Biology Today - May 2018

Coronary Artery Bypass Grafting (CABG)

C

oronary Artery Bypass Grafting (CABG) is a procedure to treat

severe Coronary Heart Disease (CHD) or Coronary Artery Disease

(CAD)usually caused by atherosclerosis which builds up plaque on the

artery walls causing the lumen of the arteries to become narrower. This

slows down the flow of blood. Coronary artery disease can be diagnosed

by Electrocardiogram (EKG), Treadmill stress test, Cardiac catheterisation,

etc. If the blockages are significant enough, the end result will be heart

attack or sudden death. CABG surgery is performed to treat narrowed

and blocked arteries, allowing sufficient blood flow to deliver oxygen

and nutrients to the heart muscle. CABG began in the late 1960s along

two parallel paths that included bypassing coronary artery obstructions

using either the Internal Mammary Artery (IMA) as the bypass conduit

or reversed Saphenous Vein Graft (SVG) from the leg. The use of latter became the dominant approach as it could be

BIO-GRAMused to graft any coronary artery site.

After the grafting is done, the

heart is restarted (in case of

on-pump) or the stabilising

devices are removed (in case of

off-pump). Protamine is given

to the patient to reverse the

effects of heparin. Chest tubes

are placed in the mediastinal

and pleural space to drain blood

from around the heart and

lungs. The sternum is wired

together and the incisions are

sutured closed.

7

The final stage of the

grafting procedure

is the construction

of proximal vein

graft anastomo-

ses. The aorta wall

punch is used to

create opening in

aorta for anastomo-

ses and the distal

segment of the

vein graft is anas-

tomosed with aorta.

6

Process of CABG

The majority of patients who undergo CABG surgery today receive a left IMA graft to the left anterior descending coronary artery and reversed
saphenous vein grafts with proximal aortic anastomoses.

Vessel graft

Off-pump coronary artery bypass graft surgery

Heart

stabilising

device

Sternal

retractor

Heart

After the cut, in case of off-pump

surgery, the surgeon places devices

to stabilise the heart. This type of

surgery is called beating heart

bypass grafting because the heart

does not stop beating and a heart

lung bypass machine (cardiac

pulmonary bypass) is not used. In

case of on-pump coronary artery

bypass grafting, cardiac pulmonary

bypass has to be established by

arterial cannulation onto aortic arch

and venous cannulation through

the right atrial appendage into the

inferior vena cava.

2

3
Greater Saphenous Vein (GSV) of the lower extremity is
harvested in two different ways. First, directly through
multiple incisions and tunneling over the vein along the
medial thigh and leg. Second, endoscopic vein harvest in
which two small incisions are made one above the knee
and the second on upper thigh.

1

A

B

Different types of

surgical accesses are

used in CABG, but

the most common

name is sternotomy.

In sternotomy, the

cardiac surgeon

makes an incision

down the middle of

the chest (A – B) and

then saws through

the breastbone

(sternum).

When harvesting is done, heparin is given to inhibit blood clotting.

The saphenous vein is slightly tilted and anastomosed to the coronary artery with a single suture.

Coronary

artery

Saphenous

vein

4

(^5) In case of Internal Mammary Artery (IMA) graft, internal
mammary artery is anastomosed to the Left Anterior
Descending coronary artery (LAD). Once an adequate IMA
with pedicle (artery with surrounding tissue) is determined,
the LAD is incised and the IMA incised on an angle at an
appropriate distal site.
Coronary artery
Internal
mammary artery
Narrowed
artery
Dead heart muscle
Heart Normal
artery
Plaque