Influence of cyclic variation of right ventricular volume on left ventricular mechanical parameters measured with conductance catheter

The conductance catheter is widely used for the continuous measurement of t he left ventricular (LV) pressure-volume loops. Cyclical change of the righ t ventricular (RV) volume may alter the parallel conductance volume, thereb y affecting the LV mechanical parameters. Using 8 open-chest adult mongrel dogs, multiple LV pressure-volume loops were obtained by 2 methods: first w ith a vena cava occlusion (VCO) method, which involved RV volume alteration , and second with a right-heart-bypass (RHB) preparation, which decompresse d the right ventricle completely. The slope of the end-systolic pressure-vo lume relation (E-es), the end-systolic volume associated with the end-systo lic pressure of 100 mmHg (V-100,V-es), stiffness constant (beta), and the e nd-diastolic volume associated with the end-diastolic pressure of 9 mmHg (V -9,V-ed) were calculated from each loop. There was minimal influence from R V volume alteration on systolic-phase indices [E-es (VCO method, 6.37 +/-1. 91 mmHg/ml; RHB preparation, 6.60 +/-1.66 mmHg/ml; p=0.356), and V-100,V-es (VCO method, 18.4 +/-9.3 ml; RHB preparation, 17.8 +/-9.0 ml; p=0.681)], b ut there was a significant influence on diastolic-phase indices [beta (VCO method, 0.0599 +/-0.0152; RHB preparation, 0.0839 +/-0.0150; p=0.007), and V-9,V-ed (VCO method, 35.6 +/- 11.3ml; RHB preparation, 31.9 +/- 12.3ml; p= 0.001)]. The increase in the RV volume in the diastolic phase increased the parallel conductance volume, causing overestimation of the LV diastolic vo lume measured by the conductance catheter.