MCQ: Murmur | Fixed Splitting |Hypoplastic Thumb | CHD

Correct Answer: A. Atrial septal defect

Explanation

This child has Holt-Oram syndrome (heart-hand syndrome), a congenital disorder characterized by abnormalities of the upper limbs, particularly the radial ray and thumb, together with congenital heart disease and, in some patients, cardiac conduction abnormalities.

The key clue is the combination of:

• Hypoplastic thumb
• Thenar eminence hypoplasia
• A congenital heart defect
• A wide, fixed split S2 with an ejection systolic murmur at the left upper sternal border

The cardiac examination is typical of an atrial septal defect (ASD). A significant left-to-right shunt across an ASD causes increased right ventricular stroke volume and increased pulmonary blood flow. This produces a fixed, wide splitting of S2 and an ejection systolic murmur at the upper left sternal border, caused by increased flow across the pulmonary valve.

Holt-Oram syndrome is most commonly associated with septal defects, particularly ostium secundum ASD and ventricular septal defect (VSD). Among the choices given, ASD is the best answer.

Why this is Holt-Oram syndrome

The upper-limb abnormalities in Holt-Oram syndrome involve the radial ray, which includes the thumb, radius, carpal bones, and thenar structures.

The severity can vary considerably. Findings range from:

• Thenar hypoplasia
• Hypoplastic or absent thumb
• Triphalangeal thumb
• Radial hypoplasia or aplasia
• Abnormal carpal bones
• More severe forearm abnormalities

The abnormalities may be unilateral or bilateral and may be asymmetric. Therefore, the absence of an obvious bilateral limb deformity does not exclude Holt-Oram syndrome.

Cardiac manifestations

Approximately 90% of individuals with Holt-Oram syndrome have a congenital heart malformation, with the cardiac abnormalities most commonly involving the cardiac septa. ASD and VSD are the principal associated defects.

Cardiac conduction abnormalities are also an important feature. Patients may develop:

• Sinus bradycardia
• First-degree AV block
• Progressive AV conduction disease
• Complete heart block

Therefore, evaluation of a patient with suspected Holt-Oram syndrome should include both echocardiography and ECG.

Why the other options are incorrect

B. Coarctation of the aorta

Coarctation is not the characteristic cardiac lesion associated with Holt-Oram syndrome. The syndrome predominantly involves septal defects, particularly ASD and VSD.

C. Patent ductus arteriosus

PDA is not the characteristic congenital heart defect of Holt-Oram syndrome. The combination of a radial-ray abnormality and a septal cardiac defect is much more typical.

D. Tetralogy of Fallot

Tetralogy of Fallot is not the classic cardiac association. Although complex congenital heart defects can occasionally occur in Holt-Oram syndrome, ASD and VSD are much more characteristic.

E. Ventricular septal defect

VSD is an important association with Holt-Oram syndrome and is therefore a plausible distractor. However, this child’s fixed, wide splitting of S2 and pulmonary ejection flow murmur specifically point toward an ASD.

Clinical correlation

The chest radiograph shows increased pulmonary vascular markings, consistent with increased pulmonary blood flow from a significant left-to-right shunt.

The absence of cyanosis and clubbing is also consistent with an uncomplicated ASD. Recurrent respiratory infections and reduced exercise tolerance can occur with a significant ASD because of chronic pulmonary overcirculation.

High-Yield Exam Pearl

Think of Holt-Oram syndrome as the “heart-hand” syndrome:

Radial-ray/thumb abnormality + septal heart defect ± conduction disease

The most characteristic cardiac lesions are:

ASD > VSD

The most characteristic limb findings include:

Hypoplastic/absent thumb, thenar hypoplasia, and radial abnormalities.

The usual molecular cause is a pathogenic variant in TBX5, with autosomal dominant inheritance.

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