Benedict Glover

Use of frequency analysis on the ECG for the prognosis of low energy cardioversion treatment of atrial fibrillation

Electric cardioversion is the most effective therapy for restoring sinus rhythm in patient with atrial fibrillation (AF), however, there is not a guiding criteria for advising on when and in whom it will be successful. The objective of this study was to employ frequency analysis on the surface electrocardiogram (ECG) to predict the outcome of low energy internal cardioversion in patients with AF. Thirty nine patients with AF, for elective DC cardioversion were included in this study. One catheter was positioned in the right atrial appendage and another in the coronary sinus. A voltage step-up protocol (50–300 V) was used for patient cardioversion. Prior to shock delivery, residual atrial activity signal (RAAS) was derived from 60 seconds of surface ECG from defibrillator pads, by bandpass filtering and ventricular activity (QRST) cancellation. Dominant atrial fibrillatory frequency (DAFF) was estimated from the RAAS power spectrum as the dominant frequency within the 3–12 Hz band. DAFF was calculated from whole 60 seconds segment (DAFF_L) and from the finals 10 seconds segment (DAFF_S) of the RAAS. Lower DAFF_L and DAFF_S were found in successfully cardioverted patients than in those nonsuccessful ones, with energy ≤3 and ≤6 joules. Therapy result (employing 3J or less) was predicted in 35/39 (89.7%) patients with DAFF_L=5.40Hz, and DAFF_L was ≥5.75Hz in a 100% of noncardioverted patients. In conclusion, frequency analysis of the RAAS could be useful for predicting success of low energy internal cardioversion of patients with atrial fibrillation.

Reverse atrial electrical remodeling induced by cardiac resynchronization therapy

PURPOSE Cardiac resynchronization therapy (CRT) has been shown to improve left atrial function; however the effect on reverse electrical remodeling has been poorly evaluated. We hypothesized that CRT might induce reverse atrial electrical remodeling manifesting in the surface ECG as a shortening in P-wave duration. METHODS Patients with CRT and more than 92% biventricular pacing at minimum follow-up of 1 year were included in the analysis. Those with prior history of atrial fibrillation (AF) were excluded. Data were recorded for clinical, echocardiographic and ECG variables prior to implant and at least 12 months post implantation. Semiautomatic calipers and scanned ECGs at 300 DPI maximized × 8 were used to measure P-wave duration and diagnose advanced interatrial block (aIAB) during sinus rhythm. The occurrence of AF was assessed through analyses of intracardiac electrograms and clinical presentations. RESULTS 41 patients were included in the study with mean age of 67.4 ±9.6 years, 71% were male, left atrial diameter 41.1 ± 8.5 mm and LV EF 28.5 ± 6.5%. Over a mean follow up of 55 months, a significant reduction in P-wave duration (142.7 ms vs. 133.1 ms; p < 0.001) was noted. The presence of aIAB was significantly reduced (36% vs. 17%; p = 0.03). The incidence of new onset AF was 36%. Time to AF onset after CRT implantation was not influenced by a reduction in P-wave duration. CONCLUSION CRT induces atrial reverse electrical remodeling manifested as a reduction in P-wave duration. Larger studies are needed to determine the impact on AF incidence after CRT implantation.

Interatrial block and interatrial septal thickness in patients with paroxysmal atrial fibrillation undergoing catheter ablation: Long-term follow-up study

Interatrial block (IAB) is a strong predictor of recurrence of atrial fibrillation (AF). IAB is a conduction delay through the Bachman region, which is located in the upper region of the interatrial space. During IAB, the impulse travels from the right atrium to the interatrial septum (IAS) and coronary sinus to finally reach the left atrium in a caudocranial direction. No relation between the presence of IAB and IAS thickness has been established yet.

Frequency Analysis of Atrial Fibrillation Predicts Success for Low Energy Intracardiac Cardioversion

The aim of this study was to evaluate the relation between atrial fibrillatory frequency (AFF) and the probability of successful internal cardioversion of atrial fibrillation (AF). Thirty consecutive patients suggested for DC cardioversion at the Royal Victoria Hospital in Belfast, were included in the study. Two catheters were positioned in the right atrial appendage (RAA) and the coronary sinus (CS), for delivering a biphasic shock waveform, 6/6 msec, synchronized with the Rwave on the ECG signal. The atrial fibrillatory activity was derived from 60 seconds of surface ECG from the defibrillator pads, prior to shock delivery, by bandpass filtering and ventricular activity (QRST) cancellation. QRST complexes subtraction was implemented by means of a template matching and signal averaging algorithm. FFT was applied to the residual atrial fibrillatory signal. Atrial fibrillatory frequency was estimated from the dominant frequency in the 3–12Hz band of the power spectrum. Eighteen patients were successfully cardioverted using a voltage step up protocol beginning from 50V up to 300V (biphasic pulse amplitude). Twelve of the cases were not successfully cardioverted to sinus rhythm. The AFF was 5.42±1.03 Hz (within the range of 3.69 – 7.38 Hz) in patients successfully cardioverted vs. 6.5 ± 0.68 Hz (within the range of 5.38–7.56 Hz) in patients which failed cardioversion, P < 0.004. AFF was < 6.26 Hz in 15 of the 18 patients with successful cardioversion. AF cardioversion was predicted with a specificity of 83.33% in the best cases, and with an acceptable sensitivity of 75%. Also, there was a positive correlation (ρ = 0.624 and P < 0.01) between the minimal defibrillation energy and the fibrillatory frequency in cardioverted patients. In conclusion, calculated AFF from the surface ECG, may predict the success of internal low energy cardioversion of patients with atrial fibrillation.

Lyme Carditis and High-Degree Atrioventricular Block

Canada has seen a sixfold increase in Lyme disease since being nationally notifiable in 2009. This is the first Canadian series on Lyme carditis manifested as high-degree atrioventricular block. We report 5 recent cases presented over a 2-year period. The variation of nonspecific presentations requires a high index of suspicion for prompt diagnosis and correct management. Recognizing this early would curtail the progression of conduction disorders and potentially avoid permanent pacemaker implantation.

Hybrid ablation for atrial fibrillation: current approaches and future directions

Purpose of review Catheter ablation of atrial fibrillation has rapidly evolved during the past decade: although the treatment of paroxysmal atrial fibrillation via a transcatheter approach has been consistently successful, persistent and long-standing atrial fibrillation still represents a major clinical challenge with less favorable outcomes to date. Because novel, minimally invasive surgical approaches have been developed for atrial fibrillation ablation, the aim of the present review is to analyze the current evidence surrounding the integration of surgical and transcatheter strategies in a hybrid fashion for the treatment of atrial fibrillation. Recent findings Long-standing persistent, atrial fibrillation requires further understanding. Wide antral circumferential ablation of the pulmonary veins represents the cornerstone of any ablation therapy. Additional linear lesions and/or targeting complex fractionated atrial electrograms may also be considered. One of the limitations is achieving a transmural lesion. The combined endocardial and epicardial approach may represent a superior approach. Summary Hybrid ablation of atrial fibrillation represents a novel therapeutic strategy for the treatment of complex scenarios, such as long-standing persistent atrial fibrillation. A specialized team including dedicated surgeons and cardiologists appears to be crucial in order to achieve durable and satisfactory outcomes following hybrid ablation of atrial fibrillation.

Catheter ablation for atrial flutter: a survey by the European Heart Rhythm Association and Canadian Heart Rhythm Society.

The purpose of this EP wire survey was to examine current practice in the management of both cavotricuspid isthmus (CTI)-dependent and non-CTI-dependent atrial flutter (AFL) ablation amongst electrophysiologists in European and Canadian centres and to understand how current opinions vary from guidelines. The results of the survey were collected from a detailed questionnaire that was created by the European Heart Rhythm Association Research Network and the Canadian Heart Rhythm Society. Responses were received from 89 centres in 12 countries. The survey highlighted variability within certain aspects of the management of AFL ablation. The variability in opinion regarding other procedural details suggests a need for further research in this area and consideration of the development of guidelines specific to AFL. Overall, there is reasonable consensus regarding oral anticoagulation and the desired endpoints of ablation for patients with CTI-dependent AFL and for non-CTI-dependent AFL.

The impact of lifestyle intervention on atrial fibrillation

Purpose of review Atrial fibrillation is the most common sustained cardiac arrhythmia, attributable to several factors that may be amenable through lifestyle modification. There is emerging evidence to suggest that the successful management of several cardiovascular risk factors [obesity, hypertension (HTN), diabetes mellitus, and obstructive sleep apnea (OSA)] can lead to fewer complications and atrial fibrillation prevention. However, the long-term sustainability and reproducibility of these effects have yet to be explored in larger studies. This review explores recent findings for exercise and lifestyle modifications to promote alternative strategies to interventional therapy for atrial fibrillation management. Recent findings Several studies have highlighted the impact of established modifiable risk factors on atrial fibrillation burden and the potential for effective risk management in a clinical setting. Higher SBP, HTN, pulse pressure, and antihypertensive treatment have been linked to alterations in left atrial diameter and dysfunction. Effective treatment of HTN has been shown to reduce all-cause mortality, cardiovascular mortality, and the overall risk of developing atrial fibrillation. Given the impact of obesity on the development of atrial fibrillation, diet has been identified as a modifiable risk factor for stroke. Maintenance of proper glycemic control through structured exercise training for prediabetes and continuous positive airway pressure utilization for OSA, have also been correlated with reductions in atrial fibrillation recurrence. Summary Early intervention of modifiable cardiometabolic factors leads to lifestyle and behavioral change, which has significant potential to evolve atrial fibrillation management in the coming years.

Implantable loop recorders in the real world: a study of two Canadian centers

PurposeImplantable loop recorders (ILRs) are increasingly being used for ambulatory electrocardiography. We sought to evaluate ILR indications, diagnostic yield, ILR-guided interventions, and complications in two Canadian centers.MethodsThis was a retrospective study using electronic medical records to identify ILR implants at Queen’s University and the University of Manitoba. Information was collected on patient characteristics, medications, indication for implant, results of prior investigations, diagnostic outcome, and subsequent management.ResultsA total of 540 patients were identified; 386 had completed monitoring at time of analysis. Forty patients were lost to follow-up. Indications were unexplained syncope 84.8%, palpitations 12.8%, and suspected atrial fibrillation 11.7%. For syncope, ILRs documented arrhythmia or conduction disorder in 46%. Most common conditions were asystole/sinus pause (22%), complete heart block (10.4%), and atrial fibrillation (AF) (6.9%). After ILR diagnosis, 39.9% of implanted patients received pacemaker/ICD and 2.7% underwent catheter ablation. For palpitations, ILRs documented arrhythmia or conduction disorder in 60.4%. Most common conditions were AVNRT, AF, complete heart block, and ventricular tachycardia. After diagnosis, 25% underwent catheter ablation and 22.9% received pacemaker/ICD. For suspected AF, AF was diagnosed in 40%. Complications were observed in 3.3% of implanted patients: implant site infection 1.5%, non-infectious implant site pain requiring device removal or pocket revision 1.5%, 0.2% hypertrophic scar, and 0.2% device malfunction.ConclusionsAn ILR has excellent diagnostic yield for syncope, palpitations, and suspected AF, and a considerable proportion of patients undergo ILR-directed interventions following monitoring. ILR implantation is a low-risk procedure.

Nonlinear analysis of the ECG during atrial fibrillation in patients for low energy internal cardioversion

The goal of this study was to investigate the usefulness of nonlinear analysis in determining the success of low energy internal cardioversion (IC) in patients with atrial fibrillation (AF). Nonlinear analysis has previously been used for characterizing AF patterns, and spontaneous termination in its paroxysmal form. However, the relationship between the probability to restore sinus rhythm by IC and quantitative nonlinear analysis based electrocardiographic (ECG) markers has not been explored before. Thirty nine patients with AF, for elective DC cardioversion at the Royal Victoria Hospital in Belfast, were included in this study. One catheter was positioned in the right atrial appendage and another in the coronary sinus, to deliver a biphasic shock waveform. A voltage step-up protocol (50–300 V) was used for patient cardioversion. Residual atrial fibrillatory signal (RAFS) was derived from 60 seconds of surface ECG from defibrillator pads, prior to shock delivery, by bandpass filtering and ventricular activity (QRST) cancellation. QRST complexes were cancelled using a recursive least squared (RLS) adaptive filter. The maximal Lyapunov exponent (λ), correlation dimension (course grained estimation, CDcg) and approximate entropy (ApEn) were extracted from the RAFS. These variables were calculated from 10 s of the RAFS before shock delivery. 26 patients were successfully cardioverted, employing a maximum energy of 11.84 joules. A lower λ (0.037±0.006 vs. 0.044±0.008, P=0.01) and CDcg (5.552±2.075 vs. 6.592±1.130, P=0.049) were found in successfully cardioverted patients than in those non successful ones, with an energy ≤3 joules. Also, there was a significant positive correlation between the minimal defibrillation energy and λ (r=0.483, P=0.013) in cardioverted patients. In conclusion, complexity analysis of the RAFS is useful for assessing the prospective efficacy of internal low energy cardioversion of patients with atrial fibrillation.