TRANSVALVULAR IMPEDANCE (TVI) RECORDING UNDER ELECTRICAL AND PHARMACOLOGICAL CARDIAC STIMULATION

The cardiac electric impedance was recorded between right atrium and v entricle, throughout the cardiac cycle, by means of a tripolar single pass lead for VDD pacing. The transvalvular impedance signal (TVI) is a sharp periodic wave, with high signal-to-noise ratio, that is detect ed exclusively in the presence of cardiac mechanical activity. The min im um TVI value is attained during the atrial systole, the maximum at the end of ventricular systole. Different parameters of TVI waveform a re affected by changes in the inotropic state, and could therefore be proposed as potential signals for new rate responsive algorithms based on the correlation between inotropic and chronotropic regulation. The signal might be used, moreover, for pacing and sensing validation in autoregulating pacemarkers and for fibrillation recognition in ICDs.