Functional conduction system mapping in sheep reveals Purkinje spikes in the free wall of the right ventricular outflow tract

Figures

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  FIGURE 1. Delayed activation of the sheep RVOT. (A) Epicardial activation map of one sheep heart showing late activation of the RVOT. (B) Quantitative analysis of the average activation time in the RVOT, right ventricular free wall, and left ventricular free wall. (C) Epicardial and endocardial activation maps of the RVOT were simultaneously measured using separate electrode grids. (D) Endocardial activation maps of the distal RVOT showing the occurrence of Purkinje spikes preceding myocardial activation. RA, right atrium; AO, aorta; PT, pulmonary trunk; LA, left atrium; RV, right ventricle; LV, left ventricle.

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  FIGURE 2. High-resolution endocardial activation mapping of the RVOT reveals Purkinje activity preceding ventricular premature beats (VPBs). (A) Left: photograph of the opened right ventricular cavity exposing the endocardial surface of the RVOT free wall. Middle: endocardial activation map of the RVOT recorded during sinus rhythm. Right: corresponding unipolar and coaxial (Hoogendijk et al.) electrogram traces from sites a-d in the activation map. Note the absence of Purkinje spikes in the unipolar electrogram and the single moment of activation in the coaxial electrogram. (B) Unipolar electrograms recorded from the RVOT endocardium while moving the catheter multi-electrode. Each VPB was preceded by a Purkinje spike (see insets). (C) Local activation maps corresponding to the maximal -dV/dT for Purkinje activation (top row) and myocardial activation (bottom row).

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  FIGURE 3. The sheep RVOT contains a Purkinje network that extends into the myocardial wall. (A) Photograph of the luminal side of the RVOT free wall after dissection. From this view, the presence of a Purkinje network is clearly visible. Scale in cm. (B) Example of a RVOT section stained with Picrosirius Red. Purkinje fibers were identified immediately below the pulmonary valve leaflets (B’) and toward the right ventricular free wall (B”). (C) Super-resolution microscopy images of Connexin 40-positive Purkinje fibers in the RVOT endocardium and within the myocardial wall.

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  FIGURE 4. Quantitative analysis of Purkinje fiber distribution in the sheep RVOT. (A) Schematic explaining the selection of longitudinal sections from the RVOT free wall. (B) Purkinje fiber distribution per section from left-right of the RVOT wall (N = 2) within 0–5 mm, 5–10 mm, and 10–15 mm below the valve. (C) Quantitative analysis of Purkinje fiber number within 0–5 mm, 5–10 mm, and 10–15 mm below the valve (n = 38 sections). (D) Analysis of the shortest distance from Purkinje fiber to the endocardial (endo) and epicardial (epi) wall. (E) Heatmaps of quantitative analysis of the average number of Purkinje fibers for each RVOT between the endocardium and epicardium. Segment width equals 10% RVOT wall thickness.