We present the case of a female 20-year-old patient who consults for a febrile syndrome of 7 days evolution, with asthenia and adynamia. As a relevant history, the patient presented pulmonary valve stenosis and aortic valve dysplasia at birth, as part of the clinical suspicion of Noonan syndrome. Throughout her growth, the patient had to undergo several surgeries: at one year of age, she was submitted to enlargement of the pulmonary artery outflow tract and plastic repair of the aortic valve; at 13 years, she required aortic valve replacement with a number 18 ATS type bi-disc mechanical prosthesis, with annulus enlargement and pulmonary valve replacement with a Nº 19 Freestyle type biological prosthesis; and then, at 17 years, given the marked increase in gradients through the lung graft, a number 20 Melody type valve was percutaneously implanted. It should be noted that despite the multiple interventions the patient had a normal physical, social, and intellectual development.

Given the relevant cardiological history, it was decided to hospitalize the patient to clarify and identify the focus that caused the fever. As positive data, the gram negative Cardiobacterium bacillus of the HACEK group was identified in serial blood cultures. The transesophageal color Doppler echo showed a marked increase in the Melody-type pulmonary valve gradients, with mobile structures compatible with vegetations (Figure 1. A and B) and the positron emission tomography (PET/CT) scan revealed a clear increase in the uptake of the pulmonary valve region (Figure 1. C).

Fig. 1 Preoperative studies. A, B: Pulmonary valve echocardiogram. C: PET/CT scan with prosthetic uptake. 

Considering the clinical diagnosis and complementary studies, the febrile condition was interpreted as endocarditis of the pulmonary endoprosthesis, so a new surgery was performed to replace the clearly infected prosthesis and the pulmonary artery outflow tract with a number 21 homograft. The prosthetic aortic valve was undamaged, so its replacement was not required (Figure 2. A, B and C).

Fig. 2 Intraoperative images. A: Intact aortic valve. B/C: prothesis in pulmonary position with clear signs of endocarditis 

The postoperative evolution was satisfactory and the antibiotic therapy included ceftriaxone and gentamicin according the sensitivity of the Cardiobacterium. At one- year follow-up, the patient leads a normal, hemodynamically stable life, free of cardiac infection, with normal functioning of the pulmonary homograft.

The risk of infective endocarditis (IE) after percutaneous Melody pulmonary valve implantation (MPVI) is significant, at least during the first 3 years after implantation. However, the reported incidence varies considerably between different studies.

In a meta-analysis that included 851 patients, the cumulative incidence of IE on MPVI ranged from 3.2% to 25%, with an annualized incidence rate ranging from 1.3% to 9.1% patient-years. The median (interquartile range) time from MPVI to IE onset was 18 months (9-30.4), with a range between 1 and 72 months. The incidence of IE occurred in 32% of cases in the first year, 27% in the second year, 18% in the third year, and 23% beyond 3 years of MPVI. ¹

In a study conducted by McElhinney et al. in 309 patients with a follow-up of nearly 5 years, multivariate analysis found age under 12 years at the time of MPVI (OR 2.8; 95% CI 1.3-5.7; p=0.006) and a maximum gradient immediately after implantation greater than 15 mmHg (OR 2.6; 95% CI 1.3-5.2; p=0.008) as IE predictors. ²

The diagnosis of this type of IE is challenging, es pecially in terms of documentation of the valve prosthesis infectious process. The modified classic Duke criteria, based on echocardiographic signs, confirm that the IE diagnosis after MPVI is not so simple. It is well known that echocardiography, especially transthoracic echocardiography (TTE), offers only modest sensitivity (30%) for the detection of pulmonary valve vegetations, probably due to the anterior position of the right ventricular outflow tract and prosthetic valve artifacts (stent, valve degeneration, calcification of the conduit, etc.). Moreover, transesophageal echocardiography (TEE), unlike the high sensitivity of IE detection in the aortic and mitral valves, does not always offer added value with respect to the TTE in pulmonary prosthetic valve IE. In the case reported, we believe that the PET/CT scan was able to identify the infectious process in the pulmonary prosthesis and ruled out aortic valve involvement, an extremely important data when planning a surgical strategy.

18F-FDG PET/CT combines a technique with high sensitivity to detect inflammatory-infectious activity and high anatomical resolution to assess structural lesions associated with endocarditis. With 91-97% diagnostic sensitivity, PET/CT has become a useful diagnostic tool in suspected IE of patients with prosthetic valves and/or devices, becoming a major criterion in the diagnostic algorithm for current guidelines. ³

The most common clinical findings found in MPVI IE were positive blood cultures (93%), fever (89%), and progressive increase in the pulmonary transvalvular gradient (79%). Vegetations by TTE were detected only in 34% of cases. These data reported in the literature were also presented by our patient, with TTE being too weak to define the origin of the infective condition. In the cited meta-analysis, among 69 patients who developed IE after MPVI, 6 (8.7%) died and 35 (52%) underwent surgical and/or transcatheter reoperation. ¹

The most common germs that have been detected in the blood cultures of patients with IE post MPVI are: Staphylococcus 42%, Streptococcus 30.4%, Corynebacterium 5.8%, HACEK group 4.3% and Haemophilus 2.9%; and negative blood cultures have been detected in just over 7% of patients. ^1,4 Cardiobacterium hominis (germ responsible in our case) is a member of the HACEK group, which produces subacute IE; its natural habitat is the oropharynx.

The microbial entry route is related in most cases to oral processes. However, there are reports in patients with a history of gastroenteritis, cystitis, pneu monia, skin and nail processes, as well as skin tattoos. ⁵

The incidence of IE after implantation of a percutaneous pulmonary valve is highly variable as reported in the studies, and it occurs mainly during the first 3 years after the procedure and mostly in the presence of increased transpulmonary gradients. The cardiac history should suggest IE in the presence of a febrile condition of unknown origin. Multi-imaging studies, including PET/CT scan, have been extremely useful in identifying the focus of infection secondary to Cardiobacterium IE in our patient. We believe that the satisfactory resolution of the case was due to the interaction of the members of the cardiology and surgery service in adult congenital pathologies, given the complexity of decision-making and previous surgical interventions. The homograft has allowed us to resolve a complex surgical situation.