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Archive for the ‘cardiology -congenital heart disease’ Category

Most  cardiologists  are familiar with  “Circulation” . We know  it  is a top  cardiology  journal with highest impact factor.  Few of us are  aware  of  a journal called  “Circulation  research” ( I wonder  why it is named  like that ,  as if  the regular   circulation journal  does  not carry research stuff  !)

It is one of the  path breaking   journals that regularly  churn out state  of  the art , often  mind  boggling research stuff.  Once in while we should get a feel of  basic science  research  as it  happens.

How else we are going to know an  atrial cell is to be bio engineered  shortly to behave like a  SA node  in patients with sinus node dysfunction. (Biological pacing )

This team from academic  medical  centre Amsterdam   should be credited   for  publishing   this gem of  an  article   from  a  study  involving the  measly mice !

It  deals elaborately  about the embryonic basis of AV nodal  disorders  . Specifically it  explains  the genesis of  WPW syndrome and how AV rings get muscularised  .

(It  is  due to   error in  bio-genetic forces ,which  affect the    incorporation  of AV nodal tissue  in the  fibrous  skeleton .This   results  in ectopic  junctional  tissues appear   any where along  the AV ring . This is the basis of  accessory AV pathway and   clinical  re-excitation.)

Final message

Once in a while  we should develop the habit of reading  tough  journals  like circulation research . After all ,   if a cardiologist  is not reading   these stuff who else  . . . will  ?

Reference

http://circres.ahajournals.org/content/107/6/728.full.pdf+html

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Before answering the above question ,  there need to be a correction to the question itself . PDA is persistence of ductus arteriosus . In pulmonary atresia ductus itself is not formed .So  the question should  ideally be  Why  ductus  is absent in pulmonary atresia  with VSD  !

Ductus  is formed from the dorsal portion of left 6th arch  .The sixth arch also gives raise to  right and left pulmonary artery.This can happen only if everything from aortic arch and pulmonary artery development is normal

Ductus  has to connect aorta with left pulmonary artery  , when pulmonary artery itself is  poorly developed or not developed   how can the  ductus  connect to  LPA ?

Pulmonary atresia is essentially a defect in the development of pulmonary arterial tree (Please note pulmonary valve and  MPA  is formed  from different  structures in different times and it  would  get  docked  with developing LPA,RPA  and  subsequently to the rest of the  pulmonary tree .)

In fact , one of the terminologies used for pulmonary atresia with VSD  is ,  total anomalous pulmonary arterial connection(TAPAC)  .In fetal    life,   blood flow in ductus is from RV  to  pulmonary artery  and then to  descending aorta  through the  ductus . When RV is disconnected with pulmonary artery( Rather there is no pulmonary artery )  ductus can not be  formed  for  both anatomical and physiological reasons . Some consider the  left 6th arch  in these patients  would become  a poorly   identifiable  minor Aorto pulmonary channel .

A Link to  3D vedio  of aortopulmonary collateral

Embryology of major aorto pulmonary collaterals.

  • The lung perfusion in patients with pulmonary atresia is important only after birth,  as fetal  lung is largely non functional.
  • In patients with pulmonary atresia with  intact IVS this becomes  critical and  usually death ensues unless intervened.
  • If VSD is present it allows the baby to survive as the  lung gets perfused by major or minor aortopulmonary collaterals.
  • These collaterals can range between extensive and   sparse.  Hence the  symptoms can  also vary from volume overload  /cardiac failure to  severe oiligemia  and recurrent  hypoxic spells.*

MAPCOS ,  if present can connect directly the aorta  to  hilar pulmonary artery or indirectly  from the branches of  aorta (subclavian /LIMA/RIMA etc) . These arteries  supply  with or without  a central confluence . It may enter the lung through the hilum or  away from hilum .The MAPCOS can be located anywhere from the arch of aorta to descending thoracic aorta.It is very rare in the ascending Aorta .

There is also  strong argument for MAPCOS are  nothing but dilated bronchial arteries.(Link to Full text )

*The  natural history  directly depends  on  extent of aorto pulmonary collaterals and its anatomical patency .

Final message

Embryologically   both  the  major  arteries of thorax  Aorta and Pulmonary artery have  the  same parent structure namely the dorsal aorta and its six  arches.Hence there  is no surprise  ,  when these embryological  divisions and fusions   goes awry ,   pulmonary artery fails to get  carved out from  the dorsal aorta  in the normal fashion .The randomly formed pulmonary  arteries continue  to have link  with   the parent -dorsal aorta .These are manifested in various ways as major aorto pulmonary collaterals .

(It is to be noted  in pulmonary atresia  , VSD is an offshoot developmental defect  . Embryologically  VSD   is not linked to the primary defect of pulmonary artery development . This is the reason many would consider   PA with VSD as a  distinct entity with that of TOF (Which is a cono truncal anomaly) This also explains the lack of MAPCOS in true TOF .

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 Inter atrial septum(IAS)  is a delicate structure , formed by a  “curious IAS  embryological process”  , when  two septums ,  two ostiums  cross each  other .They  fold  and unfold  like  curtains  in different times ,  ultimately result in a  single membrane separating LA and RA  with a  central physiological   hollowness called foramen  ovale .

All along this process ,  blood has to shunt  from  RA to LA  untill the baby comes out ,  when the direction reverses that  result in the flap  of foramen ovale locking  against the septum secundum with raising LA pressure . So , basically the genesis of  IAS is all  about growing,   resorbing  and  sticking of two septums . This starts in utero and continues well after birth. One can imagine  complexity of  the factors that determine the thickness of IAS.

The IAS thickness varies between 2mm to 4  mm . With increasing use of trans esophageal echocardiography and also the need for cardiologists to puncture the IAS , it is becoming important to study the anatomy of IAS in detail.

A new  cause of  thickened IAS  is reported recently .

 This is refered to as Double Inter atrial septum,  fused like a sandwich  with a  potential space  in between  .

The embryological basis is not clear. (A septum primum and secundum fusion ?)

The PFO   is an  oblique orifice in many .It is some times refered to as tubular PFO . A large tubular PFO can mimic a double IAS.

An  aneurysm of IAS  may get  fused to appear like a double septum

or Is it  IAS dissection which  give an appearance like double IAS ?

Personal perspective

  • It is very difficult to embryologically  explain the concept of double IAS .  I would think  , it is  double layer  of single embryological  septum   with a  potential  space  in between .
  • It is possible an intra mural hematoma (Spontaneous or acquired ) may cleave the septal plane and mimic a double IAS   when the   thrombus gets dissolved later.

Other causes of thick IAS

Septal thickness an issue during transeptal puncture . During PTMC and left heart catheterization a thick septum may be a hurdle.

Infiltrative  myopathies especially amyloidosis is known for a very thick non -puncturable IAS  

Reference

1.http://ejechocard.oxfordjournals.org/content/9/5/707.full

2. http://www.ncbi.nlm.nih.gov/pubmed/16950474?dopt=Abstract

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Patent foramen ovale (PFO) is the new generation hole in the heart for  21st century  cardiologist. Present in about 20% of population  , would correspond to 140 crore  “man holes”  as  on  2012   in this planet. PFOs are embryological remnants across the inter atrial septum.

These minute  holes measuring few mm  are largely a  benign finding .In the recent  decades , it is being increasingly debated these holes  may  not  be innocent after all .Extensive  use of echocardiography in recent times   has contributed to  the awareness  as well as anxiety.

Evidence  is mounting  linking PFO to

  • Migraine,
  • Stroke and
  • Peripheral embolism.

While the above   observation may be true  ,  the  fact that >100 crore people have this entity   , raises  a serious question ,  as labeling  all of  them as heart disease will create chaos among the already health obsessed   population .

So , the main purpose should be ,  to identify the high risk subsets* of PFO population .(This will be a <5 %  at the most). People with PFO may  carry  a mental  stigma because it is referred to as a hole in  the heart by the  general  public .For many  the sense of living with a hole in heart is often more damaging than the hole itself ! (Incidentally , many develop  migraine only after reporting about this hole !)In a strict sense  PFO  is not a hole , rather  it is a communication it may be tunnel  or  slit like .It is argued physician should avoid calling PFO as a hole .

*What is a significant PFO ?

  • Large PFOs >5mm
  • PFOs that shunt blood
  • PFOs with septal aneurysms
  • PFOs with documented stroke or embolism
  • PFOs with atrial chiary network
  • PFO in  persons with systemic pro-coagulant states (Except probably in  pregnancy )

Final message 

PFO is a common residual congenital  atrial septal  anomaly . Usually  benign  . One can  live with it perfect harmony. Only occasional patients  are  at risk.

So the prime job of cardiologists is to not diagnose and create panic about  this entity. rather reassure  them (Is it better do not reveal to them if it is found incidentally ? Patient empowerment group would call  this a  foul !  I do not support blind empowerment  )

At the same time our main  aim is to identify the  high  risk subsets who are prone for events.

Closure of   PFO with device is required in a fraction . (*By the way ,  if   PFO is really dangerous ,  why It is never an indication for surgical closure ?  )

Reference

Your  search for best information  on PFO  would end here .  Here is  land mark   article  in JACC  by  Hara   also contributed by  Renu Virmani . A US  Japan  combines initiative  : A must read by every cardiologists

http://content.onlinejacc.org/cgi/reprint/46/9/1768.pdf

http://www.anesthesia-analgesia.org/content/93/5/1137.full

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Management of  severe  pulmonary hypertension continues to be a difficult task .Medical therapy is not definitive, in-spite of the new prostocyclins, endothelin antagonists and  sildenafil analogues.Natural history  depends mainly on  the presence of  any treatable cause ( Especially ,connective tissue disorders)  ,  supportive management along with anticoagulation.

Ultimate  strategy  would involve a   plan  for a “Lung “or  “Heart -Lung”transplantation  , if feasible. Last decade saw an innovative modality of creating an  artificial inter atrial  shunt to decompress the right heart .This had varied response in the  real world  , still  most  showed some benefit .In fact , in 1998 the world symposium on PHT ,  formulated guidelines for BAS (Balloon atrial septostomy)

Principle of  Balloon atrial septostomy (BAS)  and mechanism of benefit

The symptomatology  of  pulmonary HT  is largely  determined by mean RA pressure .

Puncturing  the  IAS and diverting blood  flow into left atrium would decompress the RA ( or even the RV )  and reduce the Mean RAP.

The resultant  right to left to shunt  can   increase the cardiac output  only  slightly ,  still  good enough to  provide   relief from the fatigue.(Though at the cost of  desaturation.)

What is the risk involved in the BAS.

Procedural risk of  a cath study in a sick  patient with hypertensive lungs (Can be really high !)

In some patients  even a small  fall in systemic  oxygen saturation can be counter productive.

What is the balloon used ?

Mansfield or Tyshak balloons are good choices .

Balloon diameters are between 5 -14 mm

Technique

Involves standard Brockenborough needle /Mullin sheath /Guide wire in pulmonary vein.

Atrial anatomy to  be well  analysed prior to BAS  . (Please note even though it is similar to PTMC , anatomically we encounter a large right atrium rather than left atrium .)

Fluroscopy with  TEE guide optimal

Pulmonary angiogram might help.

Intra-cardiac  Echo may be  ideal.

Blade septostomy may be preferred if hardware is available

The endpoint of procedure

  • Size of ASD > 5mm
  • Fall of arterial saturation < 80 %
  • Sustained atrial fibrillation with hypotension
  • Any  disabling complication

Hemodynamic impact

  • Cardiac output increase by 750 ml to 1 liter
  • It is expected ,  RA  mean pressure  would fall at least 5mmhg from  the baseline value.
  • PA pressure , no significant impact expected.
  • Tricuspid regurgitation regresses.
  • RA,RV size marginal reduction observed.

Follow up and outcome

  1. Greatest  relief is from syncope.
  2. Functional class improvement  in >50% .
  3. One year survival benefit is substantial (75-90%)  .Beats the  natural history (40%) convincingly.
  4. Late deterioration  can occur as ASD gets closed in few.

When  BAS is contraindicated ?

  1. Critical RV failure
  2. Patient in class 4
  3. Mean RA pressure > 20mmhg
  4. Pulmonary vascular resistance index> 55 Wood units / sq.meter

* BAV should not be considered as a  live saving  procedure  in any dying patient with PAH.  It needs to be  selected early and carefully .In fact,  the very high procedural complication  rate is related to late selection of patients.

Natural foramen  PFO better than BAV ?

We do not know yet.It is highly possible  natural opening up of PFO is good thing to happen for patients with severe pulmonary hypertension.

Reference

1 . SS Kothari  et all  Indian heart journal 2002

2. http://content.onlinejacc.org/cgi/reprint/32/2/297.pdf

3. http://www.ncbi.nlm.nih.gov/pmc/articles/PMC484602/pdf/heart00028-0066.pdf

  4. http://erj.ersjournals.com/content/early/2011/02/24/09031936.00072210.abstract

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Myocardial infarction is the self-inflicted ,  modern-day death sentence  especially  among the  young generation who are   addicted to the affluent life style .

We know the  cardio vascular events  are  precipitated  due to a  sudden trigger in those  people  who have a base line risk profile. The major  risk factors are ,

  • Diabetes
  • Smoking
  • Hyperlipidemia
  • Hyper tension
  • Obesity

When one or more of the above factors   progress unabated he or she is at high risk for acute coronary event .

Is that a fatal stock market rhythm !

A loaded gun  needs a trigger to fire  , similarly  in a vulnerable patient (Plaque )  any of the following can act as a  trigger to precipitate an MI.

  • Hemodynamic stress (Fall or raise of BP )
  • Any  systemic illness( fever etc)
  • Physical stress
  • Mental stress , any strong surge of  emotion (Negative or positive)*
  • Non cardiac surgery

*Anger, fear , euphoria , guilt , bereavement ,

Now there is evidence pouring in  ,   natural calamities (  perceived fear of death) can  act as trigger  for MI.

We have reports  of  excess cardiac events   following  . . .

  • Earth quakes
  • Terrorist attacks
  • Flight scares

Any events which can release  sudden pulse of adrenaline into the plaques can trigger an acute coronary event.

Now,  this study from Shangai ,  documents how the coronary events dance to the tunes of stock market movements in the financial capital of  China .

http://eurheartj.oxfordjournals.org/content/32/8/1006.abstract

Final message

Chaos theory states no two events are isolated in this world  !   When stock market swings it can  pull down your heart too .

be cautious !

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The link between migraine and PFO is  . . .

  1. Incidental  & man-made
  2. Almost certain
  3. Definite
  4. A wild imagination

Answer : One of the above  is correct  , but  we do not know  which one is   !

There has been many  patients with TIAs , cryptogenic strokes , who  had  documented PFO  ,complain of prolonged  head aches . This was the beginning of suspicion of PFO as a cause for migraine .Then the device industry foresaw a huge opportunity . Things began to unfold and  the concept is currently as nebulous as it can be .

Mechanism of migraine in PFO

(All are  presumptions )

  • Right to left shunting of  vasoactive amines from venous circulation (Serrotonin)   which bye- passes  the lung where they are supposed to get filtered.
  • Venous micro emboli (Antiplatelet agents reduce migraine as well as TIA ! )
  • Hypoxia transient – cerebro vascular hypersensitivity
  • Atrial naturetic  peptide spills more into systemic circulation through  PFO

Counter arguments

  • If right to left shunting is causing the migraine , why it  is not fully disappearing even after closure of  PFO (MIST data with  starflex  device ,  migraine persisted in a significant chunk !)
  • What is the incidence of migraine in the  prototype  right to left to shunt situations like TOF, Eisenmenger , pulmonary AV fistula ?  if shunting is the mechanism , logically  migraine incidence  should be very high  in this population , but it is not .
  • Migraine occurs in 10 % of population, PFO  is present in 20%  .  What are  the chances of over lap ?  It could be the simple statistics at play !

Where is the evidence  ?  The mystery called MIST study.

This study , done in UK generated more controversy , which  it was supposed to remove  . Still  this  study is considered to be a major evidence for the link between PFO and migraine . Star flex device  was promoted by NMT medical Boston .

http://www.medscape.com/viewarticle/541260

Link to  best review article on PFO

http://chestjournal.chestpubs.org/content/130/3/896.full.pdf+html

Final message

The link between migraine and PFO can be a fact or myth depending upon our belief in current  methods of  research in  science. The issue is  debatable . Of course ,  one issue is probably  closed  forever  , even  if they  are  linked casually (or seriously )  device closure can  never be a  sensible treatment  option for migraine ! *

We  expect a  proof / disproof  in this   mysterious migraine -PFO  hypothesis very  shortly.  Of course , many  cardiologists  already  have their  own conclusions !

 

*Please note , PFO  device closure  for  stroke in young is a different story

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