Correlation between measured inferior vena cava diameter and right atrial pressure depends on the echocardiographic method used in patients who are mechanically ventilated

cava. All measurements were taken in the supine position. IVCD at end-expiration and end-diastole, with ECG synchronization, using the M-mode, and IVCD at end-expiration, without ECG synchronization, using the 2-dimensional long-axis view, correlate linearly with RAP (0.81, P < .0001 and 0.71, P .0004). Mean bias between the 2 TTE methods (Bland-Altman analysis) was 1.6 mm (SD 2.03 mm). In conclusion, this study confirms that variation of correlation between TTE IVCD measurement and RAP depends on the ultrasonographic methodology used and the timing of measurement during the cardiac cycle. IVCD at end-expiration and enddiastole, with ECG synchronization, using the Mmode (IVCD-MM) correlates more satisfactory with RAP than with IVCD at end-expiration, without ECG synchronization, using the 2-dimensional long-axis view, in patients during mechanical ventilation. (J Am Soc Echocardiogr 2002;15:944-9.)