On-line echocardiographic assessment of hemodynamic indexes by an adaptive Doppler analysis algorithm and signal/noise ratio calculation

Automated Spectral Doppler Profile Tracing

OBJECTIVE

The authors hypothesized that automated tracings of both pulsed wave (PW) and continuous wave (CW) Doppler correlate well with manual measurements performed by an experienced echocardiographer.

DESIGN

The authors performed a retrospective analysis of spectral Doppler profile measurements performed by automated software and an echocardiographer.

SETTING

University hospital, single institution.

PARTICIPANTS

The authors reviewed transesophageal echocardiographic examinations from patients undergoing transcatheter aortic valve (AV) replacement procedures at their institution.

INTERVENTIONS

No interventions were performed solely for research purposes.

MEASUREMENTS AND MAIN RESULTS

PW and CW spectral envelopes at the left ventricular outflow tract (LVOT) and AV were analyzed. Blinded, a board-certified echocardiographer performed manual measurements of the identical spectral envelopes. Peak velocities, mean gradients, and velocity time integrals (VTI) were collected. A total of 33 PW as well as 33 CW Doppler spectral envelopes were evaluated. There was no significant difference between the measurements provided by the automated software and manual tracings. LVOT PW VTI automated versus manual: 18.2 cm versus 15.9 cm, p = 0.11. AV CW VTI automated versus manual: 65.8 cm versus 64.8 cm, p = 0.90. AV CW mean gradient automated versus manual: 24.3 mmHg versus 23.4 mmHg, p = 0.84. AV CW peak velocity automated versus manual: 3.00 m/s versus 2.98 m/s, p = 0.93. Correlation coefficients were all above 0.9.

CONCLUSIONS

Automated measurements of peak velocities, mean gradients, and VTI of spectral Doppler correlate closely with manual measurements performed by an experienced echocardiographer.

Flow dynamics of stenotic aortic valves assessed by signal processing of Doppler spectrograms

Clinical assessment of aortic stenosis (AS) is sometimes challenging, because all hemodynamic indexes of severity are modified by flow rate. However, the mechanisms underlying flow dependence remain controversial. Analysis of instantaneous flow dynamics has provided crucial information in a number of cardiovascular disorders and may add new insight into this phenomenon. This study was designed to analyze in vivo the effects of flow interventions on instantaneous valvular dynamics of stenotic valves. For this purpose, a custom algorithm for signal processing of Doppler spectrograms was developed and validated against a control population. Digital Doppler recordings at the aortic valve and left ventricular outflow tract were obtained in 15 patients with AS, at baseline and during low-dose dobutamine infusion; 10 normal subjects were studied as controls. Spectrograms were processed by signal averaging, time alignment, modal-velocity enhancement, envelope tracing, and numerical interpolation. Instantaneous relative aortic valve area (rAVA) was obtained by the continuity equation and plotted against normalized ejection time. Curves were classified as either type A (rapid, early-systolic opening) or type B (slow, end-systolic opening). Curves from controls closely matched prior knowledge of normal valve dynamics, but curves from patients were clearly different: all controls except 2 (80%) had type A, whereas all patients except 3 (80%) had a type B pattern (p = 0.03). Dobutamine infusion in patients increased and slightly anticipated peak rAVA by accelerating valve opening. Despite similar values of area and pressure difference, type B dynamics were associated with lower blood pressure (p = 0.01) and worse long-term outcome (>3 years) than type A flow dynamics (p = 0.02). Signal processing of Doppler spectrograms allows a comprehensive assessment of aortic flow dynamics. Differences in timing of valve aperture and in maximal leaflet excursion account for flow-mediated changes in valve area, suggesting complementary effects of inertia and elasticity on the kinetics of stenotic aortic valves. Flow-dynamic analysis provides novel clinical information regarding physiology of AS unavailable to conventional indexes.