Infective endocarditis is an infection of the endocardial surface of the heart, most often a valve. It is uncommon, it is frequently missed early, and untreated it is close to uniformly fatal — which is why a patient with unexplained fever and a reason to have a susceptible heart deserves active suspicion rather than reassurance. What makes it distinctive is that it is an *endovascular* infection. The organism is not walled off in a tissue abscess; it is sitting on a surface washed by every litre of blood the heart moves. That single fact explains almost everything else about the disease: the persistent bacteraemia, the need for prolonged intravenous therapy, the fever that does not settle, and the sudden catastrophic complications when a fragment breaks free. This lesson is written for Canadian registered-nurse practice. It covers recognising the disease, collecting blood cultures correctly, administering and monitoring prolonged antimicrobial therapy, watching for embolic and heart-failure complications, and escalating deterioration. Laboratory values follow SI units. On the exam, writers often pair stable-sounding options with unstable data—notice the mismatch before you commit. If...