Combination of Millar and conductance catheter to assess equine left ventricular function

Simultaneous measurement of left ventricular (LV) pressure (P) and volume (V) permits assessment of systolic elastance (Emax), stroke work and myocardial oxygen consumption (MVO₂) using the P-V-area method. The conductance catheter has been applied to obtain V for clinical evaluations in human patients, and for experimental investigations in animals. While there is a tendency to miniaturize catheters for the study of small species such as rats, larger but also clinically relevant animals like the horse have not been evaluated with this instrument. Due to their large size, it may be anticipated that the number of sensing electrodes on the catheter can be increased, thus permitting the detailed regional study of many stacked slices in the larger LV. We investigated the P-V-relationship in three anesthetized ventilated horses, employing a 7F Millar P-catheter and a large-size conductance catheter with five equidistant sensing electrodes. The results indicate that PV loops can be determined on a beat-to-beat basis in the anesthetized horse