Ventricular Electrogram Mapping
EPICARDIAL ACTIVATION MAPPING
Red portions of the normal activation map represent areas of earliest epicardial activation (generally on the anterior wall during normal sinus rhythm) and blue denotes latest activation (generally posterior). On the left is the 2D Hammer projection, and below is an animation of the activation sequence represented by a progressing contour. To navigate through the static activation map in 3D, click the heart on the right [this can be displayed with the SGI Cosmo Player web browser plugin]
A noradrenaline-induced ventricular arrhythmia Subepicardial infusion of noradrenaline caused a ventricular arrhythmia, which severely compromised the haemodynamic function. At the onset of the arrhythmia, the earliest site of epicardial activation (red) moved to the randomly chosen infusion site. This provided a new ventricular pacemaker, which significantly altered the cardiac activation sequence. Moreover, the total epicardial activation time approximately doubled compared to normal sinus rhythm.
The normal (left) and arrhythmic (right) epicardial activation sequences are shown here using anterior and posterior views of ventricles. As the wave of electrical activation proceeds, the epicardial surface shading is changed from blue to red to represent tissue depolarisation (note that repolarisation is not indicated and that the control and arrhythmic movies may not be synchronised).
The control activation proceeds relatively quickly (19 ms from earliest to latest site of activation), which is probably due to the predominantly transmural spread of ventricular excitation. The arrhythmic activation sequence is comparatively slower (43 ms epicardial spread) as the wave proceeds in a predominantly circumferential fashion, due to the new site of earliest ventricular activation (ie. new pacemaker).
We have also characterised the ventricular epicardial activation sequence during localised ventricular ischaemia.
Nash, M.P., Thornton, J.M., Sears, C.E., Varghese, A., O'Neill, M. & Paterson, D.J. (2001). Ventricular activation during sympathetic imbalance and its computational reconstruction. J Appl Physiol 90(1): 287-298. [Abstract] [Full Text] [PDF Reprint 801KB]
There are also some posters and conference abstracts outlining this on-going research.
EPICARDIAL ELECTROPOTENTIAL MAPPING
The time-varying electropotential field (red: positive; blue: negative potentials) is shown on the epicardial surface of the ventricles during normal sinus rhythm (displayed using a Hammer projection: left and right side boundaries represent a cut throught the middle of the RV free wall with apex/base at the bottom/top respectively).
Page written by Dr Martyn Nash