| Sumario: | Introduction We aimed to determine the accuracy of the echocardiographic assessment of cardiac index ( CI) in subjects with preserved left ventricular ejection fraction ( LVEF). Methods Thirty-three subjects with LVEF >50%, normal sinus rhythm, and a broad spectrum of hemodynamic profiles underwent echocardiography immediately followed by right heart catheterization. As gold standards, CI was assessed using thermodilution [ CI ( TD)] and the Fick method [ CI (F)]. Echocardiographic CI was assessed by four methods: from the left ventricular outflow tract ( LVOT) velocity time integral and the LVOT diameter as measured [ CI ( LVOTm)] as well as estimated from body surface area [ CI ( LVOTe)], and from stroke volume indices assessed using the biplane [ CI ( BP)] and monoplane [ CI ( MP)] methods. Results The mean CI ( TD), CI (F), CI ( LVOTm), CI ( LVOTe), CI ( BP), and CI ( MP) were 3.0 ± 0.9, 3.1 ± 0.7, 2.8 ± 0.6, 3.3 ± 0.6, 2.0 ± 0.6, and 2.2 ± 0.7 L/min/m2. There were modest correlations between CI ( TD) and CI (F) and all four noninvasive measures of CI with r2 values ranging from 0.09 to 0.30. CI ( LVOTm) underestimated CI ( TD) and CI (F) by 0.3 and 0.3 L/min/m2, CI ( LVOTe) overestimated CI ( TD) and CI (F) by 0.3 and 0.2 L/min/m2, and CI ( BP) and CI ( MP) underestimated CI ( TD) and CI (F) by 1.1 and 1.1 L/min/m2 and 0.9 and 0.9 L/min/m2, respectively, with large limits of agreement for all comparisons. Conclusions In subjects with nondilated left ventricles with preserved LVEF, flow- or volume-based measures of CI by 2D echocardiography may not accurately reflect CI ( TD) and CI (F). Further larger studies are required to verify our findings and to evaluate the accuracy of contrast and 3D echocardiography in this setting.
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