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PubMed This is a summary of 16 peer-reviewed journal articles Updated
Cardiology

Solving the Puzzle: How Doctors Diagnose Endocarditis

At a Glance

Doctors diagnose infective endocarditis using the updated 2023 Duke-ISCVID criteria, which combine major and minor evidence. A diagnosis relies on blood cultures to identify the exact bacteria and imaging like TEE or PET/CT scans to locate the infection on your heart valves.

Diagnosing infective endocarditis (IE) is like solving a complex puzzle. Doctors don’t rely on just one test; instead, they use a standardized set of rules called the Duke Criteria to piece together your symptoms, blood work, and imaging results. In 2023, these rules were significantly updated (now called the 2023 Duke-ISCVID criteria) to include more advanced technology and a better understanding of how different germs behave [1][2].

The Three Outcomes of Diagnosis

When your doctors apply these criteria, they will place you into one of three categories:

  1. Definite IE: There is enough evidence (from cultures, imaging, or surgery) to be certain of the infection [3].
  2. Possible IE: There are strong signs of infection, but not quite enough to meet the “definite” threshold. This category is still treated with high caution, as many “possible” cases are later confirmed to be “definite” [4][5].
  3. Rejected: The evidence points toward a different diagnosis or the symptoms have resolved [3].

The Tools of Discovery

To reach a diagnosis, your medical team uses two primary types of “evidence”: Major Criteria (strong evidence like positive blood cultures or clear imaging) and Minor Criteria (supporting evidence like a fever or pre-existing heart conditions) [1].

1. Blood Cultures: The Gold Standard

Blood cultures are the most important part of the diagnosis. They tell doctors exactly which germ is in your blood. The 2023 update expanded which bacteria are considered “major” signs, recognizing that certain germs are more likely to cause heart infections than previously thought [6][7].

2. Echocardiography: Looking at the Valves

An echocardiogram (echo) uses sound waves to create a picture of your heart. There are two main types:

  • TTE (Transthoracic Echo): This is the standard “outside-in” ultrasound where a probe is moved over your chest. It is a great first step but can sometimes miss small infections [8][9].
  • TEE (Transesophageal Echo): This is an “inside-out” ultrasound. You are usually sedated, and a thin tube is passed down your esophagus (food pipe), which sits right behind the heart. TEE is much more sensitive and can see tiny vegetations or abscesses that a TTE might miss [8][10].

3. Advanced Imaging: PET/CT and Cardiac CT

If you have a prosthetic (artificial) valve or a pacemaker, standard echoes can be blurry due to the metal or plastic parts. In these cases, the 2023 guidelines officially recognize two advanced tools:

  • 18F-FDG PET/CT: This scan uses a small amount of radioactive sugar to find areas of “hot” inflammation. It is especially powerful for finding infections on artificial valves [11][12].
  • Cardiac CT (CTA): This provides a highly detailed 3D map of the heart’s anatomy, helping surgeons see if the infection has spread into the surrounding tissue [13][14].

By combining these advanced scans with your blood results, your Endocarditis Team can move from a “possible” diagnosis to a “definite” one, ensuring you get the right treatment as quickly as possible [15][16].

Common questions in this guide

What is the Duke Criteria for diagnosing endocarditis?
The Duke Criteria is a standardized set of rules doctors use to diagnose infective endocarditis. It combines major evidence, like positive blood cultures or echocardiogram results, with minor evidence like fevers to determine if you have a definite or possible infection.
What is the difference between a TTE and a TEE for endocarditis?
A TTE is a standard ultrasound performed on the outside of your chest, while a TEE is performed using a thin tube passed down your esophagus while you are sedated. TEE provides a much clearer, inside-out picture of your heart valves and is better at spotting tiny infections.
Why might I need a PET/CT scan if I already had an echocardiogram?
Standard echocardiograms can be blurry if you have a prosthetic heart valve or a pacemaker due to the metal and plastic parts. A PET/CT scan looks for 'hot' areas of inflammation, making it highly effective at finding infections on artificial valves.
What does it mean if my endocarditis diagnosis is classified as possible?
A 'possible' diagnosis means you have strong signs of a heart infection, but not quite enough evidence to be absolutely certain. Doctors treat 'possible' cases with high caution, as many are later confirmed to be definite infections as more test results come back.
Why are blood cultures so important for diagnosing a heart infection?
Blood cultures are the gold standard for diagnosing endocarditis because they identify the exact bacteria causing the infection. Knowing the specific germ helps your medical team confirm the diagnosis and guide your overall treatment plan.

Questions to Ask Your Doctor

Curated prompts to bring to your next appointment.

  1. 1.How many 'major' and 'minor' criteria do I currently meet under the 2023 Duke-ISCVID guidelines?
  2. 2.If my initial heart ultrasound (TTE) was negative, do we need to proceed to a TEE to get a clearer picture?
  3. 3.Would a PET/CT or a Cardiac CT help in my case, especially if my infection is on a prosthetic valve or device?
  4. 4.How are we managing my case if it's currently classified as 'possible' endocarditis?
  5. 5.What specific bacteria are growing in my blood cultures and how does that influence the diagnosis?

Questions For You

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References

References (16)
  1. 1

    External Validation of the 2023 Duke-International Society for Cardiovascular Infectious Diseases Diagnostic Criteria for Infective Endocarditis.

    van der Vaart TW, Bossuyt PMM, Durack DT, et al.

    Clinical infectious diseases : an official publication of the Infectious Diseases Society of America 2024; (78(4)):922-929 doi:10.1093/cid/ciae033.

    PMID: 38330166
  2. 2

    The Clinical Challenge of Prosthetic Valve Endocarditis: JACC Focus Seminar 3/4.

    Cuervo G, Quintana E, Regueiro A, et al.

    Journal of the American College of Cardiology 2024; (83(15)):1418-1430 doi:10.1016/j.jacc.2024.01.037.

    PMID: 38599718
  3. 3

    Evaluation of the Specificity of the 2023 Duke-International Society of Cardiovascular Infectious Diseases Classification for Infective Endocarditis.

    Moisset H, Rio J, Benhard J, et al.

    Clinical infectious diseases : an official publication of the Infectious Diseases Society of America 2024; (78(4)):930-936 doi:10.1093/cid/ciae034.

    PMID: 38330172
  4. 4

    Performance of the 2023 Duke-International Society of Cardiovascular Infectious Diseases Diagnostic Criteria for Infective Endocarditis in Relation to the Modified Duke Criteria and to Clinical Management-Reanalysis of Retrospective Bacteremia Cohorts.

    Lindberg H, Berge A, Jovanovic-Stjernqvist M, et al.

    Clinical infectious diseases : an official publication of the Infectious Diseases Society of America 2024; (78(4)):956-963 doi:10.1093/cid/ciae040.

    PMID: 38330240
  5. 5

    A multimodality imaging approach to the diagnosis of infective endocarditis: incremental value of combining modalities.

    Boyle S, Arvanitaki A, Oldfield K, et al.

    The international journal of cardiovascular imaging 2025; (41(10)):1907-1919 doi:10.1007/s10554-025-03480-0.

    PMID: 40824410
  6. 6

    Evaluation of the 2023 Duke-International Society of Cardiovascular Infectious Diseases Criteria in a Multicenter Cohort of Patients With Intravenous Drug Use: A Retrospective Study.

    Han QJ, Henson DM, Yucel E, et al.

    Open forum infectious diseases 2025; (12(3)):ofaf126 doi:10.1093/ofid/ofaf126.

    PMID: 40124200
  7. 7

    Infectious endocarditis complicated with intracranial infected aneurysm rupture and sinus of valsalva aneurysm rupture.

    Sun Z, Xu X, Liu Z

    BMC neurology 2024; (24(1)):372 doi:10.1186/s12883-024-03870-2.

    PMID: 39367294
  8. 8

    A comparative analysis between transthoracic and transesophageal echocardiography in screening for infective endocarditis in patients with Staphylococcus aureus bacteremia.

    Corbyn Cravero J, Young J, Zamin SA

    Proceedings (Baylor University. Medical Center) 2025; (38(6)):801-805 doi:10.1080/08998280.2025.2546271.

    PMID: 41341094
  9. 9

    Hemodynamic monitoring using trans esophageal echocardiography in patients with shock.

    Boissier F, Bagate F, Mekontso Dessap A

    Annals of translational medicine 2020; (8(12)):791 doi:10.21037/atm-2020-hdm-23.

    PMID: 32647716
  10. 10

    Aortic Periannular Abscess Missed by Transthoracic Echocardiography: A Case Report.

    He W, Peng Y, Yi Y, et al.

    Clinical case reports 2025; (13(1)):e70114 doi:10.1002/ccr3.70114.

    PMID: 39831136
  11. 11

    Contemporary Role of Positron Emission Tomography (PET) in Endocarditis: A Narrative Review.

    Sammartino AM, Bonfioli GB, Dondi F, et al.

    Journal of clinical medicine 2024; (13(14)) doi:10.3390/jcm13144124.

    PMID: 39064164
  12. 12

    Diagnosis of Infective Endocarditis by Subtype Using 18F-Fluorodeoxyglucose Positron Emission Tomography/Computed Tomography: A Contemporary Meta-Analysis.

    Wang TKM, Sánchez-Nadales A, Igbinomwanhia E, et al.

    Circulation. Cardiovascular imaging 2020; (13(6)):e010600 doi:10.1161/CIRCIMAGING.120.010600.

    PMID: 32507019
  13. 13

    Multimodality Imaging in Infective Endocarditis: A Clinical Approach to Diagnosis.

    Brugiatelli L, Patani F, Lofiego C, et al.

    Medicina (Kaunas, Lithuania) 2025; (61(12)) doi:10.3390/medicina61122241.

    PMID: 41470242
  14. 14

    Multimodality imaging of an aortic graft infection.

    Uslu A, Kup A, Güner A, et al.

    Echocardiography (Mount Kisco, N.Y.) 2019; (36(12)):2271-2273 doi:10.1111/echo.14545.

    PMID: 31758716
  15. 15

    Neurological Complications of Infective Endocarditis.

    Sotero FD, Rosário M, Fonseca AC, Ferro JM

    Current neurology and neuroscience reports 2019; (19(5)):23 doi:10.1007/s11910-019-0935-x.

    PMID: 30927133
  16. 16

    Fewer Minor Modified Duke Criteria on Admission Are Associated with Worse 90-Day Mortality in Patients with Confirmed Infective Endocarditis.

    von Sanden F, Orlovius K, Andreß S, et al.

    Journal of clinical medicine 2025; (14(21)) doi:10.3390/jcm14217703.

    PMID: 41227098

This page explains diagnostic criteria and testing for infective endocarditis for educational purposes only. Always rely on your cardiology and infectious disease team to interpret your specific test results.

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