RETROCONDUCTION SELECTIVE RECOGNITION IN WIDE-DIPOLE FLOATING ATRIAL SENSING

DI GREGORIO, F., ET AL.: Retroconduction Selective Recognition in Wide Dipole Floating Atrial Sensing. Effective discrimination of retrograd ely conducted P waves would allow distinguishing sinus tachycardia fro m supraventricular tachycardias due to AV or nodal reentry, and would prevent pacemaker-mediated tachycardia in AV sequential pacing. This m ight be especially relevant in VDD implants, where retroconduction cou ld be induced by escape ventricular stimulation. In order to analyze t he respective waveform properties, anterograde and retrograde atrial s ignals were recorded by a wide floating electrode dipole, on the impla ntation of a permanent single-pass lead for VDD pacing. Generally, bip olar recording did not allow reliable discrimination, while the signal nature could be readily diagnosed from the main features of the unipo lar atrial electrograms. The unipolar waveform recorded under sinus rh ythm in high right atrium, close to the superior vena cava opening (pr oximal EGM), started with a negative deflection in 88% of the patients . In 7% of the patients, the first deflection of the signal was positi ve in some cardiac cycles only, and, on the average, the amplitude of the positive phase was not higher than 5% of the signal peak-to-peak a mplitude. Conversely, under retroconduction, the starting deflection a ttained higher positive values in 98% of the patients, being stably ov er 15% of the peak-to-peak amplitude in 86% of the cases. Furthermore, in 69% of the cases, the lag time between the onset of the negative d eflection of proximal and distal (mid-low atrium) unipolar EGM changed unambiguously when retroconduction occurred, exceeding the range of v ariation observed in each patient during sinus activity. The combined evaluation of unipolar EGM shape and lag time allowed specific retroco nduction recognition in 95% of the patients. We suggest that this appr oach may yield useful information for the discrimination of retrograde atrial signals, provided that the recording dipole is sufficiently lo ng and the proximal electrode is properly positioned in the high right atrium.