Perivalvular Abscess and Related Complications

The diagnosis of perivalvular abscess is more difficult in patients with prosthetic IE, because increased perivalvular thickness is a common finding in these patients even in the absence of IE. A previous study for comparison is useful in the assessment of these patients, and repeat studies in seven to ten days to look for evolutional changes as previously discussed with native valve IE remains very pertinent. Perivalvular abnormalities are common even in patients who have had early cardiac surgery to treat perivalvular abscess, and a recent study showed that these complications were present in about a third of these patients [28].

Transthoracic Echo

Perivalvular complications are more difficult to diagnose because the reverberation artifact from the prosthetic valve can mask surrounding structures (Table 7.10). This is particularly a problem with the posterior aortic root, which is obscured in patients with mechanical aortic prostheses. As infection disrupts the sewing ring annulus, part of the ring can dehisce leading to abnormal excessive rocking of a prosthesis. A rocking motion in excess of 15 degrees out of concordance with the supporting structures of the valve has been proposed as a criteria for perivalvular abscess [38]. The degree of rocking is proportional to the circumferential extent of LV-aortic discontinuity. This can vary from as little as one-quarter to as much as three-quarters of the circumference of the annulus [30]. When examined at autopsy and surgery, valves with excessive rocking have been shown to have dehiscence between 40% to 95% of the circumference of the sewing ring. The main false-positive sign of abnormal valve rocking relates to mitral and tricuspid prostheses in patients with very large mitral and tricuspid annuli and usually large atria [38]. In such patients, abnormal valve rocking can be seen without periannular abscess.

Transesophageal Echo

TEE can overcome many limitations of TTE in assessing the perivalvular region in patients with prosthetic valve IE [19,28,35]. Thus most patients with prosthetic valve IE should have TEE even if the image quality of TTE is adequate. An abscess on the anterior surface of the aortic root in the setting of a prosthetic aortic valve can be difficult to detect by TEE since the aortic prosthesis can shadow the anterior aortic root which is in the far field of the TEE image plane. In such cases images from TTE compliment the TEE images, by showing the anterior aspect of the aortic root and ascending aorta.

Perivalvular regurgitation in the setting of mitral valve prosthesis is optimally assessed by TEE, which provides detailed information regarding number, size, and location of the regurgitation jets (Figure 7.16). This information can be useful in the selection of patient for device closure of the perivalvular leak after the infection has been adequately treated. Other perivalvular complications including pseudoa-neurysm and fistula are also better imaged with TEE which should be performed in most patients suspected to have these perivalvular complications particularly if surgical intervention is contemplated (Figure 7.17).

Summary

1. Increased aortic wall thickness and excessive prosthetic valve rocking are signs of perivalvular abscess.

2. TEE should be performed in all patients with prosthetic valves and suspected perivalvular complications.

3. TEE may not adequately assess prosthetic valves in the aortic position.

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