EXTRINSIC FACTORS INFLUENCING LEFT-VENTRICULAR CONDUCTANCE IN-SITU

Background The accuracy of conductance measurement of left ventricular (LV) volume is affected by parallel conductance (V-p) from right vent ricular (RV) Volume as well as surroundings of the heart. No studies h ave quantified the extrinsic influences on V-p. Methods and Results In six anesthetized pigs, using a median sternotomy and pericardial well , implantable cardioverter defibrillator patches, normal saline, or ec hocardiography gel were introduced and removed. LV end-diastolic press ure (LVEDP) did not change significantly with these interventions. Raw LV conductance was used to estimate end-diastolic volume (LVEDV), end -systolic volume (LVESV), and stroke volume (SV). Saline significantly increased mean+/-SEM calculated LVEDV from 106+/-8 to 131+/-6 mL and calculated LVESV from 81+/-7 to 110+/-5 mL; calculated SV decreased fr om 25+/-3 to 21+/-2 mL (P<.05, paired t test). Implantable cardioverte r defibrillator patches and gel did not significantly change calculate d LV volumes. LV conductance was also measured in arrested hearts duri ng LV filling (5 to 60 mL) at four levels of RV volume (RVV). Using a fixed value for V-p, calculated mean LV volume was 30+/-3 mL at RVV=0, 32+/-3 mL at RVV=20, 33+/-3 mL at RVV=40, and 36+/-3 mL at RVV=60 (P< .01, repeated-measures ANOVA). Conclusions While implantable cardiover ter defibrillator patches and gel have no statistically significant ef fect, saline and RVV affect LV volume calculations by conductance, req uiring special techniques during cardiopulmonary bypass or caval occlu sion.