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The 12-lead ECG shows sequential atrial and ventricular pacing (Figure 1A). A tracing, obtained simultaneously during pacemaker interrogation, disclosed pacemaker functioning as VDD mode (Figure 1B). The careful examination of this pacemaker tracing showed that there is a pacing stimulus before each P wave (compatible with DDD mode). This paradox can only be explained by displacement of the temporary pacing lead to right atrium and right atrial stimulation by temporary pacemaker. In this setting, each temporary pacemaker-induced atrial depolarization is tracked by the right atrial lead of the permanent pacemaker as intrinsic P wave. Fluoroscopic study confirmed this explanation (Figure 2). The displaced temporary pacing lead was seen near the lateral right atrial wall. Temporary pacemaker lead had been inserted before replacement of permanent pacemaker.

Background: The implantable cardioverter defibrillators (ICDs) are increasingly being used as a treatment modality for life threatening tachyarrhythmia. The purpose of this study was to compare the frequency of complications and mortality between single-chamber and dual-chamber ICD implantation in Shahid Rajaie cardiovascular center. Methods and results: Between January 2000 and December 2004, 234 patients received ICD by a percutaneous transvenous approach and were followed for 33 ± 23 months. The cumulative incidence of complications was 9.4% over the follow-up period. There was no significant difference in overall complication rate between single chamber (VR) and dual chamber (DR) ICD groups in the follow-up period (P= 0.11). The risk of complications did not have any statistically significant difference in secondary versus primary prevention groups (P=0.06). The complications were not associated with the severity of left ventricular systolic dysfunction (P=0.16).The frequency of lead-related complications was higher in dual chamber ICDs in comparison with single chamber ICDs (P=0.02). There was no significant difference in mortality between different sex groups (P=0.37), different indications for ICD implantation (P=0.43) or between VR and DR ICD groups (P= 0.55). Predictors of mortality were NYHA class III or more (P<0.001), age >65 years (P=0.011) and LVEF<30% (P<0.001). The mortality in patients with CAD and DCM were significantly higher than those with other structural heart diseases (P=0.001). Conclusions: Close monitoring of patients during the first 2 month after ICD implantation is recommended because the majority of complications occur early after the procedure.

ECG in sinus rhythm with ventricular preexcitation and changing QRS morphology was seen that was initially interpreted as the multiple accessory pathway from elsewhere. (Figure 1A). The following mechanisms are potentially involved in the electrogenesis of changing QRS morphology in WPW syndrome: 1) multiple accessory pathways1; 2) simultaneous occurrence of aberrant atrioventricular conduction with accessory pathway conduction 2; 3) ventricular fusion of preexcited sinus impulse with ectopic impulse. Electrophysiologic study showed short PR (75 ms) interval with wide QRS (152 ms) and negative HV (-12 ms) interval. No change in delta wave polarity was observed during HRA and CS pacing. In full preexcitation, no breakthrough was seen in the CS. During incremental ventricular pacing, atrial breakthrough site is initially recorded on the HRA catheter and then changed to distal pole of CS catheter with progressive decrease in pacing cycle length. During ventricular pacing at cycle length of 500 ms (S1), earliest atrial activity is recorded on HRA catheter. Changing QRS could not be explained by presence of multiple APs because only right-sided AP had bidirectional conduction and no distal CS breakthrough was seen simultaneous with changing QRS morphology. The possibility of aberrant conduction is excluded by presence of negative HV interval in the beats with differing QRS morphology. No sinus cycle length variation before and after the beats with different morphologies are against the occurrence of functional LBBB. The prematurity of ventricular electrogram in His recording catheter with variable HV (H-electrogram is recorded after V-electrogram in second beat and before V-electrogram in third beat) and fixed V-RB intervals (interval from ventricular electrogram in His to the RB potential) are compatible with ventricular fusion of preexcited sinus impulse with ectopic ventricular impulse originating from parahissian area (explaining LBBB and inferior axis morphology of the beats with changing QRS) but not from the His bundle or RBB itself (because H-electrogram and RB potential is recorded after V-electrogram in the second beat with greater degree of ventricular fusion)(Figure 1B).

Background: Understanding the predictors of appropriate implantable cardioverter defibrillator (ICD) therapy could help to better identify candidates for ICD implantation. Methods: One hundred and sixty two patients with ICD (111 with coronary artery disease [CAD] and 51 with dilated cardiomyopathy [DCM]) were included in the study. Clinical, electrocardiographic, and ICD stored data and electrograms were collected. Results: During mean follow up of 15±11 months 54 patients (33%) received ≥ 1 appropriate ICD therapy (AICDT). We used binary logistic regression analysis with forward selection method to find the potential predictors of appropriate ICD therapy after device implantation. Male gender (odds ratio [OR] = 2.76, 95% confidence interval [CI] = 1.1 – 7.1, P=0.021), DCM as underlying heart disease (OR = 4.2, 95% CI = 1.9 – 9.5, P=0.001), and QRS width > 100 ms (OR = 2.58, 95% CI = 1.2 – 5.4, P=0.010) were correlated with increased likelihood of AICDT during the follow up period. In subgroup analysis of the patients with CAD and DCM, QRS duration > 100 ms was correlated with the probability of ≥ 1 AICDT. In our patients indication of ICD implantation (primary versus secondary prevention) did not influence probability of ≥ 1 AICDT (adjusted OR = 1.66, 95% CI = 0.7 – 4.0, Mantel-Haenszel P value P=0.355.) Conclusion: QRS width could be used as an additional simple risk stratifier beyond EF to identify potential candidates who would benefit more from ICD implantation. This may have practical implications for patient selection especially in developing countries. Indication of ICD implantation (primary versus secondary prevention) did not affect the probability of ≥ 1 AICDT during the follow up period.

Background: By analyzing stored intracardiac electrograms during spontaneous monomorphic ventricular tachycardia (VT), we examined the patterns of the VT initiation in a group of patients with implantable cardioverter defibrillators (ICDs). Methods: Stored electrograms (EGMs) were monomorphic VTs and at least 5 beats before the initiation and after the termination of VT were analyzed. Cycle length, sinus rate, and the prematurity index for each episode were noted. Results: We studied 182 episodes of VT among 50 patients with ICDs. VPC-induced (extrasystolic initiation) episode was the most frequent pattern (106; 58%) followed by 76 episodes (42%) in sudden-onset group. Among the VPC-induced group, VPCs in 85 episodes (80%) were different in morphology from subsequent VT. Sudden-onset episodes had longer cycle lengths (377±30ms) in comparison with the VPC-induced ones (349±29ms; P= 0.001). Sinus rate before VT was faster in the sudden-onset compared to that in VPC-induced one (599±227ms versus 664±213ms; P=0.005). Both of these episodes responded similarly to ICD tiered therapy. There was no statistically significant difference in coupling interval, prematurity index, underlying heart disease, ejection fraction, and antiarrhythmic drug usage between two groups (P=NS). Conclusions: Dissimilarities between VT initiation patterns could not be explained by differences in electrical (coupling interval, and prematurity index) or clinical (heart disease, ejection fraction, and antiarrhythmic drug) variables among the patients. There is no association between pattern of VT initiation and the success rate of electrical therapy.

Double tachycardia is a relatively rare condition. We describe a 21 year old woman with history of frequent palpitations. In one of these episodes, she had wide complex tachycardia with right bundle branch and inferior axis morphology. A typical atrioventricular nodal tachycardia was induced during electrophysiologic study, aimed at induction of clinically documented tachycardia. Initially no ventricular tachycardia was inducible. After successful ablation of slow pathway, a wide complex tachycardia was induced by programmed stimulation from right ventricular outflow tract. Mapping localized the focus of tachycardia in left ventricular outflow tract and successfully ablated via retrograde aortic approach. During 7 month's follow-up, she has been symptom free with no recurrence. This work describes successful ablation of rare combination of typical atrioventricular nodal tachycardia and left ventricular outflow tract tachycardia in the same patient during one session.

We report a 26-year-old woman with frequent episodes of palpitation and dizziness. Resting electrocardiography showed no evidence of ventricular preexcitation. During electrophysiologic study, a concealed right posteroseptal accessory pathway was detected and orthodromic atrioventricular reentrant tachycardia incorporating this pathway as a retrograde limb was reproducibly induced. After successful ablation of right posteroseptal accessory pathway, another tachycardia was induced using a concealed right posterolateral accessory pathway in tachycardia circuit. After loss of retrograde conduction of second accessory pathway with radiofrequency ablation, dual atrioventricular nodal physiology was detected and typical atrioventricular nodal reentrant tachycardia was repeatedly induced. Slow pathway ablation was done successfully. Finally sustained self-terminating atrial tachycardia was induced under isoproterenol infusion but no attempt was made for ablation. During 8-month follow-up, no recurrence of symptoms attributable to tachycardia was observed.

Observation of Coincident arrhythmias is not uncommon but the co-existence of idiopathic verapamil sensitive left ventricular tachycardia (ILVT) with other arrhythmias is very rare. We hereby presented a 30 year old male patient with a history of frequent episodes of palpitations and sustained narrow complex tachycardia. During electrophysiologic study two arrhythmias, one with narrow complexes which was shown to be typical atrioventricular nodal re-entrant tachycardia and the other with wide QRS complexes and right bundle branch block and left axis morphology, compatible with ILVT, were inducible. Radiofrequency catheter ablation of both arrhythmias was done at two consecutive sessions. The patient has remained asymptomatic without antiarrhythmic therapy for the past six months.

Key Clinical Message Focal atrial tachycardia (FAT) is an organized atrial rhythm >100 beats per minute initiated from a discrete origin and spreading over both atria in a centrifugal pattern. The arrhythmia may be sustained or incessant. Dynamic forms with recurrent interruptions and reinitiating may be frequent. In this report, we present a 36‐year‐old man who came to the emergency room complaining of palpitation and shortness of breath. All laboratory evaluations were normal. With an initial electrocardiogram (ECG) the patient was admitted with the initial diagnosis of atrial flutter. Finally, after the electrophysiologist's examination, with the diagnosis of FAT, ablation was successfully performed. Atrial tachycardia (AT), excluding atrial fibrillation (AF) and cavotricuspid isthmus‐dependent atrial flutter (AFL), account for 10% of supraventricular tachycardia referred for ablation procedures. More than 70% of these cases are focal and occur in patients with no records of cardiac surgery or ablation of AF. FAT originating from the right pulmonary veins (PV) can be challenging to differentiate from atrial flutter due to their proximity and overlapping symptoms. The right PV is close to the right atrium, and the abnormal electrical activity in FAT may mimic the organized circuit found in atrial flutter. Distinguishing between FAT and atrial flutter is crucial for choosing the best therapeutic option. This can be done most of the time by focusing on the differences in the pattern of their P and QRS waves, R‐R wave intervals, and also their baseline changes on ECG, as well as their cycle duration, response to adenosine and risk factors of the patient.

Background: Pulsed‐field ablation (PFA) is a cutting‐edge technique that employs non‐thermal energy to cause cell death by inducing irreversible electroporation of cell membranes. This systematic review evaluates the PFA effectiveness as a potential alternative to radiofrequency and cryo‐ablation for treating ventricular tachycardia. Methods: PubMed, Embase, Scopus, and Web of Science were systematically searched using keywords related to ventricular tachycardia and pulsed‐field ablation. Eligible Studies evaluating this therapeutic approach for ventricular tachycardia were included in the final analysis. Results: We included six studies (five case reports and one case series) in our systematic review. Eight (88.8%) of procedures were successful with 100% long‐term efficacy. No procedural complications or ventricular tachycardia (VT) recurrence were observed in the cases. Conclusion: The absence of complications, high effectiveness, and long‐term success rate make PFAs a good VT treatment option. However, PFA safety and efficacy studies for VT treatment are scarce. Thus, larger investigations on this topic are urgently needed. [ABSTRACT FROM AUTHOR]

Background: Postoperative atrial fibrillation (POAF) is one of the most common types of acute AF and can complicate the treatment course of approximately one third of patients undergoing cardiac surgery. Sodium‐glucose cotransporter‐2 (SGLT2) inhibitors are among the newest antidiabetic drugs which can be therapeutic options for preventing POAF by different mechanisms. Methods: Empagliflozin to Prevent POAF (EMPOAF) is an interventional, investigator‐initiated, double‐blind, placebo‐controlled, multicenter, randomized controlled trial which will be conducted in two referral teaching cardiology hospitals in Tehran. Four‐hundred ninety‐two adult patients who are scheduled for elective isolated coronary artery bypass graft (CABG) surgery will be randomly assigned to one of the groups of intervention (empagliflozin 10 mg daily) or placebo starting at least 3 days before surgery until discharge. Key exclusion criteria are a history of diabetes mellitus, AF, ketoacidosis, or recurrent urinary tract infections along with severe renal or hepatic impairment, unstable hemodynamics, and patients receiving SGLT2 inhibitors for another indication. The primary outcome will be the incidence of POAF. Key secondary endpoints will be the composite rate of life‐threatening arrhythmias, postoperative acute kidney injury, hospitalization length, in‐hospital mortality, stroke, and systemic embolization. Key safety endpoints will be the rate of life‐threatening and/or genitourinary tract infections, hypoglycemia, and ketoacidosis. Conclusions: EMPOAF will prospectively evaluate whether empagliflozin 10 mg daily can reduce the rate of POAF in patients undergoing elective CABG. Enrolment into this study has started by November 2023 and is expected to be ended before the end of 2025. [ABSTRACT FROM AUTHOR]

BACKGROUND: Atrial fibrillation (AF) augments the risk of stroke by 4-5 times. Vitamin D is pivotal in numerous metabolic pathways. A handful of studies have explored the correlation between vitamin D deficiency (VDD) and AF outcomes. Hence, the authors sought to assess the relationship between VDD and AF outcomes. METHODS: From December 2021 to February 2023, 190 patients with AF were incorporated into the authors’ study. Given the seasonal fluctuation of vitamin D levels, these levels were examined from the start of December until the end of March. RESULTS: The final analysis comprised 190 patients (55.8% male) with an average age of 46.22±15.03. Vitamin D deficiency, insufficiency, and sufficiency were noted in 77 (40.5%), 46 (24.2%), and 67 (35.3%) patients, respectively. Fatigue and syncope were significantly more prevalent in the VDD group than in other groups. Three-vessel disease was more frequent in the VDD group (p-value=0.04). Mortality was more prevalent in patients with VDD (6.31%) compared to the VDI (2.10%) and VDS (0.05%) groups (p = 0.03). Successful cardioversion was significantly more prevalent in the VDS group (p = 0.03). CONCLUSION: A sufficient level of vitamin D was linked with a better response to cardioversion. However, low vitamin D levels are correlated with higher mortality in AF patients. [ABSTRACT FROM AUTHOR]