Utility of virtual unipolar electrogram morphologies to detect transverse conduction block and turnaround points of typical atrial flutter

Abstract

BackgroundNoncontact mapping is useful for the diagnosis of various arrhythmias. Virtual unipolar electrogram morphologies (VUEM) of the conduction block and the turnaround points, however, are not well defined. We compared the VUEM characteristics of a transverse conduction block in the posterior right atrium (RA) with those of contact bipolar electrograms obtained during typical atrial flutter (AFL).MethodsContact bipolar electrograms were used to map the posterior RA during typical AFL in 16 patients. Twenty points of the VUEM recorded along the block line were analyzed and compared with contact bipolar electrograms.ResultsSeventeen AFLs were analyzed. Fifteen AFLs showed an incomplete transverse conduction block in the posterior RA by contact bipolar mapping. A double potential on the block line corresponded to the two components of the VUEM, in which the second component showed an Rs, RS, or rS pattern. At the turnaround point, a fused double potential of the contact bipolar electrograms corresponded to a change of the second component of the VUEM from an rS to a QS morphology. Two AFLs showed a complete block line in the posterior RA. The contact bipolar electrogram showed double potentials from the inferior vena cava to the superior vena cava, whereas the second component of the VUEM remained in an unchanged Rs, RS, or rS pattern.ConclusionVUEM analysis was a reliable method for identifying the posterior block line during AFL. This method may also be applicable for detecting block lines and turnaround points of circuits in other unmappable arrhythmias.

Rate‐Dependent and Site‐Specific Conduction Block at the Posterior Right Atrium and Drug Effects Evaluated Using a Noncontact Mapping System in Patients with Typical Atrial Flutter

“…Fukuzawa et al ., 17 however, observed the upper turnover portion of the reentry circuit in AFL at the posterior SVC in a majority of AFL patients using a CARTO mapping system. Findings of some other previous studies support this notion 10,18,19 . In this study, only 4 of 33 AFL showed a complete block line (block proportion 100%) in the posterior RA during AFL.…”

“…We did not record contact bipolar mapping to identify the block line in the posterior RA. Previously, however, we reported the relationship between the virtual unipolar morphologies and contact bipolar morphologies at the conduction block during typical AFL 10 . In 12 of 40 patients, a sustained AFL was not induced at the time of the electrophysiologic study.…”

“…The top of the conduction block line was determined by the color‐coded isopotential map and the morphologies of 20 points of virtual unipolar electrograms at the block line. We previously reported the specific changes of the second component of virtual unipolar electrogram morphologies, which change to a QS pattern at the top of the block line 10 . The block proportion was defined as the percentage of the length of the posterior block line divided by the length of the posterior RA (Fig.…”

“…We previously compared the characteristics of the virtual unipolar electrograms morphologies along the block line with those of a contact bipolar electrogram. At the turnaround point, the virtual unipolar electrogram changed from an rS to a QS morphology 10 . In this study, we used the same method to detect the top of the block line.…”

“…We previously reported the specific changes of the second component of virtual unipolar electrogram morphologies, which change to a QS pattern at the top of the block line. 10 The block proportion was defined as the percentage of the length of the posterior block line divided by the length of the posterior RA ( Fig. 1).…”