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.