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LEFT INTERNAL MAMMARY ARTERY

Highlights

Created on - 09 May, 2016

Introduction
LIMA as conduit has proved to be superior and better for early and late survival after CABG.
It is a first choice conduit because of its superior biologic characteristics, unparalleled long term patency, better clinical outcomes.
Anatomy
•    1. It arises from first portion of subclavian artery.
•    2. Travels downwards on the inside of ribcage from approximately a centimeter from sternum.
•    3. It is accompanied by IT vein.
•    4. It divides into musculophrenic artery and the superior epigastric artery at 6th ICS.
•    5. RITA is closer to sternal margin.
Branches
•    1. Mediastinal branches
•    2. Thymic branches
•    3. Pericardiophrenic artery
•    4. Sternal branches
•    5. Perforating branches
•    6. Twelve anterior intercostal branches, two on each side
•    7. Musculophrenic artery
•    8. Superior epigastric artery
Characteristics:
•    1. It has resistance for atherosclerosis development, may be because of resistance of endothelium for injury.
•    2. The internal elastic lamina

inhibits cellular migration

prevents initiation of intimal hyperplasia.
•    3. Also, medial layer is thin with few SMCs

less proliferative response to mitogens like platelet derived growth factor and pulsatile muscular stretch.
•    4. Endothelium of ITA is unique. It produces vasodilators nitric oxide and prostacyclin in abundance

So has favorable response to drugs in postop period

eg. Milrinone – dilates it, noradrenaline – does not constrict it, NTG vasodilates it but not SVG.
•    5. “Downstream” effect on the coronary vasculature

coronary target appears protected distal to anastomosis

due to this endogenous secretion of vasodilators.
•    6. “Re modelling” seen in ITA

adapts to demand for flow by this diameter.
•    7. It increases flow in same way as normal coronary by increse in velocity and caliber mediated by endothelium.
Blood supply to:
•    1. ITA supplies blood to pericardium, phrenic nerve, sternum, anterior chest wall, pectoralis major, mammary gland, anterior abdominal wall, diaphragm.
•    2. Pedicle harvesting: into pedicled, semi skeletonized, skeletonized.
Sprayed / wrapped in papavarine solution.

Skeletonization – Only artery is mobilised leaving internal thoracic venous plexus intact, leads to decrease in sternal ischaemia which is seen on LIMA harvest.
In semiskeletonized

ITA and veins also mobilized
Skeletonization has advantages:
•    1. It increases luminal diameter and free flow compared to pedicled graft.
•    2. Provides larger conduit

allows more sequential grafts

more targets are revascularized.
Limitations of skeletonization:
Concerns regarding vascular integrity, vasoreactivity and patency.
Patency:
They demonstrated decreases in MI / reoperation / cardiac events in LIMA.
Patency    LIMA –> LAD    SVG -> LAD
1 yr                 98%                87%
4 yr                 91%                83%
10 yr               95%                61%
15 yr               88%                32%

- by Dr Amarja

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