Inductance cardiography (thoracocardiography): A novel, noninvasive technique for monitoring left ventricular filling

Purpose: Thoracocardiography noninvasively records left ventricular volume curves by an inductive plethysmographic transducer transversely encircling the chest near the xiphoid process. Amplitudes of thoracocardiographic curv es track stroke volume as previously validated by thermodilution. We invest igated whether thoracocardiographic curves reflect left ventricular filling . Materials and Methods: We studied nine men in horizontal and 30 degrees hea d-up position during tidal breathing and Valsalva maneuvers. The ratio of p eak slope of left ventricular volume curves during early rapid filling rela tive to that during atrial contraction (E/A ratio) and isovolumic relaxatio n time (interval from aortic component of second heart sound to early rapid filling onset) were measured with thoracocardiography and compared with Do ppler-echocardiographic-derived indices of transmitral flow velocity, Results: Isovolumic relaxation times estimated by the two methods agreed cl osely (bias = -2 ms, limits of agreement = -28 to +24 ms, 75 comparisons). E/A ratios by thoracocardiography and Doppler echocardiography were signifi cantly correlated (R = 0.53, n = 75, P < .001), but individual values diffe red. Both methods provided identical trends of changes in E/A ratios with i nterventions in 50 of 66 (76%) comparisons. Conclusions: Thoracocardiography reflects characteristics of left ventricul ar filling similar to Doppler echocardiography, Because it does not require hand-holding a transducer, thoracocardiography has the potential for conti nuous monitoring of mechanical cardiac performance, Copyright (C) 1999 by W .B. Saunders Company.