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 ≤5 mmHg (low-gradient group) was also identified.
Results: Of the 37 patients, seven (19%) had obstruction, 10 (27%) had significant valvular or perivalvular insufficiency, and 20 (54%) were deemed NPHG. NPHG patients had a similar net atrioventricular compliance (Cn) to those with obstruction and insufficiency, which was significantly lower than the low-gradient group. The cardiac index (CI) was significantly higher in the NPHG group (3.4 ± 0.9 l/min/m2) compared to all other groups (p = 0.001). Receiver operator characteristic curves showed that the indexed effective orifice area (EOAi), effective orifice area (EOA) and velocity-time integral ratio distinguished NPHG from abnormal prosthesis function in patients with mean gradients ≥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.