Validation of admittance computed left ventricular volumes against real‐time three‐dimensional echocardiography in the porcine heart
Authors: Kutty Shelby , Kottam Anil T. , Padiyath Asif , Bidasee Keshore R. , Li Ling , Gao Shunji , Wu Juefei , Lof John , Danford David A. , Kuehne Titus 
Published: February 2013

New Findings
What is the central question of this study?How do left ventricular volumes measured in a large animal using admittance catheterization compare with those measured using three‐dimensional echocardiography or traditional conductance?
What is the main finding and its importance?Admittance computed left ventricular volumes were validated in baseline conditions and during inotropic stimulation with dobutamine. These results serve as a foundation for the use of admittance in large‐animal experimental models of cardiovascular disease.
The admittance and Wei's equation is a new technique for ventricular volumetry to determine pressure–volume relations that addresses traditional conductance‐related issues of parallel conductance and field correction factor. These issues with conductance have prevented researchers from obtaining real‐time absolute ventricular volumes. Moreover, the time‐consuming steps involved in processing conductance catheter data warrant the need for a better catheter‐based technique for ventricular volumetry. We aimed to compare the accuracy of left ventricular (LV) volumetry between the new admittance catheterization technique and transoesophageal real‐time three‐dimensional echocardiography (RT3DE) in a large‐animal model. Eight anaesthetized pigs were used. A 7 French admittance catheter was positioned in the LV via the right carotid artery. The catheter was connected to an admittance control unit (ADVantage; Transonic Scisense Inc.), and data were recorded on a four‐channel acquisition system (FA404; iWorx Systems). Admittance catheterization data and transoesophageal RT3DE (X7‐2; Philips) data were simultaneously obtained with the animal ventilated, under neuromuscular blockade and monitored in baseline conditions and during dobutamine infusion. Left ventricular volumes measured from admittance catheterization (Labscribe; iWorx Systems) and RT3DE (Qlab; Philips) were compared. In a subset of four animals, admittance volumes were compared with those obtained from traditional conductance catheterization (MPVS Ultra; Millar Instruments). Of 37 sets of measurements compared, admittance‐ and RT3DE‐derived LV volumes and ejection fractions at baseline and in the presence of dobutamine exhibited general agreement, with mean percentage intermethod differences of 10% for end‐diastolic volumes, 14% for end‐systolic volumes and 9% for ejection fraction; the respective intermethod differences between admittance and conductance in eight data sets compared were 11, 11 and 12%. Admittance volumes were generally higher than those obtained by RT3DE, especially among the larger ventricles. It is concluded that it is feasible to derive pressure–volume relations using admittance catheterization in large animals. This study demonstrated agreements between admittance and RT3DE to within 10–14% mean intermethod difference in the estimation of LV volumes. Further investigation will be required to examine the accuracy of volumes in largest ventricles, where intermethod divergence is greatest.