[The provocation of dynamic obstruction of the left ventricular outflow tract 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 echocardiography 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 non-specific phenomenon which also occurs in secondary left-heart hypertrophy. These findings may have therapeutic consequences.