Echo Diagnosis of Prosthetic Valve Endocarditis

Abstract & Commentary

Synopsis: Mild, perivalvular regurgitation cannot be used as a diagnostic criteria for prosthetic valve endocarditis.

Source: Ronderos RE, et al. J Am Soc Echocardiogr. 2004;17:644-649.

Even with transesophageal echocardiography (TEE), the diagnosis of infectious endocarditis is difficult in patients with prosthetic valves. Thus, Ronderos and colleagues sought to determine the accuracy of various findings indicative of prosthetic valve endocarditis. They evaluated 58 episodes of suspected prosthetic valve endocarditis in 49 patients: 32 patients had definite endocarditis by Durack’s criteria and 17 did not, by surgical criteria or long-term clinical follow-up (8-38 months). TEE features that distinguished the definite endocarditis groups were: valve dehiscence (4 episodes), pseudo-aneurysms (3), fistulae (2), and moderate-to-severe perivalvular regurgitation (15). These findings were not present in the non endocarditis group. Apparent vegetations were seen in 17 episodes of definite endocarditis and 1 negative patient. Perivalvular abscesses were seen in 19 positive cases and 1 negative case. Mild perivalvular regurgitation was seen in only 1 positive case, but 14 negative cases. Using the above findings, with the exclusion of mild perivalvular regurgitation, resulted in a positive predictive value for diagnosing endocarditis of 94%, and a negative predictive value of 96%. TEE findings were confirmed at operation in all but 2 patients: 1, with a TEE finding of vegetation, had a degenerated bioprosthetic valve, and 1 perivalvular abscess by TEE, was sterile at surgery. Mortality in the definite endocarditis group was 34%, but echo findings did not predict death. Ronderos et al concluded that mild perivalvular regurgitation cannot be used as a diagnostic criteria for prosthetic valve endocarditis.

Comment by Michael H. Crawford, MD

Prosthetic valves are strong echo reflectors and produce reverberation and shadowing artifacts that challenge the diagnostic accuracy for findings of endocarditis. Also, various non-infective surgical sequelae, such as sutures and hematomas, reduce the accuracy of diagnosing vegetations and abscesses. In addition, small amounts of perivalvular leaks are not uncommon because of suture failure or perivalvular atheromatosis plaques. Thus, even on TEE, diagnosing prosthetic valve endocarditis can be difficult. Yet, this diagnosis is critical since surgery is almost always the appropriate treatment.

This study provides some useful experience that helps with the diagnosis of prosthetic valve endocarditis. Fistulae, pseudo-aneurysms, dehiscence, or 3-4+ perivalvular regurgitation all had a 100% positive predictive value; whereas, mild perivalvular leaks had a positive predictive value of 6%. They defined pseudo-aneurysms as perivalvular cavities with flow in and out of them. Abscesses (cavities > 10 mm without blood flow) and vegetations were highly predictive, but there were false positives. Interestingly, vegetations, the hallmark of native valve endocarditis, were only seen in 50% of the definitely positive cases. One case that appeared to have a vegetation turned out to be a severely degenerated bioprosthetic valve. Although not observed in this study, sutures and small perivalvular strands can cause confusion as well.

The study has some limitations. The small number of cases requires that the 100% positive predictive values be taken with a grain of salt. One more case could drop these values. Also, 80% of the valves were mechanical, so conclusions about bioprosthetic valve endocarditis should be interpreted cautiously.

Dr. Crawford, Professor of Medicine, Associate Chief of Cardiology for Clinical Programs University of California San Francisco, is Editor of Clinical Cardiology Alert.