1. A normal artery,
no hardened fat deposits (plaque) on the inner surface of the artery
wall, so there is no
restriction of blood flow away from the heart.
2. Fatty deposits
(plaque) can build up on the
inside wall of the artery restricting blood flow.
The cross-section
of the lumen is reduced e.g. the equivalent of narrowing a 'pipe'
and reducing blood flow - reducing the rate of oxygen transfer to
heart muscles.
Cholesterol is a fatty substance the body
needs to build cell membranes.
However, too much of fatty substances,
including 'bad' LDL cholesterol, in your blood stream can lead
to an excessive and dangerous build up of fatty deposits on the
walls of the arteries.
The fatty deposits harden over time to
form lots of atheromas which restricts blood flow.
These bits of atheromas damage the blood
vessel and if one breaks off it can cause a blood clot.
This damage to the arteries causes high
blood pressure with increased risk of heart attacks, angina and
strokes.
Thick fat deposits can block a blood
vessel or cause blood clots to form which can block the flow of
blood completely.
If this involves an artery supply blood to the
heart muscle, the heart muscle is deprived of oxygen and
glucose and can
cause a heart attack.
There is less energy available for the
heart muscles to contract.
Such blockages can also deprive the brain
of oxygen causing a stroke.
3. With
the help of a catheter, whose position is monitored by X-rays, a very thin-walled tubular
bare metal stent is
inserted that pushes against the inside artery wall. The stent squashes the
fat deposits and so widening the artery to allow normal blood flow -
increases the cross-section area of the artery, so increasing flow
rate - hopefully bringing the oxygen supply to the heart back to normal!
By allowing normal blood flow rate, stents are a very effective way of
lowering the risk of a heart attack or a stroke for people suffering from
coronary heart disease.
After the operation, recovery time is
short and the stents have a long working life of many years.
Repeat surgery might be necessary if the
artery narrows again.
However, such procedures are not without
risk -
(i) there may be complications during
the operation (including, ironically, a heart attack),
(ii) there is always a risk of
infection with any surgical procedure, and,
(iii) a risk of a blood clot
developing in the patient near the stent - known as a thrombosis. This restricts blood flow and possibly
stopping the flow - not good!
NOTE An alternative stent
A
drug-eluting stent (DES) is a peripheral or coronary stent (a
scaffold) placed into narrowed, diseased peripheral or coronary
arteries that slowly releases a drug to block cell
proliferation.
This prevents the
artery from getting narrowed by the growth of tissue cells.
Bypass surgery
There
is little risk in having stents implanted, but the fatty deposits
can build up again.
However, if the coronary artery is too
badly damaged, bypass surgery must be used.
The blood vessels may be so badly blocked
that stents won't work.
In this situation, the blood flow to the
heart can be improved with coronary bypass surgery.
A healthy blood vessel (e.g. a vein in the
leg) is transplanted and surgically inserted and connected to
bypass the blocked damage artery.
Bypass surgery has the advantage of no
rejection, but still carries risks of any major surgery.
It is a more invasive procedure than
having stents fitted, requires a longer hospital stay and
requires a longer recovery time.
There is a lower chance that repeat bypass
surgery would be necessary, whereas with stents, this may be
needed if the artery narrows again.
(image adapted from
https://en.wikipedia.org/wiki/Angioplasty )
Angioplasty, is a minimally invasive endovascular procedure used
to widen narrowed or obstructed arteries or veins in the treatment
of arterial atherosclerosis.
A:
A deflated balloon attached to a catheter (a balloon
catheter) is passed via a guide-wire into the narrowed vessel.
B:
The balloon inflated to a fixed size (balloon angioplasty).
C:
The balloon forces expansion the blood vessel and the surrounding
muscular wall, allowing an improved blood flow.
Note: (i) A stent may be inserted at the time of
ballooning to ensure the expanded blood vessel remains open, and the
balloon is then deflated and withdrawn.
(II) Angioplasty has come to include all manner of vascular
interventions that are typically performed by needle-puncture of the
skin rather than by using an 'open' approach where inner organs or
tissue are exposed.
An
example of angioplasty