Infective endocarditis without biological inflammatory syndrome: Description of a particular entity

Background: Bacterial infective endocarditis (IE) is rarely suspected in patients with a low C-reactive protein (CRP) concentration. Aims: To address the incidence, characteristics and outcome of left-sided valvular IE with low CRP concentration. Methods: This was a retrospective analysis of cases of IE discharged from our institution between January 2009 and May 2017. The 10% lowest CRP concentration (< 20 mg/L) was used to define low CRP concentration. Right-sided cardiac device-related IE, non-bacterial IE, sequelar IE and IE previously treated by antibiotics were excluded. Results: Of the 469 patients, 13 (2.8%; median age 68 [61–76] years) had definite (n = 8) or possible (n = 5) left-sided valvular IE with CRP < 20 mg/L (median 9.3 [4.7–14.2] mg/L). The median white blood cell count was 6.3 (5.3–7.5) G/L. The main presentations were heart failure (n = 7; 54%) and stroke (n = 3; 23%). Transthoracic echocardiography (TTE) showed vegetations (n = 5) or isolated valvular regurgitation (n = 4). Overall, eight patients (62%) had severe valvular lesions on transoesophageal echocardiography (TOE), and nine patients (69%) underwent cardiac surgery. All patients survived at 1-year follow-up. Bacterial pathogens were documented in eight patients (streptococci, coagulase-negative Staphylococcus, Corynebacterium jeikeium, HACEK group, Coxiella burnetii, Bartonella henselae) using blood cultures, serology or valve culture and/or polymerase chain reaction analysis. Conclusions: Left-sided valvular IE with limited or no biological syndrome is rare, but is often associated with severe valvular and paravalvular lesions. TOE should be performed in presence of unexplained heart failure, new valvular regurgitation or cardioembolic stroke when TTE is insufficient to rule out endocarditis, even in patients with a low CRP concentration.