Obstruction of inferior vena caval orifice by giant left atrium in patients with mitral stenosis. A Doppler echocardiographic study from the right parasternal approach.
Authors: Minagoe S , Yoshikawa J , Yoshida K , Akasaka T , Shakudo M , Maeda K , Tei C 
Published: June 2012

BACKGROUND
To examine whether an extremely enlarged left atrium (giant left atrium) obstructs the venous return from the inferior vena cava (IVC), the velocity of IVC flow was measured at its junction with the right atrium (IVC orifice) in patients with mitral stenosis by use of color and pulsed-wave Doppler echocardiography from a right parasternal longitudinal plane.

METHODS AND RESULTS
The maximum dimension of the IVC orifice by two-dimensional echocardiography and the maximum IVC orifice flow velocity by pulsed-wave Doppler echocardiography were measured in 74 patients with mitral stenosis and atrial fibrillation (mean age, 59 years). The control population consisted of 16 subjects with atrial fibrillation alone (mean age, 61 years). Flow velocities in the superior vena cava and hepatic vein were also obtained by pulsed-wave Doppler echocardiography from the supraclavicular and subcostal views, respectively. Fifty-one mitral stenosis patients without severe tricuspid regurgitation were divided into two groups according to the left atrial dimension (LAD), which was measured by the standard left parasternal long-axis view (group A: n = 33, LAD less than 65 mm; group B: n = 18, LAD greater than or equal to 65 mm). Peak inspiratory and expiratory velocities of IVC orifice flow in diastole averaged over three consecutive inspirations in group B (mean +/- SD, 93.4 +/- 32.0 and 47.6 +/- 19.8 cm/sec) were significantly greater (p less than 0.01) than in the control subjects (67.9 +/- 12.8 and 34.5 +/- 7.0 cm/sec) and in group A (70.2 +/- 18.4 and 38.1 +/- 11.5 cm/sec, respectively). However, there were no significant differences in superior vena caval and hepatic vein flow velocities among the three groups. The maximum IVC orifice dimension in group B (11.4 +/- 4.4 mm) was significantly smaller than in the control subjects (20.1 +/- 2.1 mm) and in group A (18.6 +/- 5.4 mm) because of displacement of the atrial septum into the right atrium. There were significant negative correlations between the IVC orifice dimension and the peak IVC orifice flow velocity (r = -0.62, SEE = 0.33 cm/sec, n = 67, y = e(-0.01x + 3.6), p less than 0.01) as well as the left atrial dimension (r = -0.71, SEE = 0.32 mm, n = 67, y = e(-0.02x + 3.8), p less than 0.01) in these 51 patients and control subjects. In the remaining 23 patients with severe tricuspid regurgitation, the peak inspiratory IVC orifice velocity (n = 9, 88.6 +/- 30.0 cm/sec) was significantly greater (p less than 0.05) and the IVC orifice dimension (23.8 +/- 9.7 mm) significantly smaller (p less than 0.05) in patients with a giant left atrium than in those without (n = 14, 69.9 +/- 15.3 cm/sec and 30.5 +/- 9.6 mm, respectively); in the latter, the IVC orifice dimension was significantly (p less than 0.05) greater than in the controls.

CONCLUSIONS
A giant left atrium in patients with mitral stenosis obstructs venous return at the IVC orifice by marked displacement of the atrial septum toward the right atrium.