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Archive for the ‘cardiology -congenital heart disease’ Category

In L TGV  ventricles are Inverted . Since , coronary  arteries go with  the respective ventricle  , LAD originates from Right sinus , and RCA arises from Left sinus . (Complex anomalies  in origin, course still possible )  LAD supplies   venous ventricle . RCA  supplies systemic ventricle .

The most surprising Irony is that major epicardial  branches run in their respective grooves in the bulk of the patients with L TGV .The LAD runs  in anterior interventricular  groove and LCX in left AV groove etc. (That’s real  power of nature , these epicardial branches home in to their grooves even in the midst of bizarre AV and VA connection !)

Here is the the ultimate reference  article ;  A  study from 255 hearts with C TGV . I wonder ,  we will  never  get a study like this ! 

coronary anatomy in corrected transpostion og great arteries ltga c tgv Ltgv annals of thoracic surgery 1994

Questions to ponder

  1. Is RCA  blood flow adequate to support systemic ventricle ?
  2. If this RCA is a non dominant  one what happens to this ventricular function ?

Implication in surgery

Progressive RV dysfunction is a major determiant of long term outcome . Unless we do an arterial switch  diverting respective ventricular flow  it  is not going to help much in the long term

coronary anatomy in corrected transpostion og great arteries ltga c tgv Ltgv 2
Link to full text article

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ASD is  the most common acyanotic heart disease  with  left to right shunt . Highest qp/qs  are  seen  with ASDs

The shunt  begins  from left  atrium  and goes on to complete a circuit.

LA——-ASD———RA————RV———-PA———-PVs———LA

In this circuit all chambers  enlarge except the LA . (Inspite of the fact about 200-300 % cardiac output traverses this chamber )

Why ?

Post -test

The most popular answer in the above poll  is LA is  a transit chamber .

If it is so . . .  RA is equally  a transit chamber ,  why it enlarges significantly ?

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When I asked this seemingly simple  question to my cardiology fellows , I found they struggled  to come out with a proper  answer .I hope this will  make the  issue simpler .

Why the onset of PAH in VSD is early and late in ASD ?

Though number of factors are involved in the genesis of PAH , the single important reason  is  behavior of pulmonary circulation  especially the pulmonary arteriolar muscle .

Normal pulmonary vasculature losses it’s muscle rapidly after  birth and the pulmonary vascular resistance (PVR) falls to the adult level by 6 months .(Bulk of the fall occur in first 60 days) This is the same time the RV dominance is lost and RVH regresses . This also coincides with peaking of  left to right  shunting peaks and may result in cardiac failure .

Though  both ASD and VSD shunts are  highly dependent on PVR ,   VSD  shunting has more muscle power namely the LV contractility  , hence  VSD shunt is established  much earlier   than ASD . This can be ascertained in bedside as  VSD murmurs are heard even within 30 days while ASD is silent for many moths or even years . (Does not apply for Primum defects)

ASD  shunt rarely  meddles   lung  maturation process .(Maturation here means loss of  pulmonary arterioloar smooth  muscle -also  called as Involution  )  This vital  initial period lasts up to 6 months of life .VSD  interferes with this  involution of pulmonary arteriolar smooth muscle .( Please note near complete  involution still can occur in small VSDs with very little shunting )

In large VSD the PVR  will never ,  ever fall to normal levels  and   making it easier for  progressive vascular changes  that occur in  untreated large VSDs that  lead to Eisenmenger syndrome

*Please note  ASD can also reach that stage but it takes many years as the pulmonary vascular resistance has to raise from  very low levels which was made possible by complete involution of pulmonary vasculature .

It is obvious   AP window , PDA  express more  powerful left to right shunts which are associated with very high PVRs .

Final message

A simplified version of answer

Version 1

In VSD  the onset  of left to right  shunt occurs early even within 3 months of life  since VSD shunt is augmented by LV contraction . This is the crucial time of lung  vascular maturation   which gets interfered with  .ASD shunt is  established only after the pulmonary vasculature  involutes .This explains early onset of PAH in VSD  and late in ASD .

Version 2

ASD shunting is primarily depend on RV compliance which is high in early infancy so it takes time to establish the shunt .while VSD shunting does not  depend upon this RV regression.

* Please note  regression of  RV  dominance and compliance is directly dependent on maturation of lung.

** Note these  explanations are not absolute .Some of the complex forms of ASD and intrinsic vascular injury of pulmonary circulation (Various  fetal distress )  can progress into accelerated pulmonary arterial hypertension

Reference

  1. Excellent discusions are available in old edition of Moss and Adams
  2. Rabinovitch has done pioneering work on this topic .
  3. Robert Roberts text book of Adult congenital heart disease also explains it succinctly

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It was in 1984   this paper came from mayo clinic proceedings .

Hagen PT, Scholz DG, Edwards WD. Incidence and size of patent foramen ovale during the first 10 decades of life: an autopsy study of 965 normal hearts. Mayo Clin Proc. 1984;59:17-20.

When interventional   cardiology was not even in infancy . Now it remains the only data base of nearly 100o hearts  studied  after autopsy .

After reading the article  I got  few surprises

  • The mean  incidence  is 27.3 % of general population ( That is  27 crore people with PFO  in India )
  • In first three decades it goes up to 40 % .
  • PFOs size increase with age  due to stretch of inter atrial septum
  • It measures 3.4mm  in the first decade and it can grow up to 5.8 mm in later decades .

http://download.journals.elsevierhealth.com/pdfs/journals/0025-6196/PIIS0025619611632606.pdf

Mayo clinic continues to be pioneers in  providing vital  research about PFO

Following  is another excellent review article  on PFO and stroke

patent foramen ovale and stroke

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There was a big debate in one of my classes with cardiology fellows  regarding the shunt quantification  of ASD . We were talking about the significance of ASD shunting . We suddenly realised  2:1 left to right shunt is not a  simple equation  to comprehend . I was  thinking 2:1 shunt would mean pulmonary flow would be twice the systemic flow . It  was not to be !

Is the ratio of shunting and  Qp/Qs convey the same thing ?

No . Qp /Qs is the ratio of pulmonary to systemic blood flow  flow . When we want to quantify shunt we  express it in two different ways .

1. The amount of blood shunted form left side to right side of the heart .

2. The amount of pulmonary blood flow  to systemic blood flow in absolute terms .

Though both are closely linked entities  they do not denote the same meaning . When we say 2: 1 shunt  we refer  to the  shunted blood across the  defect but when we  calculate pulmonary blood flow  we take into account venous blood  which does not take part in the shunting .

The confusion arises because we use both terms interchangeably.The following illustration will try to  prove  A  2: 1 shunt would actually correspond  to  a qp/qs of  three  (Pulmonary flow is 3 times  the systemic flow !)

Let us begin with a hypothetical  ASD patient who  has  systemic  cardiac output of 4 liters.

He shunts 2  :  1   from left to right  . ie he shunts 2 /3  of three parts  into RA (66%  ) .

A patient who delivers 4 liters from LA in the presence of  2;1  ASD shunt  would mean he would  receive 12 liters from the lung  as pulmonary blood flow.

Final message

I am still not fully convinced about the above reasoning . I guess  it is correct.  I argue  the fellows  to give further insight into this equation. The complexities in bi- directional shunt and effective pulmonary blood flow in Eisenmenger syndrome is going beyond my heads !

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I stumbled upon this image from the Heart journal. A good depiction of  IAS aneurysm in three dimension.

Image courtesy  : Heart 2012;98:79-88   Three dimensional echocardiography in congenital heart disease   by  Joseph John Vettukattil

Further  reading

Clinical implication of IAS aneurysm

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Who is the father of interventional cardiology ?

William Rashkind a cardiologist from Children’s hospital, Philadelphia in 1966  probably is the first person who thought it was indeed possible to use a wire and balloon as cardiac therapeutic intervention .When surgeons were groping in dark with  sick cyanotic new borns with dTGV , He along with Miller executed their idea.

It was published in JAMA

How the Rashkind  has revolutionized  our approach to congenital  heart disease  is evident from the current guidelines in 2011.

The procedure has since evolved with improving hardware and we are able to ferry a blade into the IAS for cutting .

Current  recommendations for Atrial  septostomy

It is primarily useful

1. Atrial septostomy  to enhance atrial  mixing (eg, transposition of the great vessels with restrictive/intact atrial communication) or to decompress the left atrium
2.During Extra corporeal membrane oxygenation (ECMO)   to decompression   of left atrial hypertension

3.If there is poor cardiac return from ECMO  circuit  low venous saturations  (Class 1 Evidence  C)
It may also be tried in  (Class 2 )
1.  Hypoplastic left heart syndrome  with  restrictive atrial communication.

2.  Static balloon dilation of  l synthetic / bioprosthetic  IAS  (eg, Gore-Tex)

3. Tricuspid atresia with restrictive atrial  communication

4 .Pulmonary atresia with intact IVS

5. TAPVC with  restrictive atrial communication.

6. Primary pulmonary hypertension / Eisenmneger VSD/PDA .(Occasionally useful )

Reference

http://circ.ahajournals.org/content/123/22/2607.full.pdf+html

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