Flow in Mildly Narrowed Vessels

Arterial disease is usually due to fat in the Artery walls called "Atheroma" - or more commonly known as "hardening of the arteries". Atheroma is caused by things that damage the arterial walls - including smoking, high blood pressure and diabetes. Having fat in our blood means that this damage allows a route for the fat (or cholesterol) to get into the wall.

Once the fat is in the wall, the wall bulges causing a narrowing of the artery. This bulge is called the Atheroma. The narrowing is called a Stenosis.

The affect of narrowings (or stenoses) in the arteries depends on how tight the narrowing is and how fast the blood if flowing. This is explained in the following sections.

Flow in Mildly Narrowed Artery:

The animation on the left shows what happens to flow in an artery with a mild narrowing (a mild stenosis).

As you can see the blood flow is very similar to that in the normal artery.

Although the narrowing means that the flow is speeded up, and the blood next to the wall is disturbed, the overall pattern of flow is the same - ie: Laminar Flow.

Pressure Change in Mildly Narrowed Artery:

The animation on the right shows the pressure changes in the blood flowing in the artery above.

In this situation the two pressure measures - labelled P1 and P2 - once again show there is no drop in pressure across this section of artery.

Once again this is not surprising as the flow is essentially the same - ie: laminar flow.

Such a narrowing or stenosis is called a non-critical stenosis.