No abstract

SUMMARY Analysis of a tapering, pulsatile flow field predicts that substantial subvaivular pressure gradients exist in patients with valvular aortic stenosis (AS) without invoking a second anatomic site of obstruction. Using a catheter with two laterally mounted micromanometers, we examined the left ventricle in 11 patients with AS, mean age 64 ± 11 years (± SD); the mean valve area was 1.0 ± 0.3 cm2. Simultaneous measurements were made in (1) the left ventricular (LV) chamber and the LV outflow tract (LVOT) and (2) the LVOT and ascending aorta (AO). No patient had anatomic evidence of a subvalvular obstruction, but large subvalvular gradients were present in all. The average peak LV-LVOT and LV-AO gradients were 41 ± 17 mm Hg and 58 ± 23 mm Hg, respectively. Flow velocity was electromagnetically derived in two patients. The LV-LVOT gradient was associated with an increased flow velocity in the LVOT. This study suggests that large subvalvular gradients are present in AS and help overcome blood's inertia to convective and local accelerations in the tapering subvalvular flow field.SUBSTANTIAL intraventricular pressure differences and gradients* are traditionally considered to reflect an organic "outflow obstruction" in the region across which they are measured.1-9 It is commonly postulated that organic obstructions can be fixed or dynamic, and range from the collar type to the hypertrophic cardiomyopathy variants of subvalvular stenosis.'I--3 Aortic valvular stenosis can coexist with various types of subvalvular obstruction.2-14A9 These associated lesions cannot always be demonstrated angiographically, even by left ventriculography in several views. In such cases, obstructive lesions are best diagnosed from pressure gradients detected by catheter pullback from the ventricle to the proximal aorta.2 3, 10, 12, 19 Persistence or recurrence of intraventricular gradients shown by repeated or serial postoperative catheterization signals inadequate resection or regrowth of subvalvular obstructive lesions and possibly the need for further surgical resection.6 [20][21][22][23][24][25] Clinical investigation of normal ejection dynamics has shown that dynamic factors associated with flow contribute to physiologic transvalvular pressure gradients.26 Studies of flow dynamics in hypertrophic cardiomyopathy have cast strong doubt on the premise that large intraventricular pressure gradients are always a consequence of an anatomic obstruction of the outflow tract region.27 Improved instrumentation for measuring pressure28 33 has led to the frequent observation of subvalvular gradients in patients with valvular aortic stenosis without subvalvular pathology in our *The term gradients in this paper is used in the conventional hemodynamic sense, but in fluid dynamic terms represents a driving pressure difference evaluated across a finite distance in the direction of flow.

Therapeutic/epidemiologic study, level IV.

Changes in the physiologic state of the patient may affect indices of valvular aortic stenosis. We determined the effects of supine exercise on the Gorlin valve area, Cannon valve area, aortic valve resistance, and a modified stroke work loss index in 80 patients with aortic stenosis. Exercise caused a significant increase in the Gorlin and Cannon valve area, while work loss and valve resistance decreased significantly. The average percent change in work loss, 12.2%, was lower than the other indices (P less than 0.02), i.e., 15.3% for valve resistance, 18.6% for the Gorlin area, and 19.3% for the Cannon area. The correlation between the rest and exercise measurements was highest for work loss (r = 0.94), compared to 0.93, 0.88, and 0.89 for the other 3 indices, respectively. In patients with a Gorlin area below 1 cm2, exercise caused a significant decrease in work loss, but not Cannon area or valve resistance. However, the percent change was significantly lower and the correlation was better with the work loss index. We conclude that the work loss index is less affected by supine exercise than other indices of aortic stenosis.

No abstract