The measurement of impedance to assess myocardial contractility and rhythmstability

By introducing an alternating current through the ventricular cavity via a multipolar catheter the potential difference measured between adjacent elec trodes can be used to assess ventricular volume. This is possible by the me asurement of intracardiac impedance. The data obtained can be used to const ruct pressure-volume loops allowing the continuous real-time assessment of myocardial contractility. Clinical applications of this research tool are n ow becoming apparent. Further derivations of impedance measurement have bee n incorporated into commercially available permanent pacing systems. allowi ng effective heart rate modulation.