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Archive for November, 2010

Classification of myocardial scars : Is it possible ?

Posted in Cardiology - Electrophysiology -Pacemaker, Uncategorized, tagged , , , , , , , on November 29, 2010| 1 Comment »

Myocardial scars remain forever ! It forms the focus for many chronic  ventricular tachycardias following MI. A healed scar is not often benign . It blocks the electrical wavelets and deflects into multiple directions some of them may reenter and form re-entrant VT .

This scar fascinated  one man from Holland -De Bakker . . . his quest for myocardial  scars produced this excellent paper .

No one  can do  such a meticulous work  today !

He did a extraordinary  study with the scarred  papillary muscle of infarcted myocardium . It included stunning histo-pathological analysis .He found for the first time , how the scar  even though mechanically idle conducts in multiple directions that precipitate the arrhythmias

 

We need to classify myocardial scar for understanding better the VT circuits. The newer imaging like Carto system can help us in imaging the ventricular scars.

 

A rough approach for myocardial scar classification could be .

Location

  • Epicardial
  • Endocardial
  • Transmural

Combined

  • Predominantly endocardial
  • Predominately epicardial

Septal scars

Anterior

Apical

Posterior scars

*With or with out Pap Muscle

Based on thickness and volume**

Small< 2CC  >5CC

Intermediate up to 10cc

Large >20cc

**Scar volume

Based on electro-physiological properties

  • Inert
  • Inducible
  • Spontaneous with clinical VT

Based on Metabolic activity

PET matched

Mismatched

Scars with reference to vascularity

  • Vascularised scars
  • Avascular scars
  • Revascularised scars

Further modification of the scheme by the readers are welcome

 

Clinical implication of scars apart from arrhythmias ?

CRT lead positioning

 

 

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What is right for left coronary artery could be wrong for “Right” !

Posted in Cardiology -Interventional -PCI, Cardiology -unresolved questions, Hemodynamics, Infrequently asked questions in cardiology (iFAQs), Uncategorized, tagged , , , on November 27, 2010| Leave a Comment »

Coronary circulation is an enigma . This is true even after 50 years of coronary angiography.  What we visualise  in CAG is  only a  fraction ,  when  compared with what we do not see !  The intricacies of  coronary collateral circulation and micro circulation is comparable only to the  ultimate force of   invisibility “The  God ”

But , we will never ever believe what we do not see  . . .  but we have to accept the following  fact . How is it possible   for  some of the coronary  arteries  to maintain  a near normal blood flow from a donor (Contralateral ) coronary  artery  in spite of  100 % occlusion ?  Is it not common to see TIMI 3 flow even with 99 % occlusion .(Link to related article in  this blog  and  video ) . This is because the coronary  vascular bed has an extraordinary capacity to drop its distal pressure to negate the effects of obstruction.

Does the distal vascular bed anatomy and physiology same in RCA and LCA ?

We presume it so . The problem in medical science  is , these   presumptions  often  become  facts in due course  ! Now we have (It is in fact 30 years old !) RCA has lesser ability to withstand the stress  of stenosis than LCA.

The prime reason for this observed difference could be the LCA has a well developed microvascular bed which can reduce the distal coronary resistance .(Again , this is my  presumption  . . . !!! )

This interesting article was published in Circulation 1980 .



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Lesser known cardiology journals : “Heart view” – A treasure from Qatar !

Posted in cardiology journals, Great websites in cardiology, Uncategorized, tagged , , , , , , on November 27, 2010| Leave a Comment »

Great people  do not boast  . While there are thousands of hyped up publications in cardiology ,

This one form Qatar excels , which  I  stumbled upon recently  contains very useful information about wide ranging issues in cardiology .

Let us congratulate the   Hamad medical corporation for  their unique  academic vision  .

http://www.hmc.org.qa/hmc/heartviews/ARCHIVES/ARCHIVES.HTM

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Medical Kick backs : Watch dogs are sleeping and they are unlikely to be awakened !

Posted in Uncategorized on November 24, 2010| Leave a Comment »

That was a slightly  modified title of an article published by the renowned Nephrologist from India Dr.M.K.Mani

Who is also involved in the fight against live kidney bazaar  in India.

In this article he shares  his experience  ,  how   desperately he is  trying to correct a major conflict in physician laboratory nexus in India . It is has been an  elusive search for  the past 15 years.

And  the article  seems to the conclude  , there is no other option   , we (And our patients )  have to live with it .

But , what we need to realize is  we have our own  watch dogs lie within our mind , and it need to bark every time a thief is seen .

Let us awake our self for the benefit of our patient kind .

By the way , how many  among us know such an important journal is published from India !

http://www.issuesinmedicalethics.org/044ed105.html

Further reading

No doubt ,  such kick backs and gifts and ads make medical care artificially high and unaffordable.

The pathetic stories of how modern medical care create new breed of  poverty.

the poor can not get even the basic  treatment because they are poor  , while  the rich get costly and  inappropriate  some times dangerous treatment and become poor .

Link to The WHO article that exposes the Issue

I know there is  a book written by Dr M.K Mani ,  Yamarj’s Brother

I have not read it .I wish i get it soon .That Iam sure will enlighten us

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One small mistake in cath lab . . . A giant leap for man kind !

Posted in Cardiology -Interventional -PCI, history of cardiology, tagged , , , , , , , , , , , , on November 21, 2010| 1 Comment »

In any field  , errors and mistakes  transform into   experience in retrospect. (Of course only  if we  realize  our mistakes !) . Many would argue prevention of such errors is the  only way to move  forward in science  , but ,the opposite could also be true.

In Medicine ,

  • Most errors are mild ,
  • Some errors  can   be fatal but it helps us prevent further fatalities.
  • Some errors create history  and  re-define the science.

That’s   what  happened on 1958 , to be precise on  October  3oth , 1958  in a lonely laboratory of Henry  Ford hospital/Cleveland clinic *

*A correction -This  invention actually happened in Cleveland.  ( Sones learnt  all his techniques in Henry ford)

When  Sones along  with his assistant were trying  to do an  Aortogram in a patient with RHD,  the entire dye meant for aorta went straight  into  the right coronary artery.When every one was stunned ,the  patient happily  survived the injection  with a few skipped beats.

The man behind  this horrendous medical mistake was   Mr . Sones . He   was guilty for many days ,  spent many sleepless nights  ( In spite of  the patient surviving  the episode ). In fact , he was much amused  about the patient’s  survival . At that point of time,  even a spill over of dye into coronary artery was considered forbidden.  He pondered over the incident for months  .

Had  two queries  lingering in his mind .

  1. How the  right coronary artery  was able to withstand the 40cc dye  injected with  force .
  2. If 40 m l was tolerated ,  well what about routinely injecting  3-5 ml for visualizing the coronary  tree   by intentionally  seeking the coronary ostium .

That was the moment , the concept of diagnostic coronary  angiogram  was born . He published his observation as an  abstract in Circulation journal. Later he did many experiments  with video  engineering at Kodak labs , X  ray  technology to improve the cine imaging .By 1964 , he devised a perfect protocol  for doing  selective coronary angiogram. Then along with Rene Favaloro he pioneered CABG surgery in USA.

Final message

Cardiac  catheterisation was invented by  Forssman , Cournand , and Richards ,(Nobel prize 1956 ). It was  Sones who took it into the coronary arteries  and thus it was  made possible  for a whole new specialty  of coronary  diagnostics  and therapeutic PCI  which was  conceptualized by another extraordinary human life called   Gruentzig. Sones along with Gruentzig definitely deserve a Nobel in medicine which i think will happen soon ! They lived a great life constantly thinking, innovating  putting  patients interest in the fore front .

Mean while , I argue our youngsters  to  portray  the images of  these giants in  every   cath lab they  work   .You may get their blessings from heaven  , provided you do your interventions with integrity and honesty without any conflict of interest in the patient care.

Do not cry foul when some genuine errors happen in cath lab.Few among us (like Sones ) may innovate those mistakes into glory !

Reference

http://en.wikipedia.org/wiki/F._Mason_Sones#cite_note-3

http://www.wired.com/thisdayintech/2009/10/1030first-coronary-angiogram/

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Best review articles on pregnancy and perioperative anticoagulation

Posted in cardiac drugs, Cardiology -unresolved questions, tagged , , , , , , , on November 17, 2010| 1 Comment »

This one is from Cleveland clinic in their CCJM 2009.  It answers all those tricky questions when we plan   anti – coagulation in  pregnant women .

  • Should heparin substitution/bridge   always necessary  during  pregnancy  ?
  • When is warfarin safe  pregnancy ?
  • Simple  cessation of warfarin around  the time of labor and resuming  it after delivery  (Without heparin  substitution  )  Is it an option ?
  • How safe is LMWH in pregnancy ?

 

The ultimate reference article 
on peri-operative anticoagulation

 

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Anticoagulation protocol in pregnancy with prosthetic valve

Posted in cardiac drugs, Cardiology - Clinical, Uncategorized, tagged , , , on November 16, 2010| Leave a Comment »

A simplified animation strictly  meant  for understanding the concept

Link to the review article on the topic

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My favorite medical quote . . . from Sir William osler

Posted in medical quotes, tagged , , , on November 14, 2010| Leave a Comment »

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Bi-phasic DC shocks : It is different !

Posted in Cardiology - Electrophysiology -Pacemaker, cardiology -ECG, Uncategorized, tagged , , , , , , , , , on November 14, 2010| 1 Comment »

No one would have believed a century ago when electricity was first dosvovered  for the mankind by Benjamin Franklin  with glorious  purpose , would now  be used as a drug for treating  life threatening heart ailments  !

Yes , electricity is a drug by definition.

It is administered percutaneously  by focusing  a beam  of current into the heart.

  • There is a dose , shape , energy  and direction for this drug.
  • Paddle size determine the energy.
  • Paddle location determine the direction of  current vector.
  • Dose is selected by the  physician.

Mechanism of DC shock / Defibrillation *

When  heart suddenly behaves abnormally  and start generating its own electricity and sends it through abnormal channels other than its natural paths ,  it becomes a dangerous arrhythmia .This propagation of wave front can occur in multiple directions  in a chaotic manner , resulting in VT/VF and imminent death.

Like an air to air missile ,this  abnormal wave front  can  be tackled only by an another electrical  wave front . Nothing else will work.

* The difference between DC shock  and defibrillation is only technical. If one gives a  synchronised shock  ( with qrs complex ) it becomes  DC shock .If not ,  it is defibrillation

The success of defibrillation depends on many factors .

The following are most important.

  • The critical myocardial mass must be depolarized by the current delivered.Sufficient  amount  of sodium channels /less  of calcium  currents  need be activated for this to happen .(JACC 2008)
  • The direction  and the angle  of current entry with reference to  advancing  end of abnormal wave front. is also  important .
  • Distance between the paddles.(Antero posterior paddles more effective than Apex /Sternal pads )
  • Energy level (seems to be less important ! )

Two shock forms are used

  • Monophasic shocks
  • Biphasic shocks

A biphasic DC shock has  replaced the traditional mono phasic  sine wave  shocks in most machines.

What is  the  fundamental difference between the two  ?

  • In bi phasic  shocks , the current traverses the myocardium twice .
  • So, it has a second chance to interrupt the critical tachycardia  circuit , if the first one fails. In other words, biphasic shocks are  technically equivalent  to  “two  sequential low energy shocks”  delivered in opposite polarity . This change in direction happens in micro seconds .
  • The shape of biphasic DC current  wave form can be a truncated  sine wave or square wave .The maximum  energy of DC shock in biphasic mode  is  200 joules (In Monophasic it is  360joules) . All AEDs, ICDs, now use bi phasic shocks to conserve energy .

Final message

A biphasic shock waveform has a proven advantage . It has  greater efficacy ( because it traverses the heart twice ) , requires fewer shocks  with low  delivered energy and hence  less myocardial  and  dermal injury.

References

Even though there is general  acceptance of superiority of bi phasic  shocks ,  it is still considered by some ,  that there is no great difference in the  overall outcome .

http://content.onlinejacc.org/cgi/reprint/52/10/828.pdf?ijkey=5a8f50ff2542182c857d4f3fe553aef8df6e3fd3

http://circ.ahajournals.org/cgi/content/full/94/10/2507

Bi phasic shocks in atrial fibrillation

http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1768486/

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Cardiovascular engineering : A journal for the new generation cardiologists !

Posted in cardiology journal club, cardiology journals, tagged , , on November 13, 2010| Leave a Comment »

It is often said medical   professionals lack engineering sense and vice versa. The filed of bio medical  engineering is is not  a new one . It is  there for over 50 years .The gap is narrowing very fast.

We are in the era of developing hybrid imaging , where a PET and CT come together. Raman spectroscopy is sending live  images of tissue histology from the coronary arteries .

A  journal exclusively catering to the cardiovascular enginnering is new development . Let us thank to the unique initiative from Purdue university .

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