Diagnosis by gross morphology

The normal aorta has three gentle bulges, the aortic sinuses, just distal to the semilunar attachments of the three leaflets of the aortic valve. The cross sectional diameter of the aorta at the nadir of the leaflet attachment where the aorta and ventricular muscle meet, and at the upper limit of the attachment at the sinutubu-lar junction, are very similar, with the leaflets supported with a spatial relation as if to the sides of a cylinder. The diameter of the more distal circle at the sinutubular junction is, if anything, slightly smaller than the left ventricular outflow. This relation is lost in the Marfan syndrome. The aortic root becomes bulbous and the attachments of the leaflets are splayed out. The commissures are attached to an aorta of much greater circumference than at the nadir of leaflet attachment, the leaflets no longer co-apt, and the valve leaks centrally. The widest part of the aorta is in the sinuses of Val-salva where the echocardiographer picks up the very tips of the leaflets as the valve opens. The coronary orifices are displaced upwards as the aortic wall proximal to them dilates.

Now that we know that there are nearly as many molecular subsets of the disease as there are families, several earlier conundrums become clear. One is the occurrence of inherited aortic dilatation with a propensity for dissection in people who are skeletally unremarkable

Figure 21.1. Histological appearance of a Marfan aorta. On the left is the severe form of medial degeneration called "cystic medial necrosis".

The term formfruste was used for the situation in which the aortic root is characteristic of Marfan syndrome but other features were absent. With the new knowledge about the variation in the genetic abnormality from one family to another, it begins to make sense that there is clinical variability between families. There appear to be those at risk of dissecting an aorta with Marfan morphology but who look normal. On the contrary there are Marfan families with severely affected skeletons whose aortas are not particularly large and who do not dissect. A distinction must be made, however, between the very characteristic morphology of Marfan syndrome and the more funnel shaped aortic dilatation seen in hypertension and post-stenotic dilatation associated with bicuspid valves.

Blood Pressure Health

Blood Pressure Health

Your heart pumps blood throughout your body using a network of tubing called arteries and capillaries which return the blood back to your heart via your veins. Blood pressure is the force of the blood pushing against the walls of your arteries as your heart beats.Learn more...

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