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
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 !
Iam saying it as PFO . . . How do you say it is an ASD ?