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Introduction Epicardial catheter ablation is increasingly used to treat arrhythmias with an epicardial component. Nevertheless, percutaneous epicardial access remains associated with a significant risk of major complications. Developing a technology capable of confirming proper placement within the pericardial space could decrease complication rates. The purpose of this study was to examine differences in bioimpedance among the pericardial space, anterior mediastinum, and right ventricle. Methods An ovine model (n = 3) was used in this proof-of-concept study. A decapolar catheter was used to collect bipolar impedance readings; data were collected between each of five electrode pairs of varying distances. Data were collected from three test regions: the pericardial space, anterior mediastinum, and right ventricle. A control region in the inferior vena cava was used to normalize the data from the test regions. Analysis of variance was used to test for differences among regions. Results A total of 10 impedance values were collected in each animal between each of the five electrode pairs in the three test regions (n = 340) and the control region (n = 145). The average normalized impedance values were significantly different among the pericardial space (1.760 ± 0.370), anterior mediastinum (3.209 ± 0.227), and right ventricle (1.024 ± 0.207; P < 0.0001). In post hoc testing, the differences between each pair of regions were significant, as well (P < 0.001 for all). Conclusion Impedance values are significantly different among these three anatomical compartments. Therefore, impedance can be potentially used as a means to guide percutaneous epicardial access. [ABSTRACT FROM AUTHOR]

Introduction: Knowledge of the global atrial activation pattern is critical to ablation of an atrial arrhythmia. We hypothesized that the variability in post-pacing intervals (PPIs) with pacing at different cycle lengths (CLs) from the same pacing site, regardless of distance to the circuit, can be used to identify atrial activation patterns during tachycardia. Methods and Results: Consecutive patients referred for ablation of organized atrial arrhythmias were included (n = 28, 31 total tachycardias). The variability in PPIs (PPIV) was calculated by comparing the difference in PPIs after overdrive pacing with 5-second trains 10, 20, and 30 ms shorter than the tachycardia cycle length (TCL). The global activation pattern was defined as circuitous (macroreentrant atrial circuit) or centrifugal (focal origin with centrifugal radiation) by electroanatomic mapping. Except for one case, all pacing was performed from the proximal coronary sinus bipole. Circuitous tachycardias (n = 17, all macro-reentrant) exhibited minimal variability with pacing at 10 ms and 30 ms shorter than TCL (6.0 ± 2.5 ms), whereas centrifugal tachycardias (n = 14, 8 microreentrant) displayed a high degree of variability (56.5 ± 20.6 ms). Rank sum analysis of PPIV suggests that the two groups are indeed distinct (P < 0.001). Using PPIV cutoffs of ≤10 ms and ≥30 ms, circuitous and centrifugal activation patterns could be distinguished with a high degree of sensitivity (94% circuitous, 92.8% centrifugal) and 100% specificity. Conclusions: Our data support the use of PPIV to rapidly and accurately predict the global activation pattern during atrial arrhythmia. [ABSTRACT FROM AUTHOR]

Introduction: Ventricular fibrillation and ventricular flutter (cycle length ≤230 msec) induced at electrophysiologic studies are thought to be nonspecific findings in patients presenting with syncope of unknown origin. However, there are limited data on the prognosis of these patients in long-term follow-up. Methods and Results: We followed 274 consecutive patients with coronary artery disease presenting with syncope or presyncope who underwent electrophysiologic studies from January 1992 to June 1999 and assessed the risk of subsequent arrhythmias stratified by the electrophysiologic result at the time of their presentation with syncope. Ventricular fibrillation was induced in 23 patients (8%); ventricular flutter in 24 (9%), sustained ventricular tachycardia in 41 (15%); and nonsustained ventricular tachycardia 42 (15%). In 37 ± 25 months of follow-up, there have been ventricular arrhythmias in 34 patients, including 3 (13%) of 23 who had induced ventricular fibrillation, and 7 (30%) of 24 with induced ventricular flutter, compared to 13 (32%) of 41 with sustained ventricular tachycardia, 7 (17%) of 42 with nonsustained ventricular tachycardia, and only 4 (3%) of 144 noninducible patients (P < 0.001 for induced ventricular fibrillation and ventricular flutter vs noninducible patients). The inducibility of ventricular fibrillation and ventricular flutter were independent risk factors for arrhythmia occurrence in follow-up. Conclusion: Ventricular fibrillation and ventricular flutter induced at electrophysiologic studies have prognostic significance for arrhythmia occurrence in patients presenting with syncope. These induced arrhythmias may not be as nonspecific as previously thought and treatment should be considered for these patients. [ABSTRACT FROM AUTHOR]

The article discusses ways to troubleshoot implantable cardioverter-defibrillators (ICDs), a prevention therapy for sudden cardiac death in high-risk patients. ICDs are devices programmed to detect arrhythmia using the signal rate recorded by the right ventricular lead as the first detection criterion. Problems encountered by patients with ICDs are grouped in various categories including shocks delivered by the device, palpitations, dizziness, syncope and the device alerts or audible beeps.