Normal values of the mitral-aortic intervalvular fibrosa thickness: A multimodality study

Background: The avascular region of the fibrous body between the mitral and aortic valves, named mitral-aortic intervalvular fibrosa (MAIVF), is often involved in the periaortic diffusion of infective endocarditis (IE), resulting in abscess or pseudoaneurysm formation. The early recognition of these life-threatening complications is of crucial importance, as urgent surgical correction is necessary. In the first stages of the abscess formation, the only sign is an increased thickness of the MAIVF. To the best of our knowledge, normal transesophageal echocardiography (TEE) examination reference values for MAIVF thickness has not yet been established. The aim of the study was to define the normal ranges of MAIVF thickness in a population of healthy adults who underwent a TEE examination. Materials and Methods: A population of consecutive adult patients who underwent a TEE examination was enrolled in the study. Measurement was performed in short-axis (SAX) and long-axis (LAX) views. Mean-2 standard deviations (mean-2SDs) and 5%, 10%, 90%, and 95% confidence intervals were evaluated. A comparison with MAIVF thickness in patients affected by aortic IE complicated by abscess formation was performed, and receiver operating characteristic (ROC) curves were constructed to achieve the optimal cutoff value of normality. Results: A total of 477 consecutive Caucasian adult patients were enrolled (mean age: 69 years, range: 27-93 years). Mean-2SD MAIVF measurement in SAX view was 0.325 cm (95% confidence interval [CI]: 0.319-0.330 cm) and in LAX view was 0.340 cm (95% CI: 0.334-0.346 cm). Computed tomography-MAIVF mean measurement (+/- 2SD) was 0.237 cm (95% CI: 0.110-0.340 cm). ROC curves showed that a cutoff SAX value measurement of 0.552 (area under the curve [AUC]: 95.2%) had a sensibility of 88.2% and a specificity of 92.4%; a LAX measurement value of 0.623 (AUC: 93.3%) had a sensibility of 82.7% and a specificity of 85.7%. The multivariate analysis showed no significant correlation between MAIVF thickness, age, and sex. Conclusion: In healthy patients, MAIVF thickness should not exceed 0.600 cm. Above these values, the suspicion of a periaortic abscess formation should be raised. MAIVF increased thickness may be an early sign of perivalvular diffusion requiring an urgent endocarditis team evaluation.