A Diagnostic Odyssey: From Pulmonic to Prosthetic Valve Endocarditis

Infective endocarditis (IE) carries substantial morbidity and mortality despite appropriate antibiotic therapy and surgery. Right-sided IE is uncommon, and isolated pulmonic valve involvement is particularly rare. Echocardiography, transthoracic (TTE) and especially transesophageal (TEE), remains the cornerstone of diagnosis, although sensitivity may be limited, particularly in prosthetic valves. We report a 65-year-old man with prior bioprosthetic aortic valve replacement who presented after outpatient blood cultures grew gram-positive cocci. He described six weeks of exertional dyspnea, drenching night sweats, and 20-lb unintentional weight loss without recreational substance use. Blood cultures speciated to Streptococcus mitis (oral group). Initial TEE revealed a mobile vegetation on the pulmonic valve consistent with IE. Despite vancomycin and ceftriaxone, his symptoms persisted. Three subsequent TEEs failed to show prosthetic valve involvement. A fourth TEE ultimately demonstrated a large vegetation on the bioprosthetic aortic valve. He underwent redo-sternotomy and repeat aortic valve replacement, followed by a six-week antibiotic course with gradual clinical recovery. This case underscores the diagnostic complexity of IE with atypical presentations. Isolated pulmonic valve involvement without traditional risk factors is unusual and may resemble non-infectious processes. Prosthetic valve infection can emerge later in the disease course and evade detection on earlier imaging. In our patient, persistent but nonspecific symptoms, initially negative studies, and partial response to therapy obscured progression to prosthetic valve involvement. These features highlight the need for sustained clinical vigilance and timely repeat high-quality imaging when findings remain incongruent with the clinical course. Our report contributes to the limited literature on isolated pulmonic valve IE and its potential evolution to prosthetic valve infection.