Case Presentation: A 63-year-old man with a history intravenous heroin use disorder and chronic homelessness was readmitted for worsening right lower extremity pain secondary to recently diagnosed unprovoked bilateral deep vein thrombosis (DVT). He reported substernal chest pain without radiation and dyspnea but denied fevers, chills, weight loss or recent heroin use. His temperature was 36.9C; pulse 83/min; and blood pressure, 147/82 mm Hg. Physical exam revealed a moderately distressed patient due to pain with bilateral lower extremity swelling. Cardiac exam was absent of right-sided murmur. Laboratory data revealed no leukocytosis and initial blood cultures were negative. Following a negative work-up for acute coronary syndrome and pulmonary embolism a transthoracic echocardiogram (TTE) incidentally revealed a long filamentous highly mobile echogenicity, 2.1 x 0.5 cm, attached to the posterior tricuspid leaflet suspicious for a vegetation. Mild tricuspid regurgitation was also noted with an elevated right ventricular systolic pressure of 49 mmHg. Infective endocarditis (IE) was suspected due to the patient’s heroin use history and TTE findings. The patient did not meet a diagnosis of IE by the Modified Duke Infective Endocarditis Criteria and empiric antibiotics were held pending further evaluation. Cardiology, cardiothoracic surgery and infectious disease were consulted. Cardiothoracic surgery declined surgical intervention due to asymptomatic mild tricuspid regurgitation. Infectious disease recommended holding empiric antibiotic therapy and subsequent blood cultures were negative. Cardiology recommended transesophageal echocardiogram (TEE) which was prematurely terminated due to sinus arrest likely secondary to vasovagal response. Cardiology determined that the echogenicity was not consistent with a vegetation but was due to a large Chiari network that did not require medical or surgical intervention. The patient was subsequently discharged on rivaroxaban for treatment of bilateral lower extremity DVT in stable condition.

Discussion: A Chiari network is an embryologic remnant that results due to incomplete resportion of the right valve of the sinus venosus. It is described as a net-like structure and is a normal anatomical variant. Typically diagnosed incidentally, it has been reported in up to 2% of cases of patients undergoing TEE and 1.3% to 4% of autopsy studies. Despite its limited clinical significance, it can be mistaken for right-sided pathologies, such as vegetations due to endocarditis, particularly in the setting of constitutional symptoms, congestive heart failure and venous thromboembolism. This misdiagnosis can potentially lead to unnecessary antibiotic therapy and invasive surgical intervention.

Conclusions: This case highlights the importance of employing a multidisciplinary team including cardiology, cardiothoracic surgery and infectious disease in the evaluation of echogenic structures detected by TTE in the inpatient setting. Irrespective of suspected vegetation size, clinicians should use caution when treating empirically for endocarditis. The Modified Duke Infective Endocarditis Criteria may be employed in the management of echogenic masses when IE is suspected, prior to initiation of antibiotic therapy.