Systolic and diastolic ventricular dysfunction frequently coexist. Both are important determinants of prognosis; consequently, a clinical measurement that assesses both systolic and diastolic function may be more useful than one that addresses only one aspect of ventricular function. Recently, a Doppler-derived index (referred to as the Tei index, or myocardial performance index) that combines systolic and diastolic time intervals has been developed to assess global cardiac function. 1 In this brief review we will discuss the measurement and utility of the Tei index.The Tei index, which may be used to assess either left or right ventricular function, is equal to the sum of the isovolumic contraction time (ICT) and isovolumic relaxation time (IRT) divided by ejection time (ET). As originally described by Tei, 1 the time intervals used to calculate the index are measured using pulsed-wave Doppler velocity spectra of ventricular inflow and outflow. Mitral or tricuspid flow velocity spectra are obtained by positioning the pulsed-wave Doppler sample volume at the tips of the mitral or tricuspid valve leaflets in the apical four-chamber view. Left ventricular outflow velocity spectra may be obtained from either the apical five-chamber or the long-axis view, by positioning the pulsed-wave Doppler sample volume at the level of the aorAddress for correspondence and reprint requests: tic annulus. Right ventricular outflow velocity spectra are obtained from the parasternal short-axis view, with the pulsed-wave Doppler sample volume positioned at the pulmonic annulus. Calculation of the Tei index ( Fig. 1) involves measuring the time interval a, extending from the cessation of mitral or tricuspid inflow to its subsequent onset, and ejection time b, which is the duration of the left or right Figure 1. Schema of Doppler flow velocity spectra representing the time intervals used for calculation of the Tei index. Interval 'a' extends from the cessation to the onset of mitral or tricuspid inflow. It includes the isovolumic contraction time, ejection time, and isovolumic relaxation time. Interval 'b' is the duration of left or right ventricular outflow (ejection time). The Tei index is equal to (a − b)/b. ET, ejection time; ICT, isovolumic contraction time; IRT, isovolumic relaxation time.
In the first part of this series on Doppler ultrasound physics and instrumentation, 1 we discussed the application of the Doppler equation to the measurement of blood and cardiac tissue velocities. The purpose of this article is to describe the instrumentation principles of continuous-(CW) and pulsed-wave (PW) Doppler, referred to as spectral Doppler. Instrument DesignDesigns of CW-and PW-Doppler instruments are illustrated in Figures 1 and 2. 2,3 With CW Doppler, continuous electrical stimulation of piezoelectric elements occurs with a resultant continuously emitted ultrasound beam. The frequency of the emitted ultrasound wave is determined by the frequency of the stimulating electrical current. As we have previously described, 1 the propagating ultrasound wave undergoes a change in frequency (termed a Doppler shift) upon reflection from a moving target. The returning Doppler-shifted ultrasound wave induces "receiving" piezoelectric elements to resonate, resulting in an electrical signal whose frequency is then compared to the emitted ultrasound frequency. The difference between the emitted and reflected frequencies (the Doppler-shift frequency) is then calculated. A filter removes low-frequency high-amplitude signals originating from slow-moving reflectors (cardiac walls), leaving low-amplitude higher
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