Patent ductus arteriosus — viva

Examiner prompt 1 — interpretation of the stimulus

Examiner. What is the most likely diagnosis, and what physiological process explains these findings? [1]

Candidate. This is a long-standing large patent ductus arteriosus that has crossed into Eisenmenger physiology. The previously continuous murmur has softened and shortened because the aorta-to-pulmonary-artery pressure gradient has narrowed as the pulmonary vascular resistance has risen to equal systemic pressure. The loud pulmonary component of the second sound reflects the pulmonary hypertension, and the differential cyanosis (cyanotic toes, pink fingers) is the hallmark of shunt reversal — deoxygenated blood now flows right-to-left through the duct into the descending aorta, distal to the subclavian arteries. This is not spontaneous closure; it is the dangerous endpoint of an unrepaired large shunt. [1] [4]

Examiner prompt 2 — the decision to close

Examiner. Should this duct be closed? [4]

Candidate. No. Once the pulmonary vascular resistance is fixed and non-reactive, closing the duct removes the low-pressure pop-off into the pulmonary bed and can precipitate right-heart failure. The 2018 AHA/ACC and 2020 ESC adult-congenital guidelines both contraindicate closure in established Eisenmenger physiology. The next step is to confirm the haemodynamics with cardiac catheterisation and vasodilator (oxygen or nitric oxide) testing to measure the pulmonary vascular resistance and test reversibility; if it is fixed and non-reactive, closure is withheld and management shifts to pulmonary-arterial-hypertension therapy, with heart-lung transplantation reserved for end-stage disease. The single most important judgement in a late-presenting PDA is recognising the operable boundary. [4] [5]

Examiner prompt 3 — contrast with the operable duct

Examiner. How would your management differ for a 3-year-old with a moderate duct and preserved, reversible pulmonary pressures? [1]

Candidate. That duct sits within the operable window and should be closed by transcatheter device occlusion with an Amplatzer Duct Occluder. The Masura landmark study established the device for the moderate-to-large duct, closure rates exceed 95%, and it is performed as a day-stay procedure from a femoral venous approach. Before the procedure I would confirm a structurally normal heart to exclude a duct-dependent circulation and document the pulmonary pressure, and the device would be selected to the Krichenko angiographic shape (the type A conical duct is the shape the standard device was designed for). Surgical ligation would be reserved for the small infant or the device-unfriendly duct. [1] [2]

Examiner prompt 4 — the small duct and prophylaxis

Examiner. And a silent duct found incidentally in a well child — would you close it to prevent infection? [3]

Candidate. Observation is the default. The 2007 American Heart Association endocarditis-prophylaxis revision removed routine antibiotic prophylaxis for the unrepaired PDA, on the evidence that the absolute risk is very low and prophylaxis does not reliably prevent endocarditis in this setting. That revision removed the main historical rationale for closing every silent duct, and the modern approach is to individualise the decision with the family, weighing the small procedural risk against the small infection risk, with observation as the default. A small, high-velocity, restrictive duct with a normal-sized heart may also close spontaneously. [1] [3]