IVC plethora is lack of the normal inspiratory collapse of a dilated IVC on echocardiography. Normally the IVC diameter decreases about 50% during inspiration. IVC plethora is seen in right heart failure and constrictive pericarditis [1,2]. IVC plethora indicates high right atrial pressure and an overfilled and less compliant venous system. While calculating the estimated right ventricular systolic pressure (RVSP) from tricuspid regurgitation (TR) gradient, corrections have to be applied in cases of IVC plethora. Usually 10 mm Hg is added to TR gradient to get the RVSP. But when the IVC is grossly dilated and not showing inspiratory collapse, 20 mm Hg has to be added to the TR gradient to get the estimated RVSP.
Himelman RB and colleagues described IVC plethora as an important echocardiographic sign in cardiac tamponade . They described a less than fifty percent decrease in inferior vena caval diameter on inspiration or with sniff as IVC plethora. But IVC plethora may not occur in low pressure cardiac tamponade in which right atrial pressure is less than 12 mm Hg .
It may be noted that during positive pressure ventilation, inspiration is generated by positive pressure and hence inferior vena cava expands rather than collapses .
Himelman RB, Lee E, Schiller NB. Septal bounce, vena cava plethora, and pericardial adhesion: informative two-dimensional echocardiographic signs in the diagnosis of pericardial constriction. J Am Soc Echocardiogr. 1988 Sep-Oct;1(5):333-40.