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ABSTRACT
Incremental Doppler stress echocardiographic evaluation of cardiovascular reserve in
heart failure: A case comparison of 2D independent CW Doppler and thermodilution.
R.A.Phillips, M.J.West, D.J.Burstow, J.Wright, L.H.Naylor, D.J.Green, G.O’Driscoll
The University of Queensland, Brisbane, Australia, the Royal Perth Hospital and the University of Western
Australia, Perth, Australia
Background: Heart failure is a common and serious condition characterised by
impaired cardiac output (CO), and increased morbidity and mortality. Doppler ultrasound
is a reliable and reproducible method of measuring CO, and is routinely used to
determine the severity of cardiac failure. Intractable cardiac failure may require cardiac
transplantation for the prolongation of life. While pharmacotherapy may maintain
reasonable health, ventricular assist devices (VAD), which by-pass blood from the
ventricle or atrium to the aorta on the left, or the atrium to the pulmonary artery on the
right, reducing ventricular pressures, volumes and wall stress, can be used for
haemodynamic support prior to transplantation. Assessment of cardiovascular reserve,
the ability to upregulate CO on demand, may be influential in determining appropriate
short and long term management. One method currently used to evaluate cardiovascular
reserve is thermodilution CO measurements during incremental exercise testing. CW
Doppler ultrasound may provide such measurements non-invasively.
This presentation compares serial CO measurements in a subject in cardiac failure at
rest, during exercise, and post biVAD implantation, using invasive thermodilution and a
dedicated 2D independent CW Doppler ultrasound device.
Method: Serial simultaneous haemodynamic measurements were made using both
methods with the subject supine at rest, erect at rest, and during incremental bicycle
exercise testing and post biVAD implantation. Five consecutive CW Doppler outputs
were averaged for comparison with each invasive measure to minimise the effects of
beat to beat physiologic variability. Continuous and injectate derived outputs were
compared to the CW results using mean values and Bland-Altman bias analysis.
Results: The mean cardiac output at rest and during exercise by thermodilution was
3.51±0.66l/min, and 3.42±0.51l/min for CW Doppler (n=16). There was a mean
difference between methods of 0.09±0.58l/m. Using the Critchley criteria (precision of
new method/mean value of the reference method x 100), and despite the small sample
numbers, the CW method compared well with thermodilution (16.8%), with the resolution
required for validation of a new CO measurement method being <30% (J Clin Monit.
1999).
Conclusion: This case demonstrates favourable comparison of CO measurements at
rest and during exercise, using CW Doppler and thermodilution. This 2D independent
CW Doppler device may be a cost effective, non-invasive alternative for evaluation of
subjects with cardiac failure.
July 22, 2003
International Society of Cardiovascular Ultrasound, Buenos Aires, 2003