ABSTRACT
To be able to study the relation between the time sequence of electrical activation and myocardial contraction of the left ventricular free wall in detail, the use of methods to assess both electrical and mechanical activity simultaneously in various regions is required. This chapter examines the preliminary results of a study on this relation during normoxia and ischemia, using systems for mapping electrical activation and myocardial contraction. To obtain a detailed map of the sequence of electrical activation, 192 extracellular recordings are made with the use of a brush applied to the epicardium of the left ventricle. The brush consists of unipolar silver electrodes. Epicardial fiber shortening can be assessed from the epicardial deformation parameters circumferential shortening, base-to-apex shortening, and shear deformation which is associated with torsion of the left ventricle around the base-to-apex axis. Electrical stimulation of the heart was limited to pacing from the right ventricular outflow tract and the left ventricular apex.
