Conductance artifacts in a novel in vitro model of ventriculothoracic electrical coupling

The utility of open chest conductance (COND) ventriculography is limited by artifacts altering the relationship between COND and left ventricular (LV) volume. Pressure-COND loops often lean to the left during LV volume reduct ion by caval occlusion. Time varying alterations in the pericardial-LV cont act area affect electrical coupling in the open chest during the cardiac cy cle, producing COND artifacts. In this study, an open-mediastinum model was constructed. Components represented the LV, blood, pericardium, and thorac ic contents. Varying ventriculothoracic coupling was simulated by changing the volume of pericardial saline (0, 30, 60 ml). Raw dual field COND was re peatedly (n = 20) compared with volumes of normal saline from 60 to 120 ml at 5 ml intervals. Groups were compared by linear regression and repeated m easures ANOVA. Artifacts significantly (p < 0.01) altered parallel COND, in dicated by the y-intercept, with the exception of 0 verses 30 ml. The slope constant also changed significantly, with the exception of 30 versus 60 ml . These results suggest that variable pericardial-LV contact can cause time varying artifacts in COND in the open chest. Therefore, posterior insulati on may reduce artifacts in COND ventriculography and should be tested for t his effect.