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Posts Tagged ‘acute dilatation of right atrium ra’

Spontaneous closure of VSD is  a well recognised  phenomenon, than ASD  though both happen in equal frequency.The simple reason being VSD is a noisy disease , ironically the smaller the size of VSD  more noisy it is . Hence  it is rarely  missed  while ASD is largely silent in children. For this reason  it is  possible ASD may be the most common congenital disease .

Natural history of ASD(OS) closure

  • ASDs of size 3-4 mm 100 % will close by 3  years
  • Bulk of the ASD < 8  mm close spontaneously by 5 years.
  • ASD> 10mm is unlikely to close

Factors that determine spontaneous closure

  • Apart from size and location
  • Closure  is accelerated by remnant of flap of foramen  ovale
  • Fenestrations and  Septal  aneurysms also  favor spontaneous closure.
  • Margins  of the defect if rough  triggers fibrotic reactions

spontaneous closure of asd

Why SVC and primum defect do not close easily ?

Plane of ASD  secundum is single and  bridging of tissue is possible .

Sinus venous and  primum defects exhibit  holes which run in multiple planes hence approximation not possible . They also do not  have a valve mechanism.

Un-natural history of ASD

In the current era, one more  force interferes  with spontaneous closure of ASD . It  comes from the  hyper trained aggressive Interventional cardiologists who compete with the nature and easily prevail over it !

Reference

asd spontaneous closure

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Pectinate muscles are specialized Intracardiac  muscle

  • Pectinate muscles are located mainly in the right atrium  , more  in right atrial  appendage , sparse in left atrium
  • Has muscle fibers arranged in a  comb like fashion.
  • Has less mechanical activity, no significant contribution to atrial contractility.
  • Can stretch and improve the voluminous nature of right atrium
  • The pectinate muscle  folds act as RA volume reserve  during adverse loading conditions . It helps RA dilate with out much wall stress.
  • Rarely it can be a cell of origin for focal atrial tachycardia

Image Source : Greys anatomy

The concertina like effect of pectinate muscle .

The atrial infolding increases the surface area of atrial chamber at times of dilatation , like  the music instrument .So,  these macro  folds ( like intestinal villi )  help overcome the  constantly changing volume status of right atrium.Since the  variation  left atrial blood flow is  not that much ,  the pectinate muscles  are not well developed  in the left atrium.

The same rules would apply for  why  there is excess  trabeculations  in right  ventricle  than  left  ventricle .

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