A new multisensor pacing system using stroke volume, respiratory rate, mixed venous oxygen saturation, and...

A new multisensor pacing device using respiratory rate (RR), stroke volume (SV), oxygen saturation (SO2), temperature (T), right atrial pressure (RAP), right ventricular pressure (RVP) and right ventricular dP/dt, has been developed. It consists of a 7F multisensor catheter and an external pacing unit. It allows simultaneous recording of the input signals and the corresponding data can be compared among the different parameters under identical conditions. Furthermore, several parameters can be combined in such a way as to form a new combination better suitable for rate responsive pacing. The response of each parameter to exercise was studied in 12 healthy volunteers (mean age: 28 years). Exercise testing was carried out using a bicycle ergometer, with workloads up to 200 W. The dynamic characteristics, response and sensitivity to changes of workloads of each parameter were analyzed and compared to one another. SO2 proved to be a quick responding parameter (less than 10 sec) with higher sensitivity in the low exercise range (less than 75 W), T, on the other hand, responded slowly (greater than 30 sec) to exercise changes and had the highest sensitivity in the exercise range beyond 75 W. RR displayed a slow response (greater than 30 sec) and an adequate sensitivity was only found in the upper exercise range (greater than 100 W). SV reacted rapidly to workload changes (less than 10 sec) but showed poor sensitivity at all exercise levels. RAP, RVP and dP/dt displayed quick responses and constantly good sensitivity throughout the workload range. Furthermore, respiratory rate was easily derived from the RAP curve. Special algorithms were developed for each parameter so that pacing rate would reproduce sinus rate behavior. We found that SO2 and all pressure parameter imitated sinus rate response quite well. When using parameter combinations, SO2 and T proved to be superior. Five patients (mean age 68 years) with third degree AV-block were stimulated temporarily using this system. Compared to fixed rate stimulation (VVI 70), exercise performance improved, using SO2 as the input parameter for rate response, by 25% to 50%.