Benjamin Gasul is a well-known name in cardiology community especially among the old generation . He and his team from Cook county children’s hospital Illinois, Chicago, created a stir among pediatric cardiologists in late 1950s and 60s . His concept was rather controversial .He suggested Tetrology of Fallot can be an acquired defect as a sequel to large peri-membranous VSD.
He and his team published a series of papers one in 1957 and other in 1963 (JAMA and circulation ) .Later in 1970s Kieth and Tyrrell from children’s hospital Toronto tried to confirm this. Though they were not fully agreeing with Gasul they could not dispute the concept either !
Clinical importance of Gasul VSD
This entity was suspected based on a curious observation in children with large VSDs , who initially struggle with the defect and show signs of failure . After a critical time frame (If they survive ) they begin to stabilise and some of them do extremely well in functionality too !
For this to happen , we presume the quantum of shunt must reduce by any means. Ironically , we also know , even patients who are destined to develop dangerous Eisenmenger reaction also live a blissful life for a decade or so before it strikes and take their life . This is one aspect of the natural history . . .
While some ther children did well without developing pulmonary hypertension .This bothered Gasul .When he analysed those patients (Mind you there was no echocardiography those days !) he found something curious was happening in the RVOT area. (It was almost like TOF !) This he documented in few patients who showed progressive infundibular narrowing acting as a check dam (Artificial banding ? ) and resulted in improvement of VSD hemo-dynamics .In extreme situations there was a significant right to left shunt as well. It was so tempting to label it as acquired TOF !
Who are likely to develop Gasul like reaction ? (Reference : Kieth 1978 Heart disease in Infancy and child hood.)
- Persons with oblique RVOT angle normal <40 ( 40-60 degrees)
- Aortic override ride > 30%
- Patient with anomalous muscle bundle
- Children with right aortic arch
Why the concept of Gasul was disputed ?
Gasul concept primarily relied on the fact that there would be some resistance at RVOT for all those dramatic improvement in failure as the children grows . This he consistently documented in many children who had significant regression of cardiomegaly .
There can be other mechanisms for the signs of stabilisation in large VSDs.
Relative reduction of VSD size as child grows could be an important factor . The falling pulmonary vascular resistance allows to accommodate the shunted blood without any major issue as RV after- load regress .
Is concept of Gasul alive in the year 2012 ?
Since it represent the natural history of the defect , most VSDs are closed surgically , one may not get an occasion to see a Gasul VSD today . More intriguing is the fact we will ever get an oppurtunity to confirm the concept .
Special situations in VSD / PS . Can RVOT obstruction exist with raised pulmonary arterial pressure ?
This is a challenge to the traditional teaching . Logically pulmonary obstruction and high pulmonary pressure does not go hand in hand.Do not get fooled by logic .(We know aorta can record even 200mmhg in critical aortic stenosis ).
The respect and command we give to clinical medicine even today is because , it can defy logic in any random patient .
If a patient with Eisenmenger develop Gasul reaction what will happen ? PAH will persist as do the RVOT obstruction .They are the blessed ones and belong to the category of Eisenmenger surviving into 4th 5th decades . (Batisda of Brazil extrapolated this and suggested huge benefits with PA banding in adult Eisenmenger !)
Summary and verdict
TOF is a cono-truncal anomaly due to defective genes. The Mal-aligned conal septum is responsible for RVOT obstruction . Hence this defect can not be termed as acquired , by any sort of imagination .
Still , a subset of patient with large VSD can mal-align their conal septum for hemo-dynamic reasons .This is especially likely to occur if the flow is heavy the infundibulum slides horizontally to generate the obstructive gradient . Hence Gasul was indeed right when he pointed to us some of the grown children with VSD mimic TOF .
However, the controversy remains whether the equation “Adult VSD + IPS” = Adult TOF is true or false !
Incidentally , the classic book on congenital heart disease by J.K Perlof has a chapter on VSD with PS and not on TOF ! Does it light a spark ? Is it worth pondering this question ? Probably not , instead we may use our resources to correct these anomaly .