Repolarization indicates electrical instability in ventricular arrhythmia originating from papillary muscle

Figures

• 

  Figure 1. Experimental set-up for endocardial and epicardial mapping of VA from PM in ovine heart. (A) Echocardiography of anterior PM (APM) and posterior PM (PPM) of the left ventricle. (B) Echocardiography during application of aconitine via injection needle. Note the multi-spline basket catheter positioned via retrograde access. (C) Left ventricular (LV) wall after formalin fixation, longitudinal dissection on level of anterior PM, correct needle position for injection of aconitine. (D) Position of the basket catheter in the left ventricle between APM and PPM, mitral valve (MV). Note the false tendons connecting LV apex to the PMs. Right: anterior PM with Purkinje fibres (Indian ink-staining). (E) Epicardial electrode sock in situ. (F) Fluoroscopic view of the heart in anterior–posterior projection with electrode sock on the epicardium and steerable catheter in coronary sinus (CS). APM, anterior papillary muscle; CS, coronary sinus; PPM, posterior papillary muscle.

• 

  Figure 2. Endocardial activation mapping of VA: stable VA with earliest activation at injection site in PM and faster propagation in basal direction. (A and B) Endocardial activation map of focal VA during stable VA (sequential acquisition including multiple beats) after injection of aconitine into the anterior PM, earliest activation in anterior-basal segment, by high-density mapping, legend denotes the orientation of space coordinates from mapping system and activation time colourcode (ms) (A) as represented in clinical high-density mapping, basket catheter in left ventricle (B); 3D reconstruction pseudocolour indicates LAT; see Supplementary material online, Movie for full 3D representation.

• 

  Figure 3. Epicardial mapping of (A) LAT and (B) ARI. (A) Epicardial maps of sequential beats during ventricular tachycardia show consistent activation pattern of earliest area (global single-beat mapping). (B) Pseudocolour visualization of epicardial ARI during single beat. Epicardial maps represent ARI in frontal, dorsal, and apical projection. One exemplary unipolar signal from a single sock electrode demonstrates determination of ARI as the LAT subtracted from the repolarization time (RT). (C) ARI correlates to the monophasic action potential (MAP)6 illustrated by the exemplary overlay of the MAP signal on the unipolar electrogram. ARI, activation recovery interval; LAT, local activation time; MAP, monophasic action potential; RT, repolarization time.

• 

  Figure 4. Steeper electrical restitution curve for short ARI during VA (12 animals) compared with non-VA including ventricular pacing and SR (14 animals). (A) ARI in relation to DI, monoexponential model f(x) = z − ae−x/b, where x = DI and ARI is a function of x. Constants of the fitted model a = 271.9 (P = 1.8−51), b = 85.8 (P = 4.8−21), z = 248.9 (P = 5.8−280) for VA (including 135 heart beats) and for non-VA a = 194.7 (P = 2.1−56), b = 364.8 (P = 5.5−05), z = 333.9 (P = 1.2−55), 84 heart beats. Monoexponential curves have a horizontal asymptote at z (upper dotted line) and a vertical asymptote dependent on a. A tangent is positioned at z/2, slope computed as f′(x)=ab.ex/b at the specified point and was 1.45 for VA (left) and 0.46 for non-VA (right). (B) Normal vector at the vertex of the curve (slope of tangent = 1) was used to classify VA as fast or slow VA. Fifteen of 17 (88%) of degenerating VA and 11 of 118 (9.3%) non-degenerating VA were located below the normal vector. Individual data points represent the median ARI and DI for a beat’s median interval for each of the nine anatomical regions (left anterior basal, right anterior basal, left posterior basal, right posterior basal,…

• 

  Figure 5. Repolarization time/cycle length separates degenerating from self-limiting VA and VA from non-VA. Leftmost panel: degenerating, self-limiting VA, and non-VA beats where global Kruskal–Wallis test P < 0.05, P-values from pairwise two-sided Wilcoxon’s test results are indicated. Centre and right panels: electrical restitution characteristics ARI vs. DI with pseudocolour overlay for predictive parameter (RT/cycle length). Solid lines indicate electrical restitution curve model f(x) = z − ae−x/b where x = DI and ARI is a function of x. Dashed lines: tangent at vertex of the model; dot-dashed line: normal vector through vertex of the model separating fast from slow VA. Pseudocolour overlay indicates RT normalized to cycle length. VA, ventricular arrhythmia.