From Valve to Vessel: Disseminated Staphylococcus aureus Endocarditis Leading to Splenic Artery Pseudoaneurysm and Mycotic Aneurysm

Infective endocarditis (IE) is an infection of the endocardial surface of the heart, with Staphylococcus aureus as the leading cause in the United States. Identified risk factors include advanced age, male sex, intravenous drug use (IVDU), prior IE, structural or valvular heart disease, HIV infection, and chronic hemodialysis. In IVDU, IE most commonly affects the right-sided valves, while bivalvular involvement is uncommon but associated with more severe disease and increased risk of rapid deterioration. Multiple complications arise from IE, including variable vascular phenomena and systemic embolic complications. A 62-year-old male with a history of polysubstance abuse and intravenous drug use (heroin) presented with altered mental status. He was febrile and tachycardic, with laboratory studies revealing a white blood cell count (WBC) of 24.8 × 10³/µL, an elevated erythrocyte sedimentation rate (ESR) of 130 mm/hr, and a C-reactive protein (CRP) of 248 mg/L. Blood cultures grew methicillin-sensitive Staphylococcus aureus (MSSA). Transesophageal echocardiography revealed vegetations on both the mitral and tricuspid valves, confirming bivalvular IE. His disease course was complicated by a cardioembolic stroke, L1-L2 osteomyelitis, bilateral psoas abscesses, septic pulmonary emboli, and splenic infarctions. During hospitalization, he developed a ruptured splenic artery pseudoaneurysm (SAPA), successfully managed with selective endovascular embolization requiring multiple blood transfusions and ICU-level monitoring for hemodynamic instability. Following stabilization, he returned to the medical floor to continue intravenous antibiotics and supportive care, but subsequently developed an enlarging abdominal aortic mycotic aneurysm (MA). Patient underwent mitral and tricuspid valve replacements, which were complicated by second-degree atrioventricular block progressing to complete heart block, necessitating permanent pacemaker placement. His hospital course was further complicated by bilateral pleural effusions requiring thoracentesis and a pericardial effusion requiring emergent subxiphoid pericardial window creation. He was discharged to a rehabilitation facility on chronic suppressive therapy with oral cephalexin and levofloxacin for a concomitant Serratia infection and subsequently underwent endovascular aortic repair. This case highlights the aggressive and disseminated course of S. aureus IE in IVDU, with bivalvular involvement, which may be associated with an increased risk of systemic embolization. Large, mobile vegetations exceeding 10 mm in size, especially when located on the left-sided valves, are strong indications for early surgical intervention. While the brain and spleen are common embolic sites, this case demonstrates rare vascular complications such as SAPA and MA, which can be life-threatening due to the risk of rupture and hemorrhage. The patient ultimately required bivalvular replacement, which also increases the risk of heart block due to the proximity of the valves to the conduction system. Early detection through imaging, timely multidisciplinary management, and consideration of surgical or endovascular intervention even during active infection are critical for improving outcomes in patients with complex, disseminated IE.