Value of Echocardiography for Detecting Mechanical Prosthetic Valve Dysfunction

Abstract & Commentary

By Michael H. Crawford, MD Dr. Crawford is the Professor of Medicine, Chief of Clinical Cardiology, University of California, San Francisco; and is the Editor of Clinical Cardiology Alert.

Synopsis: In the aortic position, TTE and TEE allow a quantitative evaluation of leaflet(s) dynamics only in a minority of patients and cinefluoroscopy still remains the first-choice technique.

Source: Muratori M, et al. Feasibility and Diagnostic Accuracy of Quantitative Assessment of Mechanical Prostheses Leaflet Motion By Transthoracic and Transesophageal Echocardiography in Suspected Prosthetic Valve Dysfunction. Am J Cardiol. 2006;97:94-100.

Cinefluoroscopy (cf) has been the gold standard for the evaluation of suspected mechanical prosthetic valve thrombosis, but only provides an analysis of leaflet motion. Echocardiography, either transthoracic (TTE) or transesophageal (TEE), could potentially evaluate leaflet motion and provide thrombus visualization, which may be more accurate for detecting valve thrombosis. Thus, Muratori and colleagues from Milan, Italy, studied 111 consecutive patients with suspected mechanical valve thrombosis (n = 71) or who were being evaluated prior to electrical cardioversion of atrial fibrillation (n = 40). The majority had bileaflet valves in either the aortic or mitral position. Each underwent TTE, TEE, and CF on the same day. Valve opening and closing angles on CF were compared to a reference group of normally functioning valves and values > 2 standard deviations were considered abnormal.

Results: CF found abnormal prosthetic valve function in 71 patients and normal function in 40. With the one exception of identifying normal mitral prosthesis function, TEE was superior to TTE. Since the specificity of TEE for mitral and aortic prostheses was 100%, so was the positive predictive value. Sensitivity was 100% with TEE of the mitral valve, so the negative predictive value was 100%. Sensitivity of detecting an abnormal aortic prosthesis by TEE was 85% and the negative predictive value was 94%. Valve leaflet opening and closing angles were correctly determined in all mitral prostheses using TEE, but in a minority of aortic prostheses. In all 40 patients who were treated for prosthetic valve dysfunction, the presence of thrombus was confirmed (38 at surgery, 2 with improvement after thrombolysis). Muratori et al concluded that mitral mechanical prosthetic valve dysfunction can be accurately detected by TEE, but in aortic prostheses CF is still the method of choice.

Commentary

Since CF is considered the gold standard for diagnosing mechanical prosthetic valve dysfunction, one could argue that this simple test should be employed first to rule the diagnosis in or out. However, in many hospitals getting access to the catheterization laboratory and finding someone who is experienced at getting the correct imaging angle to make leaflet angle measurements is not always as easy as getting an echo done. Also, echo will provide other details that may explain the patient’s symptoms, such as depressed LV function, new native valve disease, pericardial effusion, etc.; so in real life, a TTE is done first. The key findings on TTE are increased gradients across the prostheses, new regurgitation or, in some cases, obvious masses or fixed leaflets. Such findings by TTE in the mitral position are diagnostic of prosthetic valve dysfunction, and further studies would only be confirmatory. A normal-appearing mitral mechanical prosthesis with a normal gradient and no new regurgitation is less helpful because up to one-third of proven malfunctioning mitral prosthetic valves will have these findings on TTE. TEE, however, is highly accurate for detecting mitral valve dysfunction, and could be the next step or CF can be done. In the aortic position, TTE is inaccurate, and TEE is only accurate if the valve is abnormal (positive predictive value 100%). So a normal-appearing TTE in the aortic position, as with the mitral position, requires further testing. In contrast to the mitral position with a normal-appearing TTE of the aortic prosthesis, TEE is not sufficiently sensitive; so, CF is the test of choice. To summarize, assuming most patients get TTE first, with an abnormal mitral prosthesis you are home free (100% accurate); any other result requires confirmation, which could be TEE or CF, with a CF preferred for a normal-appearing aortic prosthesis.