Background-Endocardial mapping before sustained monomorphic ventricular tachycardia (SMVT) induction may reduce mapping time during tachycardia and facilitate the ablation of unmappable VT. Methods and Results-Left ventricular electroanatomic voltage maps obtained during right ventricular apex pacing in 26 patients with chronic myocardial infarction referred for VT ablation were analyzed to identify conducting channels (CCs) inside the scar tissue. A CC was defined by the presence of a corridor of consecutive electrograms differentiated by higher voltage amplitude than the surrounding area. The effect of different levels of voltage scar definition, from 0.5 to 0.1 mV, was analyzed. Twenty-three channels were identified in 20 patients. The majority of CCs were identified when the voltage scar definition was Յ0.2 mV. Electrograms with Ն2 components were recorded more frequently at the inner than at the entrance of CCs (100% versus 75%, PՅ0.01). The activation time of the latest component was longer at the inner than at the entrance of CCs (200Ϯ40 versus 164Ϯ53 ms, PՅ0.001). Pacing from these CCs gave rise to a long-stimulus QRS interval (110Ϯ49 ms). Radiofrequency lesion applied to CCs suppressed the inducibility in 88% of CC-related tachycardias. During a follow-up of 17Ϯ11 months, 23% of the patients experienced a VT recurrence. Conclusions-CCs represent areas of slow conduction that can be identified in 75% of patients with SMVT. A tiered decreasing-voltage definition of the scar is critical for CC identification.

SMVT substrate can be identified by ceMRI scar heterogeneity analysis. This information could help identify patients at risk of VT and facilitate VT ablation.

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Objective To study mechanisms of formation of fractionated electrograms on the posterior left atrial wall (PLAW) in human paroxysmal atrial fibrillation (AF). Background The mechanisms responsible for complex fractionated atrial electrograms formation during AF are poorly understood. Methods In 24 pts we induced sustained AF by pacing from a pulmonary vein (PV). We analyzed transitions between organized patterns and changes in electrogram morphology leading to fractionation in relation to interbeat interval duration (systolic interval) and dominant frequency (DF). Computer simulations of rotors helped in the interpretation of the results. Results Organized patterns were recorded 31±18% of the time. In 47% of organized patterns, the electrograms and PLAW activation sequence were similar to those of incoming waves during PV stimulation that induced AF. Transitions to fractionation were preceded by significant increases in electrogram duration, spikes number, and systolic interval shortening (R2=0.94). Similarly, adenosine infusion during organized patterns caused significant systolic interval shortening leading to fractionated electrogram formation. Activation maps during organization showed incoming wave patterns, with earliest activation located closest to the highest DF site. Activation maps during transitions to fragmentation showed areas of slowed conduction and unidirectional block. Simulations predicted that systolic interval abbreviation that heralds fractionated electrograms formation may result from a Doppler effect on wavefronts preceding an approaching rotor, or by acceleration of a stationary or meandering, remotely located source. Conclusions During induced AF, systolic interval shortening following either drift or acceleration of a source results in intermittent fibrillatory conduction and formation of fractionated electrograms at the PLAW.

Age at the onset of symptoms, sensation of rapid regular pounding in the neck during tachycardia, and female sex are the only significant clinical variables in the differential diagnosis of paroxysmal atrioventricular reciprocating tachycardias in patients without pre-excitation in sinus rhythm. Their consideration adds significant diagnostic information to the ECG.

Guidelines and Expert Consensus documents are proposed to help physicians to select the best possible diagnostic or therapeutic strategies for an individual patient with a specific disease. Recommendations issued from these documents are based on an extensive review of the literature and on discussions among experts when hard data are incomplete or missing. It has been shown that patient outcomes improve when guidelines recommendations are applied in clinical practice. Publication and promotion of these guidelines is one of the most important tasks of scientific societies. The recently created European Heart Rhythm Association (EHRA) wants to meet this commitment in its specific field of competence and one assignment of the scientific committee of EHRA is to propose and promote Guidelines in the management of heart rhythm disturbances not already covered by the European Society of Cardiology (ESC).

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The difference SA-VA provides a simpler electrophysiologic maneuver that reliably differentiates atypical AVNRT from AVRT regardless of concealed AP location.