Silent lower aortic obstruction.

Three cases of lower aortic obstruction are described in which the diagnosis was made at operation. Profound hypothermia with circulatory arrest was used for replacement of the mitral valve by a Starr Edwards prosthesis. Femoral perfusion was used and the diagnosis was made in the first case only because the rectal temperature fell precipitously during cooling, while the temperature in the upper part of the body was slow to fall. In this case disobliteration was not carried out, but in two further cases this was done through a bilateral femoral arteriotomy using Fogarty catheters. All cases were seen during a period of 18 months among 35 mitral valve replacements. Silent lower aortic obstruction may not therefore be a rare condition and might be responsible for hypotension during normothermic cardiopulmonary bypass when the femoral artery is used for cannulation. If the aortic root is used, the condition will not be discovered. If exercise tolerance is greatly improved after successful operation symptoms of the obstruction may become manifest, and if further thrombosis occurs and symptoms are more acute they may be wrongly attributed to embolization from the valve replacement. Routine abdominal aortography during left heart studies should disclose a clinically silent obstruction.