SYSTOLIC FUNCTION OF THE UNIVENTRICULAR HEART - COMPARISON OF THE SIMPSONS RULE WITH ACOUSTIC QUANTIFICATION

BACKGROUND: Acoustic quantification (Aa) is a new method of obtaining real-time information about systolic ventricular function. This method establishes a 'blood-tissue interface' and computes an intraventricul ar blood volume in real time to derive a beat to beat instantaneous ej ection fraction. AQ assessment of systolic function has been reported previously in patients with normal cardiotypes and varying degrees of myocardial dysfunction. OBJECTIVE: To determine the potential utility of AQ in patients with abnormal ventricular morphology, in whom systol ic function may be difficult to measure by traditional methods. PATIEN TS AND DESIGN: Seventeen children (nine females) ranging in age from f ive days to 18 years (mean 6.9 years) with univentricular left ventric le heart morphology underwent a prospective and comparative echocardio graphic study of ventricular function with the use of AR and manual pl animetry (single plane Simpson's rule). Imaging was done during steady state without sedation. Routine scan planes were performed, followed by repeat scanning of the univentricle from the apical four-chamber vi ew in the Aa mode. Subsequently, manual planimetry using Simpson's rul e was performed from an online graphical analysis package to measure s ystolic and diastolic frames from the conventional replay images. Thes e data were used to calculate ejection fraction using standards previo usly established. The results were then compared with real-time Aa res ults. SETTING: Tertiary care referral center. RESULTS: Scan time for t he combined standard and Aa imaging averaged 45 mins (range 35 to 65 m ins). Measured ejection fraction by AQ and manual planimetry were 44 /- 11% and 46 +/- 10%, respectively. Statistical analysis by repeated measures ANOVA with Bonferroni/Dunn correction (F=0.6, df=1,32, P=0.44 ) demonstrated significant agreement between AQ and manual planimetry with an intraclass correlation coefficient of 0.93. Bland-Altman analy sis was used to provide a graphic display of the clinical significance of differences in the comparison of the two methods of measurement. C ONCLUSIONS: These findings support the use of AQ for continuous online determination of indexes of systolic function for patients with unive ntricular left ventricle morphology. The variability in the morphology inherently present within this group of patients results in a wider v ariability of determined ejection fraction. Particular attention must be directed to the technical aspects of image acquisition and Aa appli cation to ensure accuracy.