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 (LVOT(A)) 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 LVOT(A) 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 LVOT(A) multiplied with VTI (SV₁) or biplane Simpson (SV₃). Direct SV measurements by RT3DE were used as gold standard (SV(ref)). 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 LVOT(A) is therefore an appealing method for LVSV assessment in clinical routine.