LVA mapping and analysis
After external cardioversion, a detailed bipolar LA voltage map was
constructed during pacing from the distal CS in all patients. The LVA
mapping method has been described previously.5,6,7 The
mapping points were systematically acquired with the HDG, which has 16
electrodes and 3 mm equidistant electrode spacing to create a high
density contact voltage map via the Ensite Velocity 3D mapping system.
The algorithm displays the signals amalgamated from orthogonal
recordings of each bipole and displays the highest amplitude signal (HD
wave solution). An interpolation threshold of 10 mm on the NavX system
was used for the surface color projection. Adequate endocardial contact
was evaluated by stable electrograms and consideration of the distance
to the geometry surface. Only true sinus beats were selected. Bipolar
electrograms were filtered by a bandpass of frequencies between 30 and
500Hz. In accordance with the previous studies 5,6,7,
an LVA was defined as an area with a bipolar peak-to-peak electrogram
amplitude of <0.5mV and electrical scar areas as
<0.1mV. The LA surface area was defined as the LA body area
without the PV antrum regions inside the PVI line. The registration for
evaluating the MDCT image with the NavX map consisted of an AF image
imported (pre-ablation) with a post cardioversion SR map in all patients
in order to obtain the anatomical information, and the overlap between
the LVAs and high-DF sites was evaluated manually by 2 independent
blinded observers.