Development of a thin, soft, single segment conductance catheter for monitoring left ventricular pressure and volume

Abstract: Knowledge of the leftventricular (LV) pressure-volume relation, along withparameters derived from this relation, have led to newpossibilities for the characterisation of cardiac pumpfunction, in both experimental studies and clinicalsettings.The pressure-volume diagram is apowerful tool for visualising LV performance, but in order tobe clinically useful it is necessary to make plots continuouslyand on-line. The conductance catheter technique offers thispossibility. The conductance catheter system has experiencedgrowing interest among cardiologists, physiologists, surgeons,and anaesthesiologists around the world as a powerful newresearch tool, but the invasiveness of this technique has beena limiting factor for most clinical applications. The catheterneeds to be thinner and softer in order to make this techniquemore suitable for human use.This thesis reports of a newthin and soft conductance catheter for continuously and on-linemeasurements of LV pressure and volume.One way to reduce both cathetersize and stiffness is to decrease the number of electrodes onthe catheter. Theoretical calculations shown in this thesisproves that it is possible to obtain the same performance witha single segment catheter as with a five-segment catheter. Thethin catheter has been tested and compared to a commercialfive-segment conductance catheter in animal studies.We conclude that the thin singlesegment conductance catheter can measure left ventricularvolume and pessure. The regression coefficient between the twomethods is good independent of loading condition and duringbaseline conditions the catheters produce very similar volumecurves. During preload reduction the estimated volume reductionis different in the two systems.Our thin catheter does notdisturb the heart's normal electrophysiology, neither by thecatheter current nor by any mechanical stimuli. The resultsdemonstrates that our thin, soft, single segment conductancecatheter has performance characteristics which warrant furtherdevelopment, with the goal to make the method available forhuman use.