following congenital heart diseases is most likely responsible for this clinical presentation?

INI-CET EXAM -2026

Child Health Nursing (Pediatrics)

Medium

Appeared in: INI-CET EXAM -2026

Explanation

A large patent ductus arteriosus (PDA) is a connection between the aorta and the pulmonary artery that fails to close after birth.
In the presence of high pulmonary vascular resistance (pulmonary hypertension), deoxygenated blood from the pulmonary artery shunts from right-to-left into the aorta.
This shunt enters the aorta distal to the arteries supplying the head and arms.
Consequently, the upper extremities receive oxygenated blood from the left ventricle and remain pink, while the lower extremities receive the deoxygenated shunted blood, causing them to appear cyanotic.
This specific clinical picture is known as differential cyanosis and is a classic presentation of a large PDA with a right-to-left shunt.

Option A: An atrioventricular septal defect involves mixing of blood at the atrial and ventricular levels, which is central. Any resulting cyanosis would be distributed systemically, causing generalized cyanosis, not differential cyanosis.
Option B: Severe mitral stenosis obstructs blood flow into the left ventricle, causing backup into the lungs (pulmonary edema) and pulmonary hypertension. It does not create the specific post-ductal shunt needed for differential cyanosis.
Option D: Peripheral vascular disease refers to circulation problems in the extremities, usually due to atherosclerosis in adults. It is not a congenital heart defect and is an incorrect diagnosis for a neonate with central cyanosis.

Clinical Relevance

Nursing practice connection: Use the key finding related to Pathophysiology of differential cyanosis in congenital heart disease to guide bedside assessment, documentation, and the next nursing action.
Recognizing differential cyanosis is a critical nursing assessment skill that can quickly point towards a ductal-dependent cardiac lesion.
In some congenital heart defects, keeping the ductus arteriosus open with a prostaglandin E1 infusion is a life-saving intervention until surgery can be performed. In this case, however, the large PDA is the problem itself.
Nurses must perform four-limb blood pressure and oxygen saturation monitoring (pre-ductal in the right hand and post-ductal in a foot) to confirm the diagnosis and assess the severity of the shunt.

How to Approach the Question

First, identify the key clinical finding in the question stem: 'differential cyanosis' with a specific pattern ('pink upper extremities and cyanosed lower extremities').
Understand the meaning of this pattern. Pink upper body means it's receiving oxygenated blood. Blue lower body means it's receiving deoxygenated or poorly oxygenated blood.
Consider the anatomy of the heart and great vessels. The separation in oxygenation must occur after the blood supply to the arms has branched off the aorta.
Evaluate the options based on this anatomical requirement. The ductus arteriosus connects the pulmonary artery to the aorta just after the subclavian artery takeoff.
A right-to-left shunt through a PDA would deliver deoxygenated blood specifically to the descending aorta, matching the clinical picture perfectly.
Rule out other options as they cause generalized cyanosis (mixing occurs centrally) or are irrelevant to congenital heart disease in a neonate (PVD).

Concept Tested & Keywords

Concept Tested: Pathophysiology of differential cyanosis in congenital heart disease.
Stem keywords: neonate, differential cyanosis, pink upper extremities, cyanosed lower extremities, congenital heart disease
Lead-in keywords: most likely
Clinical cues: The specific pattern of 'pink upper extremities and cyanosed lower extremities' is a hallmark sign pointing to a right-to-left shunt occurring at the level of the ductus arteriosus.

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