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Posts Tagged ‘coronary collateral circulation’

Note :This is a copy of  my earlier blog on coronary micro-circulation  published few years ago.Recently this got numerous hits .Hence I have just reposted it with slight modification.

Human coronary circulation stands unique among  others as it is a  life-sustaining circulation.It is indeed a great medical achievement  to visualise  the right and left coronary artery  system by coronary angiogram.  Actually,  what we see is  only a fraction  of  the surface area of coronary circulation .The surface area of  epicardial coronary arteries   constitutes  less than 5 % of entire coronary vascular tree .

And  . . .

An in vitro heart with special catheters showing the true extent of coronary circulation: Courtesy http://eurheartj.oxfordjournals.org/content/28/3/278.full.pdf+html

This  is the reason  normal coronary angiogram can never mean normal  coronary circulation !

This huge gap in our perception is the single important factor  that  explains the vagaries  of modern coronary care .

This also make any clinical coronary  scenario  a  reality .

“A patient with normal coronary angiogram getting a myocardial infarction , the next day and a severe triple vessel disease living comfortably  for  decades with medical management”

So , it is essentially a  false  sense of  scientific accomplishment  by the cardiac scientists  at  least in the  of coronary circulatory physiology.

What determines the extent of these invisible coronary micro circulation ?

There are innumerable channels of micro vessels traversing across the heart, sharing , bridging , branching, penetrating  and  perfusing the muscle mass.They can be anatomically patent , physiologically non patent .They can be recruited by hemodynamic stress .These are never visualized by current imaging modalities..It is also influenzed by  favorable growth milieu and hormonal and neural stimuli.

Ignorance based cardiology

What is the mechanism  of primary VF following acute STEMI ?

The quantum of  coronary micro circulation is like the vast  cerebral neuronal net work .We have every reasons to believe they are have unique genetic imprint.How else you can explain a man with full blown STEMI come 24 hours later comfortably to the OPD while another loses his life with a stormy primary VF before even boarding the ambulance !

Why many cardiologists   do not give due credit  the   coronary collateral  circulation  ?

Right from the days  of  Levine in 1970s( Who made a seminal contribution  about coronary collateral)  the  utility value of  coronary  collateral  circulation  was never able to convince the cardiology professionals .

It has been our traditional  teaching ( without much evidence of course  !) coronary collateral circulation  is not effective to support blood flow during exercise . This fact has been  disproved  many times . Coronary collateral circulation was indeed useful in limiting damage in ACS and  relieve symptoms in stable angina.It helps  in reverse remodeling and provided electrical stabilty as well in post MI population.

Still , the concept  was  alienated  and   made   totally irrelevant  in the interventional  era  . Many   cardiologists  found well-developed collateral’s as an interference to their expertise and ego since it has a potential to alter the indication of PCI.They  continue to have  strong  scientific conviction (Pseudo ?)   that man made collaterals must always been superior to God made collaterals !

Whenever  some credible  reports emerge about  collateral circulation   being   equivalent to  revascularisation procedure , these concepts were  prematurely buried for some reason.

In the last decade there was a concern  about  performing  PCI in patients with well-developed collaterals  .The argument was , they tend to develop early stent occlusion and restenosis . It  was a genuine  query  raised by few thought leaders in the field as  collateralised vessels  suffer from  low flow   after PCI ,   if the pre -existing collateral continue to function.

But  then , few  studies countered this , and PCI was shown to be safe and  in fact may  fare well   in  patients  with  extensive collaterals .

In these  studies  interventionist’s  argument looked  amusing !  as they  seem to  define a  successful  PCI  as  not only to open the occluded vessel  but also  make sure to close  all functioning  collaterals  .(What a  a pity for our natural biological  angiogenic forces which had  worked  and  grown meticulously for months!)

Cardiac science in the current format,  makes   the future look  bleak for coronary a collateral circulation .With  early PCI  becoming a norm we will never ever allow the natural collaterals to  grow  ,  and even the  established collaterals  will have to face a stiff   fight  for survival  with  sophisticated coronary interventions .

Competing interest in the filed of  coronary collateral   research

While the basic scientists want  to  grow collaterals with angiogenesis ,  stem cells etc  interventionists   continue to  indulge in rampant angioplasties which  will suppress  collateral growth.

This implies we will struggle to  establish  the true  importance of  coronary collateral circulation .

Final message

Can it be an  effective form of revascularisation  ? 

My personal  inference  is   coronary collateral  circulation  “would and should”  have  a definite role  in at- least  some of the subsets  with chronic coronary  syndromes. If we think otherwise . . .    it’s against the principle of  natural biological science .

A good  collateral   system with optimal medical management  can save not only our  patient’s  lives but also  their hard earned currencies !

Reference

Here is a rare article in European heart   journal that discuses coronary collateral circulation  . Let us welcome such wonderful  reviews which keep the interest alive on the filed.

http://eurheartj.oxfordjournals.org/content/28/3/278.full.pdf+html

Read Full Post »

Hi all ,

I get frequent comments about my blog. I do try to answer many of them . This is a very unique one , and it is making me think further.Since he has specifically wished his clinical data could be eye opener for others ,  I am jut posting it here . The comment was in response to my article  Who said coronary collateral circulation will not support exercise ?   here is  the extract

Dr. Venkatesan,

I read your blog with great interest and I think I may have something useful to contribute from my own personal experience. I am a 68 year old male with a long history of smoking (for fifty years), and a history of uncorrected hypertension over the years (it has been corrected to normal with medication for many years now). I am a non-smoker now for the past 18 months. I have PAD and a moderate aortic aneurysm of about 3.5CM (ascending and descending) which is being watched with regular vascular scans.
The common femoral arteries in both of my legs are nearly 100% occluded between my thighs and my knees, and yet my ankle and toe blood pressures (and my circulation in my ankles and feet) is almost normal. The reason for that is that according to the vascular scan, my deep femoral arteries are much larger caliber than normal with extensive vascular collateralization by passing the common femoral occlusions.
About twenty years ago before the PAD diagnosis, I realized that I had claudication in both of my calves when I walked a short distance. I expected this was being caused by an arterial blockage in my legs, so I went to the gym every day for about three years, and walked through the pain every day. I believe this contributed to the formation of the collaterals that have perhaps saved my legs and feet.
I also have heart disease, and had a fairly minor heart attack in 1999. No stents were placed nor angioplasty performed at that time. I recently had an arteriogram and cardiac stress MRI which showed that two of the three coronary arteries are now 100% occluded (apparently I had another cardiac event and did not know it). The cardiologist says that the LAD is in extremely good condition and has numerous collaterals branching from it. I have no symptoms whatever from all of this, except that my LVEF is low (about 35%). I walk at a very brisk pace six miles per day, five days per week, and I monitor my pulse rate with a pulse monitor when I walk. I keep my pulse between 115 and 120 which I calculate to be 80% of maximum for my age. I believe this cardio exercise / walking has also helped with the collateral formation, and I am hoping to bring the LVEF back up to a reasonable number with this exercise regimen.
My cardiologist has recommended an ICD, but I have decided against that since I have never had VT or VF or any other type of cardiac arrythmia (except for non-symptomatic PVC’s which I was born with).
I believe that I am the lucky recipient of good genetics to begin with, but also I am highly motivated now to take better care of myself, and know as much as I can about the conditions that I have. I plan to have an echocardiogram in six months to see if the LVEF numbers have improved, and I fully expect that they will have. I give credit to the smoking history for the vascular problems that I have including the cardiac problems. I am a lucky person I think, and suspect that not everyone has the fortunate ability to heal themselves the way I have.
I have asked for copies of my arteriogram and stress MRI records. If you are interested in looking at these I would be happy to share them with you.

The letter ends .

Dear Mr Weigel

Yours is an extremely interesting story  told in a most scientific manner.Thank you .

It gives me great insight  ,  how a  human vascular system  can  transform when confronted with  natural disasters like multiple blocks on its way .A flowing river will definitely reach its destination  however bizarre the path it takes . Human biology is vested with vast reserves of genetic building blocks put on sleep  mode. While billions of dollars are being pumped into do research in human angiogenesis we have tuned a  blind eye to the vast net work of natural collaterals.

Our clinical experiences also tell the same thing . In chronic total occlusion  majority of patients would develop good collaterals if only we do not  tamper  the  main vessel  .None of scientific studied available has proven opening CTOs (Chronic total occlusions) has improved the clinical outcome .

Regarding  the guidelines  for revascualrisation ,  I am yet to come across a standard scientific guidelines that includes the extent of collateral circulation  as one of the determinant for need for revascularisation !

I will definitely use your case study for the benefit of so many patients !  I always feel , a properly interpreted experience  , even from a  single patient   can make a tremendous impact in the growth of science .

Thanks again for sharing your personal health issues !

Dr Venkatesan
Chennai .India .

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Human coronary circulation stands  unique among  others as it is a   life-sustaining circulation.It is  considered   a great  medical achievement   to visualise   the right and left coronary artery  system by coronary angiogram.  Actually  what we see is   only  a  fraction   of  the surface area  of  coronary circulation . The surface area of  epicardial coronary arteries   constitutes  less than 5 % of entire coronary vascular tree .

This  is the reason  normal coronary angiogram can never mean normal  coronary circulation !

This huge gap in our perception is the single important factor  that  explains the vagaries  of modern coronary care .

This also  make any coronary  scenario  a  reality .

“A patient with normal coronary angiogram getting a myocardial infarction the next day and a severe triple vessel disease living comfortably with medical management”

So ,  it is essentially a   false  sense of  scientific accomplishment   by the  cardiac scientists  at  least in the  of coronary circulatory physiology.

There are innumerable channels of micro vessels traversing across the heart, sharing , bridging , branching, penetrating  and  perfusing the muscle mass.They can be anatomicaly patent , physiologically non patent .They can be recruited by hemodynamic stress . It is also influenzed by  favirable growth milleu and hormonal and neural stimuli.

What determines the extent of these invisible circulation ?

and

An in vitro heart with special catheters showing the true extent of coronary circulation: Courtesy http://eurheartj.oxfordjournals.org/content/28/3/278.full.pdf+html

Why many cardiologists   do not give due credit  the   coronary collateral  circulation  ?

Right from the days  of  Levine in 1970s( Who made a seminal contribution  about coronary collateral)  the  utility value of  coronary  collateral  circulation   was  never able to convince the cardiology professionals .

It has been our traditional  teaching ( without much evidence of course  !) coronary collateral circulation  is not effective to support blood flow during exercise . This fact has been  disproved  many times . Coronary collateral circulation was indeed useful in limiting damage in ACS and  relieve symptoms in stable angina.It helps  in reverse remodeling and provided electrical stabilty as well in post MI population.

Still  the concept  was  alienated  and   made   totally irrelevant  in the interventional  era  . Many   cardiologists  found well-developed collateral’s as an interference to their expertise and ego since it has a potential to alter the indication of PCI.They  continue to have  strong  scientific conviction (Pseudo ?)   that man made collaterals must always been superior to God made collaterals !

Whenever  some credible  reports emerge about  collateral circulation   being   equivalent to  revascularisation procedure , these concepts were  prematurely buried for some reason.

In the last decade there was a concern  about  performing  PCI in patients with well-developed collaterals  .The argument was , they tend to develop early stent occlusion and restenosis . It  was a genuine  query  raised by few thought leaders in the field as  collateralised vessels  suffer from  low flow states  after PCI ,   if the pre -existing collateral continue to function.

But then , few  studies countered this  , and   said PCI  is safe and  in fact may  fares well   in  patients  with  extensive collaterals .

In these  studies  interventionist’s  argument looked  amusing !  as they  seem to  define a  successful  PCI  as  not only to open the occluded vessel  but also  make sure to close  all functioning  collaterals  .(What a  a pity for our natural biological  angiogenic forces which had  worked  and  grown meticulously for months!)

Cardiac science in the current format,  makes   the future look  bleak for coronary a collateral circulation .With  early PCI  becoming a norm we will never ever allow the natural collaterals to  grow  ,  and even the  established collaterals  will have to face a stiff   fight  for survival  with  sophisticated coronary interventions .

Competing interest in the filed of  coronary collateral   research

While the basic scientists want  to  grow collaterals with angiogenesis ,  stem cells etc  interventionists   continue to  indulge in rampant angioplasties which  will suppress  collateral growth.

This implies we will struggle to  establish  the true  importance of  coronary collateral circulation .

Final message

Can it be an  effective form of revascularisation  ? 

My personal  inference  is   coronary collateral  circulation  “would and should”  have  a definite role  in at- least  some of the subsets  with chronic coronary  syndromes. If we think otherwise . . .    it’s against the principle of  natural biological science .

A good  collateral   system with optimal medical management  can save not only our  patient’s  lives but also  their hard earned currencies !

Reference

Here is a rare article in European heart   journal that discuses coronary collateral circulation  . Let us welcome such wonderful  reviews which keep the interest alive on the filed.

http://eurheartj.oxfordjournals.org/content/28/3/278.full.pdf+html

Read Full Post »

Thousands of  coronary angiograms are done every day. Cardiologist no longer get excited to see exotic coronary lesions .Still , some images can be striking and dramatic. Here is an angiogram from a middle aged man  with stable angina  , who was  one among the routine early morning diagnostic studies  in our cath lab.

Who chopped the neck of this LAD ?

How this man was able to fill up the distal LAD almost completely? (With a complete cut off  right in the neck of LAD )

Are you sure there is antegrade flow ?

Do you get any clue ?

  • Can a trickle of  ante grade flow  sustain  a  TIMI 3 FLOW  ?
  • Or is it a  very efficient  instant collaterals  from LCX ?

Yes . The first one is right . An almost invisible antegrade channel  doing a exemplary job !

How is it possible ?

Realize an important fact . The distal flow beyond an obstruction  is not primarily dependent on degree of obstruction but the status of the distal vascular  bed .  If it is normal  even a hair-line patency  can  profusely perfuse the distal myocardial segment. This is what is happening to this man with a stable angina and perfectly normal micro vascular bed.

Lessens  from this Image.

Do not get fooled by the lay man’s logic. Realise there is  no simple relation  between  the degree of obstruction and degree of  blood flow impediment.It can be linear , curvilinear , or even inverse depending upon   the evolution and timing of obstruction  ,  number of lesions , presence or absence of collateral support , finally and  most importantly  the integrity of microvascular bed .

The  distal vascular bed drops its resistance drastically  once it senses  the problem in  proximal segment . This is based on Bernoulli principle and  is akin to how a  garden hose pipe  can simply increase  the velocity  by tightening the nozzle.*


* The garden hose analogy is a gross simplification of   complex factors that determine coronary blood flow.But it effectively clarifies a point ie  coronary blood flow is least dependent on coronary  stenosis (until  very late stages)

**Note further : This  hemodynamic  principle may not apply in acute occlusion as in STEMI  , where   acute  obstruction  often has a linear relationship with the quantum of blood flow.

By the way what happened to the above patient ?

Since he had significant angina there were no debates regarding management.  He  is posted for elective PCI this week-end .(We  can’t  get a stent just like that unless it is a real emergency  .Ours is a  Govt hospital !)

What is your take . Is it a going to be tough cross ?

I feel so , but my colleague Dr Gnanavelu   strongly  differs !

Let me post  our experience during PCI shortly.

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Coronary collateral circulation can be termed as one of the  mysterious  circulation in our body.Cardiologists generally do not  give much importance to it and some interventionists even ridicule it !  . But  ,  God has given it ,  with  a purpose. He adds a riddle though !  .Collaterals  grow  in  almost  every  individual  when   obstruction occurs gradually ( chronic coronary syndrome ) but only in  a few ,  it  will open up  during a real emergency like ACS !

How and why , only  few of us can  recruit  coronary collaterals   during   acute occlusion ?

God  blesses acute coronary collaterals only in selected few  , who  are on the right side of his good books .This can be  the other name for our  destiny !

Role of coronary collateral circulation  in acute coronary syndrome.

  • Limits  infarct size and volume
  • Promotes salvage
  • Converts q  MI to non q  MI
  • Prevents Unstable angina from becoming MI
  • Prevent primary VT and VF*

All  of the above can be vital  in saving a life  . Even as  we realise 30 % of STEMI do not even reach hospital  , it seems certain men and women with early collateral recruitment  will never  fail to reach the hospital alive

Is there a simple  method to identify  people who are blessed with acutely recruitable   collaterlas ?

I am afraid it is  almost equal to  asking   for a glimpse of GOD   !

Wait . . .  when we were on cath lab  few  days ago a  stunning  phenomenon happened  that could pave way for identifying  potential acute  collaterals  in any human being.  Follow this site  . . .the details will be posted !

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  • Coronary collateral circulation continues to be a poorly understood phenomenon.
  • It reduces the impact  of ischemia , salvage myocardium, keep it viable, and  can  even  be  life saving during a STEMI
  • It can support either the same coronary artery  or the contra lateral coronary artery (Like the above patient )
  • The usefulness of  collaterals  at times of exertion is controversial .Most interventionists do not believe in  it . (Facts are opposite of course !)
  • Bridging coronary  arterial collateral often indicate hardened total occlusion and success of  PCI is reduced

Here is  the  angiogram  which shows classical intra coronary bridging  collaterals.



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Coronary collateral circulation is probably the most poorly understood circulation than any other.This  is ignorance at it’s best ,  in spite of the life saving potential  of this circulation. A popular  (mis )perception is  coronary collaterals  can support only  resting blood flow and it would  struggle  to compensate at times of exertion. This is based on few case studies and not based on large , authentic scientific data.

Does this reasoning mean  , coronary  collaterals   can never / ever be complete  ?

If we believe so   . . .we are grossly underestimating the power of  nature .(In fact , mankind  was humiliated by the nature  time and again !)

Lessons  from  a unique patient we have  encountered.

Here is an example of total LAD/LCX  occlusion with good collateral  from  RCA. He was having  stable  angina on medical  management . This patient  was not only  asymptomatic and was also negative for exercise  stress test at moderate work load .

 

 

 

 

 

 

 

 

 

 

 

There was an  intense debate about the management  when this angiogram was presented in the cath meeting .


 

 

 

 

 

 

 

 

 

 

  • Most of the cardiologists believed so !  But they had no answers why his stress test was negative.
  • The other argument for CABG was one can not allow a patient with a functionally single coronary  artery (RCA) However good is the collateral circulation.This at least  has some logic. not the first one !
  • One more suggestion was to quantitate  and map the real extent of ischemia by PET scanning and then decide about revascularisation.
  • One critical opinion was , since he was doing well with medical management what was the need to do coronary  angiogram at all ?

Any answers  . . .

He  ultimately went on to receive CABG (By popular opinion ) , but the point here is the collaterals were  good enough to support exertion.We have  documented quiet a few similar patients with collateral circulation supporting exercise.

What  happened to the collaterals  and (of course ) the patient after surgery ?

I will post you the  curious story soon   . . .

Final message

Coronary  collateral circulation , if well developed  can provide hemo-dynamically useful support even at times of exertion *

* The existing literature  is  biased against this concept. It generalizes all grades of collaterals into a single   entity. It is better  if we  spend more time to understand the nuances of coronary collateral circulation .

This is the  message from our observation. Do not ever believe whatever is published as facts in scientific literature. Observe, analyse , create your own inference ,  and concepts. Mainstream cardiologists would brand it unscientific  , Simply ignore it . Many times it is rewarding  to our patients.

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