USCOM: an accurate system for cardiac output measurement?

Introduction

The CardioWest device (Syncardia, Tucson, AZ, USA) is an FDA-approved, total artificial heart system designed to sustain optimized hemodynamics in intractable heart failure patients until suitable organ replacement can be effected. The CardioWest consists of a pneumatic blood pump that delivers accurately measured pulsatile flow to an implanted artificial heart and the native circulation, and displays the delivered hemodynamic parameters. The USCOM device (USCOM Ltd, Sydney, Australia) is a novel non-invasive two-dimensional independent CW Doppler device for assessment of right-sided and left-sided cardiac hemodynamics. This study was to compare and validate the hemodynamic values measured by the USCOM device with those of the controlled CardioWest circulatory model and determine the accuracy of the USCOM device in the clinical setting.

Methods

Four hundred and sixty serial measurements on four patients were made of right-sided and left-sided cardiac output (CO), stroke volume (SV), and heart rate (HR) using the USCOM device and compared with contemporaneous averaged values recorded on the CardioWest. Flow cross-sectional areas were determined from the CardioWest engineers and used to calculate USCOM flow volumes.

Results

Mean CO, SV and HR values by USCOM and CardioWest were 7.26 ± 0.66 and 7.23 ± 0.57 l/min, 55.0 ± 4.6 and 54.6 ± 3.7 ml, and 132 ± 5 and 132 ± 4 bpm, respectively. The mean differences between methods for CO, SV, and HR were 0.03 ± 0.49 l/min, 0.42 ± 3.66 ml, and -0.38 ± 3.7 bpm, respectively, with mean errors between measures of 0.34%, 0.64% and -0.38%. See Table 1. There was a good correlation of CO, SV, and HR measures by both methods without significant difference (all P < 0.005).

Table 1

Conclusions

This study confirms both the accuracy of flow measurements using the USCOM device, and the feasibility of obtaining reliable non-invasive cardiac output and other parameters on patients in a clinical setting.