Spontaneous pre-excited supraventricular tachycardias in a Labrador Retriever.

A 4-year-old Labrador Retriever was presented for intermittent tachycardia. The electrocardiogram showed sinus rhythm conducted with ventricular pre-excitation and short runs of orthodromic atrioventricular reciprocating tachycardia. Four months later, the rhythm degenerated into a symptomatic sustained tachycardia, suspected to be pre-excited atrial fibrillation, a potentially life-threatening rhythm in the presence of an accessory pathway with a short refractory period. Two days after initiating oral diltiazem, the dog deteriorated and represented with sustained orthodromic atrioventricular reciprocating tachycardia, which was terminated by a precordial chest thump. It proceeded to sinus rhythm with ventricular pre-excitation followed by an episode of pre-excited focal atrial tachycardia. A bolus of lidocaine IV successfully restored sinus rhythm and sotalol treatment was started. The dog clinically recovered but died spontaneously 24 h later. This is the first case report that describes spontaneous pre-excited focal atrial tachycardia.

Electrical remodeling of atrioventricular junction: a study on retrogradely perfused chick embryonic heart.

Atrioventricular (AV) accessory pathways (APs) provide additional electrical connections between the atria and ventricles, resulting in severe electrical disturbances. It is generally accepted that APs originate in the altered annulus fibrosus maturation in the late prenatal and perinatal period. However, current experimental methods cannot address their development in specific locations around the annulus fibrosus due to the inaccessibility of late fetal hearts for electrophysiological investigation under physiological conditions. In this study, we describe an approach for optical mapping of the retrogradely perfused chick heart in the last third of the incubation period. This system showed stability for electrophysiological measurement for several hours. This feature allowed analysis of the number and functionality of the APs separately in each clinically relevant position. Under physiological conditions, we also recorded the shortening of the AV delay with annulus fibrosus maturation and analyzed ventricular activation patterns after conduction through APs at specific locations. We observed a gradual regression of AP with an area-specific rate (left-sided APs disappeared first). The results also revealed a sudden drop in the number of active APs between ED16 and ED18. Accessory myocardial AV connections were histologically documented in all positions around the annulus fibrosus even after hatching. The fact that no electrically active AP was present at this stage highlights the necessity of electrophysiological evaluation of accessory atrioventricular connections in studying AP formation.

[Efficacy of Decitabine Combined with Preexcitation Regimen in Treatment of Newly Diagnosed AML Patients Who Did not Respond to Initial Standard Induction Chemotherapy].

OBJECTIVE: To investigate the efficacy of decitabine combined with preexcitation regimen in the treatment of newly diagnosed acute myeloid leukemia (AML) patients who have not been relieved by the first standard induction chemotherapy and its influence on the relative content of regulatory T lymphocytes (Tregs). METHODS: The clinical data of 102 newly diagnosed AML patients (except acute promyelocytic leukemia) who did not relieve after initial standard induction chemotherapy in Shaanxi Provincial People's Hospital from March 2013 to March 2019 were retrospectively analyzed. Fifty-one patients who accepted pre-excitation regimen were divided into regular group, while another 51 patients treated with decitabine combined with pre-excitation regimen were divided into combination group. The efficacy, incidence of toxic and side effects, Core Scale of Quality of Life (QLQ-C30) score before and after treatment, T lymphocyte subsets (CD3+, CD4+, CD4+/CD8+, Tregs) and 3-year overall survival (OS) rate were compared between the two groups. RESULTS: The total effective rate of combination group was 80.39%, which was significantly higher than 62.75% of regular group (P < 0.05). After treatment, the QLQ-C30 score of combination group was 60.27±6.96, which was significantly lower than 65.73±7.96 of regular group (P < 0.001). There was no statistical difference in the incidence of toxic and side effects between the two groups (P >0.05). After treatment, the levels of CD3+, CD4+, CD4+/CD8+ in the combination group were higher than those in the regular group (all P < 0.001), while Treg was lower (P < 0.001). The 3-year OS rate in the combination group was 72.55%, which was significantly higher than 52.94% in the regular group (P < 0.001). CONCLUSION: Decitabine combined with preexcitation regimen has a significant effect on AML patients who have not been alleviated by standard induction chemotherapy in the first course of treatment. It can reduce anti-tumor immune suppression and improve immune function by regulating the relative content of Tregs, thus prolongs survival time and improves life quality of patients without increasing adverse reactions.

Characteristics of Right-Sided Accessory Pathways Associated With Right Cardiac Veins.

BACKGROUND: The anatomy of myocardial fibers around the right cardiac veins (RCVs) and their roles in accessory pathways (APs) are rarely reported. METHODS: Six RCV-APs were identified from 566 patients with right-sided APs. Mapping of retrograde atrial activation was performed using CARTO 3 system under orthodromic tachycardia or right ventricular pacing. Venography of RCVs was acquired at the earliest retrograde atrial activation. RESULTS: Patients enrolled had a median age of 30 (11-51) years, 5 of them were male. Venography of RCVs could be classified into 3 distinct patterns based on the identified ventricular branches, right marginal vein only (type I; n=3), both right marginal vein and anterior cardiac veins (type II; n=2), and anterior cardiac vein only (type III; n=1). Patients with type I venography had rS QRS pattern in lead V1, negative delta wave in lead III and negative or isoelectric delta wave in lead aVF. However, patients with type II and III venography had QS QRS patterns in lead V1 and variable patterns of delta wave in inferior leads. Earliest retrograde atrial activation was found at a median of 16.75 (14.60-20.00) mm away from the tricuspid annulus, all with A larger than V. At the earliest retrograde atrial activation, far-field ventricular electrogram was found 30 ms later than QRS onset in 1 patient under sinus rhythm. AP conduction was eliminated by mechanical pressure in 2 and by radiofrequency ablation in 4 at the ostium of the veins colocalizing with the earliest retrograde activation of the right atrium. No recurrence was observed during 36 (10-60) months follow-up. CONCLUSIONS: The RCV-AP is a rare form of right-sided APs characterized by atrial insertions distant from the annulus. ECG-speculated ventricular insertion sites conformed to the location of identified RCVs.

Accessory pathway localization with probabilistic density maps generated by a mobile application: Assessment of a full pre-excitation net-vector method.

INTRODUCTION: Precise electrocardiographic localization of accessory pathways (AP) can be challenging. Seminal AP localization studies were limited by complexity of algorithms and sample size. We aimed to create a nonalgorithmic method for AP localization based on color-coded maps of AP distribution generated by a web-based application. METHODS: APs were categorized into 19 regions/types based on invasive electrophysiologic mapping. Preexcited QRS complexes were categorized into 6 types based on polarity and notch/slur. For each QRS type in each lead the distribution of APs was visualized on a gradient map. The principle of common set was used to combine the single lead maps to create the distribution map for AP with any combination of QRS types in several leads. For the validation phase, a separate cohort of APs was obtained. RESULTS: A total of 800 patients with overt APs were studied. The application used the exploratory data set of 553 consecutive APs and the corresponding QRS complexes to generate AP localization maps for any possible combination of QRS types in 12 leads. Optimized approach (on average 3 steps) for evaluation of preexcited electrcardiogram was developed. The area of maximum probability of AP localization was pinpointed by providing the QRS type for the subsequent leads. The exploratory data set was validated with the separate cohort of APs (n = 256); p = .23 for difference in AP distribution. CONCLUSIONS: In the largest data set of APs to-date, a novel probabilistic and semi-automatic approach to electrocardiographic localization of APs was highly predictive for anatomic localization.

EPM algorithm: A stepwise approach to accessory pathway localization in ventricular pre-excitation.

BACKGROUND: Accurate estimation of accessory pathway (AP) localization in patients with ventricular pre-excitation or Wolff-Parkinson-White (WPW) syndrome remains a diagnostic challenge. Existing algorithms have contributed significantly to this area, but alternative algorithms can offer additional perspectives and approaches to AP localization. OBJECTIVE: This study introduces and evaluates the diagnostic accuracy of the EPM algorithm in AP localization, comparing it with established algorithms Arruda and EASY. METHODS: A retrospective analysis was conducted on 138 patients from Hospital São Paulo who underwent catheter ablation. Three blinded examiners assessed the EPM algorithm's diagnostic accuracy against the Arruda and EASY algorithms. The gold standard for comparison was the radioscopic position of the AP where radiofrequency ablation led to pre-excitation disappearance on the ECG. RESULTS: EPM showed a diagnostic accuracy of 51.45%, closely aligning with Arruda (53.29%) and EASY (44.69%). Adjacency accuracy for EPM was 70.67%, with Arruda at 66.18% and EASY at 72.22%. Sensitivity for EPM in distinguishing left vs. right APs was 95.73%, with a specificity of 74.33%. For identifying septal vs. lateral right APs, EPM sensitivity was 82.79% with a specificity of 46.15%. These measures were comparable to those of Arruda and EASY. Inter-observer variability was excellent for EPM, with Kappa statistics over 0.9. CONCLUSION: The EPM algorithm emerges as a reliable tool for AP localization, offering a systematic approach beneficial for therapeutic decision-making in electrophysiology. Its comparable diagnostic accuracy and excellent inter-observer variability underscore its potential clinical applicability. Future research may further validate its efficacy in a broader clinical setting.

Pregnancy outcomes in patients complicated with pre-excitation syndrome.

INTRODUCTION: Pregnant women with pre-excitation syndrome are more likely to develop supraventricular tachycardia (SVT) during pregnancy and delivery, leading to an increased risk of adverse events. METHOD: This was a retrospective study of 309 pregnancies in 280 women (29 women had two pregnancies in this series) with pre-excitation syndrome who delivered at West China Second University Hospital from June 2011 to October 2021. All the 309 pregnant women with pre-excitation syndrome were divided into SVT and non-SVT groups to analyze the cardiac and obstetric complications. RESULTS: Among the included pregnant women in the past 10 years, the prevalence of pre-excitation syndrome was 0.24% (309/127725). There were 309 cases with pre-excitation syndrome in all hospitalized pregnant women. Among them, 62 (20.1%, 62/309) had a history of SVT. In the 62 cases with SVT during pregnancy, 22 (35.5%) cases had a history of SVT. Gestational diabetes mellitus was associated with SVT during pregnancy. The cesarean section rate was 88.7% in the SVT group, which was significantly higher than that in the non-SVT group (64.8%) (P < 0.001). Cases with SVT during pregnancy had more cardiac and obstetric complications. Four fetal deaths were recorded in the SVT group. Additionally, 29 women experienced two pregnancies during the study period, among whom, five received radiofrequency ablation after the first delivery and obtained better outcomes in the second pregnancy. CONCLUSION: The adverse outcomes such as cardiac complications, maternal and fetal complications (PROM, prematurity, SGA, fetal distress, etc.) in pregnant women with pre-excitation syndrome were closely related to SVT, with possible risk factors including history of SVT before pregnancy, cardiac function, heart organic abnormalities, and gestational diabetes mellitus.

[Historical developments in the diagnosis and treatment of pre-excitation syndromes (WPW)]. / Historische Entwicklung in Diagnostik und Therapie bei Präexzitationssyndromen (WPW).

In 1930, Wolff, Parkinson and White described the syndrome that bears their names. The mechanisms of supraventricular tachycardias were analyzed by brilliant electrocardiography interpretation by Pick and Langendorf. Wellens and Durrer using electrophysiologic studies analyzed the tachycardia mechanism invasively. In Germany the group by Seipel and Breithardt as well as Neuss and Schlepper studied the tachycardia mechanisms and response to antiarrhythmic drugs invasively by electrophysiological studies. Following the first successful interruption of an accessory pathway by Sealy in 1967, surgeons and electrophysiologists cooperated in Germany. Two centers, Hannover and Düsseldorf were established. Direct current (DC) ablation of accessory pathways was introduced by Morady and Scheinman. Because of side effects induced by barotrauma of DC, alternative strategies were studied. In 1987, radiofrequency ablation was introduced and thereafter established as curative therapy of accessory pathways in all locations.

Coexistence of a Classical Nodoventricular Accessory Pathway With a Left-Sided Mahaim Accessory Pathway.

The coexistence of 2 Mahaim pathways represents a diagnostic challenge. We present a case in which the SH/HA intervals were useful for identifying concealed nodoventricular or His-ventricular pathways.

Multi-catheter cryotherapy for the treatment of resistant accessory pathways.

OBJECTIVE: To investigate the utility of simultaneous multi-catheter cryotherapy for the treatment of APs that were previously resistant to standard radiofrequency (RF) catheter ablation. BACKGROUND: Catheter ablation is established in the treatment of accessory pathways (AP), with high rates of permanent procedural success with a single attempt. However, there are still instances of acute procedural failure and AP recurrences with standard RF and cryotherapy methods. METHODS: Seven consecutive cases of pre-excitation syndromes with prior failed RF catheter ablation had the novel treatment. Cryotherapy was delivered using two 8 mm tip focal cryoablation catheters (Freezor® Max, Medtronic, Minneapolis, Minnesota, USA). RESULTS: Accessory pathway localisation was septal in 5 cases, left posterolateral in 1, right lateral in 1. In all cases, ablation of the AP was acutely successful with no procedural complications. Median procedure and fluoroscopy durations were 199 and 35 min, sequentially. Median Procedure duration fell significantly in the second half of series (174 min) compared to the first half (233 min, P = 0.05). One patient had evidence of a recurring AP conduction with pre-excitation at 5-week follow up. After a median follow up of 66.8+-6.5 months, 6 out of 7 patients remained asymptomatic and free of pre-excitation. CONCLUSION: Simultaneous multi-catheter cryotherapy is feasible, safe and can provide definitive cure of accessory pathways that were previously resistant to standard radiofrequency ablation. Further study is required in the assessment of this novel form of advanced cryotherapy to treat complex and resistant arrhythmias.

Intermittent ventricular pre-excitation in symptomatic adults: Always a marker of low risk?

BACKGROUND: Intermittent ventricular pre-excitation was considered a low-risk marker for sudden death. However, to date, some studies do not exclude the existence of accessory pathways (APs) with high-risk intermittent antegrade conductive properties. According to current European Guidelines, high-risk features of APs are antegrade pathway conduction ≤250 ms in baseline or during the adrenergic stimulus, inducibility of atrioventricular reciprocating tachycardias (AVRT), inducibility of pre-excited atrial fibrillation (AF), and presence of multiple APs. For all of these transcatheter ablation is recommended. The aim of our study was to evaluate the existence of differences in risk characteristics between patients with intermittent pre-excitation (IPX) and those with persistent pre-excitation (PPX), from a sample of adults with ventricular pre-excitation and symptoms like palpitations. METHODS: 293 adults [IPX: 51 (17.4%); PPX: 242 (82.6%)] underwent electrophysiological study and then catheter ablation of their APs if arrhythmia inducibility (AVRT/AF) was noted, or, conversely, if it was appreciated a fast AP antegrade conduction, in baseline or during intravenous isoproterenol infusion, or if multiple APs were detected. RESULTS: There were no statistically significant differences in demographic characteristics (age and gender), AVRT/AF inducibility, antegrade conductive properties, the prevalence of multiple APs, and APs locations between IPX and PPX patients. CONCLUSIONS: In our study, patients with IPX did not show significant differences in clinical and electrophysiological features versus PPX patients.

Radiofrequency catheter ablation for improving myocardial work in patients with ventricular pre-excitation.

Background: Previous studies have not consistently found significant improvements in left ventricular ejection fraction or global longitudinal strain (GLS) after radiofrequency catheter ablation (RFCA) in patients with ventricular pre-excitation. The aim of this study was thus to explore the effects of RFCA on left ventricular function in patients with ventricular pre-excitation using a new noninvasive echocardiographic method of myocardial work. Methods: A total of 34 patients with ventricular pre-excitation who underwent RFCA and 18 healthy controls were prospectively included in this study. Before and after participants underwent RFCA, electrocardiographic and echocardiographic data of the patients were collected at resting and pacing heart rates (HRs) of 100 beats per minute (bpm) and 120 bpm (controlled by high right atrial pacing during the procedure). Clinical data of the healthy controls at resting HR were also collected. A self-controlled paired sample t test was used to compare the differences before and after participants underwent RFCA. Results: After participants underwent RFCA, the global wasted work (GWW) of the included patients decreased (resting HR: 165.3±68.8 vs. 92.6±42.5 mmHg%, P<0.001; HR of 100 bpm: 276.3±121.2 vs. 187.9±96.0 mmHg%, P<0.001; HR of 120 bpm: 323.9±126.7 vs. 181.0%±74.3 mmHg%. P<0.001), while the global work efficiency (GWE) increased (resting HR: 91.5%±3.8% vs. 94.9%±1.6%; P<0.001; HR of 100 bpm: 87.0%±5.2% vs. 91.0%±3.3%, P<0.001; HR of 120 bpm: 85.0%±5.1% vs. 90.3%±3.7%, P<0.001). Conclusions: In patients with ventricular pre-excitation, impaired GWW and GWE can be improved with RFCA. In clinical practice, noninvasive myocardial work assessment can be used in patients with ventricular pre-excitation.

Wolff-Parkinson-White in a College Athlete: Why Didn't We Pursue an EP Study?

We report the case of a collegiate volleyball player incidentally discovered to have Wolff-Parkinson-White pattern on preparticipation electrocardiogram screening. Noninvasive testing identified a low-risk pathway. By using a shared decision-making process with the athlete, she was ultimately able to successfully complete her senior season without further workup or adverse events. (Level of Difficulty: Intermediate.).

Abnormal Conduction-Induced Cardiomyopathy: JACC Review Topic of the Week.

Nonischemic cardiomyopathies are a frequent occurrence. The understanding of the mechanism(s) and triggers of these cardiomyopathies have led to improvement and even recovery of left ventricular function. Although chronic right ventricular pacing-induced cardiomyopathy has been recognized for many years, left bundle branch block and pre-excitation have been recently identified as potential reversible causes of cardiomyopathy. These cardiomyopathies share a similar abnormal ventricular propagation that can be recognized by a wide QRS duration with left bundle branch block pattern; thus, we coined the term abnormal conduction-induced cardiomyopathies. Such abnormal propagation results in an abnormal contractility that can only be recognized by cardiac imaging as ventricular dyssynchrony. Appropriate diagnosis and treatment will not only lead to improved left ventricular ejection fraction and functional class, but may also reduce morbidity and mortality. This review presents an update of the mechanisms, prevalence, incidence, and risk factors, as well as their diagnosis and management, while highlighting current gaps of knowledge.

Three-dimensional electro-anatomical mapping and radiofrequency ablation as a novel treatment for atrioventricular accessory pathway in a horse: A case report.

We describe the diagnosis and treatment of an atrioventricular accessory pathway (AP) in a horse using 3-dimensional electro-anatomical mapping (3D EAM) and radiofrequency catheter ablation (RFCA). During routine evaluation of the horse, intermittent ventricular pre-excitation was identified on the ECG, characterized by a short PQ interval and abnormal QRS morphology. A right cranial location of the AP was suspected from the 12-lead ECG and vectorcardiography. After precise localization of the AP using 3D EAM, ablation was performed and AP conduction was eliminated. Immediately after recovery from anesthesia an occasional pre-excited complex still was observed, but a 24-hour ECG and an ECG during exercise 1 and 6 weeks after the procedure showed complete disappearance of pre-excitation. This case shows the feasibility of 3D EAM and RFCA to identify and treat an AP in horses.