Funding Acknowledgements Type of funding sources: None. Background Ultra high-density (UHD) mapping allows accurate identification of local abnormal electrograms and low voltage within a small area range, allowing precise identification of reentry circuits. Areas with high isochronal density in a small area known as deceleration zones (DZ) are responsible for reentry. Purpose Identify the DZ and areas of low voltage in sinus rhythm (SR) and evaluate the feasibility of performing atrial flutter (AFL) ablation by targeting those zones. Methods We prospectively enrolled patients in SR referred for AFL ablation (either typical or atypical). An isochronal late activation mapping (ILAM) during SR with UHD catheter was performed, annotating latest deflection of local electrograms. DZ were defined as areas with >3 isochrones within 1cm radius, prioritizing zones with maximal density. Atrial flutter was then induced and ILAM during flutter was performed for comparison. Voltage mapping was also assessed (0.1-0.5mV). Ablation targeted DZ in SR that displayed the higher voltage. DZ in SR were compared to DZ in AFL. Number of radiofrequency (RF) applications needed to terminate AFL were assessed. After AFL termination, complete line of the slow conduction zone was completed, and pulmonary vein isolation (PVI) was done in case of left AFL. Categorical variables are presented in absolute and relative values and median and interquartile range were used for numerical variables, as well t-student test for correlation of numerical variables. Results We studied 6 AFL (4 atypical, 66.7%) in 5 patients, 2 male (40%), median age 70 (64- 72). UHD ILAM in SR with 2195 points (1212-2865) and 2197 points (1356-3102) in AFL (p = 0.62).  The UHD ILAM identified a median of (QR) DZ in SR, that colocalized with AFL isthmus and DZ in AFL in 100%. DZ were not always located in low voltage areas. Aiming at the higher voltage in the DZ terminated the AFL in all cases, with a median RF time of 38 (25-58) seconds and AFL was no longer inducible. However, according to protocol, the complete line of slow conduction zone was done, with a median RF time of 1049.5 (274-1194) seconds (p = 0,009). Conclusions Isochronal mapping in sinus rhythm with UHD catheters can display the functional substrate for reentry in AFL, allowing a substrate guided ablation in case of non-inducible AFL. Targeting the areas of high isochronal density, is effective in terminating AFL, obviating the need for extensive ablation. Abstract Figure.

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Strongyloides stercoralis infects at least 100 million humans worldwide each year, but its prevalence is underestimated. It is endemic in hot and humid climates as well as resource poor countries with inadequate sanitary conditions. The rise of international travel and immigration has a positive impact in strongyloidiasis. Due to its unique auto infection life-cycle, Strongyloides may lead to chronic infections remaining undetected for decades. Strongyloidiasis is most often asymptomatic but it has a wide range of clinical presentations. The two most severe forms of strongyloidiasis are hyperinfection and disseminated syndromes. These occur most often in patients with impaired cell mediated immunity. A 42-year-old immunocompetent man presented with chronic watery diarrhea, malaise, upper abdominal pain, anorexia and weight lost. Strongyloides stercoralis was identified in stool samples and duodenal biopsy. The patient was successfully treated with albendazole. The authors report a case of strongyloidiasis hyperinfection in an immunocompetent host 20 years away from an endemic area and make a literature review.

Funding Acknowledgements Type of funding sources: Private hospital(s). Main funding source(s): Learning Health Background and aim Electrocardiographic imaging (ECGI) is capable of performing an activation map with a single beat. The endo-epicardial system based on extracellular potentials allows for the reconstruction of endo-epicardial potentials both in the ventricles and the atria. The aim of this study was to compare the accuracy of the system to predict the site of origin (SOO) of ventricular focal arrhythmias (VAs) versus atrial focal arrhythmias (AAs). Methods We studied 55 consecutive patients referred for ablation of VAs or AAs that had an ECGI performed before ablation. Ablations were performed with remote magnetic navigation or manually. The localization of the VAs and AAs based on the ECGI and invasive electroanatomic mapping was performed using a segmental model of the atria and the ventricles. A perfect match (PM) was defined as a predicted location within the same anatomic segment, whereas a near match (NM) as a predicted location within the same segment or a contiguous one. The number of leads used for ECGI mapping, the agreement between the ECGI and the invasive map, and the success of the procedure were evaluated. Results Ablation was performed in 49 patients. We mapped 54 arrhythmias, 37 VAs (37 patients) and 17 AAs (12 patients). The results according to the atrial or ventricular origin of the arrhythmia are depicted in the table. Patients with AAs were older, no other differences were significant. The ECGI system correctly identified the SOO of both VAs and AAs in the same segment or a contiguous one in 100% of AAs and 97% of VAs, p=1.000. However, the percentage of a PM (Figure) was higher for AAs than for VAs (100% vs 76%, p=0.044). Conclusions The endo-epicardial ECGI correctly identified the origin of both ventricular and atrial arrhythmias. However, the accuracy was higher for the latter.

We present a very rare variation of a persistent primitive hypoglossal artery (PPHA) arising from the internal carotid artery, detected during a diagnostic angiography. A 50-year-old female patient was admitted with an atypical intracranial hematoma in the left frontal lobe. Catheter angiography revealed intracranial vasculopathy with segmental stenoses, a small aneurysm of the right internal carotid artery bifurcation and a "string of beads" appearance of the left carotid artery, consistent with fibromuscular disease. On the left side, a vertebral artery ending in the posterior inferior cerebellar artery (PICA) was detected, whereas on the right side the vertebral artery was aplastic. During selective angiography of the right common carotid artery, a persistent hypoglossal artery was seen supplying the basilar artery. The literature of persistent embryonal carotid-vertebrobasilar anastomosis and their anatomical variations is discussed with respect to clinical importance for ischemia, interventional procedures, and surgery.