Intracavitary gradients – range, shape, and correlation with
apical 4 chamber echocardiographic measurements
In 62 of 87 patients with clearly definable intracavitary gradients, the
gradient was 35 mmHg or less (14 +/- 10 mmHg: range 2-31 mmHg) vs 36
mmHg or more (44.3 +/- 12 mmHg: range 36-61 mmHg) in the remaining 25
patients. The shape of the spectral profile in patients with smaller
gradients looked different from those with higher gradients (Figure 2).
As the gradient increased, the ratio of peak/mean gradient concomitantly
rose (r 0.49) (p<0.0001) (Figure 3). Of the 62 patients with a
gradient of 35 mmHg or less, the peak/mean gradient ratio was 3.3 (SD
0.68), vs 3.85 (SD 0.85) for the patients with gradients of 36 mmHg or
higher (p = 0.007).
In the 65/87 patients with clearly quantifiable LV cavity on apical 4
chamber views, there was a positive correlation between the magnitude of
the peak ICG (mmHg) and the extent of cavity obliteration expressed as a
percentage of the end-diastolic length minus the end systolic length
divided by the end-diastolic length: r = 0.64 (P<0.0001)
(Figure 4). The difference was more obvious when comparing the 40
patients with 35 mmHg or less gradient vs the 25 patients with 36 mmHg
or more (34.9% vs 51.3% respectively) (p<0.0001) (Figure 5).
The magnitude of the ICG also correlated, as a group, although weakly,
with the duration of obliteration: r = 0.37 (p<0.001) (Figure
4). The difference in time of apposition was highlighted, however, by
comparing the 40 patients with 35 mmHg or less gradient vs the 25
patients with 36 mmHg or more (mean 75 msec vs mean 134 msec
respectively (p=0.0005) indicating that the group of patients with
higher gradients have more prolonged apposition than the group with
smaller gradients (Figure 5). Comparing the baseline and
echocardiographic data between the 40 patients with ICG of 35 mmHg or
less vs the 20 patients with ICG gradient of 36 mmHg or more, there was
no significant difference in age (74 +/- 14 vs 76 +/- 14), gender (F
26/40 vs F 21/25), or the echocardiographic parameters of
interventricular septal thickness (12 vs 11 mm), posterior wall
thickness (11 vs 11 mm), EF (76 vs 77%), left atrial area (18.5 vs 17.0
cm2), left ventricular outflow tract velocity time integral (30.2 cm vs
29 cm), or PA systolic pressure (33 vs 39 mmHg). There was a significant
difference in left ventricular end diastolic cavity M mode dimension (37
vs 33 mm [p=0.02]) and left ventricular end systolic cavity M mode
dimension (23 vs 21 mm [p=0.03]) indicating the left ventricular
cavity size was smaller in the patients with ICG of 36 mmHg or higher.