24th June 2026

Diagnosis

The diagnosis of IE should be based on a combination of signs, symptoms, and investigation results.

Clinical Manifestations

The clinical presentation of IE is extremely variable; it may present with acutely unwell and deteriorating patients, or as a sub-acute condition with non-specific symptoms.

Common signs and symptoms of patients with IE are those of infection:

• fever (seen in approximately 90% of patients)
• chills
• anorexia
• weight loss
• fatigue
• myalgias
• arthralgia
• night sweats
• dyspnoea
• headache
• symptoms related to the cause may also be present, such as toothache

Clinical signs that may be elicited on examination include:

• heart murmurs (seen in 85% of patients with IE)
• splenomegaly
• petechiae
• splinter haemorrhages
• Janeway lesions
• Osler’s nodes
• Roth spots
• heart failure (due to valvular incompetence)
• neurological symptoms (due to septic emboli, intracranial haemorrhage or cerebral abscess)

Image Source: Wikimeadia Commons (2017). January Lesion, Licensed under a creative commons licence. Available for free at: https://commons.wikimedia.org/wiki/File:Janeway_lesion.JPG (Accessed 2 May 2025)

Image Source: Wikimedia Commons (2017). Osler’s Nodes, Licensed under a creative commons licence. Available for free at: https://commons.wikimedia.org/wiki/File:Osler_Nodules_Hand.jpg (Accessed 2 My 2025)

If septic emboli are involved, patients may have signs consistent with renal or splenic infarction, or may have signs consistent with an infective source of the IE (septic arthritis, psoas abscess, osteomyelitis).

In patients presenting with subacute IE, the symptoms may be vague and non-specific, and a high degree of suspicion is required to make the diagnosis. Patients may present with congestive heart failure or a stroke with no other symptoms suggestive of endocarditis.

In patients with a prosthetic valve, whilst the presenting features may be similar to those in patients with NVIE, there are some particular features to be aware of. The frequency of new murmurs, a changing murmur, and presence of conduction defects on an ECG are seen more frequently in patients with IE with a prosthetic valve.

Investigations

All patients with suspected IE should have the following investigations:

• Blood cultures: at least 3 sets, ideally before antibiotics are given, taken from separate sites
• Bloods including WCC, U&Es and CRP/ESR
• ECG: looking for PR prolongation, which may be seen in the presence of an aortic root abscess
• Urine dip: evidence of renal failure
• Chest x-ray
• Trans-thoracic echocardiogram (TTE): first-line imaging investigation for IE

Other investigations to consider are:

• Trans-oesophageal echocardiogram (TOE): may be required if IE suspected but initial TTE is negative
• CT chest: indicated if an aortic root abscess is suspected; may also be required preoperatively in patients requiring surgical management
• Serological testing for culture negative organisms
• Other imaging to look for soft tissue abscess/vertebral osteomyelitis/evidence of septic emboli may also be required

Image Source: Wikimedia Commons (2017). Infective Endocarditis, Licensed under a creative licence. Available for free at: https://commons.wikimedia.org/wiki/Category:Bacterial_endocarditis (Accessed 2 May 2025)

Diagnostic Criteria

The diagnosis of IE is made based on the modified Duke’s criteria, outlined in the table below. A definite diagnosis of IE is defined as the presence of: two major criteria; one major and three minor criteria; or five minor criteria. A possible diagnosis is defined as: one major and one minor criterion or; three minor criteria. These are summarised in table 2:

Table 2: modified Duke criteria for infective endocarditis