RESUMEN
Background: The mechanism involved in dyspnea in patients with mitral valve stenosis (MS) is not completely understood. Aim: To evaluate in patients with MS, changes in hemodynamic parameters during the assessment of inspiratory muscle endurance (IME) and the relationship between IME, hemodynamics and dyspnea. Subjects and methods: We studied 13 patients (9 in NYHA class II and 4 in class III). Endurance was evaluated using a two minute incremental threshold loading test, to obtain the maximal sustainable inspiratory pressure (SIP), and maximal inspiratory load (MIL). During the test, cardiac output (CO), mean pulmonary and capillary pressures (PAP and PCP, respectively), were evaluated. Results: Compared to six normal subjects, MS patients had reduced SIP and MIL (p <0.01), which correlated with baseline index of dyspnea (r= 0.57 and r=0.52, respectively, p <0.05). At the end of the test period, basal CO, cardiac index (CI), PAP and PCP increased from 3.4 to 4.0 l/min-1; 2.1 to 2.5 l/min-1/m-2; 15 to 25 and 11 to 18 mmHg, respectively (p <0.01). No relationship between IME and hemodynamic parameters was found. Conclusions: IME is reduced and is closely related to dyspnea in these patients with MS. The observed low CI, suggests that muscle underperfusion could contribute to this dysfunction during the inspiratory effort.