PROVOCATION OF DYNAMIC LEFT-VENTRICULAR OUTFLOW TRACT OBSTRUCTION IN SECONDARY MYOCARDIAL HYPERTROPHY

The effect of the Valsalva manoeuvre before and after sublingual administration of 1.6 mg nitroglycerin on maximal velocity (Vmax), acceleration time (AT) and ejection time (ET) of left-ventricular outflow was measured by Doppler echo cardiography in 49 patients (28 men and 21 women; mean age 65 [48-84] years) with secondary left-heart hypertrophy, and in 8 controls. Changes in flow profile typical of dynamic obstruction in the left-ventricular outflow tract (LVOT) occurred in 30 of the patients, Vmax increasing from a mean of 137 to 302 cm/s. Latent LVOT obstruction was associated with a thickened posterior wall, an accelerated left-ventricular outflow even at rest and systolic anterior motion of the anterior mitral leaflet (SAM phenomenon). The size of the provoked LVOT gradient correlated significantly with Vmax or the AT/ET ratio at rest. Obstruction of the LVOT is apparently a nonspecific phenomenon which also occurs in secondary left-heart hyper-trophy. These findings may have therapeutic consequences.