Major clinical outcomes in symptomatic vs. asymptomatic atrial fibrillation: a meta-analysis.

BACKGROUND AND AIMS: Current guidelines suggest that asymptomatic atrial fibrillation (AF) is independently associated with increased risks of stroke and mortality compared with symptomatic AF. Considering that recent investigations have provided conflicting results, the present study aimed to evaluate the association between symptom status and clinical outcomes in patients with AF. METHODS: Medline, Cochrane Library, and Scopus were searched until 25 March 2024. Triple-independent study selection, data extraction and quality assessment were performed. Evidence was pooled using random-effects meta-analyses. RESULTS: Thirty-six studies (217 850 participants) were included. Based on the frequentist analysis, symptomatic individuals had no significant difference in the risk of all-cause mortality [hazard ratio (HR) .97, 95% confidence interval (CI) .80-1.17], cardiovascular mortality (HR 1.04, 95% CI .72-1.49), thromboembolism (HR 1.06, 95% CI .87-1.28), stroke (HR 1.06, 95% CI .84-1.34), hospitalization (HR 1.34, 95% CI .89-2.02), and myocardial infarction (HR .98, 95% CI .70-1.36), compared to the asymptomatic group. Symptomatic patients had a 33% increased risk of new-onset heart failure (HR 1.33, 95% CI 1.19-1.49) and a 30% lower risk of progression to permanent AF (HR .70, 95% CI .54-.89). The Bayesian analysis yielded comparable results, yet the association between symptom status and new-onset heart failure was not significant (HR 1.27, 95% credible interval .76-1.93; Bayes factor = 1.2). Symptomatic patients had higher odds of receiving antiarrhythmic drugs (odds ratio [OR] 1.64, 95% CI 1.33-2.03) and ablation therapy (OR 1.47, 95% CI 1.06-2.05) compared to asymptomatic cases. CONCLUSIONS: The risk of major clinical outcomes did not differ between individuals with and without AF-related symptoms. Asymptomatic patients had a greater hazard of progression to permanent AF.

Anatomical Ablation of the Atrioventricular Node.

Background: Atrioventricular (AV) conduction ablation has been achieved by targeting the area of penetration of the conduction axis as defined by recording a His bundle potential. Ablation of the His bundle may reduce the possibility of a robust junctional escape rhythm. It was hypothesised that specific AV nodal ablation is feasible and safe. Methods: The anatomical position of the AV node in relation to the site of penetration of the conduction axis was identified as described in dissections and histological sections of human hearts. Radiofrequency (RF) ablation was accomplished based on the anatomical criteria. Results: Specific anatomical ablation of the AV node was attempted in 72 patients. Successful AV nodal ablation was accomplished in 63 patients (87.5%), following 60 minutes (IQR 50-70 minutes) of procedure time, 3.4 minutes (IQR 2.4-5.5 minutes) of fluoroscopy time, and delivery of 4 (IQR 3-6) RF lesions. An escape rhythm was present in 45 patients (71%), and the QRS complex was similar to that before ablation in all 45 patients. Atropine was administered in six patients after the 10-min waiting period and did not result in restoration of conduction. In nine patients, AV conduction could not be interrupted, and AV block was achieved with ablation of the His after delivery of 12 (IQR 8-15) RF lesions. No cases of sudden death were encountered, and all patients had persistent AV block during a median 10.5 months (IQR 5-14 months) of follow-up. Conclusion: Anatomical ablation of the AV node is feasible and safe, and results in an escape rhythm similar to that before ablation.

High-resolution mapping of the circuit of typical atrioventricular nodal reentrant tachycardia.

BACKGROUND: Recent anatomic and electrophysiologic evidence has provided new insight into the anatomic substrate. Previous reports on electroanatomic mapping (EAM) of the circuit of atrioventricular nodal reentrant tachycardia (AVNRT) have been limited by mapping only the triangle of Koch on the right side of the septum and by the use of conventional mapping tools. The objectives are to obtain comprehensive high-resolution mapping of typical AVNRT and to investigate the role of the atrioventricular ring tissues in the circuit. METHODS: We employed EAM with the use of novel modules and algorithms for studying typical AVNRT from the right and the left sides of the septum. RESULTS: We performed extensive mapping of both the atrial septum and the septal vestibule of the tricuspid valve during typical AVNRT in 9 (6 females) patients, aged 49.6 ± 12.1 years. In two of these, left septal mapping was also obtained through the aorta. The earliest initial activation was variable, emanating from the superior or medial septum. The impulse consistently appeared below the orifice of the coronary sinus, at the site where its inferoanterior margin merged with the septal vestibule of the tricuspid valve at its entrance to the right atrium. It then returned to the initial activation site, presumably through the septal vestibular myocardium. The left septal activation area corresponded to that recorded on the right side. CONCLUSIONS: Typical AVNRT uses a circuit confined within the pyramid of Koch from the AV node to the septal isthmus, involving the myocardial walls of the pyramidal space.

Quantitative assessment of the fast pathway in atrioventricular nodal reentrant tachycardia.

BACKGROUND: Mathematical modelling has allowed calculation of the length of the slow and fast pathways in typical atrioventricular nodal reentrant tachycardia (AVNRT). The length of the slow pathway has been correlated with the measured length of the right inferior extension in human histologic specimens, but no histology data exist about the fast pathway. METHODS: In preparations of cadaveric human hearts, the AV node was identified, and the site of the fast pathway was projected according to both existing evidence and results of our electroanatomic mapping. This permitted measurement of the length of the fast pathway as a limb of the tachycardia circuit. RESULTS: Measurements of the length of the projected area of the fast pathway on histology specimens were performed in 8 hearts. The estimated length of the fast pathway was 39.6 ± 5.8 mm (range: 30.4-45.9 mm). These numbers are comparable to those produced by mathematical calculations of the length of the fast pathway. CONCLUSIONS: Typical AVNRT uses a circuit from the AV node to the septal isthmus of an average size of 5-6 cm, confined within the pyramid of Koch.

Arrhythmogenic Mitral Valve Prolapse.

Mitral valve prolapse (MVP) is a common condition present in 1-3% of the population. There has been evidence that a subset of MVP patients is at higher risk of sudden cardiac death. The arrhythmogenic mechanism is related to fibrotic changes in the papillary muscles caused by the prolapsing valve. ECG features include ST-segment depression, T wave inversion or biphasic T waves in inferior leads, and premature ventricular contractions arising from the papillary muscles and the fascicular system. Echocardiography can identify MVP and mitral annular disjunction, a feature that has significant negative prognostic value in MVP. Cardiac MRI is indicated for identifying fibrosis. Patients with high-risk features should be referred for further evaluation. Catheter ablation and mitral valve repair might reduce the risk of malignant arrhythmia. MVP patients with high-risk features and clinically documented ventricular arrhythmia may also be considered for an ICD.

A simplified differential pacing technique for the evaluation of bidirectional cavo-tricuspid isthmus block during ablation of typical atrial flutter.

PURPOSE: Bidirectional block of the cavo-tricuspid isthmus (CTI) is an established endpoint of CTI-dependent atrial flutter (AFl) ablation. Differential pacing has been used to evaluate the CTI block. The purpose of this study is to describe a modified differential pacing technique to evaluate the CTI block. METHODS: Sixty-two patients underwent radiofrequency (RF) ablation of CTI-dependent AFl. The acute endpoints were non-inducibility of the AFl, and verification of the bidirectional CTI block by our methodology. Pacing was performed in the CS with an ablation catheter positioned immediately lateral to the CTI ablation line, and then 1-2 cm more laterally. The stimulus-to-ablation catheter atrial electrogram intervals were measured at these sites (StimCS-Abl1 and StimCS-Abl2, respectively). Pacing with the ablation catheter also was performed at these 2 sites, and the stimulus-to-CS electrogram intervals (StimABL1-CS and StimABL2-CS) were measured. The criteria for the bidirectional block were StimCS-Abl1 > StimCS-Abl2, and StimABL1-CS > StimABL2-CS. Clinical efficacy was defined as freedom from recurrent AFl during follow-up. RESULTS: Following 12.2 ± 3.7 min of RF delivery across the CTI, intervals were StimCS-Abl1 = 181.2 ± 22.7 ms and StimABL1-CS = 181.0 ± 23.6 ms, and StimCS-Abl2 = 152.2 ± 26.5 ms and StimABL2-CS = 151.2 ± 22.7 (P < 0.001). Atrial flutter was rendered not inducible in all patients, and no procedural complications were encountered. During the next 15.9 ± 0.7 months, two patients were lost to follow-up, and among the 62 other patients, one (1.7%) had flutter recurrence. CONCLUSIONS: The bidirectional CTI block can be assessed quickly and easily using only the ablation and CS catheters for differential pacing.

Spatial characterization of the tachycardia circuit of atrioventricular nodal re-entrant tachycardia.

AIMS: The exact circuit of atrioventricular nodal re-entrant tachycardia (AVNRT) remains elusive. To assess the location and dimensions of the AVNRT circuit. METHODS AND RESULTS: Both typical and atypical AVNRT were induced at electrophysiology study of 14 patients. We calculated the activation time of the fast and slow pathways, and consequently, the length of the slow pathway, by assuming an average conduction velocity of 0.04 mm/ms in the nodal area. The distance between the compact atrioventricular node and the slow pathway ablating electrode was measured on three-dimensionally reconstructed fluoroscopic images obtained in diastole and systole. We also measured the length of the histologically discrete right inferior nodal extension in 31 human hearts. The length of the slow pathway was calculated to be 10.8 ± 1.3 mm (range 8.2-12.8 mm). The distance from the node to the ablating electrode was measured in five patients 17.0 ± 1.6 mm (range 14.9-19.2 mm) and was consistently longer than the estimated length of the slow pathway (P < 0.001). The length of the right nodal inferior extension in histologic specimens was 8.1 ± 2.3 mm (range 5.3-13.7 mm). There were no statistically significant differences between these values and the calculated slow pathway lengths. CONCLUSION: Successful ablation affects the tachycardia circuit without necessarily abolishing slow conduction, probably by interrupting the circuit at the septal isthmus.

Low-Level Tragus Stimulation Modulates Atrial Alternans and Fibrillation Burden in Patients With Paroxysmal Atrial Fibrillation.

Background Low-level tragus stimulation (LLTS) has been shown to significantly reduce atrial fibrillation (AF) burden in patients with paroxysmal AF. P-wave alternans (PWA) is believed to be generated by the same substrate responsible for AF. Hence, PWA may serve as a marker in guiding LLTS therapy. We investigated the utility of PWA in guiding LLTS therapy in patients with AF. Methods and Results Twenty-eight patients with AF were randomized to either active LLTS or sham (earlobe stimulation). LLTS was delivered through a transcutaneous electrical nerve stimulation device (pulse width 200 µs, frequency 20 Hz, amplitude 10-50 mA), for 1 hour daily over a 6-month period. AF burden over 2-week periods was assessed by noninvasive continuous ECG monitoring at baseline, 3 months, and 6 months. A 5-minute control ECG for PWA analysis was recorded during all 3 follow-up visits. Following the control ECG, an additional 5-minute ECG was recorded during active LLTS in all patients. At baseline, acute LLTS led to a significant rise in PWA burden. However, active patients receiving chronic LLTS demonstrated a significant reduction in both PWA and AF burden after 6 months (P<0.05). Active patients who demonstrated an increase in PWA burden with acute LLTS showed a significant drop in AF burden after 6 months of chronic LLTS. Conclusions Chronic, intermittent LLTS resulted in lower PWA and AF burden than did sham control stimulation. Our results support the use of PWA as a potential marker for guiding LLTS treatment of paroxysmal AF.

Trends in ablation procedures in Greece over the 2008-2018 period: Results from the Hellenic Cardiology Society Ablation Registry.

OBJECTIVE: In 2008, the radiofrequency ablation (RFA) procedures registry of the Hellenic Society of Cardiology was created. This online database allowed electrophysiologists around the country to input data for all performed ablation procedures. The aim of this study is to provide a thorough report and interpretation of the data submitted to the registry between 2008 and 2018. METHODS: In 2008, a total of 27 centers/medical teams in 24 hospitals were licensed to perform RFA in Greece. By 2018, the number had risen to 31. Each center was tasked with inserting their own data into the registry, which included patient demographics (anonymized), type of procedure and technique, complications, and outcomes. RESULTS: A total of 18587 procedures in 17900 patients were recorded in the period of 2008-2018. By 2018, slightly more than 70% of procedures were performed in 7 high-volume centers (>100 cases/year). The most common procedure since 2014 was atrial fibrillation ablation, followed by atrioventricular nodal reentry tachycardia ablation. Complication rates were low, and success rates remained high, whereas the 6-month relapse rates declined steadily. CONCLUSION: This online RFA registry has proved that ablation procedures in Greece have reached a very high standard, with results and complication rates comparable to European and American standards. Ablation procedures for atrial fibrillation are increasing constantly, with it being the most common intervention over the last 6-year period, although the absolute number of procedures still remains low, compared to other European countries.