Variability in echocardiographic measurements of left ventricular function in septic shock patients.

BACKGROUND

Echocardiography is increasingly used for haemodynamic evaluation and titration of therapy in intensive care, warranting reliable and reproducible measurements. The aim of this study was to evaluate the observer dependence of echocardiographic findings of left ventricular (LV) diastolic and systolic dysfunction in patients with septic shock.

METHODS

Echocardiograms performed in 47 adult patients admitted with septic shock to a general intensive care unit (ICU) were independently evaluated by one cardiologist and one intensivist for the following signs: decreased diastolic tissue velocity of the base of the LV septum (é), increased early mitral inflow (E) to é ratio (E/é), decreased LV ejection fraction (EF) and decreased LV global longitudinal peak strain (GLPS). Diastolic dysfunction was defined as é <8.0 cm/s and/or E/é ≥15 and systolic dysfunction as EF <50% and/or GLPS > -15%. Ten randomly selected examinations were re-analysed two months later. Pearson's r was used to test the correlation and Bland-Altman plots to assess the agreement between observers. Kappa statistics were used to test the consistency between readers and intraclass correlation coefficients (ICC) for inter- and intraobserver variability.

RESULTS

In 44 patients (94%), image quality was sufficient for echocardiographic measurements. The agreement between observers was moderate (k = 0.60 for é, k = 0.50 for E/é and k = 0.60 for EF) to good (k = 0.71 for GLPS). Pearson's r was 0.76 for é, 0.85 for E/é, 0.78 for EF and 0.84 for GLPS (p < 0.001 for all four). The ICC between observers for é was very good (0.85; 95% confidence interval (CI) 0.73-0.92), good for E/é (0.70; 95% CI 0.45 - 0.84), very good for EF (0.87; 95% CI 0.77 - 0.93), excellent for GLPS (0.91; 95% CI 0.74 - 0.95), and very good for all measures repeated by one of the observers. On Bland-Altman analysis, the mean differences and 95% limits of agreement for é, E/é, EF and GLPS were -0.01 (0.04 - 0.07), 2.0 (-14.2 - 18.1), 0.86 (-16 - 14.3) and 0.04 (-5.04 - 5.12), respectively.

CONCLUSIONS

Moderate observer-related differences in assessing LV dysfunction were seen. GLPS is the least user dependent and most reproducible echocardiographic measurement of LV function in septic shock.