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1-month-old (male) turning blue

by Mohammad Hajighasemi-Ossareh, MD, MBA
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    00:02 A 1-month old baby is brought to the emergency department because he had a coughing spell while feeding and turned “blue”.

    00:10 The mother says that the "blue" color went away when she picked up the baby and brought his knees to his chest.

    00:16 The physician orders a chest x-ray which shows a boot-shaped heart and he tells the mother that the baby has a condition that is caused by an anterosuperior displacement of the infundibular septum.

    00:31 What are the four features of the baby’s cardiac condition? Answer choice (A) - pulmonary stenosis, left ventricular hypertrophy, ventricular septal defect and overriding aorta (B) - pulmonary regurgitation, left ventricular hypertrophy, ventricular septal defect and overriding aorta (C) - pulmonary regurgitation, right ventricular hypertrophy, atrial septal defect and overriding aorta (D) - pulmonary stenosis, right ventricular hypertrophy, atrial septal defect and overriding pulmonary artery and (E) - pulmonary stenosis, right ventricular hypertrophy, ventricular septal defect and overriding aorta Now take a moment to come to your own conclusion.

    01:26 Now the question characteristics here.

    01:29 This is an embryology question, or really an embryology/cardiovascular question because we have a 1-month old child with a defect that appears to be in the heart and it’s caused by embryological abnormality.

    01:45 So we have an embryology question here.

    01:47 Now this is a 2-step question.

    01:49 First we have to come to the diagnosis of what this child has and second, we have to know the characteristics of this diagnosis.

    01:56 And here the stem is absolutely required.

    01:59 We can’t come to the conclusion by just reading the last sentence, we have to look at the details of the clinical vignette.

    02:08 Now let’s walk through this question together.

    02:10 Step 1- we have to determine this baby’s diagnosis.

    02:14 Now this baby is suffering from cyanosis, or as the mother described it, “turning blue” in a specific situation such as feeding.

    02:23 Now cyanosis results from tissue not receiving enough oxygen and can be caused by various mechanisms in newborns.

    02:31 Most notable though, are heart defects.

    02:34 The differential diagnosis for cyanotic heart defects in newborns includes the tetralogy of fallot, transposition of the great arteries and pulmonary atresia.

    02:46 Now, given the boot shaped heart on chest x-ray, and the physician mentions of 4 features, really the tetralogy of fallot is the most likely diagnosis here.

    02:57 Now, step 2 is we have to determine the defects in the tetralogy of fallot based on the answer choices we have available to us.

    03:06 Now, features of the tetralogy of fallot can be learned by heart but also derived from clinical presentation in this specific case.

    03:17 We can look at the cyanosis while feeding.

    03:19 Now, cyanosis with a cardiac etiology like tetralogy of fallot results from mixing of deoxygenated or right-heart-sided and oxygenated blood or left-heart-sided blood.

    03:34 Now, mixing requires a septal defect and occurs down the pressure gradient.

    03:41 So that means that in tetralogy of fallot, the right heart must be under higher pressure than the left and thus deoxygenated blood is entering the left side of the heart.

    03:53 Now the right heart is normally low pressure so one feature of the tetralogy of fallot is increased right heart pressure or pulmonary stenosis.

    04:05 Increased pressure results in hypertrophy of the right heart and thus a septal defect must be at where the site of significant pressure is present which is the ventricles.

    04:17 Thus the correct answer here is pulmonary stenosis, right ventricular hypertrophy, ventricular septal defect and overriding aorta.

    04:29 Now one mnemonic that I was taught that many people know is PROV.

    04:33 PROV that this patient has tetralogy of fallot.

    04:37 The "P" being pulmonary stenosis, right ventricular hypertrophy being the "R", "O" being overriding aorta and "V"- being a ventricular septal defect PROV this patient has tetralogy of fallot.

    04:53 Now let’s discuss some high-yield facts from this question.

    04:56 The first thing to discuss are these cyanotic congenital heart diseases.

    05:01 Now, cyanotic congenital heart diseases involve right to left shunts in which deoxygenated blood is not passed through the lungs but in fact then mixes directly with oxygenated blood on the left side of the heart.

    05:16 These diseases are generally structural defects and they can be in the heart but they can also be caused by resistance-increasing defects to the lungs which then put increased pressure on the right ventricle.

    05:31 Beyond cyanosis, signs and symptoms are multifold and include nail clubbing, tachycardia, tachypnea and inadequate feeding as we saw in this patient’s clinical presentation.

    05:44 Also, delay in reaching developmental milestones may also be mentioned in the question stem - keep an eye out for that.

    05:52 Now another high-yield topic to discuss here, is the tetralogy of fallot which is one of the cyanotic congenita heart diseases.

    06:00 Now the tetralogy of fallot is a cyanotic congenital heart disease with the four features of let's use our mnemonic PROV - pulmonary stenosis, right ventricular hypertrophy, overriding aorta and ventricular septal defect, And this results in a right-to-left shunt between the ventricles.

    06:20 Affected babies can have what are called “tet spells” in which during feeding, the baby turns blue acutely and this is going to be caused by decreased systemic left sided circulation, increased pressure gradient and thus a right-to-left shunt flow producing cyanosis.

    06:42 Now diagnosis is typically performed and then obtained via transthoracic echocardiogram in which you can do an ultrasound of the heart to see these abnormalities of the right ventricle and also use doppler flow to see the mixing of blood through the septal defect.

    07:03 X-ray can also be used and may reveal a classic USMLE buzz word known as ‘boot-shaped heart’ due to the patient’s right ventricular hypertrophy.

    07:14 Now treatment for this disease is surgical correction of the defects and it is generally performed in the first year of life.


    About the Lecture

    The lecture 1-month-old (male) turning blue by Mohammad Hajighasemi-Ossareh, MD, MBA is from the course Qbank Walkthrough USMLE Step 1 Tutorials.


    Author of lecture 1-month-old (male) turning blue

     Mohammad Hajighasemi-Ossareh, MD, MBA

    Mohammad Hajighasemi-Ossareh, MD, MBA


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