The incidence and doppler echocardiographic characteristics of normally functioning mitral prostheses with mean gradient ≥ 10 mm Hg [abstract] Abstract uri icon

abstract

  • Introduction: A prosthetic mitral valve mean gradient ≥ 10 mm Hg is considered abnormal. While these prostheses are often dysfunctional, secondary to obstruction or insufficiency, occasionally they are found to be functioning normally on further imaging. Methods: 41 consecutive patients with a prosthetic mitral valve and mean gradient ≥ 10 mm Hg were identified between December 2009 and August 2015. Patients without subsequent transesophageal echocardiography, fluoroscopy, surgical procedure or transthoracic echocardiography confirming normal prosthesis function or dysfunction were excluded. The remaining cohort of 30 patients were then classified as obstruction, insufficiency, or normal; high gradient. A comparison group of 25 patients with a mean transprosthetic gradient ≤ 5 mm Hg (low gradient group) was also identified. Statistical comparisons were performed. Results: Of the 30 patients, 7 (23%) had obstruction, 8 (27%) had significant valvular or perivalvular insufficiency, and 15 (50%) were deemed normal; high gradient. Patients with obstruction had a significantly higher mean gradient compared to the insufficiency or normal; high gradient groups (p-value = 0.001). Net atrioventricular compliance (Cn) was reduced (≤4 ml/ mm Hg) in all three groups with a mean gradient ≥ 10 mm Hg compared to the low gradient group (obstruction = 2.2 ± 0.6
    ml/mm Hg; insufficiency = 1.3 ± 0.3 ml/mm Hg; normal; high gradient= 2.4 ± 1.1 ml/ mm Hg; low gradient group = 5.2 ± 2.3 ml/mm Hg). All patients with obstruction had a pressure half-time (PHT) value ≥ 130msec, while no other patient had a PHT ≥ 130msec. Effective orifice area index (EOAi) differed significantly among the three groups with mean gradient ≥ 10 mm Hg (p-value ≤ 0.0001), with the normal; high gradient group having the largest EOAi values; their EOAi values were still quite small though (EOAi = 0.8±0.2). Receiver operator characteristic curves found that EOAi, EOA, and VTI Ratio distinguished normal from abnormal prosthesis function in patients with mean gradients ≥ 10 mm Hg (area under curve = 0.92, 0.86, and 0.82, respectively). Cardiac index was significantly higher for the normal; high gradient group (3.5 ± 0.9 L/min/m2) compared with all other groups (p = 0.001). Conclusion: These data suggest that at least a third of all individuals with a mean transprosthetic mitral gradient ≥ 10 mm Hg will have a normally functioning prosthesis. These patients will likely have a small EOAi and reduced Cn, along with a relatively increased cardiac index. Echo variables are useful to distinguish those with a normal mitral prosthesis despite a mean gradient ≥ 10 mm Hg.

publication date

  • 2016