Conductance–Echocardiography Correlation During Changes In Left Ventricular Volume

Conductance (COND) measurements of left ventricular volume, satisfactory under steady state conditions, may be altered by extraneous factors during complex experiments or cardiac surgery. A reference technique is needed to detect changes in the COND-left ventricular volume relationship. This technique should indicate when recalibration of COND is needed. Accordingly, we assessed the relationship between left ventricle COND and the area of left ventricular short-axis cross section (SACS) by two-dimensional echocardiography during vena caval occlusion. Thirteen anesthetized pigs underwent a median sternotomy and insertion of a COND catheter. Two-dimensional echocardiography and COND were displayed and recorded simultaneously on a digital video monitor. Data were analyzed at end-diastole during the filling phase after vena caval occlusion, because the quality of two-dimensional echocardiography was better during recovery. Results demonstrated a linear relationship between left ventricular COND and SACS at end-diastole, with a positive slope. Correlation coefficients ranged from 0.88 to 1.0 and averaged 0.96 ± 0.01 (SE). The overall mean relationship was (SACS) = 0.40 (COND) – 17. It is concluded that SACS by two-dimensional echocardiography can be employed to confirm COND measurements of left ventricular end-diastolic volume during laboratory experiments or cardiac surgery. Stability of the SACS-COND relationship indicates that COND calibration is valid. Changes in the SACS-COND relationship would require recalibration of COND. Data markedly deviating from a linear SACS-COND relation reflect experimental error and should be discarded.