Value of the Mitral Valve Resistance in Evaluation of Symptomatic Patients with Mild and Moderate Mitral Stenosis – A Dobutamine Stress Echocardiographic Study

BACKGROUND: Conventional stenosis indexes poorly reflect the major hemodynamic consequence of mitral stenosis (MS). Valve resistance (VR) is a physiologic expression of stenosis. OBJECTIVES: This study aimed to demonstrate whether the mitral valve resistance (MVR) and its changes, relate to restricted exercise capacity in patients with mild and moderate mitral stenosis. METHODS: Twenty-four patients with rheumatic mild-to-moderate MS underwent transthoracic echocardiographic study (resting and dobutamine stress echocardiography [DSE]), divided into two groups; group I: symptomatic (12 patients) and group II: asymptomatic (12 patients). Mitral valve area (MVA), mean transmitral diastolic pressure gradient (TMPG), cardiac output (CO), and MVR were measured in all patients at rest and at peak DSE. Changes (∆) in MVA, TMPG, CO, and MVR were calculated. Data underwent statistical analysis. RESULTS: From resting to peak dobutamine infusion, the MVR significantly decreased from 111.4 ± 28.2 to 83.6 ± 27.0 dynes sec/cm(5) in group II (P < 0.001). The increase in MVR in group I (13.8 ± 10.3 dynes sec/cm(5)) compared with its reduction (-27.8 ± 15.6 dynes sec/cm(5)) in group II were highly significant different (P < 0.001). A reduction in MVR by less than 21.5 dynes sec/cm(5) at peak dobutamine infusion reflect a cutoff value considered to detect the hemodynamic significance of mild-to-moderate MS with a sensitivity of 92% and a specificity of 73%. CONCLUSION: The changes in the MVR can be used as a DSE parameter for expression of stenosis severity and to describe discrepancy in symptom status in patients with mild-to-moderate mitral stenosis.