cyanotic heart disease: TOF#education

Added: 2026-05-14

[00:00:04]Hello friends, today I am starting a talk on an important congenital heart disease cyanotic heart disease that is tetrology of fellows.

[00:00:16]So friends, this is a very uh important topic in MBBS and MD exams and today's purpose of the talk is to have a core understanding of what is tetrology of fellows.

[00:00:30]It has got four components uh pulary stenosis, VSSD, overriding of aot and right ventricular hypertrophy.

[00:00:40]It is the most common cyanotic congenital heart disease. Although the most common congenital heart disease is VSSD but among the cyanotic heart diseases, it is the most common and frequently associated with syndromes like Down syndrome or diode syndrome.

[00:00:57]roughly 10% of the congenital heart disease is because of tetrology of fellows.

[00:01:06]So you can compare here the normal cardiac structure with the top structure. In the normal uh circumstances the blood from the right atrium goes to the right ventricle and through that to the pulmonary artery and from that from lungs it comes to the left atrium then left ventricle and the aorta and systemic circulation.

[00:01:32]But here in top circuit the blood is facing a resistance in the pulmonary circuit which is stenosed and as a result the pressure rises in the right ventricle side causing the pressure overload on the right ventricle resulting in hypertrophy and the blood is shunted out from the ventricular septile defect.

[00:01:59]plus slum sum of the aota is overhanging.

[00:02:05]So this is the critical element in fellow's fiology.

[00:02:10]Fellow's physiology is never without pulmonary stenosis and this is the initiator event which triggers the high pressure development in the right side.

[00:02:22]So right ventricular hypertrophy ensues and the blood flows from the right circulation to the leftsided circulation.

[00:02:33]The overriding of aorta adds to the problem and the septile part of the aotic base projects into the right ventricle. So some of the blood goes directly into the aorta also.

[00:02:49]So ventricular septal defect actually acts as a pressure release valve for the right ventricle.

[00:02:57]And whenever there is uh a problem with the right ventricular septum the shunting causes profound senosis.

[00:03:14]Now there is an important concept of pink to and cyanotic to. When the child is born the pul stenosis is very mild obstruction and the shunt is left to right mostly because of the BSD.

[00:03:32]But as the baby grows the permission stenosis becomes more significant creating an obstructive element and as a result the shunt comes as right to left because of high pressure development in the right side.

[00:03:48]So pink to is a asyotic patient presenting mostly as a insignificant murmur and in cyanotic part when the patient has developed significant stenosis the patient can be cyanotic or again he can be having profound hyperscyotic spells.

[00:04:11]So we should remember that the degree of right ventricular outflow tract obstruction is the sole determinant of the how the patient is going to present to you.

[00:04:22]So the symptoms are uh usually starting in infancy in to when the child has uh grown to certain size.

[00:04:33]There may be some uh breathing difficulty felt by the patient u because of hypoxia. On examination you will hear a systolic murmur in the paristernal area and a loud P2.

[00:04:49]In neonatal period cyanot cyanotic element is not there.

[00:04:55]One the permissionosis is not that significant and already in the from the fetal part the right ventricular pressures and resistance is high. So baby is well adapted to that and if the child continues to grow into the adulthood uh into the childhood you have uh effects of s hypoxia on the body in the terms of exercise intolerance easy fatigability persistent sinosis clubbing of the fingers and toes and frequent episodes of syncopy and hyperotic spells.

[00:05:33]So you can appreciate here that the lungs are olymic because of pulmonary stenosis. The pulmonary bay is highly vacant.

[00:05:43]The right ventricular hypertrophy creates a bootshaped appearance and this is the classical radioraph of trology of fellows.

[00:05:52]On ECG you will find right access deviation because of right ventricular hypertrophy.

[00:06:00]So the most significant element in toph is hyperyanotic T spell and this is triggered by feeding crying strenous activity like defecation any stress on the body like fever dehydration or sudden waking from sleep.

[00:06:18]The patient suddenly becomes more blue and may appear ashen gray. The child may be so hypoxic that he can lose consciousness. And because at this point there is practically very little blood flowing through the pulmonary segment, there is very little murmur that is audible.

[00:06:42]So this is the vicious cycle of spell that is commonly asked in the exam or the viva. The triggering event causes the spasm of the right ventricular outflow tract and drop in the systemic vascular resistance. Massive right to left shunt occurs through the VSSD resulting in profound hypoxia and acidosis because of anorobic metabolism. Compensatory hyperventilation takes place and which also allows more venus blood to enter the thoracic cavity worsening the cycle further. So this is a very very important question asked in the viva or theory exams.

[00:07:22]So you can summarize that there can be triggers of increased oxygen demand and strainous activities like crying, exercise, straining on defecation, feeding, crying etc. or there could be a metabolic load on the body by dehydration and fever and administration of any some c certain agents like anesthetics.

[00:07:47]So children usually uh learned how to counter this spell by is by squatting.

[00:07:56]The older children naturally absorb a knee chest position or a squatting episode. So this is very pet question of examiners how squatting helps to relieve the t spell. So you can see here that kinking of the major vessels of the lower limb occurs by squirting and systemic vascular resistance rises.

[00:08:18]So the leftsided pressures in the heart rise.

[00:08:22]As a result the shunting from the right to left decreases. So the sinosis lessens. So this is the mechanism how squatting helps in the hospital. If the patient is brought with a cyanotic spell, the first step is to put the patient in knee to chest position, give him oxygen as tolerated and immediately give some sedative or pain relief. We commonly use morphine or intraasal fentinyl to make the child calm and decrease the upright flow obstruction and decrease the hyperventilation episode because the child has gone into some acidosis.

[00:09:08]We give this support by give 10 ml per kg of slime bolus and soda by carb to counteract the metabolic acidosis.

[00:09:18]Pharmacologically we can give beta blockers or vessors to counter the right ventricular outflow tract spasm or to increase the systemic resistance by phenilephine.

[00:09:34]So you reme remember this management like a ladder shape approach. On the first ladder we have calming the infant bringing the child to knee to chest position giving oxygen and calling for help. And another is to give analesia and IV fluid support. And we should remember that uh if morphine is not available or IV excess is not available intraasal fentanyl can or medazulam can also be used.

[00:10:11]Further on you have to give the saline bolis and uh soda by carb and if the patient is not improving then you can use phenylopherine to increase the systemic resistance and beta blocker to decrease the right ventricular spasm.

[00:10:28]Ultimately the management of toph is um surgical.

[00:10:35]If the patient's anatomy is not favorable you go for a paliative shunt.

[00:10:41]The basic idea is to increase the pulmonary blood flow temporarily and this can be done by the balloon dilation of the pulmonary artery or by a shunt from the subclavian trunk to the pulmonary artery that is bloptosic thmus shunt. This is commonly asked in the viva or theory exam about the shunt surgery for toph.

[00:11:02]So this results in increased pulmonary blood flow, improves the oxygenation but shunting still keeps on taking place and this slightly relieves the hypoxia of the patient. The ultimate answer is the complete intracardiac repair which takes place in an older child bigger child and results in normal hemodynamics ultimately. So naturally it consists of right ventricular outflow tract reconstruction along with VSSD repair.

[00:11:32]So it restores the circulation to the normal pattern.

[00:11:38]So this is the um detailed blueprint about the complete intracardic repair.

[00:11:44]It is being done at lot of centers now and the patients are getting benefited by that.

[00:11:50]Naturally any major cardiac surgery is associated with long-term complications.

[00:11:55]So the pulmonary and aotic valve regurgitations can be there. VSD repair can result into conduction blocks and any operated heart further on is a risk factor for endocarditis.

[00:12:11]Overall prognosis is good if the patient is managed early and long-term survival is excellent and the unrepaired survival is very very poor.

[00:12:27]Once operated the patient remains on cardiac follow-up for complete life and uh regular ECGs, Echos and other cardiac function testing is done. Even successful pregnancies have been recorded with good hemodynamics after surgery.

[00:12:46]Surgery usually results in some restrictions for very highly competitive standard supports only but normal living there is no restriction.

[00:12:57]There are some other complications associated with and this is also one of the core area of viva exam.

[00:13:05]These are polyythemeia and the stroke in the children. So the naturally as the child is hypoxic the body tries to make more RBCs already with the normal hemoglobin when the more RBCs are formed this results in polyygmia. But we should remember that the patient is having a desaturation because of shunting. So the actual hemoglobin which is useful to the patient in oxygenated form is lesser than what is actual level in the blood.

[00:13:43]Tough patients are also susceptible for brain absesses and this is because of two effects. One is the increased polyythemia which causes the inact in the brain tissue and further on the some of the uh infection emboli from the bloodstream venus bloodstream they can be shunted from right to left and bypassing the pulmonary filter. So the microorganisms can lodge into the brain and cause absesses. Most commonly these absesses are stafylocal and fungal.

[00:14:21]So this is the summary of all the uh possible areas on which the questions can be asked. They can be asked on cyanotic spells, basic pathophysiology, the x-ray and the ECG picture or the surgical management of the child. So you can pause over these slides and note down the questions which are commonly asked in the viva and uh you should try to make a diagram take a minute pause here and try to make a diagram of the pathophysiology of the uh to which you are going to write in your exam also.

[00:15:02]So this is the diagram that you have drawn and this is given in your all other textbooks and this diagram represents the pathophysiology and if you write this diagram draw this diagram in answer the examiner is going to be impressed.

[00:15:21]So guys this is the summary of uh tetrology of fellows and there are some additional variants of toph. There is a pentalology of fellows also where ASD is also associated and very rarely try of fellows where pulmonary stenosis and right ventricular hypertrophy are there but VSSD is not there instead ASD is only there. So these are the some of the questions which have been asked in the NEITEP PG entrance. Also in in NETPG you may be given a case scenario where some intentional error has been done and you will be asked a question on spotting the error. For example, patient is of cyanotic spell but on X-ray they give that the lungs are overfilled with fluid or the ECG shows left axis deviation. So these are the incompatible findings in X-ray and HCG which are not compatible with TO. So good luck for your preparation with cyanotic heart diseases. I will be making another presentation on transposition physiology that is TGA.

[00:16:31]Thank you for watching and stay in touch and always remember life is very beautiful as you take it. Thank you.