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From the Division of Cardiology, Department of Internal Medicine,
University of Texas Southwestern Medical School and VA Medical Center, Dallas.
Correspondence to Paul A. Grayburn, MD, Division of Cardiology, UT Southwestern Medical Center, 5323 Harry Hines Blvd, Dallas, TX, 75235-9047. E-mail grayburn{at}ryburn.swmed.edu
Background—Improvement in the left
ventricular outflow tract (LVOT) gradient has been used as
a means of assessing response to therapy in patients with hypertrophic
obstructive cardiomyopathy (HOCM). To our
knowledge, no data exist regarding the spontaneous day-to-day
variability of the LVOT gradient in patients with HOCM. Defining the
magnitude of such variability is critical to properly understand how
much improvement in LVOT gradient must be present to invoke a
therapeutic response.
Methods and Results—We studied the spontaneous variation in the
continuous-wave, Doppler-derived pressure gradient on 5 consecutive
days in 12 HOCM patients and 5 aortic stenosis control
subjects. While in some patients the day-to-day variability in resting
gradient was small, in others it varied markedly. The 95% confidence
interval for attributing a change in LVOT gradient to factors other
than random variation is ±32 mm Hg for resting gradient and
±50 mm Hg for provoked gradient. The mean coefficient of
variation for gradient across 5 days for the group was 0.52±0.33 for
resting gradient and 0.46±0.16 for provoked gradient. The day-to-day
variability in pressure gradient could not be explained by changes in
heart rate, blood pressure, or left ventricular
end-diastolic dimension, each of which had a coefficient of
variation <.11. Moreover, technical factors related to the
performance or interpretation of the studies did not account
for it because the coefficient of variation for gradient in aortic
stenosis was <10% and interobserver and intraobserver
agreement was excellent (r=.96 and .98,
respectively).
Conclusions—The LVOT pressure gradient varies considerably from
day to day in stable patients with HOCM. A single measurement of
pressure gradient is not adequate to define the severity of dynamic
LVOT obstruction in HOCM.
© 1998 American Heart Association, Inc.
Clinical Investigation and Reports
Spontaneous Variability of Left Ventricular Outflow Tract Gradient in Hypertrophic Obstructive Cardiomyopathy
Key Words: cardiomyopathy • echocardiography • hypertrophy • hemodynamics • pressure
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