BACKGROUND: The study aim was to determine the prevalence of normally functioning mitral prostheses with mean gradient >/=10 mmHg, and to identify the characteristics and echocardiographic variables that might be useful to distinguish normal function from dysfunction. METHODS: A total of 56 consecutive patients with a prosthetic mitral valve and mean gradient >/=10 mmHg was retrospectively identified. Nineteen patients without subsequent imaging confirming normal prosthesis function or dysfunction were excluded; hence, 37 patients were classified as obstruction, insufficiency, or normal prosthesis (high-gradient; NPHG). A comparison group of 25 patients with a mean transprosthetic gradient of /=10 mmHg (area under curve = 0.92, 0.86, and 0.82, respectively). CONCLUSIONS: The study data suggested that a plurality of individuals with a mean transprosthetic mitral gradient >/=10 mmHg will be found to have a normally functioning prosthesis. Most of these patients will have a small EOAi, a reduced Cn, and a relatively increased CI.