Introduction to Destructive Citrobacter Endocarditis

Infective endocarditis caused by non-HACEK gram-negative bacilli remains an uncommon yet catastrophic clinical entity. Among these organisms, Citrobacter koseri represents an exceptionally rare etiology in adults that typically portends profound tissue destruction. Clinicians encounter this pathogen predominantly in immunocompromised hosts, individuals with indwelling vascular catheters, and patients with end-stage renal disease undergoing maintenance hemodialysis. Because these bacteria produce potent endotoxins and aggressive proteolytic enzymes, invasive infection frequently extends beyond the native or prosthetic valve leaflets into neighboring annular structures. Consequently, patients with destructive Citrobacter endocarditis often develop invasive root abscesses, conduction system disruption, and complex intracardiac fistulae. Timely recognition requires high clinical suspicion, repeated blood cultures, and advanced multimodality imaging. Medical therapy alone uniformly fails in this invasive setting because antibiotics cannot penetrate necrotic annular tissue or mechanical defects. Therefore, surviving this aggressive condition depends entirely on rapid hemodynamic stabilization, targeted antimicrobial regimens, and coordinated operative intervention.

Pathophysiology of Aortocavitary Fistula Formation

Periannular extension represents one of the most perilous complications of bacterial endocarditis. When invasive infection originates on the aortic valve, the microorganism easily erodes into the fibrous skeleton of the heart. In anatomically vulnerable areas, this erosion rapidly breaches the intervalvular fibrosa or penetrates the interventricular septum. Consequently, an aortic root abscess can rupture directly into adjacent low-pressure cardiac chambers, producing an aortocavitary fistula. In this clinical scenario, the destructive process created a direct shunt between the left ventricular outflow tract and the right ventricular outflow tract. Such fistulous tracts generate massive left-to-right intracardiac shunting, which abruptly increases pulmonary blood flow while causing acute right ventricular volume overload. In addition, the systemic circulation suffers from compromised forward cardiac output and severe hemodynamic instability. Transthoracic and transesophageal echocardiography remain essential diagnostic tools to delineate the precise anatomy of these shunts, quantify shunt fraction, and detect associated annular disruption before planning high-risk surgical reconstruction.

Perioperative Antiplatelet Bridging with Cangrelor

Managing surgical timing becomes exceptionally challenging when severe infective endocarditis occurs shortly after percutaneous coronary intervention. Patients with recent drug-eluting coronary stents require uninterrupted dual antiplatelet therapy to prevent catastrophic acute stent thrombosis. However, immediate cardiopulmonary bypass and extensive tissue debridement carry prohibitive bleeding risks in the presence of irreversible oral P2Y12 inhibitors. To reconcile these competing risks, clinicians frequently implement short-acting intravenous antiplatelet bridging strategies. Cangrelor serves as an ideal agent in this critical scenario because it provides potent, reversible P2Y12 platelet inhibition with an exceptionally rapid offset of action. Clinicians discontinue oral agents such as clopidogrel or ticagrelor and infuse cangrelor continuously until several hours before surgical incision. Platelet function recovers quickly once the infusion stops, which substantially mitigates intraoperative coagulopathy. Furthermore, this deliberate strategy prevents catastrophic intraoperative thrombosis within recently placed coronary stents, thereby providing a secure physiological window for complex cardiac operations.

Surgical Strategies for Complex Redo Root and RVOT Reconstruction

Eradicating extensive periannular infection requires radical debridement of all infected and nonviable cardiovascular tissue. When an aortocavitary fistula involves both outflow tracts, surgeons must perform aggressive source control followed by meticulous anatomical reconstruction. In reoperative settings, sternal reentry carries substantial risks of injuring adherent bypass grafts or cardiac chambers. After safe exposure, the surgical team completely excises the infected aortic root, clears abscess cavities, and exposes the fistulous tract. Surgeons subsequently close the communication between the left and right ventricles using resilient patches, such as glutaraldehyde-treated bovine pericardium. To restore systemic outflow, surgeons frequently implant a biological root prosthesis, such as a stentless porcine bioprosthesis, because it conforms well to distorted annular anatomy. Concurrently, reconstruction of the right ventricular outflow tract requires a pulmonary homograft to ensure an unobstructed, infection-resistant pulmonary conduit. This dual-outflow reconstruction reliably restores structural integrity and eliminates pathological intracardiac shunts.

Postoperative Care and Multidisciplinary Outcomes

Recovery following extensive redo root and right ventricular outflow tract reconstruction demands comprehensive intensive care management. Hemodialysis-dependent patients require vigilant fluid balance optimization, continuous renal replacement therapy, and close monitoring of cardiac filling pressures. In addition, postoperative monitoring must focus on potential atrioventricular conduction blocks, which frequently complicate extensive annular debridement. Concurrently, infectious disease specialists must guide prolonged targeted intravenous antibiotic regimens to prevent recurrent bacteremia and eradicate microscopic residual infection. Serial echocardiographic surveillance remains mandatory to evaluate prosthetic valve hemodynamics, monitor ventricular recovery, and verify complete closure of intracardiac fistulae. At six-month follow-up assessments, well-executed reconstructions demonstrate normally functioning bioprostheses without significant structural degeneration or conduit stenosis. Ultimately, achieving long-term survival in these fragile patients highlights the vital necessity of integrated care across cardiology, cardiac surgery, nephrology, critical care, and infectious disease services.

Frequently Asked Questions (FAQs)

What makes Citrobacter species especially dangerous in infective endocarditis?

Citrobacter species are aggressive gram-negative bacilli that produce potent endotoxins and tissue-destroying enzymes. These organisms rapidly invade periannular cardiac tissues, causing deep myocardial abscesses, fibrous skeleton disruption, and intracardiac fistulae. Because these pathogens possess intrinsic antimicrobial resistance and frequently infect debilitated hosts, standard medical therapies often fail, necessitating urgent surgical intervention.

How does cangrelor bridging assist patients requiring urgent cardiac surgery?

Cangrelor is an intravenous, reversible P2Y12 platelet inhibitor with an ultrashort plasma half-life. It maintains reliable stent thrombosis protection following recent coronary stenting while replacing oral antiplatelet agents. Because platelet function normalizes within one hour after stopping the infusion, cangrelor minimizes catastrophic intraoperative bleeding risks during urgent cardiopulmonary bypass.

Why are homografts and bioprosthetic roots favored in extensive root debridement?

Homografts and stentless bioprosthetic aortic roots offer superior anatomical pliability, allowing surgeons to reconstruct severely distorted annular structures after radical debridement. In addition, biological materials conform securely across complex abscess cavities and demonstrated lower reinfection rates compared to bulky synthetic mechanical prostheses in active, invasive bacterial endocarditis.

Disclaimer: This content is for informational and educational purposes only. It is not intended as a substitute for professional medical advice, diagnosis, or treatment. Refer to the latest local and national guidelines for clinical practice.

References

Petrikas M et al. Redo Root and RVOT Reconstruction for Destructive Citrobacter Koseri Endocarditis. JACC Case Rep. 2026 Sep 12. doi: undefined. PMID: 42732474.

Baddour LM, Wilson WR, Bayer AS, et al. Infective Endocarditis in Adults: Diagnosis, Antimicrobial Therapy, and Management of Complications: A Scientific Statement for Healthcare Professionals From the American Heart Association. Circulation. 2015;132(15):1435-1486.

Angiolillo DJ, Firstenberg MS, Price MJ, et al. Bridging antiplatelet therapy with cangrelor in patients undergoing cardiac surgery: A pooled analysis of the BRIDGE trials. Am Heart J. 2014;168(4):534-541.

El-Hamamsy I, Eryigit Z, Stevens LM, et al. Long-term outcomes after autograft versus homograft aortic root replacement in adults with infective endocarditis. Ann Thorac Surg. 2015;100(2):448-454.