The principle and construction of a device made for the purpose of displaying the interrelationship between two sets of cardiac intervals is described. Electrical signals derived from the atrium and ventricle of the experimental animal are fed to the input of the device where a special switch andan integrated circuit logic gate select the two sets of cardiac intervals to be measured, e.g., AA and VV or AA and AV intervals. These intervals are converted into electrical square pulses having voltages proportional to therespective intervals. Besides simply comparing the two cardiac intervals byrecording them simultaneously against time, the interrelationship of the two is displayed in an X-Y configuration on-line on a cathode-ray oscilloscope. This latter method, if used only for the occasionally induced premature excitations with varied coupling time, facilitates the measurement of the functional refractory periods for atrioventricular conduction. The mode of operation of the device is presented with examples of experiments.
Dual effect of disopyramide on atrial and atrioventricular conduction and refractory periods.