83) minutes including a 30-40 minute observation period after the abolition of conduction by the accessory pathway. The median total fluoroscopic time was 56 (30) minutes. 42 (88%) out of 48 patients had successful ablation of the pathway during the first session. In the six patients in whom the procedure failed, five had a midseptal pathway and one had a right anteroseptal pathway. A second attempt at ablation was made in two patients and succeeded in both. In total, 49 accessory pathways were successfully ablated in 44 (92%) out of 48 patients. The bipolar technique was used in 11 patients and succeeded in 10 patients. Standard unipolar current delivery had previously failed in seven of the 11 patients. Complications developed in two patients with a mid septal pathway (one with complete atrioventricular block and the other with a small pericardial effusion). CONCLUSION--Radiofrequency catheter ablation of septal accessory pathways is efficacious and safe. The procedure time can be shortened and success rate can be increased after improvement of the technique--that is, consideration of a bipolar approach for energy delivery in difficult cases.

Characteristics of bipolar electrograms during anterograde mapping: The importance of accessory atrioventricular pathway location

Local endocardial electrograms recorded at successful radiofrequency ablation sites during anterograde mapping (QRS-V interval, atrioventricular [AV] interval, AV ratio, the presence of accessory pathway potential, and stability of atrial and ventricular electrogram) were analyzed and compared according to location of accessory pathways. The mitral and tricuspid annuli were divided into 10 regions. Endocardial electrograms differed with regard to location of accessory AV pathways. The QRS-V interval was more negative in right posteroseptal, right free wall and right anteroseptal locations than the interval in other locations. The AV interval was longer in posteroseptal than the interval in left and right free wall sites. The stability of atrial and ventricular electrograms was better in left free wall sites than in posteroseptal sites and worst in right free wall and right anteroseptal sites. The variation in local electrograms at successful ablation sites with respect to pathway location may partly explain the low predictive value and the marked variation in previously suggested criteria for selecting target sites for radiofrequency energy delivery. The results also imply that the influence of accessory pathway location must be considered when attempts are made to establish electrogram-based criteria for predicting successful ablation of accessory pathways.

Computer modelling of misdiagnosis of atrial fibrillation as ventricular tachycardia by algorithms used in the implantable defibrillator

Inappropriate detection of atrial fibrillation as ventricular tachycardia by the implantable cardioverter defibrillator (ICD) may result in the delivery of painful shock therapies or potentially proarrhythmic antitachycardia pacing therapies. A computer model of three different contemporary ICDs was used to examine their susceptibility to atrial fibrillation. For any given programmed tachycardia detection interval (TDI) an algorithm requiring all R-R intervals to be shorter than TDI is less likely to be satisfied by spontaneously occurring atrial fibrillation than one which requires only a proportion of R-R intervals to be shorter than the TDI. This difference is most marked at longer TDIs.<<ETX>>