Aortic Dissection
Aortic dissection is a
condition in which blood under pressure escapes from the inside of the
major artery coming out of the heart (known as the aorta). Instead of
breaking through the entire thickness of the artrial wall, the blood
flows between the layers of the blood vessel wall, as depicted at left.
The blood tracks between the layers of the aorta, causing severe ripping
pain in the chest and between the shoulder blades. This pain has a very
sudden onset and demands immediate attention. The initial tear in the
aorta most commonly occurs either directly above the heart, or just
after the aorta gives off the arterial blood supply to the left arm.
The picture at right demonstrates the former case.
There
is also a tear more downstream in the part of the aorta known as the
aortic arch. The danger of this type of tear is that blood can leak
out of the damaged aortic wall and fill up the sac surrounding 
the
heart causing a condition known as pericardial tamponade. At left is
a CT scan of the heart showing a blood filled pericardial sac. If the
blood occupies too much space surrounding the heart, this pericardial
tamponade will not allow the heart to normally fill and eject blood,
leading to shock and death. The treatment of this emergency medical
condition consists of control of blood pressure and, in cases where
there is a danger of rupture or tamponade, emergency surgery.