Mattias Duytschaever

Fractionation of electrograms and linking of activation during pharmacologic cardioversion of persistent atrial fibrillation in the goat.

Introduction: During atrial fibrillation (AF), there is fractionation of extracellular potentials due to head‐to‐tail interaction and slow conduction of fibrillation waves. We hypothesized that slowing of the rate of AF by infusion of a Class I drug would increase the degree of organization of AF.

Mapping and Isolation of the Pulmonary Veins Using the PVAC Catheter

Objectives: We aimed to investigate the feasibility, efficacy, and safety of the pulmonary vein ablation catheter (PVAC) catheter (a novel multielectrode catheter using duty‐cycled bipolar and unipolar radiofrequency energy, Medtronic, Minneapolis, MN, USA) to completely isolate the pulmonary veins (PVs).

Lessons from dissociated pulmonary vein potentials: entry block implies exit block

Aims Prior reports using pacing manoeuvres, demonstrated an up to 42% prevalence of residual pulmonary vein to left atrium (PV–LA) exit conduction after apparent LA–PV entry block. We aimed to determine in a two-centre study the prevalence of residual PV–LA exit conduction in the presence of unambiguously proven entry block and without pacing manoeuvres. Methods and results Of 378 patients, 132 (35%) exhibited spontaneous pulmonary vein (PV) potentials following circumferential PV isolation guided by three-dimensional mapping and a circular mapping catheter. Pulmonary vein automaticity was regarded as unambiguous proof of LA–PV entry block. We determined the prevalence of spontaneous exit conduction of the spontaneous PV potentials toward the LA. Pulmonary vein automaticity was observed in 171 PVs: 61 right superior PV, 33 right inferior PV, 47 left superior PV, and 30 left inferior PV. Cycle length of the PV automaticity was >1000 ms in all cases. Spontaneous PV–LA exit conduction was observed in one of 171 PVs (0.6%). In a subset of 69 PVs, pacing from within the PV invariably confirmed PVLA exit block. Conclusion Unidirectional block at the LA–PV junction is unusual (0.6%). This observation is supportive of LA–PV entry block as a sufficient electrophysiological endpoint for PV isolation.

Variability in interpretation of the electrocardiogram in young athletes: an unrecognized obstacle for electrocardiogram-based screening protocols.

AIMS To assess in young athletes (i) the variability in the percentage of abnormal electrocardiograms (ECGs) using different criteria and (ii) the variability in ECG interpretation among cardiologists and sport physicians. METHODS AND RESULTS Electrocardiograms of 138 athletes were categorized by seven cardiologists according to the original European Society of Cardiology (ESC) criteria by Corrado (C), subsequently modified by Uberoi (U), Marek (M), and the Seattle criteria (S); seven sports physicians only used S criteria. The percentage of abnormal ECGs for each physician was calculated and the percentage of complete agreement was assessed. For cardiologists, the median percentage of abnormal ECGs was 14% [interquartile range (IQR) 12.5-20%] for C, 11% (IQR 9.5-12.5%) for U [not significant (NS) compared with C], 11% (IQR 10-13%) for M (NS compared with C), and 7% (IQR 5-8%) for S (P < 0.005 compared with C); complete agreement in interpretation was 64.5% for C, 76% for U (P < 0.05 compared with C), 74% for M (NS compared with C), and 84% for S (P < 0.0005 compared with C). Sport physicians classified a median of 7% (IQR 7-11%) of ECGs as abnormal by S (P = NS compared with cardiologists using S); complete agreement was 72% (P < 0.05 compared with cardiologists using S). CONCLUSION Seattle criteria reduced the number of abnormal ECGs in athletes and increased agreement in classification. However, variability in ECG interpretation by cardiologists and sport physicians remains high and is a limitation for ECG-based screening programs.

Incidence, timing, and characteristics of acute changes in heart rate during ongoing circumferential pulmonary vein isolation

AIMS Previous studies showed that catheter ablation of atrial fibrillation (AF) results in vagal denervation with an increase in average heart rate (HR) and a reduced overall HR variability (HRV) at follow-up. We analysed acute ablation-induced changes in HR and short-term HRV during percutaneous circumferential pulmonary vein isolation (CPVI). We also studied whether observed changes were predictors of successful outcome after first CPVI. METHODS AND RESULTS A total of 46 patients (35 men, 55 +/- 10 years) undergoing CARTO and computed tomography-guided CPVI for symptomatic AF were studied. Circumferential pulmonary vein isolation was performed under general anaesthesia by widely encircling the left and right pulmonary veins during sinus rhythm (SR). Radiofrequency (RF) current (35W, 48 degrees C) was applied with a 3.5 mm open irrigated tip catheter (Navistar Thermocool, Biosense Webster, Diamond Bar, CA, USA). Time- and frequency-domain analysis of short-term HRV was performed using 5 min electrocardiogram (ECG) recordings obtained at the beginning and the end of the CPVI procedure. Sinus rhythm cycle length was monitored continuously during CPVI. Circumferential pulmonary vein isolation was performed with 119 +/- 25 RF applications. Mean HR increased from 54 +/- 8 to 62 +/- 9 bpm (P < 0.001). Heart rate variability was significantly reduced (SDNN from 34 +/- 30 ms to 14 +/- 17 ms, P < 0.001, RMSSD from 27 +/- 22 ms to 13 +/- 14 ms, P < 0.001) with a marked change in sympathovagal balance towards less vagal activity (low frequency (LF)/high frequency (HF) ratio from 3.94 +/- 0.33 to 4.20 +/- 0.17, P < 0.001). Changes in RR interval, SDNN, and LF/HF ratio correlated significantly with RR interval (R = 0.56, P < 0.001), SDNN (R = 0.84, P < 0.001), and LF/HF ratio (R = -0.74, P < 0.001) at baseline. There were acute changes during ablation in HR and HRV, at the antero-superior junction between the left atrium (LA) and the right superior pulmonary vein (RSPV) in 36 patients (78%). Both HR and HRV at baseline and changes in HR/HRV were comparable between successful (n = 36) and failed (n = 10) patients. CONCLUSION (i) Percutaneous CPVI induces acute acceleration of HR and attenuation of short-term HRV (indicating vagal denervation during the procedure). (ii) Acute changes in HR and its variability invariably occur during RF energy delivery at the antero-superior junction between the LA and the RSPV. (iii) The degree of HR and short-term HRV changes depend on the vagal tone at the beginning of the procedure. (iv) In contrast to previously reported changes in overall HRV, acute changes in HR during the procedure are no predictors of long-term clinical outcome after CPVI.

Different Methods to Measure QRS Duration in CRT Patients: Impact on the Predictive Value of QRS Duration Parameters.

Measurements of QRS duration (QRSD) in patients undergoing cardiac resynchronization therapy (CRT) are not standardized. We hypothesized that both the measurement of QRSD and its predictive value on CRT response are sensitive to the method by which QRSD is measured.

Stable reentrant circuit with spiral wave activation driving atrial tachycardia

Introduction According to the joint expert committee from the Working Group of the European Society of Cardiology and the Heart Rhythm Society, atrial tachycardia (AT) is categorized as focal if the activation starts rhythmically at a small area and spreads centrifugally or macroreentrant if characterized by reentrant activation around a “large” central obstacle. We mapped and ablated a stationary reentrant circuit with spiral activation driving AT in the left atrium (LA). Because of its regular cycle length, this case offered the unique opportunity to study in detail the characteristics of intracardiac activation and electrograms during spiral wave activation.

Novel Algorithmic Methods in Mapping of Atrial and Ventricular Tachycardia

Background—Conventional methods to assess local activation time (LAT) detect the peak of the bipolar electrogram (B-LATPeak) or the maximal negative slope of the unipolar electrogram (U-LATSlope). We evaluated 3 novel methods to assess LAT: onset (B-LATOnset) and center of mass (B-LATCoM) of bipolar electrogram, and maximal negative slope of unipolar electrogram within a predefined bipolar window (U-LATSlope-hybrid). Methods and Results—In 1753 atrial tachycardia and 1426 ventricular tachycardia recordings, the performance of the methods in detecting LAT was evaluated pair-wise (eg, B-LATPeak versus B-LATOnset). For each comparison, histogram analysis of the differences in LAT values was performed. Variation in differences (P95-P5) in low quality (LQ) was compared with high-quality electrograms. In a separate data set (12 atrial tachycardia and 10 ventricular tachycardia), we evaluated for each method the accuracy in algorithmic activation mapping. Both in atrial tachycardia and ventricular tachycardia, the variation in difference between the conventional and novel methods was larger in LQ electrograms. In contrast, variation in difference between the novel methods was comparable in LQ and high-quality electrograms. Except for LATSlope-hybrid, all methods showed decreased mapping accuracy with increasing percentage of LQ electrograms. U-LATSlope-hybrid accurately mapped activation in 16 out of 22 maps (versus B-LATCoM, 14; B-LATPeak, 14; B-LATOnset, 13; U-LATSlope, 4). Conclusions—In LQ atrial and ventricular electrograms, the novel LAT methods (B-LATOnset, B-LATCoM, and U-LATSlope-hybrid) show less variation than the conventional methods. The U-LATSlope-hybrid, a hybrid method that accurately detects the maximal negative unipolar slope, is associated with the highest accuracy in algorithmic mapping of atrial tachycardia/ventricular tachycardia.

Clinical assessment and comparison of annotation algorithms in high-density mapping of regular atrial tachycardias

High‐density automated mapping of regular atrial tachycardias (ATs) requires accurate assessment of local activation times (LATs).

Bipolar electrograms characteristics at the left atrial-pulmonary vein junction: Toward a new algorithm for automated verification of pulmonary vein isolation.

BACKGROUND Verification of pulmonary vein isolation (PVI) is challenging because of the coexistence of PV and far-field potentials in bipolar electrograms recorded at the left atrial-pulmonary vein (LA-PV) junction. OBJECTIVE The purpose of this study was to characterize algorithmically LA-PV potentials before and after PVI and to develop an algorithm to differentiate nonisolated from isolated PVs. METHODS In 61 patients, we characterized-by type (morphology) and parameters-1440 electrograms recorded during sinus rhythm before and after PVI. Based on vein-dependent prevalence of a given type before and after PVI (first step) and based on vein- and type-dependent cutoff values in parameters specific for recordings before and after PVI (second step), we developed a 2-step algorithm to differentiate nonisolated from isolated PVs. We prospectively validated this algorithm in another dataset of 20 patients. RESULTS Characteristics before and after PVI were as follows: low voltage (10% ± 7% vs 36% ± 15%), monophasic (13% ± 4% vs 27% ± 9%), biphasic (18% ± 4% vs 21% ± 9%), triphasic (22% ± 5% vs 11% ± 13%), multiphasic (26% ± 7% vs 3% ± 3%), double potentials (11% ± 5% vs 2% ± 1%), peak-to-peak amplitude (0.97 ± 0.21 mV vs 0.35 ± 0.23 mV), maximal slope (0.179 ± 0.033 mV/ms vs 0.071 ± 0.029 mV/ms), minimal slope (0.030 ± 0.003 mV/ms vs 0.024 ± 0.002 mV/ms), and sharpest peak (1.82° ± 0.26° vs 3.45° ± 0.85°, P < .01 for all except biphasic). Overall sensitivity and specificity of the 2-step algorithm was 100% and 87%, respectively. CONCLUSION We algorithmically characterized LA-PV potentials before and after PVI in a large dataset (library of types and parameters). This library enabled us to develop an accurate 2-step algorithm to automatically differentiate nonisolated from isolated PVs. The 2-step algorithm is objective and reliable for assessing PV isolation without the need for pacing maneuvers.