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Archive for June, 2011

LIMA (Left internal mammary or thoracic )  is an unique  artery ,   incidentally runs close to  heart ,  has  a  privilege  of supporting   of human  heart in its hour of crises ! .  CABG  surgery was started with saphenous grafts in 1967 .  We have  since moved  on ,  from venous grafts to  total arterial grafts .  LIMA as a graft for coronary artery was a  great innovation for cardiac surgery  .Now , it can be stated  ” CABG should not be done without a LIMA graft “

Advantages of LIMA

LIMA   has good anatomical  match for LAD. The 10 year  patency  rate is very favorable (60-80%) .LIMA is also a live graft enriched with nitric oxide , as it has native  communication with subclavian artery  .

Anatomy

The internal mammary artery  originates  from the under surface of the first portion of the subclavian, opposite the thyrocervical trunk. It descends behind  the  upper six ribs at a distance of about 1.25 cm. from the margin of the sternum, and at the level of the sixth intercostal space divides into the musculophrenic and superior epigastric arteries.

The branches of the internal mammary are:
Pericardiacophrenic. Intercostal.
Anterior Mediastinal. Perforating.
Pericardial. Musculophrenic.
Sternal. Superior Epigastric.

There are few Anatomical issues for LIMA

Subclavian -LIMA ostial stenosis : Rare

Looping of LIMA is rarely an issue in hemodynamic point of view. But some  believe  a looped up LIMA is slightly prone for graft disease.Complex looping are reported rarely.

A loop and a early branch of LIMA : What is the implication ?

Abnormal  or premature branching pattern  of LIMA  needs clipping as it may divert blood supply to LAD.Terminal branches can be used as a sequential graft to a branch of LAD  usually a diagonal. In spite of all these issues , LIMA is  rarely unsuitable either anatomically or physiologically .It is a safest vessel to graft.

Future of LIMA  graft assessment.

Currently selective LIMA angiogram is the gold standard.

MDCT (64 slice) gives stunning images of LIMA graft , but unfortunately , it has little value for functional assessment .

Functional assessment of LIMA graft By  angiographic frame count  is being attempted in our institute.Will be reported in 2012.

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Is hypertension really a major risk factor for CAD ?

    1. Yes it is !
    2. No . . . it is not !
    3. May be !
    4. I don’t think so !

Ans : Any of the above can be a  right response , depending upon our basal and perceived  level of knowledge .

Answer analysis

  1. SHT  is  one of the risk factor for CAD  agreed ,  but definitely not a major one , as SHT per-se rarely precipitate a STEMI
  2. Unless SHT occurs with dyslipidemia, smoking or diabetes it is  rare to cause ACS.
  3. The only  adverse effect of SHT  is  , it has a potential  to aggravate atherosclerosis  by promoting epithelial injury and dysfunction.
  4. Hypertension is a well known  major risk factor for cerebro vascular disease while it is minor risk factor for CAD !
  5. We do not know yet why cerebral vessels are intolerant to high blood pressure while coronaries are pretty happy  with it !

Final comment

SHT is not a major risk factor  for CAD ! At worst , it can propagate chronic CAD. This sort of reasoning  may be considered a huge controversy  . . .but it is really not !

  • One evidence for the above observation is  , we  have  been struggling hard  for over a half a century  to prove a elusive  point that controlling blood pressure  to optimal levels  would  dramatically reduce  cardiac   events !
  • Further,HT’s  relationship with acute coronary syndrome especially STEMI  is vague , it is very rare for patients with accelerated hypertension or malignant hypertension to  present with STEMI *

* Caution :Young doctors should not get confused with this seemingly  controversial observation .This write-up , tries  to convey  a point  , SHT may not be that bad for coronary arteries when compared to cerebral arteries . However BP control remains  vital in  all patients who have  developed a cardiac  event or in patients with multiple risk factors .

Please note ** SHT is still  a powerful risk factor for cardiac failure.(Acute LVF to be precise ) ***SHT can aggravate unstable angina , but very  rare to precipitate unstable angina.**** SHT ./High intra-coronary  pressure can theoretically  dissect or fissure a plaque . (The fact that , HT is so prevalent in a community  but spontaneous  coronary  dissections are not !  should make us think further !)

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What  is the   “secret of success”   among current generation  cardiologists ?

A . Strong foundations in cardiology with excellent clinical skills and a rational approach to the given problem.

B.  The  secret lies in the  nimble  fingers  which  acts  almost , like an extension of catheters  in cath lab !

C.  The speed with which he can mobilise a cath lab team in an ” off – office hour”  primary  PCI !

D. It is the the cunning art of  converting coronary  angiograms into angioplasties , by lucid  discussions  with patients and their   relatives  in the the silent cath lab corridors  !

Answer:

When this question was posed to a group of cardiologists ,  D  was considered  most important B,and C came close behind   and   A  was  probably least important  and few thought  “A” character  is rather an  impediment to  become a successful cardiologist !

*Unfortunately a successful cardiologist is defined in India by number of angioplasties he does per month, What  a disgrace to a great medical specialty called cardiology !

What is normal CAG to angioplasty conversion ratio ?

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