Assessment of left ventricular systolic function by velocity vector imaging.

OBJECTIVES: To study the usefulness of a novel echocardiographic technique, velocity vector imaging (VVI) in the measurement of left ventricular ejection fraction (LVEF). BACKGROUND: Ejection fraction measured by echocardiography forms the cornerstone in the assessment of LV systolic function. Errors in measurement of EF by routine two-dimensional echocardiography (2D ECHO) limit its utility. The VVI is a new technology which uses speckle tracking and other algorithms to track the endocardial border. This may help in more accurate assessment of EF. METHODS: Global and regional LVEF was measured in 49 patients using VVI, 2D ECHO and radionuclide-gated single photon emission computed tomography (SPECT). Results were categorised as normal, mild, moderate, or severe LV systolic dysfunction based on American Society of ECHO classification. The results were analysed by appropriate statistical tests for correlations. RESULTS: The mean EF was 35 ± 12.08% by VVI, 54.2 ± 19.51% by SPECT (P< 0.001 vs VVI) and 50.3 ± 8.92% by 2D ECHO (P < 0.001 vs VVI). There was weak linear positive correlation between EF measured by VVI and the other modalities (Pearson's correlation coefficient 0.577 for SPECT and 0.573 for 2D; P=0.01). The VVI systematically underestimated the EF compared to SPECT. Greater number of patients had moderate or severe LV systolic dysfunction by VVI (37; 74.5%) than by SPECT (17; 34.7%; P=0.037). We derived a correction factor to calculate SPECT EF from VVI EF as follows: EF (SPECT) = EF (VVI) × 0.9 + 21 or approximately VVI (EF) + 20. CONCLUSION: Measurement of EF by VVI is feasible. The VVI underestimated the EF when compared to nuclear-gated SPECT in this study. The accuracy of this technology and the need for a correction factor needs to be assessed in future studies.

Echocardiographic evaluation of ventricular dyssynchrony in patients with left bundle branch block.

OBJECTIVE: To test whether patients with left bundle branch block (LBBB) and low ejection fraction (EF) have greater dyssynchrony than those with LBBB and normal LV systolic function. METHODS: From a group of patients with LBBB, 38 patients with low EF (<50%) and 31 with normal LV systolic function (EF > or = 50%), all comparable in age and sex underwent standard Doppler echo, ECG and tissue Doppler imaging (TDI). The precontraction time (PCTm) was calculated as an index of myocardial systolic activation in 5 different basal myocardial segments (LV anterior, inferior, septal, lateral walls and RV lateral wall). Intraventricular systolic dyssynchrony was analyzed by difference of PCTm in different LV myocardial segments. Interventricular activation delay was calculated by the difference of PCTm between the most delayed LV segment and RV lateral wall. RESULTS: Patients with low LV EF showed increased QRS duration, intraventricular delay (p = 0.03) and interventricular dyssynchrony (p = 0.006). Patients with normal EF also had evidence of some dyssynchrony. The LV basal lateral segment was significantly delayed when compared to all other segments in the low EF group. The PCTm was greater for those with low EF when compared to the normal EF group. CONCLUSIONS: All patients with LBBB on baseline ECG had some degree of cardiac dyssynchrony; those with lower EF had more dyssynchrony. TDI is an effective non-invasive technique for assessing the severity of regional delay in activation of ventricular walls in patients with LBBB.

Utility of N-terminal pro-brain natriuretic peptide for the diagnosis of heart failure.

BACKGROUND: The goal of this study was to evaluate the utility of plasma N-terminal pro-brain natriuretic peptide for the diagnosis of heart failure in patients presenting with shortness of breath. METHODS AND RESULTS: We measured plasma levels of N-terminal pro-brain natriuretic peptide in 119 patients presenting with shortness of breath. The patients were divided into two groups based on the Framingham criteria and echocardiographic results--those with heart failure and those not in heart failure. Plasma levels of N-terminal pro-brain natriuretic peptide were compared in the two groups. The mean N-terminal pro-brain natriuretic peptide concentration in patients with heart failure (n=73) was higher than that in those not in heart failure (389+/-148 fmol/ml v. 142+/-54 fmol/ml, p<0.001). N-terminal pro-brain natriuretic peptide values increased significantly as the functional severity of heart failure increased (p<0.001). The mean N-terminal pro-brain natriuretic peptide levels were 261+/-34 fmol/ml for patients in New York Heart Association functional class I, 300+/-161 fmol/ml for patients in New York Heart Association functional class II, 427+/-103 fmol/ml for patients in New York Heart Association functional class III and 528+/-170 fmol/ml for patients in New York Heart Association functional class IV. Using a cut-off value of 200 fmol/ml, the sensitivity of N-terminal pro-brain natriuretic peptide was 97%, specificity was 89% and accuracy for differentiating heart failure from other causes of shortness of breath was 93%. CONCLUSIONS: Our results suggest that N-terminal pro-brain natriuretic peptide can be reliably used for the diagnosis of heart failure in an outpatient setting, and this will improve the ability of clinicians to differentiate patients with shortness of breath due to heart failure from those with other causes of shortness of breath.