Effect of exercise on valvular resistance in patients with mitral stenosis

AbstractObjectives. This exercise study assessed the relation between valvular resistance and flow in patients with mitral stenosis.Background. Valvular resistance has been proposed as an alternative measue of stenotic valvular lesions, which is speculated to remain stable under changing hemodynamic conditions.Methods. In 35 of 40 patients with pure or predominant mitral stenosis, continuous wave Doppler measurements of the mitral stenotic jet were possible at rest and during supine bicycle ergometry. Simultaneously, transvalvular flow was assessed by thermodilution technique. For calculation of valvular resistance, the mean mitral valve pressure gradient was determined according to the simplified Bernoulli equation and divided by transvalvular flow. Additionally, effective mitral valve area was calculated according to the continuity equation method, dividing flow by the mean diastolic low velocity.Results. Valvular resistance was 65 ± 32 dynes · s · cm−5at rest and increased to 82 ± 43 dynes · s · cm−5at 25 W (p < 0.001). The most prominent increase in valvular resistance (rest to 25 W 63 ±28 to 95 ± 48 dynes · s · cm−5, p < 0.001) was found in those patients who had no or only a moderate (< 20%) change in effective mitral valve area. In contrast, valvular resistance remained constant (67 ± 36 vs. 70 ± 32 dynes · s · cm−5) in patients with significant (≥ 20%) increase in mitral valve area with exercise.Conclusions. In patients with mitral stenosis, the exercise induced change in valvular resistance are heterogeneous. This is the result of the variable response of mitral valve area to an increase in flow. In the individual patient, mital valve area can significantly increase, a factor that has to be taken into account when interpreting the hemodynamic relevance of the obstruction. Calculated valvular resistance is flew dependent and has no advantage over valve area calculation for quantifying stenosis