Provocation of left ventricular outflow tract obstruction in patients with hypertrophic cardiomyopathy. Comparison of orthostasis testing and nitrate application.

Several provocation maneuvers are described in hypertrophic cardiomyopathy to Doppler echocardiographically distinguish the obstructive from the non obstructive type. No data are available about the value of orthostasis testing in comparison with nitrate application in this disease. In this study, 16 consecutive patients with hypertrophic cardiomyopathy were examined. 11 patients with hypertrophic cardiomyopathy were classified as obstructive, 5 patients with hypertrophic cardiomyopathy as non obstructive. Normal left ventricular outflow tract velocities as detected by the Doppler method were defined as < 2.0 m/s. Doppler echocardiographic measurements were performed after 10 minutes in supine position, within 10 minutes after head-up tilt and again, within 10 minutes in supine position. If systolic blood pressure during this examination exceeded 100 mm Hg 2.5 mg isosorbiddinitrate were sprayed sublingually. Measurements were done after 20 minutes in supine position and within 10 minutes after head-up tilt. Only in 7 of the 11 patients with hypertrophic obstructive cardiomyopathy maximal left ventricular outflow tract velocity in supine position measured > 2.0 m/s (2.2 +/- 0.8). During head-up tilt, all patients showed increased values (3.8 +/- 1.2 m/s). No differences in maximal left ventricular outflow tract velocity between head-up tilt and nitrate application in supine position (3.5 +/- 1.4 m/s) were present. All patients with hypertrophic non obstructive cardiomyopathy showed maximal left ventricular outflow tract velocities < 2.0 m/s in every step of the examination. Consequently, orthostasis testing was able to identify all patients with hypertrophic obstructive cardiomyopathy and demonstrated a diagnostic value similar to nitrate application.