Recommended Citation
Fletcher N, Martinez R, Graber D, Roy M. Unmasking the murmur: Native pulmonic valve endocarditis by streptococcus mitis in a patient without classic risk factors. Poster presentation at: ACMC Research Day 2026; April 29, 2026; Oak Lawn, IL.
Presentation Notes
Poster presentation at: ACMC Research Day 2026; April 29, 2026; Oak Lawn, IL
Abstract
Introduction: Infective endocarditis (IE) of the native pulmonic valve is exceedingly rare. Reported cases most commonly involve Staphylococcus aureus and occur in patients with intravenous (IV) drug use or congenital valvular disease.
Case Description: A 50-year-old woman with coronary artery disease and a secundum atrial septal defect (ASD) presented after one week of rigors, dyspnea, chest pain, and vomiting. Initial evaluation showed leukocytosis (14.3 K/mcL) and unremarkable vital signs. A previously undocumented high-pitched murmur was noted at the left upper sternal border. Blood cultures drawn in the emergency department grew Streptococcus species at 19 hours, and empiric IV ceftriaxone was started. Transthoracic echocardiogram revealed a 1.0 x 0.2 cm mobile pulmonic valve vegetation with moderate pulmonic and tricuspid regurgitation and severe right atrial dilation. Transesophageal echocardiogram also identified a large ASD with left-to-right shunt. Cultures speciated to Streptococcus mitis, which was susceptible to ceftriaxone. Cardiothoracic surgery was consulted and advised conservative management. The patient remained stable and was discharged on hospital day 7 with a six-week course of outpatient IV antibiotics.
Decision-making: The variable and often nonspecific presentation of IE complicates diagnosis. The patient denied IV drug use and fever, yet a new high-pitched murmur during bacteremia prompted evaluation. Imaging identified a pulmonic valve vegetation, and blood cultures grew S. mitis, fulfilling both major Duke criteria and yielding definite IE. Antibiotics were initially deferred due to clinical stability and unclear source. Culture growth prompted empiric IV ceftriaxone for predictable streptococcal coverage and tissue penetration. Conservative guideline-directed therapy for streptococcal endocarditis was chosen given hemodynamic stability and absence of embolic phenomena.
Conclusion: Streptococcus mitis is a rare cause of native pulmonic valve infective endocarditis in patients without classic right-sided risk factors. In this case, a 1.0-cm vegetation was successfully managed conservatively with a six-week IV ceftriaxone course.
Type
Poster