Cardiac transplantation and ventricular assist devices — formative SAQs

SAQ 1 — The infant with a refractory dilated cardiomyopathy (20 marks, ~15 minutes)

A four-month-old infant with a known idiopathic dilated cardiomyopathy and an ejection fraction of 18 percent is on a loop diuretic, an ACE inhibitor and caloric supplementation. Over two weeks the tachypnoea worsens, feeds take longer with sweating, the weight crosses two centiles downward, and the creatinine begins to rise. The advanced heart-failure team is consulted. [4]

Questions

1. Define what is happening to this infant and why it triggers escalation beyond medical therapy. (4 marks) [6]
2. Outline the device options for an infant of this size and state which durable device is most likely to be used, with the evidence that supports it. (5 marks) [1]
3. Explain the strategic goal of the device in this child and what must be excluded before the child is listed for transplantation. (5 marks) [4]
4. State the leading complications of the device you have chosen and the surveillance they require. (6 marks) [10]

Model answer (must-hit)

1. The infant has refractory advanced heart failure — the persistent progression of signs (tachypnoea, sweaty feeds, failure to thrive) and the emergence of end-organ dysfunction (rising creatinine) despite maximal guideline medical therapy. This is the trigger to escalate beyond pharmacotherapy to an advanced heart-failure centre for assessment, because the whole pathway is a race to support and transplant the child before irreversible end-organ and pulmonary vascular injury. The neurohormonal vicious cycle can no longer be interrupted medically, so mechanical support and transplantation enter the plan. [6]
2. For an infant of this size the durable device is the paracorporeal pulsatile Berlin Heart EXCOR, which has pump sizes small enough for neonates and infants and whose bridge-to-transplant role was established by the Almond 2013 cohort of US children. Short-term support such as VA-ECMO or a CentriMag would be reserved for acute collapse, and a miniaturised continuous-flow implantable device is generally not an option for the smallest patients. Device choice is governed above all by the size of the child. [1]
3. The strategic goal is a bridge to transplantation — the device unloads the ventricle, restores nutrition and growth, and supports the child through the wait for a donor organ. A bridge-to-recovery strategy would be reserved for myocarditis or a recoverable cardiomyopathy. Before listing, the team must exclude a reversible cause — in particular a tachycardia-induced cardiomyopathy from an uncontrolled supraventricular tachycardia, which resolves with rate or rhythm control — and must measure the pulmonary vascular resistance by catheterisation, because a fixed high resistance predicts donor right-heart failure and, above a threshold, contraindicates orthotopic transplantation. [4]
4. Stroke is the dominant complication of the Berlin Heart EXCOR and a leading cause of death on support, so any new neurological sign needs urgent imaging and a neurology and haematology review. Infection of the driveline, pump pocket or bloodstream is the other major morbidity, alongside bleeding from anticoagulation, haemolysis and pump thrombosis. Surveillance therefore combines mandatory anticoagulation monitoring (titrated to an institutional target), serial neurological examination, driveline-site care and infection surveillance, and serial echocardiography to confirm adequate ventricular unloading. [10]

SAQ 2 — The adolescent on a VAD who develops a stroke (20 marks, ~15 minutes)

A 12-year-old girl with a dilated cardiomyopathy has been on a continuous-flow ventricular assist device as a bridge to transplantation for three weeks and is listed. She is on a heparin infusion transitioning to warfarin. The nurse finds her with a new right-sided weakness and slurred speech. [10]

Questions

1. Give the most likely diagnosis and why it is the feared complication of paediatric mechanical circulatory support. (4 marks) [10]
2. Outline your immediate assessment and management. (5 marks) [10]
3. Explain how the complication is monitored and why anticoagulation management is difficult on a VAD. (5 marks) [5]
4. Discuss how this event affects her transplant candidacy and the strategic goal of her device. (6 marks) [4]

Model answer (must-hit)

1. The most likely diagnosis is an ischaemic stroke — a new focal neurological deficit in a child on a ventricular assist device. Stroke is the dominant and most feared complication of paediatric VADs including the Berlin Heart EXCOR and continuous-flow devices, and it is a leading cause of death on support, quantified by the PediMACS stroke analysis. Any new neurological sign on a device is a stroke until proven otherwise. [10]
2. The immediate management is to secure ABC, perform an urgent neurological assessment, and obtain urgent brain imaging (CT then MRI) to characterise the stroke as ischaemic or haemorrhagic, because that decision frames anticoagulation. Notify the advanced heart-failure, neurology and haematology teams immediately. Anticoagulation may need to be held or adjusted depending on the stroke type and the bleeding risk, and the child is managed in a tertiary intensive care setting with neuroprotection and monitoring of intracranial pressure if required. [10]
3. Anticoagulation is mandatory on any mechanical support device to prevent pump thrombosis and further thromboembolic stroke, but it is the principal driver of bleeding risk — including haemorrhagic stroke — so the therapeutic window is narrow and unforgiving. Monitoring combines serial coagulation (anti-Xa or APTT for heparin, INR for warfarin), device-flow and pump-power surveillance for thrombus, haemolysis markers (lactate dehydrogenase, plasma-free haemoglobin), and serial neurological examination. Management is centre- and device-specific and requires specialist haematology input. [5]
4. A significant stroke complicates but does not automatically preclude transplantation — candidacy is reassessed by the multidisciplinary team weighing neurological recovery against the risk of waiting longer on the device, where further stroke may occur. The strategic goal of the device (bridge to transplant) is reinforced if recovery is expected, because completing the transplant removes the device and its stroke risk. If neurological injury is severe or irreversible, the team re-evaluates candidacy against the transplant criteria and the best-interests of the child, including a palliative pathway if transplantation is no longer appropriate. [4]