Background-Bidirectional ventricular tachycardia (BVT), characterized by an alternating beatto-beat electrocardiographic QRS axis, is a rare but intriguing arrhythmia associated with digitalis toxicity, familial catecholaminergic polymorphic ventricular tachycardia (CPVT), and several other conditions which predispose cardiac myocytes to delayed afterdepolarizations (DADs) and triggered activity. Evidence from human and animal studies attributes BVT to alternating ectopic foci originating from the distal His-Purkinje system in the left and/or right ventricles, respectively.

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Background: An accurate subtype classification of acute ischemic stroke is important in clinical practice as it can greatly influence patient care in terms of acute management and devising secondary stroke prevention strategies. Approximately, one third of ischemic strokes are cryptogenic despite a comprehensive workup. Diagnostic workup for detecting cardioaortic sources of cerebral embolism commonly includes transthoracic echocardiography (TTE). However, TTE has a limited diagnostic power to detect some of the cardioaortic abnormalities and additional imaging modalities are often needed to accurately assess such abnormalities. Purpose: We evaluated the feasibility of cardiovascular magnetic resonance (CMR) imaging to detect the cardioaortic sources of ischemic stroke. Methods: A total of 106 patients were included, of which 85 had an ischemic stroke and 21 had a transient ischemic attack (TIA). Routine diagnostic workup (RDW) included brain diffusion-weighted image MRI, telemetry, magnetic resonance angiography/CT angiography of head and neck, carotid duplex ultrasonography, laboratory studies and TTE. Patients additionally underwent CMR. Subtype assignment was performed in accordance with the Stop Stroke Study of the Trial of Org 10172 in Acute Stroke Treatment classification system by a stroke neurologist after reviewing the admission notes and diagnostic test results. A second subtype classification was assigned with an additional criterion defined based on delayed enhancement (DE)-CMR findings. Additionally, the presence of non-coronary artery disease (CAD) scarring was assessed in ischemic stroke patients and compared with the TIA patients as the control group. Results: RDW detected cardioaortic embolism (CAE) stroke in 32 (37.6%) patients and cryptogenic stroke in 23 patients (27.1%). Addition of CMR resulted in a 26.1% reduction in the rate of cryptogenic strokes (6 patients). Furthermore, DE-CMR findings allowed for reclassification of three additional cryptogenic subtypes, resulting in a 39.1% reduction of cryptogenic stroke rate. Non-CAD scarring was detected in 13 (15.3%) stroke patients as opposed to only 1 (4.8%) TIA patient. Conclusions: CMR is a valuable tool for the detection of CAE sources in patients with cryptogenic ischemic stroke and provides clinicians with a unique set of information that may substantially change the long-term management of these patients. DE-CMR also detects non-CAD scarring, which may indicate a predisposition to ischemic stroke. Further studies with larger samples and long-term follow-up are needed to further evaluate the clinical significance of our findings.

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Introduction Besides the traditional concept of atrial fibrillation (AF) perpetuating atrial structural remodeling, there is increasing evidence that atrial fibrosis might precede AF, highlighting the need for better characterization of the fibrotic substrate. We aimed to assess atrial fibrosis by use of late gadolinium enhancement magnetic resonance imaging (LGE‐MRI) in non‐AF individuals and to identify predisposing risk factors. A second aim was to establish a risk score for the prevalence of AF using atrial fibrosis in addition to established clinical variables. Methods and Results Non‐AF individuals without structural heart disease (n = 91) and matched AF controls (n = 91) underwent MRI for assessment of LGE. According to the established UTAH classification, atrial LGE ≥20% was considered extensive. Mean left atrial (LA) fibrosis in non‐AF and AF individuals were 8.8 ± 6.5% and 12.5 ± 5.8%, respectively. Body mass index (BMI) >30 kg/m 2 and LA volume were predictors of atrial fibrosis. Diastolic function was not significantly different with respect to atrial fibrosis. A novel scoring system for the prevalence of AF (2 points for arterial hypertension and/or left ventricular ejection fraction <55%; 3 points for atrial fibrosis >6%) was derived demonstrating that patients in the intermediate/high‐risk group had a significantly increased risk of AF. Conclusion This study reports unexpectedly high atrial fibrosis in non‐AF patients without apparent heart disease, highlighting the concept that structural fibrotic alterations may precede AF onset in a significant proportion of individuals. BMI as a predictor of atrial fibrosis suggests that lifestyle and drug intervention, that is, weight reduction, could positively influence fibrosis development. The derived risk score for AF prevalence provides the basis for prospective studies on AF incidence.

Background: Left atrial (LA) fibrosis is thought to be a substrate for atrial fibrillation (AF) and can be quantified by late gadolinium enhancement magnetic resonance imaging (LGE-MRI). Fibrosis formation in LA is a dynamic process and may either progress or regress following AF ablation.We examined the impact of postablation progression in LA fibrosis on AF recurrence. Methods: LA enhancement in LGE-MRI was quantified in 127 consecutive patients who underwent first time AF ablation. Serial LGE-MRIs were done prior to AF ablation, 3 months postablation and at least 12 months after second LGE-MRI. Transient postablation lesion (TL) was defined as atrial enhancement caused by ablation lesions that was detected on the first (3 month) but not on the second postablation LGE-MRI. New fibrosis (NF) was defined as atrial enhancement detected on the most recent LGE-MRI, at least 15 months after the ablation procedure. AF recurrence and its correlation with TL and NF was assessed in all patients during the follow-up period.Results: An increase of 1% NF increased the chance of postablation AF recurrence by 3% (hazard ratio [HR] 1.03, 95% CI 1-1.06, P = .05). TL had no significant impact on recurrence (P = .057). After adjusting for cardiovascular risk factors, HR increased as NF became greater. Greater volume of NF (≥21%) corresponded with lower arrhythmia-free survival (37% vs 62%, P = .01).Conclusion: NF formation postablation of AF is a novel marker of long-term procedural outcome.Extensive NF is associated with significantly higher risk of atrial arrhythmia recurrence.

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Objectives To differentiate electrograms representing sites of active atrial fibrillation (AF) drivers from passive ones. Background Ablation of complex‐fractionated atrial electrograms (CFAEs) is controversial due to difficulty in distinguishing CFAEs representing sites of active AF drivers from passive mechanisms. We hypothesized that active CFAE sites exhibit repetitive wavefront directionality, thereby inscribing an electrogram conformation (Egm‐C) that is more recurrent compared with passive CFAE sites; and that can be differentiated from passive CFAEs using nonlinear recurrence quantification analysis (RQA). Methods We developed multiple computer models of active CFAE mechanisms (ie, rotors) and passive CFAE mechanisms (ie, wavebreak, slow conduction, and double potentials). CFAE signals were converted into discrete time‐series representing Egm‐C. The RQA algorithm was used to compare signals derived from active CFAE sites to those from passive CFAEs sites. The RQA algorithm was then applied to human CFAE signals collected during AF ablation (n  =  17 patients). Results RQA was performed in silico on simulated bipolar CFAEs within active (n = 45) and passive (n = 60) areas. Recurrence of Egm‐C was significantly higher in active compared with passive CFAE sites (31.8% ± 19.6% vs 0.3% ± 0.5%, respectively, P < .0001) despite no difference in mean cycle length (CL). Similarly, for human AF (n = 39 signals), Egm‐C recurrence was higher in active vs passive CFAE areas despite similar CLs (%recurrence 13.6% ± 15.5% vs 0.1% ± 0.3%, P < .002; mean CL 102.5 ± 14.3 vs 106.6 ± 14.4, P = NS). Conclusion Active CFAEs critical to AF maintenance exhibit higher Egm‐C recurrence and can be differentiated from passive bystander CFAE sites using RQA.