Direct Measurement of Left Ventricular Outflow Tract Area Using Three-Dimensional Echocardiography in Biplane Mode Improves Accuracy of Stroke Volume Assessment

Aims: The aim of the study was to investigate whether left ventricular stroke volume (LVSV) assessment using direct measurement of left ventricular outflow tract area (LVOTA) is superior to conventional methods for SV calculation. Methods and results: Thirty patients were included in the study (39 ± 12 years). LVSV was assessed by multiplying LVOT velocity time integral (VTI) by LVOTA provided by direct planimetrical measurements from real time three‐dimensional echocardiography (RT3DE) in biplane mode (SV2). These measurements were compared to conventional methods using either the LVOT diameter for LVOTA multiplied with VTI (SV1) or biplane Simpson (SV3). Direct SV measurements by RT3DE were used as gold standard (SVref). There was an excellent correlation and agreement between SV determined by SV2 and 3DE (r = 0.98, mean difference 0.5 ± 3.3 mL). However, the concordance of the traditional methods (SV1 and SV3) with 3DE was weaker (r = 0.38, mean difference −2.0 ± 17.6 mL, r = 0.84, mean difference −7.6 ± 8.7 mL, respectively). Furthermore, cardiac output (CO) measurements performed by the different modalities were not concordant with wide limits of agreement, except by SV2 the mean difference of CO by SV1 was −0.12 ± 1.05 L/min, 0.03 ± 0.20 L/min by SV2, and −0.45 ± 0.52 L/min by SV3. Conclusions: SV and CO calculations using direct measurement of LVOT area is a feasible, accurate and reproducible method and correlates extremely well with 3DE volume measurements. SV and CO calculation by LVOTA is therefore an appealing method for LVSV assessment in clinical routine. (Echocardiography 2010;27:1078‐1085)