Microelectrode voltage mapping for substrate assessment in catheter ablation of ventricular tachycardia: A dual-center experience

Introduction

The assessment of the ventricular myocardial substrate critically depends on the size of mapping electrodes, their orientation with respect to wavefront propagation, and interelectrode distance. We conducted a dual-center study to evaluate the impact of microelectrode mapping in patients undergoing catheter ablation (CA) of ventricular tachycardia (VT).

Methods

We included 21 consecutive patients (median age, 68 [12], 95% male) with structural heart disease undergoing CA for electrical storm (n = 14) or recurrent VT (n = 7) using the QDOT Micro catheter and a multipolar catheter (PentaRay, n = 9). The associations of peak-to-peak maximum standard bipolar (BV_c) and minibipolar (PentaRay, BV_p) with microbipolar (BV_μMax) voltages were respectively tested in sinus rhythm with mixed effect models. Furthermore, we compared the features of standard bipolar (BE) and microbipolar (μBE) electrograms in sinus rhythm at sites of termination with radiofrequency energy.

Results

BV_μMax was moderately associated with both BV_c (β = .85, p < .01) and BV_p (β = .56, p < .01). BV_μMax was 0.98 (95% CI: 0.93−1.04, p < .01) mV larger than corresponding BV_c, and 0.27 (95% CI: 0.16−0.37, p < .01) mV larger than matching BVp in sinus rhythm, with higher percentage differences in low voltage regions, leading to smaller endocardial dense scar (2.3 [2.7] vs. 12.1 [17] cm², p < .01) and border zone (3.2 [7.4] vs. 4.8 [20.1] cm², p = .03) regions in microbipolar maps compared to standard bipolar maps. Late potentials areas were nonsignificantly greater in microelectrode maps, compared to standard electrode maps. At sites of VT termination (n = 14), μBE were of higher amplitude (0.9 [0.8] vs. 0.4 [0.2] mV, p < .01), longer duration (117 [66] vs. 74 [38] ms, p < .01), and with greater number of peaks (4 [2] vs. 2 [1], p < .01) in sinus rhythm compared to BE.

Conclusion

microelectrode mapping is more sensitive than standard bipolar mapping in the identification of viable myocytes in SR, and may facilitate recognition of targets for CA.     

Focal arrhythmia ablation with multipolar mapping: Does it still make sense to stay off‐grid?

Multipolar mapping (MPM) has primarily been studied in complex arrhythmia substrates or reentrant circuits. Chieng et al. use a case‐control design to compare MPM and point‐by‐point mapping with an ablation catheter for focal atrial and ventricular tachycardias, showing reduced procedure times and earlier electrograms in the MPM group but no difference in clinical outcomes. It is plausible that faster mapping and better delineation of earliest signals may translate to improved clinical outcomes if studied in a randomized trial in a larger population. Future MPM systems will guide the operator toward the focus in real‐time and may even triangulate the source in three dimensions, giving an estimate of depth within the myocardium or likely focus in the opposite chamber.     

Mapping the critical diastolic pathway in intra-atrial reentrant tachycardia using an automated voltage mapping program

This case report demonstrates the use of an automated voltage mapping algorithm to facilitate the rapid mapping of the low-voltage zone and isolate the critical diastolic pathway of an intra-atrial reentrant tachycardia circuit. Catheter ablation targeted to this pathway successfully terminated the arrhythmia.     

Localization of the Origin of Arrhythmias for Ablation: From Electrocardiography to Advanced Endocardial Mapping Systems

Radiofrequency catheter ablation techniques have had a dramatic impact on the treatment of a variety of cardiac arrhythmias. However, catheter ablation of complex arrhythmias, such as intra-atrial reentry, ventricular tachycardias, and atrial fibrillation, continues to pose a major challenge. This stems from limitations of fluoroscopy and conventional catheter-based mapping techniques that limit the accurate anatomic localization of complex arrhythmogenic substrates. In this article, ECG features of complex arrhythmias are reviewed, which may facilitate the planning of an ablation procedure. The physical principles of the newly available catheter-based endocardial mapping techniques and their clinical applicability for treatment of complex arrhythmias are discussed. The role of intracardiac echocardiography to facilitate mapping and ablation is reviewed.     

Noncontact mapping of small pulmonary artery potentials preceding ectopy from the right ventricular outflow tract

Idiopathic right ventricular tachycardia typically originates from the right ventricular outflow tract (RVOT). However, it also may originate from above the pulmonic valve. We describe a patient with a 2-year history of symptoms of palpitations associated with premature ventricular contractions (PVCs) in whom radiofrequency catheter ablation at the PVC exit site in the lateral RVOT failed despite the presence of several favorable criteria. However, using a multiple electrode array catheter, we demonstrated above the pulmonic valve clear evidence of low-amplitude preceding electrical activity ("blue ghost") that swept 3 cm inferolaterally over 20 ms to the previously identified lateral RVOT exit. Catheter mapping even at 128x gain demonstrated only very-low-amplitude potentials at this site, and pacing was unable to capture the ventricle from this region. However, ablation at this site immediately terminated the arrhythmia, and the patient has remained PVC-free after 1 year. This case supports the existence of previously hypothesized myocardial sleeves above the pulmonary valve that may be responsible for RVOT tachycardia and shows that they can be detected using noncontact mapping.     

Noninvasive phase mapping of persistent atrial fibrillation in humans: Comparison with invasive catheter mapping

Background

A novel noninvasive epicardial and endocardial electrophysiology system (NEEES) to identify electrical rotors and focal activity in patients with atrial fibrillation (AF) was recently introduced. Comparison of NEEES data with results from invasive mapping is lacking.

Methods

Six male patients (59 ± 11 years) with persistent AF underwent cardiac mapping with the NEEES, which included the creation of isopotential and phase maps. Then patients underwent catheter mapping using a PentaRay NAV catheter and the CARTO 3 system. Signals acquired by the catheter were analyzed by customized software that applied the same phase mapping algorithm as for the NEEES data.

Results

In all patients, noninvasive phase mapping revealed short‐lived electrical rotors occurring 1.8 ± 0.3 times per second and demonstrating 1–4 (mean 1.2 ± 0.6) rotation cycles. Most of these rotors (72.7%) aggregated in 2–3 anatomical clusters. In two patients, focal excitation from pulmonary veins was observed. Invasive catheter mapping in the dominant rotor aggregation sites and in the three control sites demonstrated the presence of electrical rotors with properties similar to noninvasively detected rotors. Spearman's correlation coefficient between rotor occurrence rate by noninvasive and invasive mapping was 0.97 (p < .0001). Mean rotors' cycle length at dominant aggregation sites, scores of their full rotations, and the proportion of rotors with clockwise rotation were not significantly different between the mapping modalities.

Conclusion

In patients with persistent AF, phase processing of unipolar electrograms recorded by catheter mapping could reproduce electrical rotors as characterized by NEEES‐based phase mapping.     

Characteristics of Sinus Rhythm Electrograms at Sites of Ablation of Ventricular Tachycardia Relative to All Other Sites: A Noncontact Mapping Study of the Entire Left Ventricle

Noncontact Mappin g of VT During Sinus Rhythm. Introduction : Regions of the diseased ventricle that activate abnormally during sinus rhythm (SR) may be the areas of slow and disorganized conduction that form the diastolic pathway through which reentry may occur during ventricular tachycardia (VT).
Methods and Results : We examined features of electrograms recorded during SR that might indicate a site suitable for ablation of VT using a noncontact mapping system, which enables reconstruction of > 3,000 electrograms. Preablation SR electrogram characteristics at sites of successful radiofrequency ablation (RFA) were examined in 13 patients with 53 VTs. Timing of onset, lateness of activity, electrogram duration, and number of baseline crossing events of reconstructed electrograms at the sites of successful RFA were compared with the electrograms of latest onset, latest activity, longest duration, and most baseline crossing events of all ventricular sites. Onset of activation at sites of successful RFA were 26.9 ± 25.2 msec (mean ± SD) earlier than (and 2.9 ± 1.7 cm away from) the site of latest onset of SR activation. Electrogram duration at sites of successful RFA was 83%± 14.6% of (and 4.3 ± 1.8 cm away from) the longest electrogram. The baseline crossing events at sites of successful RFA were 53%± 22% of (and 4.9 ± 1.9 cm away from) the most fractionated electrogram. The latest activity at sites of successful RFA was 21.6 ± 24.8 msec earlier than (and 4.3 ± 1.6 cm away from) the site of latest activity.
Conclusion : Although the site of latest onset of endocardial activation during SR proved to be the most sensitive indicator, the characteristics of SR electrograms did not usefully predict successful ablation sites.     

Assessment of NOGA catheter stability during the entire cardiac cycle by means of a special needle-tipped catheter.

The NOGA system maps regional myocardial function and delivers local catheter-based therapeutics, requiring stability and precise localization of the catheter tip throughout the cardiac cycle. A special catheter having a retractable needle at its tip was used to compare tip stability with and without needle insertion into the myocardium, assuming this prevents catheter slippage. For multiple sites in seven pig left ventricles, we recorded sets of three consecutive point locations: pre-, post-, and during needle insertion. In-point location stability (LocStab), defined as the mean displacement between catheter tip trajectories of two consecutive cardiac cycles at a specific point, did not differ among the three groups of points (mean, 1.33 +/- 0.61 mm; P = 0.37 by ANOVA), indicating that trajectories are equally stable and repeatable with or without needle insertion. Between-point LocStab(p1,p2), i.e., displacement between the trajectories of two different points (p1 and p2) at the same location, was not increased when p1 = a needle insertion point and p2 = a noninsertion point, compared to both p1,p2 = noninsertion points, suggesting that slippage of noninsertion points is negligible. In conclusion, catheter tip trajectories at any location are highly stable throughout the cardiac cycle.     

Electroanatomic properties of the pulmonary veins: slowed conduction, low voltage and altered refractoriness in AF patients

Electroanatomic Properties of the Pulmonary Veins. Introduction: Rapid PV activity is critical in initiating and maintaining AF. The underlying substrate responsible for this remains uncertain. We sought to identify if patients with paroxysmal (PAF) and persistent atrial fibrillation (PeAF) have an abnormal substrate within the pulmonary veins (PVs). Methods and Results: Thirty‐nine patients with AF (21 PAF, 18 PeAF) were compared with 15 age‐matched controls with left‐sided accessory pathways (AVRT). High‐density 3D electroanatomic maps of the PVs were created. PV voltage, conduction, PV muscle sleeve length, effective refractory periods (ERPs) of the PVs, posterior left atrium (PLA), left atrial appendage (LAA) and distal coronary sinus (CSd), and signal complexity were assessed. Compared with controls, the PVs of AF patients had (1) lower mean‐voltage and a higher % low‐voltage; (2) shorter PV muscle sleeves; (3) slower conduction; (4) shorter ERP; and (5) more prevalent complex signals. Compared with the PAF group, the PeAF group had (1) higher % low voltage; (2) slower conduction; and (3) more complex signals. In PAF patients, the PLA and LAA ERPs were longer than controls and the PV ERP was shorter than controls; in PeAF patients PLA and LAA ERPs were reduced, but to a lesser extent than in the PVs. AF induction occurred during PV ERP testing in both AF groups, but not controls. Conclusions: PAF and PeAF patients demonstrate electrical and electroanatomic remodeling of the PVs compared to control patients without prior AF. Some of these changes were more marked in PeAF. (J Cardiovasc Electrophysiol, Vol. 22, pp. 1083‐1091, October 2011)     

经体表和心内膜标测的转子识别及其对房颤消融的影响

为及时反映海外心脏病学领域的最新进展,努力缩短国内外心电学研究的差距,自本期起,本刊推出“海外论坛”栏目。本栏目主要刊发国内外心脏病学研究领域前沿成果的专题述评、综述和重要学术会议快报等,形式不拘。欢迎海内外学者惠赐大作！开栏之初,我们有幸得到了两位国际知名心脏病学专家---欧洲心律协会（HRS ）主席Karl-Heinz Kuck 教授与德国伊丽莎白医院Contilia心脏和血管中心的Dietmar Schmitz教授的大力支持,为读者介绍有关转子标测及房颤消融和心脏再同步化治疗的最新研究进展,其中Schmitz教授的述评中囊括了今年8月31日在欧洲心脏病学会年会（ESC2014）上发布的最新数据。现将英文原文及译稿奉上,以飨读者。     

预激综合征旁道的心电图、心脏标测定位(附六例报告)

对6例预激综合征旁道进行心电图、电生理检查及心外膜标测定位和比较,结果提示综合二种心电图δ波极性作旁道定位的方法有较高的准确性。电生理检查对确定左或右旁道的存在有帮助,而作心内膜标测确定旁道位置较困难。认为显性预激综合征者,旁道切割术前不必强调作电生理检查,除非为隐匿性预激。用手指压迫预计的旁道部位,使δ波消失和/或阵发性室上性心动过速终止可能是心外膜标测的一种简便的方法。