What is a reasonable inpatient imaging modality alternative to evaluate for infective endocarditis in a morbidly obese patient with poor acoustic windows on TTE and persistent bacteremia if TEE is not feasible or contraindicated?

This is an excellent question. Retrospectively gated cardiac CTA especially with the newer generations (Siemens Somatom force or Naetom alpha) are probably your best alternative. This would need careful planning and tube setting adjustments depending on the patient's body habitus as scattered and noisy images continue to be a problem in very large patients. FDG PET/CT would be an excellent option in patients with prosthetic heart valves/implanted devices and is usually performed in addition to gated cardiac CTA as they complement each other very well.

If the patient's body size is prohibitive for both modalities, TEE would usually still be an option and would be the most sensitive of all modalities. Absolute contraindications for TEE are rather uncommon and most relative contraindications can be mitigated. A risk and benefit discussion with the patient is always helpful and as long as the TEE is performed carefully and cautiously, rate of complications would be exceedingly low especially if the procedure is planned well in advance with immediate support by our anesthesia and gastroenterology support.

PET combined with gated CTA would be good alternatives. CTA is an excellent modality for assessing for large vegetation (> 1 cm) when compared with TEE though it may miss smaller vegetations. It is also excellent at identifying aortic root abscesses. PET would be very beneficial if there is concern for prosthetic valve endocarditis and/or device-related endocarditis. It is important to recognize that PET will not be useful within 3-6 months after cardiac surgery as there will be residual inflammation that will be difficult to distinguish from infection.

When trans-esophageal echocardiogram cannot obtain acoustic windows, I agree with the CTA and PET as listed (newly added to the updated 2023 modified Duke criteria as imaging evidence - Fowler et al., PMID 37138445

Not included in the guidelines but another modality we utilize in ACHD is intracardiac echocardiography (ICE). It's particularly helpful when looking at prosthetic valves (prosthetic pulmonary valves tend to be particularly challenging where the ICE probe can be placed down the barrel of the RVOT). Some examples of published literature of ICE for SBE:

• Østergaard et al., PMID 31587968 - case series from 2019 JASE re: use in PVE
• Sanchez-Nadales et al., PMID 37172870 - 2023 literature review; 12 publications = 9 case reports/series of 10 patients and 3 series where ICE was used in 236 patients.
• Chi Yang et al., PMID 30791720 - another case report

I usually use a 9F access for an AcuNav intracardiac echo catheter (can be done with ultrasound guidance in morbid obesity) and though most use a femoral venous approach, a right internal jugular vein approach can be used as well if groin access challenging (sometimes a must with interrupted IVC or bilateral femoral venous/IVC occlusion). Excellent visualization of the tricuspid and mitral valve are frequently used by EPs prior to afib ablations. From the high RA clocked to en face view of the aorta (like parasternal short axis) and mid RV clocked to the outflow tracts, the aortic valve can be well visualized. I find the pulmonary valve best visualized from the RVOT down the barrel. The procedure can be performed with local anesthetic for access + moderate sedation for any anxiety or more if performing other procedures. For patients with orthopnea, a wedge to elevate the head can be used with groin or neck access. For cardiology fellows training in a site with ICE, I recommend spending time practicing common views of normal anatomy (such as the valves and left atrial appendage) to be able to use them when needed for innovative uses, such as evaluation for endocarditis.

FDG-PET would be a good option in this scenario. Morbid obesity generally not a contraindication to TEE but would likely require general anesthesia to be done safely.