Subvalvular Gradients Research Articles

Is the Valve OK or Not? Immediate Evaluation of a Replaced Aortic Valve

Transesophageal echocardiography is a crucial tool in intraoperative evaluation of newly implanted/repaired heart valves because suspected valvular malfunction needs to be identified and sometimes surgically corrected. Although color Doppler is often adequate in evaluating the expected regurgitant jets, as well as excluding pathologic paravalvular leaks, spectral Doppler techniques are the most commonly used methods for estimating transvalvular gradients in the operating room. However, these methods are subject to a variety of confounding factors, including subvalvular gradients and pressure recovery. Other methods of valve area estimation should also be used when evaluating a prostethic aortic valve, including the continuity equation and the left ventricular outflow tract/aortic valve velocity ratio.

Subvalvular gradients in patients with valvular aortic stenosis: prevalence, magnitude, and physiological importance.

Although subvalvular gradients in patients with aortic stenosis have been described, their behavior and response to exercise have not been well characterized. Left ventricular and aortic pressures and linear flow velocity were measured with a catheter-tip manometer at rest and during supine exercise in 27 patients with valvular aortic stenosis. A subvalvular gradient was measured in each patient that represented, on average, 48% of the total resting transvalvular gradient. With exercise, both total (rest: 80+/-26 mm Hg; exercise: 90+/-25 mm Hg) and subvalvular gradients (rest: 37+/-13 mm Hg; exercise: 60+/-22 mm Hg) increased significantly. There was a significant inverse relationship between change in exercise cardiac output and total and subvalvular gradients. However, only the exercise subvalvular gradient predicted cardiac output response. Subvalvular pressure gradients are universally present in patients with severe aortic stenosis and comprise approximately half of the total transvalvular gradient. The extent of exercise cardiac output increase is inversely related to the subvalvular gradient magnitude.

Surgical treatment of idiopathic hypertrophic subaortic stenosis with other cardiac pathology.

Twenty-nine patients underwent surgery for idiopathic hypertrophic subaortic stenosis (IHSS) solely or in combination with other cardiac pathology. Fifteen men and 14 women, 26 to 75 years of age (mean 56 years), had peak subvalvular gradients, with or without provocation, ranging up to 220 mm Hg (mean 93 mm Hg). The diagnosis of IHSS was confirmed preoperatively by echocardiography in the 23 patients on whom it was performed. Twentyseven patients underwent left ventricular septal myectomy (LVSM), one had a left ventricular myotomy, and another received mitral valve replacement (MVR) alone for palliation of IHSS. In addition, coronary artery bypass (CAB) was performed in 18 of these IHSS patients: 8 had single grafts, 5 had two, 4 had three, and one patient had five grafts. Other operations included MVR in 3 patients, aortic valve replacement, excision of a subaortic membrane, and tricuspid annuloplasty in one patient each. One operative death (3%) occurred 34 days postoperatively. There have been 2 late deaths: one at 22 months from bacterial endocarditis on a prosthetic mitral valve, and another suddenly at 29 months after septal myectomy. After a follow-up ranging from 2 to 93 months (mean 25 months), 22 of 26 patients are asymptomatic. Three asymptomatic patients have been recatheterized 12, 14, and 21 months, respectively, after operation. Marked amelioration of subaortic gradients was noted, and patent grafts were found. Left ventricular septal myectomy (LVSM) can be combined with other cardiac operations to provide effective palliation.

Fluid dynamics of aortic stenosis: subvalvular gradients without subvalvular obstruction.

Analysis of a tapering, pulsatile flow field predicts that substantial subvalvular 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.

Left ventricular cavity obliteration: hemodynamic behavior of the postextrasystolic beat

Thirteen patients with angiographic left ventricular cavity obliteration are analyzed. No transvalvular or subvalvular gradients were present except in two cases with a mild gradient after amyl nitrite inhalation. The commonest clinical features were chest pain (60%) and dyspnea (23%). Electrocardio-graphically proved left ventricular hypertrophy (70%) was prominent. The echocardiograms showed asymmetric septal hypertrophy (40%), symmetric hypertrophy (20%), systolic anterior motion of the anterior leaflet of the mitral valve (60%), and mitral valve prolapse (20%). In all the patients changes in systolic intraventricular pressure in the post-extrasystolic beat were evaluated and a decrease in intraventricular pressure was found in every case. In the four cases with extrasystoles recorded in the aorta a similar decrease of aortic pressure was found. This behavior is completely different in the hypertrophic cardiomyopathy with obstruction to the left ventricular outflow tract, where there is an increase in intraventricular pressure and a decrease in aortic pressure in the postextrasystolic beat. Left ventricular cavity obliteration is an angiographic phenomenon which is common in hypercontractile states, being an usual finding in hypertrophic cardiomyopathy. In cases without obstruction to the left ventricular outflow tract, the decrease in aortic pressure is caused by a different mechanism than the one involved in cases with obstruction. In cases without obstruction, the decrease in post-extrasystolic aortic pressure corresponds to a decrease in intraventricular pressure, whereas in subaortic stenosis there is an increase both of intraventricular pressure and gradient with the subsequent decrease in aortic pressure.