Left ventricular volume measurement in mice by conductance catheter: evaluation and optimization of calibration.
The conductance catheter (CC) allows thorough evaluation of cardiac function because it simultaneously provides measurements of pressure and volume. Calibration of the volume signal remains challenging. With different calibration techniques, in vivo left ventricular volumes (V(CC)) were measured in mice (n = 52) with a Millar CC (SPR-839) and compared with MRI-derived volumes (V(MRI)). Significant correlations between V(CC) and V(MRI) [end-diastolic volume (EDV): R(2) = 0.85, P < 0.01; end-systolic volume (ESV): R(2) = 0.88, P < 0.01] were found when injection of hypertonic saline in the pulmonary artery was used to calibrate for parallel conductance and volume conversion was done by individual cylinder calibration. However, a significant underestimation was observed [EDV = -17.3 microl (-22.7 to -11.9 microl); ESV = -8.8 microl (-12.5 to -5.1 microl)]. Intravenous injection of the hypertonic saline bolus was inferior to injection into the pulmonary artery as a calibration method. Calibration with an independent measurement of stroke volume decreased the agreement with V(MRI). Correction for an increase in blood conductivity during the in vivo experiments improved estimation of EDV. The dual-frequency method for estimation of parallel conductance failed to produce V(CC) that correlated with V(MRI). We conclude that selection of the calibration procedure for the CC has significant implications for the accuracy and precision of volume estimation and pressure-volume loop-derived variables like myocardial contractility. Although V(CC) may be underestimated compared with MRI, optimized calibration techniques enable reliable volume estimation with the CC in mice.
Nielsen
Jan Møller
JM
Department of Cardiology B, Aarhus University Hospital, Skejby, 8200 Aarhus N, Denmark. janmn@dadlnet.dk
Kristiansen
Steen B
SB
Ringgaard
Steffen
S
Nielsen
Torsten Toftegaard
TT
Flyvbjerg
Allan
A
Redington
Andrew N
AN
Bøtker
Hans Erik
HE
D000818:Animals; D001811:Blood Volume Determination / Q000379:methods* / Q000592:standards; D002138:Calibration; D006328:Cardiac Catheterization / Q000379:methods* / Q000592:standards; D003936:Diagnosis, Computer-Assisted / Q000379:methods*; D004553:Electric Conductivity; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D013318:Stroke Volume / Q000502:physiology*