Double potentials along the ablation line as a guide to radiofrequency ablation of typical atrial flutter
Hiroshi Tada, MDa,
Hakan Oral, MDa,
Christian Sticherling, MDa,
Steven P. Chough, MDa,
Robert L. Baker, MDa,
Kristina Wasmer, MDa,
Frank Pelosi, Jr, MDa,
Bradley P. Knight, MD, FACCa,
S. Adam Strickberger, MD, FACCa and
Fred Morady, MD, FACCa
a Division of Cardiology, Department of Internal Medicine, University of Michigan, Ann Arbor, Michigan, USA
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Figure 1 A 45° left anterior oblique fluoroscopic view of catheter positions during atrial flutter ablation (ABL) is shown. A duo-decapolar halo catheter is positioned around the tricuspid annulus and along the cavo-tricuspid isthmus. Electrode pairs of the halo catheter are labeled E1 to E9. Note that E1 and E2 are positioned just lateral to the intended ABL line. A quadripolar electrode catheter is positioned within the coronary sinus (CS) for pacing. The ABL catheter is positioned at the intended ABL line. The recordings displayed in Figures 2 through 5 were obtained with the catheters positioned as shown in this figure.
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Figure 2 Recordings during coronary sinus (CS) pacing before (left and middle) and after (right) complete isthmus block are shown. Displayed are leads II, III and V1, electrograms recorded by the ablation catheter (Abl), electrograms recorded at E9 through E1 of the halo catheter, an electrogram recorded in the CS and the stimulus (St) channel. The arrows in the electrograms recorded by the Abl point to the components of the double potentials (DPs). The Abl was positioned at exactly the same site in all three panels. (Left) After several applications of radiofrequency energy along the ablation line, the interval separating the two components of DPs (DP1-2) is 61 ms, and there is incomplete block. (Middle) After an additional application of radiofrequency energy, the DP1-2 interval increases to 96 ms, but isthmus block is still incomplete. (Right) After a final application of radiofrequency energy, the DP1-2 interval lengthens to 124 ms, and now there is complete block, based on both the atrial activation sequence in E1 to E9 and a change in the initial polarity of E1 and E2 from positive to negative. Note that when the DP1-2 interval was 96 ms, the segment separating the two components of the DP was not isoelectric, providing further evidence that there was a persistent gap in the ablation line. On the transition to complete block, the segment with the DP became isoelectric.
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Figure 3 Double potentials (DPs) recorded along the ablation line in the cavo-tricuspid isthmus during coronary sinus pacing are depicted. Shown are examples of DPs in which the second component (larger bold arrows) had either a negative or positive polarity. The morphology of the second component was characterized by terminology used to describe QRS complexes. The smaller arrows indicate the first component of the DPs. St = stimulus channel.
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Figure 4 The intervals separating the two components of double potentials (DP1-2) recorded along the ablation line during coronary sinus pacing before and after complete block in the cavo-tricuspid isthmus are shown. Also depicted are the mean values ± SD. Note that a DP1-2 interval <90 ms was always associated with incomplete block and a DP1-2 interval  110 ms was always associated with complete block. Although there were 30 patients in this study, the sample size during incomplete block was 25 patients, because a DP was not always present during incomplete isthmus block.
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Figure 5 An interval separating the two components of double potentials (DP1-2) of 94 ms was recorded along the ablation (Abl) line in the cavo-tricuspid isthmus during coronary sinus (CS) pacing, after several applications of radiofrequency energy. The DP1-2 interval is between 90 and 110 ms, which is equally likely when block is incomplete or complete. In this case, the fractionated, low-amplitude electrogram within the DP, along with the predominantly positive polarity of the second component of the DP, suggests that block is incomplete. The presence of incomplete block is confirmed by the atrial activation sequence in E1 to E8 and by the positive initial polarity of E1 and E2. Without moving the ablation catheter, an additional application of radiofrequency energy was delivered, and the DP1-2 interval increased to 132 ms, a value always associated with complete isthmus block. Complete block was confirmed by the atrial activation sequence in the halo catheter and by a change to negative initial polarity of E1 and E2. St = stimulus channel.
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