Characteristics of Scar-Related Ventricular Tachycardia Circuits Using Ultra-High-Density Mapping

Abstract

Background Ventricular tachycardia with structural heart disease is dependent on re-entry within scar regions. We set out to assess the VT circuit in greater detail than has hitherto been possible, using ultra highdensity mapping. Methods All ultra high-density mapping guided ventricular tachycardia ablation cases from six high-volume European centres were assessed. Maps were analysed offline to generate activation maps of tachycardia circuits. Topography, conduction velocity and voltage of the VT circuit were analyzed in complete maps. Results Thirty-six tachycardias in 31 patients were identified, 29 male and 27 ischaemic. VT circuits and isthmuses were complex, eleven were single-loop and 25 double-loop; three had two entrances, five had two exits and 15 had dead ends of activation. Isthmuses were defined by barriers which included anatomical obstacles, lines of complete block and slow conduction (in 27/36 isthmuses). Median conduction velocity was 0.08m/s in entrance zones, 0.29m/s in isthmus regions (p<0.001), and 0.11m/s in exit regions (p=0.002). Median local voltage in the isthmus was 0.12mV during tachycardia and 0.06mV in paced/sinus rhythm. Two circuits were identifiable in five patients. The median timing of activation was 16% of diastole in entrances, 47% in the mid isthmus, and 77% in exits. Conclusions VT circuits identified were complex, some of them having multiple entrances, exits and dead ends. The barriers to conduction in the isthmus appear to be partly functional in 75% of circuits. 3 Conduction velocity in the VT isthmus slowed at isthmus entrances and exits, when compared with the mid isthmus. Isthmus voltage is often higher in VT than in sinus or paced rhythms.

Local impedance guides catheter ablation in patients with ventricular tachycardia

“…Critical isthmus sites were defined a the part of the VT circuit which is delimited by conduction barriers showing the smallest activation region . Length of the isthmus was defined as the distance from the inward wavefront curvature to the outward wavefront curvature . Local signal characteristics were used as an additional parameter.…”

Updating the Risk Stratification for Sudden Cardiac Death in Cardiomyopathies: The Evolving Role of Cardiac Magnetic Resonance Imaging. An Approach for the Electrophysiologist

“…In the dense core of the scar, areas of fibrosis are interrupted by viable fibers that serve as slow conduction pathways. In addition, the tissue surrounding the core of the scar is a 'grey zone' of hypoperfused myocardium with arrhythmogenic properties [73][74][75]. The heterogeneity of the scar as well as the size of the border zone assessed by CMR parameters are all predictors of malignant arrhythmias and appropriate ICD firings in ICM [76][77][78].…”

Ventricular Tachycardia Isthmus Characteristics: Insights from High-density Mapping

“…[17] Data from human VT studies confirms this general principle. [18] A multicentre study of high-density VT maps found that isthmuses were defined by lines of block, but that multiple entrances and exits were common. Further, in humans, dead ends of activation were also common and regions of activation within dense scar, consistent with inner-loop activation, were also observed.…”

“…Further, in humans, dead ends of activation were also common and regions of activation within dense scar, consistent with inner-loop activation, were also observed. [18]…”

“…The average time from MI to VT mapping in human studies is far longer, 10–20 years, than the few months possible in an animal model. [18,19] The delay in local abnormal ventricular activity (LAVA) and degree of fractionation of EGMs are known to be associated with time from infarction, suggesting a prolonged period of remodelling, which results in increasing architectural complexity with time. [20] This complex architecture has important implications in clinical practice.…”