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Continuous Left Ventricular Ejection Fraction Monitoring by Aortic Pressure Waveform Analysis

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We developed a technique to monitor left ventricular ejection fraction (EF) by model-based analysis of the aortic pressure waveform. First, the aortic pressure waveform is represented with a lumped parameter circulatory model. Then, the model is fitted to each beat of the waveform to estimate its lumped parameters to within a constant scale factor equal to the arterial compliance (C a). Finally, the proportional parameter estimates are utilized to compute beat-to-beat absolute EF by cancelation of the C a scale factor. In this way, in contrast to conventional imaging, EF may be continuously monitored without any ventricular geometry assumptions. Moreover, with the proportional parameter estimates, relative changes in beat-to-beat left ventricular end-diastolic volume (EDV), cardiac output (CO), and maximum left ventricular elastance (E max) may also be monitored. To evaluate the technique, we measured aortic pressure waveforms, reference EF and EDV via standard echocardiography, and other cardiovascular variables from six dogs during various pharmacological influences and total intravascular volume changes. Our results showed overall EF and calibrated EDV root-mean-squared-errors of 5.6% and 4.1 mL, and reliable estimation of relative E max and beat-to-beat CO changes. These results demonstrate, perhaps for the first time, the feasibility of estimating EF from only a blood pressure waveform.

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C a :

arterial compliance (mL/mmHg)

E lv(t):

time-varying ventricular elastance function (mmHg/mL)

E max :

maximum left ventricular elastance (mmHg/mL)

E min :

minimum left ventricular elastance (mmHg/mL)

n :

discrete time or sample index (unitless)

n bs :

sample index denoting beginning of the systolic ejection interval (unitless)

n es :

sample index denoting end of the systolic ejection interval (unitless)

P a(t):

aortic pressure waveform (mmHg)

R a :

total peripheral resistance (mmHg-s/mL)

T :

sampling period (s)

T s :

time duration to reach E max from E min (s)

τ :

windkessel time constant (=R a C a) (s)

t :

time (s)

t bi :

time of beginning of the isovolumic contraction phase (s)

t bs :

time of beginning of the systolic ejection interval (s)

t es :

time of end of the systolic ejection interval (s)

V lv(t):

left ventricular (total) volume waveform (mL)

\( V_{\text{lv}}^{0} \) :

left ventricular unstressed volume (mL)


cardiac output (L/min)


electrocardiogram (mV)


left ventricular end-diastolic volume (mL)


left ventricular ejection fraction (%)


left ventricular end-systolic volume (mL)


heart rate (bpm)


mean aortic pressure (mmHg)


root-mean-squared-error (mL for EDV and % for EF)


root-mean-squared-normalized-error (%)


left ventricular stroke volume (mL)


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The authors would like to thank Mr. Joseph Prinsen, Mr. Thoralf Hoelzer-Maddox, and Dr. Augusta Pelosi, DVM, for their technical contributions to the data collection.

This work was supported by an award from the AHA and the NSF CAREER Grant 0643477.

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Correspondence to Ramakrishna Mukkamala.

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Swamy, G., Kuiper, J., Gudur, M.S.R. et al. Continuous Left Ventricular Ejection Fraction Monitoring by Aortic Pressure Waveform Analysis. Ann Biomed Eng 37, 1055–1068 (2009).

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