Characteristics of Wavefront Propagation in Reentrant Circuits Causing Human Ventricular Tachycardia

Abstract

Background-We investigated the relationship between wavefront curvature and slowing of conduction both within and outside the diastolic pathway of circuits causing ventricular tachycardia (VT) in the infarcted human heart. Methods and Results-Propagation was determined around the reentrant circuits of 11 VT (cycle length, 348Ϯ75 ms) in 8 patients undergoing high-resolution noncontact mapping. The diastolic pathway had a mean wavefront velocity of 0.82Ϯ0.49 m/s and occupied 68Ϯ7% of VT cycle length. Significant changes (Ͼ5 degrees/mm) in trajectory of propagation occurred in 8 diastolic pathway segments (10.1Ϯ3 degrees/mm) in which wavefront propagation slowed to 0.41Ϯ0.11 m/s compared with the segments immediately preceding (0.91Ϯ0.16 m/s, PϽ0.05) and following (1.07Ϯ0.33, PϽ0.05) the change in trajectory. At the turning points of entry (9.3Ϯ3.9 degrees/mm) and exit (9.0Ϯ4.8 degrees/mm) of the diastolic pathway propagation, velocity slowed at entry from 1.23Ϯ0.4 to 0.6Ϯ0.26 ms (PϽ0.001) and was more rapid at exit turning points (0.8Ϯ0.25 m/s) (PϽ0.05). There was an inverse relationship between wavefront curvature and velocity, both within and outside the diastolic pathway (rϭ0.46, Pϭ0.0001), and VT cycle length correlated with total curvature multiplied by length of the diastolic pathway (PϽ0.01). Conclusions-Slowing of propagation in circuits causing VT in the infarcted human heart occurs over regions of wavefront turning, with an inverse relationship between wavefront curvature and velocity, both within and outside the diastolic pathway. Conduction is slower at entry than exit turning points of the diastolic pathway but is slowest during turns within the diastolic pathway.

Mechanisms that initiate ventricular tachycardia in the infarcted human heart

“…Distance measurements obtained using the noncontact system were calculated to account for surface curvature, as described previously 13 . VT circuits in which >30% of the diastolic pathway could be identified were included for analysis.…”

A Phased-Array Stimulator System for Studying Planar and Curved Cardiac Activation Wavefronts

“…If the ellipse expands with fixed velocities in the longitudinal and transverse directions, given by v l and v t , respectively, then the parameters a and b are described as functions of time by (3) Equation (2) then becomes: (4) For a single stimulus applied to the center of the imaging field of the camera, the resulting expanding wave front is an ellipse centered at the origin, with semi-major axis at angle θ with the x axis. The ellipse is then described by (5) where θ is the angle between the tissue fiber direction and the x axis of the image (hereafter we use x and y to describe the camera axes). The elliptical wave front created at each point in the stimulator array is emulated by translating the center of the expanding ellipse given by Equation (5) to the edge of a circle of radius R (representing the imaging window) at angle α.…”

“…A difference in conduction velocity has been observed between the planar wave fronts created by a linear array of electrodes and the curved wave fronts produced by point stimulation [1; 2] Wave fronts of varying curvature created by conduction through an isthmus of varying width have shown a similar effect of curvature on conduction velocity [3;4]. Also, a recent study demonstrates an inverse relation between wave front curvature and velocity in reentrant circuits that cause ventricular tachycardia [5]. Along with curvature, it is well known that as a result of the anisotropy of the electrical conductivity of cardiac tissue, the propagation velocity of a wave front depends upon the direction of propagation, traveling faster along the direction of the tissue fibers than in the perpendicular direction [6;7].…”

Mechanism of Pacing-Induced Ventricular Fibrillation in the Infarcted Human Heart

“…[11][12][13] A 9F catheter-mounted 64-wire multielectrode array was positioned inside the LV retrogradely, a 3D geometry of the LV chamber was created, and high-resolution isopotential maps were recorded.…”