When the electrocardiogram goes quiet: transient low voltage in systemic capillary leak syndrome-associated myocardial oedema-a case report.

Background: Systemic capillary leak syndrome (SCLS) is a rare disorder characterized by acute episodes of hypotension, haemoconcentration, and hypoalbuminemia. Case summary: A 50-year-old woman presented with shock triggered by influenza B infection. Despite aggressive fluid resuscitation, she developed multiorgan failure and was diagnosed with severe SCLS requiring venoarterial extracorporeal membrane oxygenation due to myocardial oedema. Electrocardiography demonstrated diffuse low QRS voltage, while echocardiography revealed severe biventricular dysfunction with marked myocardial oedema. The patient was treated with immunoglobulins, corticosteroids, and plasmapheresis. Following clinical recovery, QRS voltages normalized, and cardiac function fully recovered. Discussion: SCLS is an immune-mediated rare cause of distributive shock. Cardiac involvement is uncommon but associated with high mortality. This case suggested that reversible low QRS voltage may serve as an electrocardiographic clue to myocardial oedema and severe cardiac involvement.