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Fallot tetralogy

In medicine, the tetralogy of Fallot (described by Etienne Fallot, 1850 - 1911, Marseille) is a significant and complex congenital heart defect. more...

Fabry's disease
Factor V Leiden mutation
Factor VIII deficiency
Fallot tetralogy
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Familial periodic paralysis
Familial polyposis
Fanconi syndrome
Fanconi's anemia
Farber's disease
Fatal familial insomnia
Fatty liver
Febrile seizure
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Fibrous dysplasia
Fissured tongue
Fitz-Hugh-Curtis syndrome
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Foix-Alajouanine syndrome
Follicular lymphoma
Fountain syndrome
Fragile X syndrome
Fraser syndrome
FRAXA syndrome
Friedreich's ataxia
Frontotemporal dementia
Fructose intolerance

The term blue baby syndrome is sometimes applied to the tetralogy of Fallot, but is less specific and includes other conditions.

Four malformations

It involves four different heart malformations:

  1. A ventricular septal defect (VSD): a hole between the two bottom chambers (ventricles) of the heart.
  2. Pulmonic stenosis: Right ventricular outflow tract obstruction, a narrowing at or just below the pulmonary valve.
  3. Overriding aorta: The aorta is positioned over the VSD instead of in the left ventricle.
  4. Right ventricular hypertrophy: The right ventricle is more muscular than normal.

Pseudotruncus arteriosus is a particularly severe variant of the tetralogy of Fallot, in which there is complete obstruction of the right ventricular outflow tract. In these individuals, there is complete right to left shunting of blood. The lungs are perfused via collaterals from the systemic arteries. These individuals are severely cyanotic and will have a continuous murmur on physical exam due to the collateral circulation to the lungs.


The tetralogy of Fallot generally results in low oxygenation of blood due to mixing of oxygenated and deoxygenated blood in the left ventricle and preferential flow of blood from the ventricles to the aorta because of obstruction to flow through the pulmonary valve. This is known as a right-to-left shunt. It is often evidenced by a bluish tint to the baby's skin (cyanosis). However there are "pink Fallots" in which the degree of obstruction in the pulmonary tract (right ventricular outflow, pulmonary valve and pulmonary arteries) is low. Blood flows preferentially from the ventricles to the lungs and only minimal desaturation occurs in the systemic circulation because of mixing of saturated and desaturated blood in the ventricles. This degree of desaturation may be undetectable to the eye and requires a pulse oximeter to identify it.

Even children who are generally not too deeply cyanosed (blue) may develop acute severe cyanosis or hypoxic "tet spells". The precise mechanism of spelling is in doubt but certainly this is a dangerous event and presumably results from an increase in resistance to blood flow to the lungs with increased preferential flow of desaturated blood to the body. Such spells may be treated with beta-blockers such as propranolol, but acute episodes may require rapid intervention with oxygen, morphine (to reduce ventilatory drive) and phenylephrine (to increase blood pressure). There are also simple procedures such as knee-chest position which reduces systemic venous return (to reduce the right-to-left shunting), increases systemic vascular resistance (and hence blood pressure) and provides a calming effect when the procedure is performed by the parent.


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Never has a three hour flight seemed so long - A Memorable Patient
From British Medical Journal, 10/21/00 by Thomas C Martin

A memorable patient

"The pilot would like to know if you would have him land the airplane in Bermuda," the British West Indies Airline flight attendant asked, quietly and professionally. "No," I replied, "there is no cardiac surgeon there."

Reisha, my 4 month old patient, had picked an unfortunate day to try to die. We knew that she had heart disease soon after she was born. She first developed cyanotic spells, the hallmark of tetralogy of Fallot, at 2 months. In Antigua and Barbuda it takes time to arrange for overseas evaluation and care, but with the help of the Rotary club and its Gift of Life programme we had been able to arrange for transport to Schneider Children's Hospital in New York.

In the three days before departure the cyanotic spells became more frequent and more pronounced. She had been treated with oxygen, morphine, and propranolol. An air ambulance would have been more appropriate for transfer, but the cost is overwhelming in a developing country. So we claimed that she was fit to fly on a commercial flight. A nurse from the special care unit at Holberton Hospital accompanied Reisha, her mother, and me.

Reisha dropped her oxygen saturation to 40% in the ambulance on the way to the airport, so we drove on to the tarmac and boarded while providing her with bag and mask ventilation with oxygen. She did not seem to like the rarefied atmosphere over the Atlantic and proceeded to drop her oxygen level to 30% on a regular basis. She was given morphine and needed ventilation for her subsequent apnoea and to try to lower her pulmonary resistance to improve lung blood flow. Her oxygen rose temporarily to 95% and then it would fall again.

We had adrenaline, which we began as a bolus to raise systemic resistance and theoretically increase the blood flow to the lungs. It worked when the oxygen level fell to 40%, but after each treatment Reisha's pulse and oxygen level were not detectable for about five minutes. My heart would stop and restart when her oxygen level rose again to 95%. We began chest compressions when we weren't sure. Between adrenaline doses the intravenous line dislodged. I didn't need to tell the nurse that failure to resite the line would result in Reisha's death. The nurse replaced the line at the first try, in a darkened airplane, at 30 000 feet.

It was then that the flight attendant made her offer. About that time the adrenaline bolus technique was becoming less effective, so we began an adrenaline infusion and occasional sodium bicarbonate. Mainlining adrenaline is a desperate measure, even at sea level.

I don't think that a three hour flight ever lasted so long. But, together with bag and mask oxygen, adrenaline, bicarbonate, and morphine, we made it to New York. We were processed in our seats and the transport team worked for 45 minutes before Reisha was stable enough for the ambulance drive. On arrival at the intensive care unit her [pa0.sub.2] was 25 torr and her pH 7.40. I worried about her brain.

She underwent emergency placement of a Blaylock-Taussig shunt and complete repair of her tetralogy of Fallot defect one year later. She is now 4 and clue to start school this fall with her twin sister and is now developing normally.

Thomas C Martin consultant paediatrician and cardiologist, Antigua

We welcome articles of up to 600 words on topics such as A memorable patient, A paper that changed my practice, My most unfortunate mistake, or any other piece conveying instruction, pathos, or humour. If possible the article should be supplied on a disk. Permission is needed from the patient or a relative if an identifiable patient is referred to. We also welcome contributions for "Endpieces," consisting of quotations of up to 80 words (but most are considerably shorter) from any source, ancient or modern, which have appealed to the reader.

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