Doppler tissue imaging offers reliable assessment of left ventricular hemodynamics when compared with B-type natriuretic peptide levels across a range of ventricular performance

Background: A blood test for B-type natriuretic peptide (BNP) has been proposed to diagnose heart failure, as well as to evaluate treatment and establish prognosis. It has been shown to correlate with left ventricular (LV) filling pressure or pulmonary capillary wedge pressure (PCWP). The relationship between BNP and newer echocardiographic measurements of LV filling pressures is not known. These methods could offer a widely available means of non-invasively assessing hemodynamics in heart failure patients. We conducted a prospective study to compare invasive right heart pressure measurements, serum BNP levels and the following echocardiographic measurements: Doppler tissue imaging, flow propagation and left ventricular inflow velocities. These values are believed to be load-independent variables of LV filling. We hypothesized that these echocardiographic measurements would correlate positively with PCWP and BNP. Methods: Our sample included twenty eight consecutive patients who were undergoing elective right heart catheterization. LV function in these patients ranged from normal to severely abnormal. At the time of catheterization the patients also underwent simultaneous echocardiographic imaging using a standard 10-minute protocol that included acquisition of LV inflow velocities and Doppler tissue imaging of the LV septum. The E (early transmitral flow velocity)/E' (early diastolic myocardial velocity) ratio was determined. Flow propagation velocity (PV) was measured as the slope of the first isovelocity contour line on color M-mode Doppler images. A sample of the patients' blood was analyzed for BNP level within two hours of sampling (Biosite assay). Linear regression was used to compare invasive and noninvasive variables. Correlation coefficients were obtained. Results: When compared to the echocardiographic determinants, the log BNP has a direct correlation to the E/E' ratio (R2 = 0.3083). There is no similar correlation between log BNP and E/PV (R2 = 0.0345). The E/E' ratio correlates with the directly measured PCWP (R2 = 0.2924), while there appears to be no correlation between PCWP and E/PV ratio (R2 = 0.0354). The log BNP is inversely related to cardiac index (R2 = 0.3901). Log BNP directly correlates with the mean pulmonary capillary wedge pressure (R2 = 0.4108). Conclusions: The echocardiographic ratio of early transmitral flow velocity and early diastolic myocardial flow velocity (E/E') correlates with invasively measured PCWP and BNP levels. However, the transmitral flow velocity to flow propagation velocity (E/PV) ratio does not appear to have a strong correlation to PCWP or BNP levels. Measurement of E/E' is widely available and may provide an additional noninvasive means of evaluating heart failure and PCWP in the clinical setting.