Image Integration to Guide Catheter Ablation in Scar-Related Ventricular Tachycardia.

BACKGROUND: Although multi-detector computed tomography (MDCT) and cardiac magnetic resonance (CMR) can assess the structural substrate of ventricular tachycardia (VT) in ischemic cardiomyopathy (ICM), non-ICM (NICM), and arrhythmogenic right ventricular cardiomyopathy (ARVC), the usefulness of systematic image integration during VT ablation remains undetermined. METHODS AND RESULTS: A total of 116 consecutive patients (67 ICM; 30 NICM; 19 ARVC) underwent VT ablation with image integration (MDCT 91%; CMR 30%; both 22%). Substrate was defined as wall thinning on MDCT and late gadolinium-enhancement on CMR in ICM/NICM, and as myocardial hypo-attenuation on MDCT in ARVC. This substrate was compared to mapping and ablation results with the endpoint of complete elimination of local abnormal ventricular activity (LAVA), and the impact of image integration on procedural management was analyzed. Imaging-derived substrate identified 89% of critical VT isthmuses and 85% of LAVA, and was more efficient in identifying LAVA in ICM and ARVC than in NICM (90% and 90% vs. 72%, P < 0.0001), and when defined from CMR than MDCT (ICM: 92% vs. 88%, P = 0.026, NICM: 88% vs. 72%, P < 0.001). Image integration motivated additional mapping and epicardial access in 57% and 33% of patients. Coronary and phrenic nerve integration modified epicardial ablation strategy in 43% of patients. The impact of image integration on procedural management was higher in ARVC/NICM than in ICM (P < 0.01), and higher in case of epicardial approach (P < 0.0001). CONCLUSIONS: Image integration is feasible in large series of patients, provides information on VT substrate, and impacts procedural management, particularly in ARVC/NICM, and in case of epicardial approach.

Noninvasive mapping to guide atrial fibrillation ablation.

Atrial fibrillation (AF) is a dynamic rhythm. Noninvasive mapping overcomes many previous barriers to mapping such a dynamic rhythm, by providing a beat-to-beat, biatrial, panoramic view of the AF process. Catheter ablation of AF drivers guided by noninvasive mapping has yielded promising clinical results and has advanced understanding of the underlying pathophysiologic processes of this common heart rhythm disorder.

Noninvasive mapping of ventricular arrhythmias.

Several decades of research has led to the development of a 252-lead electrocardiogram-based three-dimensional imaging modality to refine noninvasive diagnosis and improve the management of heart rhythm disorders. This article reviews the clinical potential of this noninvasive mapping technique in identifying the sources of electrical disorders and guiding the catheter ablation of ventricular arrhythmias (premature ventricular beats and ventricular tachycardia). The article also briefly refers to the noninvasive electrical imaging of the arrhythmogenic ventricular substrate based on the electrophysiologic characteristics of postinfarction ventricular myocardium.

Distinct localized reentrant drivers in persistent atrial fibrillation identified by noninvasive mapping: relation to f-wave morphology.

Noninvasive mapping overcomes previous barriers to provide panoramic beat-to-beat mapping during atrial fibrillation (AF). This article demonstrates the utility of noninvasive mapping in identifying localized driving sources in persistent AF. Reentrant driver activity detected by noninvasive mapping from specific regions correlated with distinct f-wave morphologies. Ablation targeting these drivers resulted in progressive AF cycle length prolongation and termination of the arrhythmia.

Substrate mapping and ablation for ventricular tachycardia: the LAVA approach.

INTRODUCTION: Catheter ablation of ventricular tachycardia (VT) is proven effective therapy particularly in patients with frequent defibrillator shocks. However, the optimal endpoint for VT ablation has been debated and additional endpoints have been proposed. At the same time, ablation strategies aiming at homogenizing the substrate of scar-related VT have been reported. METHODS AND RESULTS: Our method to homogenize the substrate consists of local abnormal ventricular activity (LAVA) elimination. LAVA are high-frequency sharp signals that represent near-field signals of slowly conducting tissue and hence potential VT isthmuses. Pacing maneuvers are sometimes required to differentiate them from far-field signals. Delayed enhancement on cardiac MRI and/or wall thinning on multidetector computed tomography are also extremely helpful to identify the areas of interest during ablation. A strategy aiming at careful LAVA mapping, ablation, and elimination is feasible and can be achieved in about 70% of patients with scar-related VT. Complete LAVA elimination is associated with a better outcome when compared to LAVA persistence even when VT is rendered noninducible. CONCLUSION: This is a simple approach, with a clear endpoint and the ability to ablate in sinus rhythm. This strategy significantly benefits from high-definition imaging, mapping, and epicardial access.

Characterization of contact force during endocardial and epicardial ventricular mapping.

BACKGROUND: The optimal contact force (CF) for ventricular mapping and ablation remains unvalidated. We assessed CF in different endocardial and epicardial regions during ventricular tachycardia substrate mapping using a CF-sensing catheter (Smartouch; Biosense-Webster) and compared the transseptal versus retroaortic approach. METHODS AND RESULTS: In total, 8979 mapping points with CF, and force vector orientation (VO) were recorded in 21 patients, comprising 13 epicardial, 12 left ventricular (6 transseptal and 6 retroaortic approach), and 12 right ventricular endocardial maps. VO was defined as adequate when the vector was directed toward the myocardium. During epicardial mapping, 46% of the points showed an adequate VO and a median CF of 8 (4-13) g, however, with significant differences among the 8 regions. When VO was inadequate, median CF was higher at 16 (10-24) g (P<0.0001). During left ventricular and right ventricular endocardial mapping, 94% of VO were adequate. Median CF of adequate VO was higher in the left ventricular and right ventricular endocardium than in the epicardium (15 [8-25] and 13 [7-22] g versus 8 [4-13] g, respectively; both P<0.001). Global median left ventricular CF with transseptal approach was not statistically different from retroaortic approach, but CF in the apicoinferior and apicoseptal regions was higher with transseptal approach (P<0.001). CONCLUSIONS: Ventricular mapping demonstrates important regional variations in CF, but in general, CF is higher endocardially than epicardially where poor catheter orientation is associated with higher CF. A transseptal approach may lead to improved contact particularly in the apicoseptal and inferior regions.

Differential sequential septal pacing: a simple maneuver to differentiate nodal versus extranodal ventriculoatrial conduction.

BACKGROUND: Distinguishing retrograde nodal conduction from extranodal conduction using an accessory pathway (AP) can sometimes be challenging. OBJECTIVE: To distinguish nodal from extranodal ventriculoatrial (VA) conduction regardless of AP location by proposing a simple method. This method is based on the principle that moving the pacing site progressively from the basal region toward the entrance of the His-Purkinje system should shorten VA time for nodal but not for AP conduction. METHODS: Sixty-seven patients with supraventricular tachycardia were prospectively recruited. Quadripolar catheters were placed at the right ventricular (RV) apex, right atrium, and His and coronary sinus. The RV septum was sequentially paced at 4 sites: (1) basal, (2) high midventricle, (3) low midventricle, and (4) apex at a cycle length 100 ms shorter than the resting cycle length. The stimulus-to-atrial (SA) interval was measured by using the proximal coronary sinus atrial electrogram. RESULTS: Group 1 (n = 33) had nodal VA conduction; all patients had typical atrioventricular nodal reentrant tachycardia. Group 2 (n = 34) had extranodal VA conduction via an AP: 19 left-sided, 6 right-sided, and 9 posteroseptal. In group 1, the SA interval decreased significantly as pacing site moved closer toward the apex (site 1: 166 ± 35 ms, site 2: 153 ± 32 ms, site 3: 149 ± 32 ms, site 4: 154 ± 33 ms, P < .001, respectively, at sites 2-4 compared with site 1). In contrast, in group 2, the SA interval increased significantly toward the apex (site 1: 149 ± 45 ms, site 2: 158 ± 43 ms, site 3: 161 ± 43 ms, and site 4: 163 ± 40 ms, P < .001, respectively, at sites 2-4 compared with site 1). The SA interval at the high midventricular site (site 2) - SA interval at the base (site 1) ≤ 0 ms for nodal and > 0 ms for extranodal conduction had optimal sensitivity and specificity (nodal: selectivity = 97.0% and specificity = 85.3%; extranodal: selectivity = 85.3% and specificity = 97.0%). CONCLUSIONS: Differential sequential pacing of the RV septum reliably distinguishes retrograde atrioventricular nodal conduction from AP conduction.

Myocardial infarction and atrial fibrillation: importance of atrial ischemia.

BACKGROUND: Myocardial infarction (MI) is associated with the development of atrial fibrillation (AF). We aimed to characterize the atrial abnormalities because of MI and determine the role of ischemia to the AF substrate. METHODS AND RESULTS: Forty-four sheep were studied. MI was induced by occlusion of the left circumflex artery (LCX) or left anterior descending artery (LAD). Excluding 11 with fatal arrhythmias, equal groups of animals (LCX; LAD; and sham-operated) underwent sequential electrophysiology study for 45 minutes to determine atrial effective refractory periods, conduction velocity, conduction heterogeneity index, and AF inducibility. Postmortem evaluation was performed with 2,3,5 triphenyl tetrazolium chloride staining. MI resulted in greater left ventricular dysfunction (P<0.05), LA pressure (P<0.0003), and reduction in atrial effective refractory periods (P<0.0001) compared with control. 2,3,5 triphenyl tetrazolium chloride staining demonstrated that the left circumflex artery, and not the LAD, group had atrial infarction. The left circumflex artery group demonstrated the following compared with the LAD or control groups: greater slowing in atrial conduction velocity (P<0.0001 and P<0.001); increased absolute range of conduction phase delay (P<0.001 and P<0.001); increased conduction heterogeneity index (P<0.0001 and P<0.001); greater AF vulnerability (P<0.05 for both); and longer AF duration (P<0.05 for both). LAD group had modest but significant slowing in conduction velocity (P<0.01) but no change in conduction heterogeneity index or AF duration compared with control. CONCLUSIONS: Left ventricular infarction, which is known to result in atrial stretch, hemodynamic change, and neurohumoral activation, contributes partially to the atrial abnormalities in MI. Atrial ischemia/infarction results in greater atrial electrophysiological changes and propensity for AF forming the dominant substrate for AF in MI.

Feasibility of high-density electrophysiological study using multiple-electrode array in isolated small animal atria.

1. High-density cardiac electrophysiological study (EPS) of small animal atria has been limited to optical mapping techniques, which require complex and expensive equipment setup. We aim to evaluate the feasibility of carrying out EPS in isolated atrial tissues using a custom made high-density multiple-electrode array (MEA). 2. Isolated rat atrial preparations were studied. The MEA (4 × 5 mm) consisted of 90 silver chloride coated electrodes (0.1 mm diameter, 0.5 mm pitch) and was connected to a conventional EP system yielding 80 bipolar signals. Atrial tissues were placed over the MEA in a dish bubbled with 100% oxygen and superfused with modified HEPES solution at pH 7.35 and 37°C. Then, 1 mmol of 2,3-butanedione monoxime was added to suppress motion artifacts from muscle contractions. Custom plaque analysis software was used for offline conduction analysis. 3. Isolated atrial tissues showed good viability of > 30 min, allowing ample time for complete EPS. High quality electrograms with excellent signal to noise ratio were obtained. All electrophysiological parameters showed good reproducibility: effective refractory period, conduction velocity and heterogeneity index. Tachycardia was also inducible in these normal atria. 4. The present study shows the feasibility of performing high-density EPS of small isolated atrial tissues with a conventional electrode-based technique. The MEA system is compatible with standard electrophysiology recording systems and provides a novel, inexpensive option for detailed EPS in small animal models. In particular, it presents new research avenues to further explore the mechanisms of atrial arrhythmias in various transgenic and knockout rodent models.