The-effect of the Valsalva maneuver, maintained for 10 sec, on the angiographic appearance of die inferior vena cava was determined in a study utilizing '11 patients. The Valsalva maneuver did not appear to narrow the inferior vena cava significantly, either in its abdominal course or at the diaphragmatic level. The erroneous angiographic impression that narrowing or discontinuity develops during the Valsalva maneuver appears to result from two hemodynamic factors: (1) hepatic venous washout and (2) layering of contrast material in the slowed caval stream as the vena cava ungulates anteriorly to enter the right atrium.
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