Local abnormal ventricular activity detection in scar-related VT: Microelectrode versus conventional bipolar electrode.

BACKGROUND: Conventional bipolar electrodes (CBE) may be suboptimal to detect local abnormal ventricular activities (LAVAs). Microelectrodes (ME) may improve the detection of LAVAs. This study sought to elucidate the detectability of LAVAs using ME compared with CBE in patients with scar-related ventricular tachycardia (VT). METHODS: We included consecutive patients with structural heart disease who underwent radiofrequency catheter ablation for scar-related VT using either of the following catheters equipped with ME: QDOTTM or IntellaTip MIFITM. Detection field of LAVA potentials were classified as three types: Type 1 (both CBE and ME detected LAVA), Type 2 (CBE did not detect LAVA while ME did), and Type 3 (CBE detected LAVA while ME did not). RESULTS: In 16 patients (68 ± 16 years; 14 males), 260 LAVAs electrograms (QDOT = 72; MIFI = 188) were analyzed. Type 1, type 2, and type 3 detections were 70.8% (QDOT, 69.4%; MIFI, 71.3%), 20.0% (QDOT, 23.6%; MIFI, 18.6%) and 9.2% (QDOT, 6.9%; MIFI, 10.1%), respectively. The LAVAs amplitudes detected by ME were higher than those detected by CBE in both catheters (QDOT: ME 0.79 ± 0.50 mV vs. CBE 0.41 ± 0.42 mV, p = .001; MIFI: ME 0.73 ± 0.64 mV vs. CBE 0.38 ± 0.36 mV, p < .001). CONCLUSIONS: ME allow to identify 20% of LAVAs missed by CBE. ME showed higher amplitude LAVAs than CBE. However, 9.2% of LAVAs can still be missed by ME.

Atrial Tachycardia With Atrial Activation Duration Exceeding the Tachycardia Cycle Length: Mechanisms and Prevalence.

OBJECTIVES: This study sought to identify atrial tachycardia (AT) demonstrating atrial activation duration (AAD) lasting longer than the length of the tachycardia cycle (TCL); to assess AT prevalence; and to evaluate the mechanisms and characteristics associated with these AT episodes by using the Rhythmia system (Boston Scientific, Marlborough, Massachusetts). BACKGROUND: Ultra-high-density mapping allows very accurate characterization of mechanisms involved in AT. Some complex patterns may involve AAD which is longer than the tachycardia cycle length (TCL) which makes maps difficult to interpret. Prevalence and characteristics of such ATs are unknown. METHODS: A cohort of 100 consecutive patients undergoing ablation of 125 right (n = 21) or left (n = 104) ATs using ultra-high-density mapping were retrospectively included. Offline calculation of right or left AAD was compared to TCL. RESULTS: Mean TCL was 293 ± 65 ms, and mean AAD was 291 ± 74 ms (p = NS). AT mechanisms were macro-re-entry in 74 cases (59%), localized re-entry in 27 cases (22%), and focal AT in 21 cases (17%) (types were mixed in 3 cases). Fifteen ATs (12%) had AADs that were longer than the TCL (71 ± 45 ms longer, from 10 to 150 ms). TCL was equal to the AAD in 97 ATs (78%), whereas 13 ATs (10%) had AAD shorter than the TCL (focal AT in each case). There were no differences between right and left atria for prevalence of ATs with AADs that were longer than the TCLs. There were significant differences in AT mechanisms according to the AAD-to-TCL ratio (p < 0.0001), with localized re-entry showing more often that AAD was longer than the TCL compared to that in focal AT and macro-re-entry. CONCLUSIONS: ATs with AAD lasting longer than the TCL were present in approximately 10% of the ATs referred for ablation, mostly in ATs caused by localized re-entry. Ultra-high-density mapping allows detection of these complex patterns of activation.

Insights from atrial surface activation throughout atrial tachycardia cycle length: A new mapping tool.

BACKGROUND: A novel "LUMIPOINT" software in the Rhythmia system (Boston Scientific) displays a histogram of activated area over the entire atrial tachycardia (AT) cycle length (CL) with a normalized score. OBJECTIVE: The purpose of this study was to examine whether the pattern of this global activation histogram (GAH) identified reentrant vs focal AT and whether a decrease in atrial activation area, shown as valleys in the GAH, identifies isthmuses. METHODS: One hundred eight activation maps of ATs (17 focal, 57 macroreentrant, 21 localized, 13 multiple loop) in 67 patients were reviewed retrospectively with the LUMIPOINT software. The ACTIVATION SEARCH feature highlighted the activated area in a given time period irrespective of the activation map. A 30-ms unit time interval was set, and the GAH patterns and electrophysiological properties of highlighted areas were examined. RESULTS: Focal ATs systematically displayed a plateau with GAH-Score <0.1 for at least 30% of the CL. Most reentrant ATs (90/91 [98.9%]) lacked this plateau and displayed activity covering the entire CL, with 2 [1-2] GAH-Valleys per tachycardia. Each GAH-Valley highlighted 1 [1-2] areas in the map. Among 264 highlighted areas, 198 (75.0%) represented slow conduction, 19 (7.2%) lines of block, 27 (10.2%) wavefront collision, 3 (1.1%) unknown, and 17 (6.4%) absence of activation in focal ATs. Practical ablation sites all matched one of the highlighted areas based on GAH-Valleys, and they corresponded better with areas highlighted by GAH-Score ≤0.2 (P <.0001). CONCLUSION: GAH shows focal vs reentrant mechanisms at first glance. Decrease in activated areas (displayed by GAH-Valleys) is mostly due to slow conduction and highlights areas of special interest, with 100% sensitivity for isthmus identification.