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Aim .To validate the National Danish Ablation Database (NDAD) by investigating to what extent data in NDAD correspond to medical records. Type of study . Non-blinded, registry-based, retrospective, validation study. Material and methods . A sample of patients who underwent ablation for atrial fibrillation in Denmark between 1 January 2016 and 31 December 2016 were included. By utilizing medical records as gold standard, positive predictive (PPV) and negative predictive values (NPV) for NDAD were assessed and presented as five main categories: arrhythmia characteristics, demographics, cardiac history, complications, and medication. PPV's and NPV's exceeding 90% were considered as high agreement. Results . 597 patients (71.0% males) were included in the study. Median age was 63.1 (IQR: 54.9-68.4) years. The median PPV and NPV estimates across all variables were respectively 90.4% (95% CI: 68%-95.2%) (PPV) and 99.4% (95% CI: 98.4%-99.8%) (NPV) at baseline, and 91.7% (95% CI: 67.4%-95.4%) (PPV) and 99.3% (98.2%-99.3%) (NPV) at follow-up. Conclusion . The data registered in NDAD agrees to a great extent with the patients' medical records, suggesting NDAD is a database with high validity. As a result of low complication rate, the PPV- and NPV-estimates among complication variables were prone to somewhat greater uncertainty compared to the rest.

Objectives: We aimed to investigate the predictors of recurrent arrhythmia after repeated pulmonary vein isolation (PVI) performed in the era of contact force without additional substrate ablation. One of the predictors studied, ablation index (AI), incorporates power, contact force, and time in a weighted formula and is reported to predict lesion size in animals. Design . Consecutive patients ( n  = 108) undergoing repeat PVI without additional substrate modification using a contact force sensing catheter were included retrospectively at a tertiary center. All ablation points were analyzed offline. A new variable, normalized AI (AI corrected for the location of the lesion-anterior vs. posterior) was calculated. The patients were systematically followed with clinical visit and 12-lead ECG as well as review of the regional electronic patient files at 3 and 12 months after the procedure with 5-day Holter at 12 months. Results . Electrical reconnection to at least one pulmonary vein (PV) was seen in 97% of the patients. The recurrence rate was 35%. There was no recurrence in patients with nAI above 1.15 ( n  = 26). Patients with electrical reconnection of up to two PVs had a higher risk of recurrence compared with patients having electrical reconnection of three or four PVs ( p  = .003), and this risk was especially high in patients with persistent atrial fibrillation (69 [39-91]%). Conclusions . The risk of recurrence is higher in patients with ablations performed with low levels of AI and in patients with reconnection to up to two PVs. Our data may indicate the need for higher target levels of AI during repeat PVI than normally used during de-novo PVI.

Objectives. Left atrial flutter has been reported in up to 10% of patients following pulmonary vein isolation or cardiac surgery. Left atrial flutter is typically highly symptomatic, responds poorly to medical antiarrhythmic treatment, and is often treated by catheter ablation. We aimed to investigate midterm freedom from recurrent arrhythmia after catheter ablation for left atrial flutter. Design . In the National Danish Ablation Registry, we identified consecutive patients, who had undergone catheter ablation for left atrial flutter between 1 January 2014 and 1 April 2017 at our centre. Results. A total of 53 patients (median age 68 years (IQR 60-71) 37 (70%) male) were included. Forty-two patients had prior left atrial catheter ablation procedures (79%), one patient prior ablation for classic atrial flutter (2%), four patients had prior surgery for congenital heart disease (8%), and six patients (11%) had no previous cardiac intervention. Acute procedural success, defined as non-inducibility of any atrial arrhythmia, was achieved in 45 of 53 patients (85%). During midterm follow-up (mean 20 ± 12 months), 26 patients experienced an episode of recurrent atrial arrhythmia. Median EHRA-score was 3 (range 2-4) before catheter ablation and reduced to median 1 (range 1-3) evaluated at follow-up visits after three and twelve months (both p  < .001, Wilcoxon rank test). Conclusion. Left atrial flutter is preceded by catheter ablation or cardiac surgery in 89% of patients. Acute procedural success is achieved in majority of patients and ablation reduces symptoms effectively. During midterm follow-up, almost half the patients experience recurrent atrial arrhythmia.

Objectives: The purinergic system has not been investigated in detail following ischemia/reperfusion (I/R) injury in the heart. In the present study, we focus on both release and response to extracellular adenosine triphosphate (ATP). Pannexin (Panx) channels have been shown to be involved in ATP release from myocytes and can activate P2X1 and P2Y2 receptors on the coronary artery., Design: We applied a well-characterized I/R model in rats, with 24 hours of reperfusion. Panx expression in the myocardial tissue was measured with quantitative polymerase chain reaction (qPCR) and flow cytometry. ATP release was detected in situ using luminescence and the vascular response to nucleotides determined in a wire myograph., Results: Here, we show that Panx expression is increased after experimental myocardial I/R, leading to an increase in extracellular ATP release, which could be inhibited by probenecid. Functional studies revealed that the P2Y2 receptor-dependent contraction is reduced in the coronary artery after I/R, which might be a response to the increased ATP levels., Conclusion: We, therefore, conclude that the regulation of the arterial purinergic system minimizes coronary contractions following ischemia.

Objectives: Recurrent arrhythmia after pulmonary vein isolation (PVI) by radiofrequency (RF) ablation in patients with atrial fibrillation (AFIB) remains a significant challenge. Using contact force (CF) sensing ablation catheters, we aimed to identify procedure related parameters associated with recurrence after de-novo PVI in patients with AFIB., Methods: Consecutive patients undergoing a de-novo PVI procedure (n = 120, 63% paroxysmal and 37% persistent AFIB) employing a force-sensing ablation catheter were included. A clinical control including electrocardiogram and 120 hour of Holter-recording at 12-months was performed in all patients. Recurrence was defined as any documented AFIB or atrial flutter more than 30 seconds on Holter-recording after an initial blanking period of three months., Results: Recurrence occurred in 44 patients (37%). Mean CF was lower in patients with recurrent arrhythmia (22.2 ± 9.5 vs. 28.8 ± 9.3 g, p < .001). In multi-variable analyses lower mean CF (OR 0.9 (95% CI 0.8-1.0), p = .03), and higher percentage of ablation time with a CF <10 grams (OR 1.1 (95% CI 1.0-1.1), p = .004) were both associated with recurrence in two distinct models. Dragging during ablation compared with point-by-point ablation technique was associated with recurrence in both models (OR 19.2 (95% CI 2.9-130.0), p = .002, and OR 21.7 (95% CI 2.7-176.2), p = .004)., Conclusions: Low CF and dragging during ablation as compared with point-by-point ablation technique were associated with recurrent arrhythmia in patients with AFIB undergoing de-novo PVI by RF ablation.

Objective: Whole body hypothermia has been suggested to reduce myocardial injury in patients with ST-segment elevation myocardial infarction. Because of the large human thermal mass, induction of generalized hypothermia is slow and the technique has encountered considerable side effects. The aim was to develop and validate a method for regional cooling during myocardial reperfusion using hypothermic autologous blood., Design: In a myocardial ischemia-reperfusion pig model (n = 10), arterial blood was cooled in a closed circuit, and returned to the myocardium during reperfusion either through a perfusion catheter or through the guiding catheter. Myocardial temperatures were recorded using temperature electrodes., Results: Stabile regional myocardial cooling was induced without complications within 4 min. Both flow rate and blood temperature had significant impact on temperature in the reperfused myocardium but did not influence systemic temperature., Conclusion: A method for organ specific hypothermic autologous arterial blood reperfusion has been developed and validated. The method is a simple and much faster alternative to systemic cooling and may have the potential to reduce myocardial injury in patients with acute myocardial infarction.