Exercise behavior of degenerative mitral stenosis.

Abstract

Mitral annular calcification (MAC) is increasingly encountered, particularly among the elderly and those with chronic kidney disease, and is often associated with a transvalvular gradient. In contrast to rheumatic mitral stenosis relatively little is known about mitral stenosis due to MAC. We aimed to clarify whether exercise limitation in this group is primarily due to valvular obstruction or ventricular dysfunction resulting from multiple comorbidities. 20 patients with severe MAC (bulky calcium deposits which restricted leaflet motion) were submitted to supine bicycle exercise, measuring Doppler and echocardiographic parameters at baseline and during exercise. They were compared 1:1 to subjects matched for age, sex, and left ventricular wall thickness. At baseline MAC subjects had higher mean mitral valve gradients (MVG) than comparison subjects (7.5 ± 3.8 vs 1.6 ± 0.8mm Hg, p < 0.0001), along with larger indexed left atrial volumes (54.4 ± 14.9 vs 34.0 ± 11.7mL, p < 0.0001) and reduced left atrial strains (reservoir, conduit, and booster pump). With exercise MAC subjects reached higher levels of MVG (17.3 ± 8.4 vs 5.5 ± 2.5mm Hg, p < 0.0001), and pulmonary artery systolic pressure (estimated from tricuspid regurgitant jet [TR] velocity) and displayed a moderate correlation between ΔMVG and ΔTR velocity (r2 = 0.57). MAC subjects whose exercise MVG was ≥ 15mm Hg all had a peak pulmonary artery systolic pressure > 60mm Hg. MAC subjects also had relative chronotropic incompetence. Patients with severe MAC and a transvalvular gradient experience large increases in MVG and pulmonary pressure with exercise, similar to what has been described in rheumatic mitral stenosis. MAC may be an under-recognized cause of dyspnea and exercise intolerance in older patients.