Right atrial pressure alterations during echocardiography-guided-catheterization predict tricuspid valvular impairment: a novel method for the creation of a rabbit model of Staphylococcus aureus endocarditis

BACKGROUND We previously reported the use of a catheter system to damage the tricuspid valve and create infectious endocarditis (IE) in an animal model. The current study aims to create a faint IE model suitable for antibiotic prophylaxis using a low bacterial inoculum. We also aim to explore a way to quantitatively assess valvular impairment and to predict the success of the IE models during catheterization. METHODS Ninety rabbits were assigned to two groups according to the density of bacteria inoculated (1 × 10(5) CFU for Group A and 1 × 10(4) CFU for Group B). A catheter system consisting of a polyethylene catheter and a guide wire were used to damage the valve. The catheter system was passed through the rabbits' tricuspid valves under echocardiographic guidance. A pressure transducer was used to assess right atrial pressure (P(RA)) before and just after valvular damage to calculate the pressure alterations (ΔP(RA)). The animals in group A and B were divided into 3 subgroups according to the ΔP(RA) (0-5 mmHg for Groups A1 and B1; 5-10 mmHg for Groups A2 and B2; 10-15 mmHg for Groups A3 and B3). Staphylococcus aureus (ATCC 29213) inoculation was performed 24 hr after cardiac catheterization. RESULTS Faint IE was confirmed in 20%, 93.3%, 26.7%, 6.7%, 20%, and 33.3% of the rabbits in Groups A1, A2, A3, B1, B2, and B3, respectively. There was no difference in the LV/RV ratio and VTR of the No-IE, faint-IE, and severe IE animals. Faint IE rabbits had a larger ΔPRA than No-IE rabbits (7.81 ± 1.21 vs. 2.48 ± 1.0, P < 0.01, for Group A; 7.60 ± 1.32 vs. 2.98 ± 1.08, P < 0.01, for Group B). The ΔPRA of severe IE and faint IE rabbits was significantly different (13.11 ± 1.31 vs. 7.81 ± 1.21, P < 0.01, for Group A; 12.73 ± 1.44 vs.7.60 ± 1.32, P < 0.01, for Group B). CONCLUSION ΔP(RA) could be used to assess valvular impairment. Controlling the value of ΔP(RA) during catheterization and inoculating of an appropriate dose of bacteria was associated with a successful IE model.