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Posts Tagged ‘cabg’

I recently came across an unusual LIMA  arterial  branching pattern .

Random thoughts

  • A naturally dividing LIMA faciliates multiple sequential grafting of LAD or diagonal branches.
  • As branches steal the LIMA flow it is not good for the patient
  • Surgeons struggle to clip the branches.
  • A branching LIMA has tendency to have  small diameter (As in the above patient )

I need a surgeons Input here.

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Coronary  atherosclerosis is the number one killer of mankind. Many would consider it as an  essential  process of aging .Modern  life styles and habits make this appear  very early in life . There is currently an endemic (or even  a pandemic ) of   CAD due to premature  atherosclerosis. We need to recognise CAD is not a  primary heart disease  .It is an irony, heart is an  innocent bystander  to the  biological derangement  of coronary  vascular system  when  it is infested with atherosclerotic plaques .

So , when we  are confronted  with  serious atherosclerotic lesions in a coronary artery   what shall we do ?

We have three options

  1. Take on the enemy in a direct confrontation (Like war on terror ) : This is  some times called as Interventional cardiology .Caution is required as the battle  is within the human coronary artery ,  cross fires and collateral  damage  are unavoidable.

2 .Next  method  is to  find the basic cause  of  terrorism , identify  the perpetuates, facilitators    and try to correct the   root cause of it (CAD ) .This approach  also refered to as medical management  in cardiology community*  . It  aims  at regression of plaque  by statins, and life style modification and preventive cardiology. This modality is most ridiculed and  insulted by the main stream cardiologists.

*Comparable to  bilateral peace talks for a political solution to terror

3. And third option is a  real  surprise !   This  neither  confronts   the lesion   nor does it  address the initiating factors . It   just ignores  the lesion and by pass it with a LIMA /SVG  fly over ,  as if  nothing has happened in this vital high way leaving the culprit scot-free  .This option is  executed by surgeons as  CABG surgery . . . and  for mysterious reasons  this is a  well accepted one .

CABG :Here the atherosclerotic  burden is untouched by surgery . The graft can get diseased  sooner or later , native vessel disease  shall  progress some times encroaching  the ostia of distal graft site . Incidence of acute coronary syndrome following CABG is not greatly reduced for the simple reason we are not doing anything primarily to the inflamed plaques .These issues  are left ,  to be  taken care by the  medical  management .

* This article  does not want to defame these great development in cardiology(PCI/CABG) . They have a  specific role to play. CABG AND PCI remain the only option for critical  lesions with limiting angina .But please remember without  proper  medical management  ( ie Targeting  the perpetuates of  crime )  both  PCI and CABG will be a big sham !

Final  message

Avoiding   the  lesion  or  attacking the lesion  is a  primitive  method to tackle CAD  . Passifying   the lesions  in a slow and gentle manner,   preventing  further progression  or regression  of lesions is the only  “sane” method for combating CAD   . PCI and by pass surgeries  can be termed  as  21st century’s   medical  adventure sports  which  has  limited role ,  in the overall control  of CAD  for the human kind .

And  now  answer this question . . .

Cardiologists attack the lesion and  surgeon avoids the lesion ?  Who is the winner in our fight against CAD  ?

Both of them are  clear losers .The winners are  all those  humble physicians and parmedical workers (or even the responsible lay public ) who  help recognise  the early forms  of  CAD  and  counsel properly to prevent it .

This is  what  Dean Ornish   in 1991  documented in  Lancet  which was never considered scientific   for the simple reason it has no commercial value !

Reference:

http://www.thelancet.it/journals/lancet/article/PII0140-6736(90)92230-F/fulltext

http://en.wikipedia.org/wiki/Dean_Ornish

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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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We  are at the mercy  of  the three major coronary arteries (LAD,LCX,RCA) that sustain our life . Their  job is clear cut  .It has to perfuse   about 300 Grams of   live bundle of energy  for  an average of 6-7 decades.

What are the hurdles it  faces ,  how it overcomes these obstacles  forms the fascinating story of   “survival  of  human heart”

When coronary blood supply is confronted with a sudden compromise  as in ACS  ,  often the heart has little  time to respond . Hence the damage  and risk of death is  more. Even here there are lots of safety mechanisms and natural lytic process that limit the loss of life to less than 30 %  of all STEMIs. This implies nature protects against the death in 70 % of individuals and help  them  to reach hospital.*

*Among those  who reach hospital , we  the cardiologists  try to reduce the  mortality to about 6-7 % (20% without treatment ) with all  those hi-tech gadgets .It is a  different story and will be addressed elsewhere .

When it comes to  chronic insults ,  the heart has a unique potential to  stage  long haul battles. It has many tricks  under its  sleeves when challenged in a slow fashion.

The main weapons are two

1. Coronary collateral circulation.

2. Ischemic preconditioning.

Here is a patient who fights his life even after all his  three coronary arteries   totally blocked and surviving with one of the branches of left main -Ramus intermedius .

If you have thought his RCA was the savior  you are  mistaken  .

To every one’s   surprise  his  RCA was awful  as well !

He had angina which was  troublesome  but manageable .Was able to live a life with acceptable standards (Indian standard )  After the angiogram he  received  CABG.  A turbulent post operative course ensued  due to various reasons . He  struggled but   fully recovered  . . .  and  ultimately  reached the  previous  standard  of life !

Final message

Modern cardiology is all about not trusting  powers of nature .

But youngsters should realise the enormous potential of those invisible powers.It may sound philosophical , but please  remember  . . .after all . . .  philosophy  is nothing but  search for truths. Atleast believe in them  once in a while !

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  • It is a complex PCI procedure meant for  high risk  bifurcation /Trifurcation lesions
  • Two stents are simultaneously  deployed.
  • It aims to prevent sudden acute occlusion of one of the major  branches .
  • It is not an easy procedure , and be used only in rare circumstances .
  • Distal left main and ostio proximal LAD/LCX  is a  classical  example.
  • Navigation can be difficult , only well experienced operators should attempt it.

*Is there a ready made two lumen stent available ?

The image is meant for concept purpose only !

 

It is one of the techniques available to stent unprotected left main

An excellent review  in  ACC intervention journal for unprotected left main .

Click on the Image to reach the article

 


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We know,  electrical deaths constitute the bulk of sudden cardiac deaths in MI.  Mechanical deaths due to pump failure, muscle rupture , valve leak , also cause significant deaths   .(Surprisingly many of the mechanical deaths   may also   fulfill  the sudden death criteria !)

Free wall rupture is  invariably a fatal event. Papillary  muscle trunk  rupture  leads to severe LVF and unless intervened sure to result in fatality.

The ones who tear their interventricular septum  are some what blessed ! Here ,  the rupture does not result in instant death as there is  no loss of blood ,   instead , there is an  volume over load of right ventricle  followed by the  left ventricle  after a  few beats. Hypotension is the  rule. Even though this is a major complication there is something about  VSR which makes it unique.

Sudden giving way of IVS has  a decompressing effect on the ailing left ventricle.This many times  bring a  temporary relief to LV and if the patient survives the first few hour he is likely to stabilise  further . In fact , sudden deaths within 24hours after the onset of VSR is an exception.This defect always gives the cardiologists and surgeon some time to plan the management. We need to use this time judiciously.

The natural history is delicate . Five themes are possible

  1. Very unstable Instant death( Fortunately a  rare theme )
  2. Unstable – Deteriorating further
  3. Unstable to Stable * fit for discharge even without surgery
  4. Stable from the onset and  continue to be stable* .
  5. Stable to Unstable (Probably the most common theme )

* Pleasant themes occasionally witnessed !)

Here is 55 year old women came with extensive anterior MI with lower septal rupture.(She belonged to type 3 of the above scheme)

)

Note the septal rupture is visible even in 2D Echo

 

Color flow showing significant shunting from LV to RV.This shunt depends upon the LV contractile function, LVEDP and ofcourse the RV pressure

 

If there is severe RV dysfunction or bi ventricular dysfunction flow across the defect is inconspicuous.Brisk left to right shunting may be an indirect marker for good LV systolic function and absence of significant pulmonary hypertension.Both imply a better outcome.

The main determinant  of survival is the  underlying LV dysfunction and associated co morbidity(Renal function ) and complications .

Infero -posterior ruptures tend to be complex and  may have multiple irregular tracks  that makes it difficult to repair.

Investigations

Echo cardiogram is the mainstay .Serial echos should be done to assess the mechanical function and the progress of VSR.Hemodynamic monitoring may be done without injuring the patient .

Medical management

  • Often supportive , but  effective . Dobutamine infusion can maintain a life for few days.
  • Paradoxically , LV dysfunction and elevated LVEDP restricts volume overloading of VSD.
  • Associated MR, Arrhythmias  need to be taken care of .

Surgeons role

  • Very Vital.
  • Experience counts.(Individual as well as  Institutional )

Timing of surgery

Continues to be a controversy . Surgeons love to operate in a stable patient. But they need to realise , surgery is often needed to stabilise  many  patients. . The issue of tissue friability  is blown out of proportion in the literature .When a  life is  is at danger we can not worry about  friable tissues !

The rule of thumb could be

  • Operate as early as possible in unstable patient.
  • Post pone surgery in stable patient as late as possible ( Late here means . . .elective non emergent surgery )

Surgical options

  • Simple VSR closure without  knowing coronary anatomy
  • Simple VSR closure after knowing coronary anatomy
  • VSR closure with CABG ( total revascularization)
  • VSR closure with partial revascularization

In our experience  each of the above , has a role in a given patient depending upon the logistic , financial , social and even  the available expertise. (A good surgeon in bad Institution !)

Is coronary angiogram mandatory  before attempting to close VSR ?

Logically yes. If it is not available  just do not bother .  But, many times , when issue is saving lives , we can not afford to be too scientific , many lives have been saved by not following  such strict  protocols .A simple emergency  thoracotomy and closure of rupture site (Without even touching the LAD ) can be a distinct  and viable option in  a selected few .

Role of cardiologists

Contrary to the popular belief the role of cardiologists is minimal , except  to prepare  the patient and hand over to the surgeon.

Interventional approach to close  a VSR  is currently  be termed as an  adventurous option ! The VSRs  can assume unpredictable shapes  and the  tears can be multiple  in  different planes. The devices , catheters and  other hard ware are not specifically made to tackle these  issues  .An acquired VSR  should never be compared with congenital VSD.

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It is a well known fact  ,   CABG and PCI  provides immediate relief  for patients with angina ,  which is refractory to medical therapy. Of course , this happens only if a critical occlusion of  at least one epicardial coronary artery is  opened . It need to be realised ,  angina  due to  microvascular  disease can not be cured by maintaining  epicardial  patency .

While angina  relief is prompt ,  dyspnea is not ! . If we  believe,  opening  up a  coronary artery  in a patient with LV dysfunction will  restore the LV function  ,  it  is grossly mistaken !

Why is it so ?

Angina  relief requires  simple  restoration  of  oxygen supply and correction of local ischemia .  This happens without any issue as the blood  seeps in to the ischemic cells and soothes the ischemic nerve fibres that trigger the pain signals   . While  ,  for LV function to improve , the blood flow has to be converted to mechanical activity in the form of myocyte actin/myosin interaction. For this,   there need to be an intact  cellular contractile mechanism . The myocyte architecture should be appropriate .In post MI ventricles we know there is  zig zag  orientation of myofibrils due to myocyte slippage that interfere with mechanical recruitment . Further , integrity of  extracellular matrix  namely the collagen frame work is also vital . Note ,  angina relief  is not concerned with any of the above .

And now ,  we also realise  dyspnea  in failing ventricles  is vitally  dependent on diastolic function ,  which is also very much  impaired in ischemic DCM .There is little proof for  PCI/CABG  to correct the  molecular   mysteries in  diastolic dysfunction !

Dysfunctional LV means what ? (read the link )

It is a collection of  variety of myocardial tissues . Viz : Fully  necrosed , partially necrosed ,  ischemic viable, non ischemic viable, ischemic non viable, non ischemic non viable , Apart from this patchy necrosis, patchy ischemic, areas are common. Finally , necrosed segments   may  also be perfused normally by  spontaneous reopening of an IRA.

One can imagine the complexity  of events in these segments  once we do the  PCI /CABG . The response  is highly variable and unpredictable. The major concept we  , the physicians  believe or ( to be precise made to believe !) is  the  sanctity  devoted to  the viable myocardium .For  many us ,  it is considered a  holy  exercise  to identify viable myocardium in patients following MI and then revascularise them if  found to have significant viable myocardium (Atleast 20% of infarcted area )

A full 2 decades were lost or (shall  we   say wasted on this futile exercise !) as   we have since  realised most of the cardiologists do not follow this rule .

Now , even a scarred myocardium is revascularised in the hope of recovery .As such , we have reached a stage where  there is no contradiction for not doing a PCI /CABG   with reference to LV dysfunction.

Now every  patient  with post MI  LV dysfunction  is considered to  have  some amount of viable myocardium that is  fit   enough  for revascularization

Are we justified in doing  this ?

Many clinical  trials  have revealed  , the  recovery of LV function  in these segments  has not been consistent at all .

The most surprising discovery is  a viable myocardium need not  be ischemic   .It might get adequate blood supply either  from invisible collaterals or trickle of antegrade flow .  Hence an adequately  perfused myocardial segment can  still be   non contractile . This shatters the myth  that  revascularisation must have a dramatic effect on the recovery of contractility in all viable segments.

The other major finding is  ,  even ischemic   viable   myocardium ( documented by metabolic activities PET etc)  need not regain it’s original contractility  after the ischemia is fully corrected .

*reference for  both the above statements are available from variety of sources including real life experiences .(Type C evidence )

Final message

  • Do a PCI/CABG promptly for patients with refractory angina.
  • Never  advocate PCI/CABG  for  a primary relief of dyspnea .  (Never is a harsh word,  let it be  “use it  with caution ” ! and  the  patient  should be  revealed  the whole facts  about  what we know and what we do not know regarding the complex  hemodyanmic events  in  revascularisation   )

Counter point

If  the above statements are really true ,   How does PCI/CABG   help  relieving  dyspnea  and functional class  what is your answer for thousands of patients  with CAD and ischemic DCM who have greatly benefited from CABG ?

The answer could  be  simple , The revascularization  piggybacks  over the   medical management (which , these patients pursue vigorously)     like  ACEI,  statins, salt restriction, betablockers  , optimal diuretics and tend to hijack the credits from the poor  drugs !

Read a related blog

Revascularisation for ischemic DCM

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