The conductance method of left ventricular volume estimation. Methodologic limitations put into perspective.

T he search for a means of measuring left ventricular volume (LVV) accurately and continuously throughout the cardiac cycle has been long standing. Such efforts have intensified during the past 15 years with the growing appreciation for the wealth of useful information available from analysis of systolic and diastolic ventricular pressure-volume relations. Recently, much effort has gone into developing and testing the conductance method of measuring LW.1-3 The technique is based on a multielectrode catheter, positioned within the LV cavity, that is used to set up an electrical current field and measure time varying voltage potential gradients within the LV chamber. From these voltage gradients, intraventricular conductance and, in principle, LVV are estimated. The electric field theory that underlies the technique is quite complex. However, a few simplifying assumptions make estimation of LVV from the measured voltage gradients relatively easy.12 To the extent that these assump-