Guidelines for plunge needle recording for effective detection of purkinje activation

Direct recording of Purkinje fiber activity may lead to a better understanding of the role of the specialized conduction system in pathological cardiac conditions. Two studies were conducted in pigs to determine guidelines for effective plunge needle recording techniques. In the first experiment, Purkinje fiber activations were recorded at 16 KHz with 3 bipolar electrodes (2 mm spacing) on epoxy plunge needles, and were later lowpass filtered and downsampled to determine the rate required for effective identification of Purkinje activation. Purkinje spikes were identifiable at sampling rates of 4 KHz and greater, but were not easily distinguished at sampling rates of 2 KHz or less. In the second experiment, 4 plunge needles with 15 electrodes (1 mm spacing) were inserted 8 times into different locations around the left ventricle. Unipolar (15 per needle) and bipolar (14 per needle) signals were recorded simultaneously at a sampling rate of 8 KHz. Purkinje activations were identified in 13/32 plunge needle sites. Of the 13 sites with identified Purkinje activations, 10 were within 2 mm of the endocardium. Bipolar recordings demonstrated Purkinje potentials that were 13% of the amplitude of the following myocardial activation, while unipolar recordings from the same electrodes recorded Purkinje potentials that were only 5% of the amplitude of the following myocardial activations. Three guidelines were developed for effective Purkinje fiber recording: 1) use a minimum sampling rate of 4 KHz., 2) record near the endocardium, and 3) use bipolar rather than unipolar recording electrodes.