Temporary transvenous atrial pacing in horses: threshold determination

The purpose of this study was to perform temporary atrial pacing and to det ermine the atrial strength-duration (S-D) curve which displays the minimal pulse intensity necessary to achieve atrial capture. In 7 horses, atrial pa cing was applied using a temporary pacing catheter and a pacemaker as elect rical pulse generator. Using the stimulus reduction method, 3 approaches fo r atrial threshold determination were used. With the fixed pulse width meth od, at several pulse widths, the corresponding minimal amplitudes to achiev e capture were determined, describing an S-D curve. With the fixed amplitud e method, the corresponding threshold pulse widths were determined at sever al fixed amplitudes, The third method proved to be the best and was a combi nation of both aforementioned methods to determine 2 points of the S-D curv e. From these 2 points the whole S-D curve was calculated using a mathemati cal equation. Temporary pacing can be used to terminate atrial flutter, to induce atrial arrhythmias or to obtain more information shout the electroph ysiological properties of the heart, such as the atrial refractory period, atrial vulnerability and atrioventricular conduction.