A boot shaped heart

An 18 month old female child presented with a history of dyspnoea on exertion. She often gets cyanosed after feeding or crying and sometimes becomes apnoeic. On examination, there was cyanosis and digital clubbing. Auscultation of the heart showed a loud ejection systolic murmur in the pulmonary area. Her chest x ray film is shown in fig 1.

Questions

(1) What does the chest x ray film show?

(2) Can you think of a likely diagnosis?

(3) What other investigations can confirm the diagnosis?

(4) What complications could the patient develop?

(5) How would you manage the patient?

Answers

(1) The chest x ray film shows a normal sized heart with upturned apex suggestive of right ventricular hypertrophy. The absence of the main pulmonary artery segment gives the cardiac shadow a characteristic appearance often termed as "coeur en sabot" or boot shaped heart.

(2) The most likely diagnosis is tetralogy of Fallot, a congenital condition of the heart, characterised by four features:

• Ventricular septal defect, communication between the two ventricles
• Pulmonary stenosis, narrowing at the pulmonary valve or at the level of right ventricular infundibulum, which lies just below the pulmonary valve
• Over-riding of the aorta, the aorta being positioned over the ventricular septal defect instead of in the left ventricle
• Right ventricular hypertrophy.
• Echocardiography is the most important investigation to confirm the diagnosis.

(3) Echocardiography is the most important investigation to confirm the diagnosis.

(4) The complications that the patient can develop are fatal anoxic spells, infective endocarditis, repeated chest infections, rarely congestive cardiac failure, and neurological complications such as:

• Anoxic infarction during anoxic spells leading to hemiplegia
• Cerebral thrombosis and paradoxical embolism to brain (venous thrombi formed due to polycythaemia can enter the systemic circulation through ventricular septal defect) leading to hemiplegia
• Brain abscess.

(5) Medical management is limited to the management of complications and correction of anaemia. And surgical management is of two types:

Palliative treatment - The pulmonary artery is anastomosed with a systemic artery, which will improve the pulmonary blood flow and supports the development of the pulmonary artery. The preferred method is anastomosis between the pulmonary and subclavian arteries using a Gore-Tex graft (modified Blalock-Taussig shunt). Other treatments include Pott's procedure and the Waterston shunt, in which the anastomosis is made between the pulmonary artery and the aorta.

Definitive treatment - This is open heart surgery with patch closure of the ventricular septal defect and of the overriding of aorta and the resection of the infundibular obstruction.

Discussion

Tetralogy of Fallot is the second most common congenital cyanotic heart disease, after transposition of the great arteries. It has an incidence of one in 2000 births and accounts for 10% of all congenital heart diseases. Also tetralogy of Fallot is the commonest cardiac malformation responsible for cyanosis after one year of age. The incidence is slightly higher in men than women. It comprises a complex of anatomical abnormalities arising because of the abnormal development of bulbar septum, which separates the ascending aorta from the pulmonary artery and which normally fuses with the outflow part of the interventricular septum. The clinical course of tetralogy of Fallot is variable and is determined by the degree of right. About a quarter of untreated patients with tetralogy of Fallot and right ventricular outflow obstruction die within the first year of life, 40% by 4 years old, 70% by age 10, and 95% by age 40.

The pulmonary stenosis causes an increase in the right ventricular pressure and concentric right ventricular hypertrophy without cardiac enlargement. When the right ventricular pressure exceeds the left ventricular pressure, right to left shunting of blood develops through the defect in the interventricular septum to decompress the right ventricle. Because this shunting occurs at insignificant pressure difference between the two ventricles, it is usually silent-that is, no murmur of ventricular septal defect can be auscultated. With increasing severity of pulmonary stenosis, the blood flow into the pulmonary artery will decrease resulting in softer ejection systolic murmur of pulmonary stenosis, however, the right to left shunting of blood will be accentuated with increased severity of cyanosis.

The definitive treatment of tetralogy of Fallot is the total surgical correction of the anatomical defects. This is usually done in the third year of life and ideally before the child reaches school age. The prognosis after total correction is good, especially if the operation is done in childhood. The mortality associated with the operation is 5%. Regular follow-up is needed to identify the patients with postoperative complications, such as residual outflow obstruction, residual ventricular septal defect, pulmonary regurgitation, rhythm disorders, and infective endocarditis.