Noninvasive evaluation of the severity of aortic stenosis in adults

A noninvasive point score system for the evaluation of severity of aortic stenosis (AS) was employed in a prospective study of 153 patients (mean age 64.8 +/- 0.8 years) referred from invasive studies or for the evaluation of a systolic murmur. Seven variables were recorded and scored as follows: LVH by ECG (0-2); aortic valve calcium by chest x-ray film (0-2); loudness of A2 (0-2); Q-peak of murmur (0-3); T-time of carotid pulse (0-3); ejection time (0-3); and LVH by echo (0-1). Range of the total score was 0-16. All patients had the aortic valve area (AVA) determined by cardiac catheterization. Data analysis revealed that the relation between the total score and the AVA was curvilinear with a score greater than or equal to 5 correctly identifying 100/107 (93 percent) of patients with a valve area of less than or equal to 1.0 cm2. If the patients with an AVA of less than or equal to 1.0 cm2 were considered severe and patients with a total score less than 5 were considered mild-moderate, the sensitivity, specificity, and predictive accuracy for a score greater than or equal to 5 were 93 percent, 96 percent, and 98 percent, respectively. The relation between the score and aortic valve gradient (AVG) was linear with a score of greater than or equal to 5 correctly identifying 84/88 (95 percent) with an AVG greater than or equal to 40 mm Hg. If the patients with a pressure gradient over 40 mm Hg were considered severe, the sensitivity, specificity, and predictive accuracy for a score greater than or equal to 5 were 95 percent, 72 percent, and 82 percent, respectively. It is concluded that a point score system employing seven noninvasive variables is simple and accurate in identifying patients with severe AS and would be a valuable addition to a Doppler determined gradient.     

Echographic evaluation of the severity of aortic stenosis in cases with associated mitral stenosis

The echocardiographic findings of six patients with pure mitral stenosis associated with pure aortic stenosis were compared with the findings from a series of ten cases of pure aortic stenosis without mitral disease. Each patient also underwent haemodynamic studies in order to quantitate the severity of the stenoses. The aortic stenosis was of the same degree of severity in both series (0.71 +/- 0.24 cm2 and 0.73 +/- 0.16 cm2). The systolic separation of the aortic valve was greater than 1 cm in 4 of the 6 cases on echocardiography, corresponding to a false negative of tight aortic stenosis. This appearance corresponded to a doming of the aortic valve on 2D echocardiography. The wall thickness was significantly less in the AS + MS series than in pure SA series (1.13 +/- 0.13 cm compared with 1.52 +/- 0.21 cm; p less than 0.01). The wall was found to be thicker, the tighter the MS. Overall, the diagnostic criteria of the severity of AS on echocardiography (restricted opening of the valve and the severity of ventricular wall hypertrophy) were absent in the association of AS + MS. The absence of myocardial hypertrophy can not be fully explained. It could be related to a decreased filling on the left ventricle and therefore a smaller systolic ejection volume because of the mitral obstruction.     

Noninvasive evaluation of aortic stenosis severity utilizing Doppler ultrasound and electrical bioimpedance

Aortic valve area was calculated noninvasively in 30 patients with aortic stenosis undergoing cardiac catheterization. Continuous wave Doppler ultrasound was employed to estimate the mean transvalvular pressure gradient. The mean left ventricular outflow tract flow velocity and cross-sectional area were determined from pulsed Doppler and two-dimensional ultrasound recordings. Electrical transthoracic bioimpedance cardiography performed simultaneously with the ultrasonic study and repeated at the time of catheterization measured heart rate, systolic ejection period and cardiac output. These noninvasive data permitted calculation of aortic valve area using the Gorlin equation (range 0.21 to 1.75 cm2) and the continuity equation (range 0.25 to 1.9 cm2). Subsequent cardiac catheterization showed valve area to range from 0.21 to 1.75 cm2. The mean Doppler pressure gradient estimate was highly predictive of the gradient measured at catheterization (r = +0.92, SEE = 10). Bioimpedance cardiac output measurements agreed with the average of Fick and indicator dye estimates (r = +0.90, SEE = 0.52). Valve area estimates utilizing continuous wave Doppler ultrasound and electrical bioimpedance were superior (r = +0.91, SEE = 0.12) to estimates obtained utilizing the continuity equation (r = +0.76, SEE = 0.29) and were more reliable in the detection of patients with severe aortic stenosis (9 of 11 versus 6 of 11). These data show that 1) electrical bioimpedance methods accurately estimate cardiac output in the presence of aortic stenosis; 2) the hybridized bioimpedance-Doppler ultrasound method yields accurate estimates of aortic stenosis area; and 3) the speed, accuracy and cost-effectiveness of aortic stenosis evaluation may be improved by this hybridized approach.     

Determination of aortic valve orifice area in aortic valve stenosis by two-dimensional transesophageal echocardiography

Two-dimensional transesophageal echocardiography was used to measure aortic valve orifice area in 24 patients with aortic valve stenosis (AS) and 15 patients without aortic valve disease. Using transesophageal echocardiography, orifice area could be measured in 20 of 24 patients with AS. With transthoracic echocardiography, orifice area could be determined in only 2 of 24 patients. In patients with AS, orifice area determined by transesophageal echocardiography was 0.75 +/- 0.34 cm2 and that calculated with Gorlin's formula was 0.75 +/- 0.32 cm2. In normal aortic valves, orifice area was 3.9 +/- 1.2 cm2 by transesophageal echocardiography. A good correlation was demonstrated between aortic valve orifice area determined using transesophageal echocardiography and calculated orifice area using Gorlin's formula in patients with AS: r = 0.92, standard error of estimate = 0.14 cm2. The absolute difference between orifice area measured with both methods ranged from 0.0 to 0.4 cm2 (mean 0.09 +/- 0.1). In 4 patients orifice area could not be determined with transesophageal echocardiography. The orifice could not be identified in 2 patients because an appropriate cross-sectional view of the aortic valve could not be achieved and in 2 patients with pinhole stenosis (aortic valve orifice area 0.3 cm2). These data show that aortic valve orifice area can be measured reliably using 2-dimensional transesophageal echocardiography.     

Relation of aortic valve weight to severity of aortic stenosis

Radiocontrast nephropathy (RCN) develops in a substantial proportion of patients with chronic kidney disease (CKD) after invasive cardiology procedures and is strongly associated with subsequent mortality and adverse outcomes. We sought to determine whether systemic hypothermia is effective in preventing RCN in patients with CKD. Patients at risk for RCN (baseline estimated creatinine clearance 20 to 50 ml/min) undergoing cardiac catheterization with iodinated contrast ≥50 ml were randomized 1:1 to hydration (control arm) versus hydration plus establishment of systemic hypothermia (33°C to 34°C) before first contrast injection and for 3 hours after the procedure. Serum creatinine levels at baseline, 24 hours, 48 hours, and 72 to 96 hours were measured at a central core laboratory. The primary efficacy end point was development of RCN, defined as an increase in serum creatinine by ≥25% from baseline. The primary safety end point was 30-day composite rate of adverse events consisting of death, myocardial infarction, dialysis, ventricular fibrillation, venous complication requiring surgery, major bleeding requiring transfusion ≥2 U, or rehospitalization. In total 128 evaluable patients (mean creatinine clearance 36.6 ml/min) were prospectively randomized at 25 medical centers. RCN developed in 18.6% of normothermic patients and in 22.4% of hypothermic patients (odds ratio 1.27, 95% confidence interval 0.53 to 3.00, p = 0.59). The primary 30-day safety end point occurred in 37.1% versus 37.9% of normothermic and hypothermic patients, respectively (odds ratio 0.97, 95% confidence interval 0.47 to 1.98, p = 0.93). In conclusion, in patients with CKD undergoing invasive cardiology procedures, systemic hypothermia is safe but is unlikely to prevent RCN.     

New approaches to quantifying aortic stenosis severity

Previously, aortic valve stenosis (AS) etiology was usually congenital or due to rheumatic disease. However, the most frequent cause is now degenerative AS, which is often part of a continuum including increased rigidity of the aorta due to atherosclerosis and left ventricular dysfunction due to coronary artery disease. This article highlights newer approaches to quantify AS taking into account the inter-relation between the different components (valvular, vascular, and ventricular) affecting clinical outcome in these patients. Emphasis is given to a more comprehensive evaluation of AS severity going beyond classical measurements and including indices such as 1) the energy loss index to quantify the valvular obstruction net of pressure recovery; 2) systemic arterial compliance to quantify vascular load; and 3) valvulo-arterial impedance to assess the global (valvular + vascular) increase in afterload. Routine use of these indices, easily measured by Doppler echocardiography, should improve clinical management of AS patients.     

The carotidogram in the diagnosis of the juxtavalvular fibrotic aortic stenosis. Report of 47 cases (author's transl)

The morphological aspect of the carotid pulse has been under study in 47 cases of juxtavalvular aortic stenosis previously confirmed through hemodynamic and surgical examinations. The study included 39 cases of subvalvular fibrous stenosis (subaortic fibrous stenosis) (SAsV) and 8 cases of supravalvular annular aortic stenosis (S AsV). In 75% of both SAsV and SAsV cases the carotid pulse showed a rapid ascent and a finely notched apex, while in 25% of the cases it followed the pattern of a typical valvular stenosis. This is more obvious for the left carotid artery. The morphology of the carotid pulse resulted as independent from the aortic ventricular gradient, but, on the other hand, connected with the simultaneous stenotic involvement of the valvular cusps. The sign possesses not only high sensitivity but also high specificity with regard to juxtavalvular aortic stenoses because it has only been met with in 2 cases of valvular aortic stenosis. The pathophysiological explanation remains as yet obscure.     

In vitro correlation between the effective and geometric orifice area in aortic stenosis

BackgroundPlanimetry of aortic stenosis can be performed when Doppler measurements are unavailable. We sought to evaluate if, as advised in guidelines, the geometric orifice area (GOA) threshold value of 1 cm² was concordant with the threshold of 1 cm² of the effective orifice area (EOA), and the factors influencing the contraction coefficient (EOA/GOA ratio).MethodsIn an in vitro mock circulatory system, we tested 6 degrees of AS severity (3 severe and 3 non-severe), and 3 levels of flow (<150 ml/s, 150?200 ml/s, >250 ml/s). The EOA was calculated by Doppler-echocardiography, and the GOA was measured with dedicated software after camera acquisition.ResultsIn all but the very low flow condition, an EOA of 1 cm² corresponded to a GOA of 1.2 cm². The contraction coefficient increased with both the flow and the stenosis severity. For very severe stenoses, the EOA and the GOA were interchangeable.ConclusionAs observed in clinical studies, the GOA was larger than the EOA, and a GOA between 1 and 1.2 cm² should not discard the possibility of severe aortic stenosis.     

Ventricular stroke work loss: validation of a method of quantifying the severity of aortic stenosis and derivation of an orifice formula

Because aortic stenosis results in the loss of left ventricular stroke work (due to resistance to flow through the valve and turbulence in the aorta), the percentage of stroke work that is lost may reflect the severity of stenosis. This index can be calculated from pressure data alone. The relation between percent stroke work loss and anatomic aortic valve orifice area (measured by planimetry from videotape) was investigated in a pulsatile flow model. Thirteen valves were studied (nine human aortic valves obtained at necropsy and four bioprosthetic valves) at stroke volumes of 40 to 100 ml, giving 57 data points. Valve area ranged from 0.3 to 2.8 cm2 and mean systolic pressure gradient from 3 to 84 mm Hg. Percent stroke work loss, calculated as mean systolic pressure gradient divided by mean ventricular systolic pressure x 100%, ranged from 7 to 68%. It was closely related to anatomic orifice area with an inverse exponential relation and was not significantly related to flow (r = -0.15). An orifice formula was derived that predicted anatomic orifice area with a 95% confidence interval of +/- 0.5 cm2 (orifice area [cm2] = 4.82 [2.39 x log percent stroke work loss], r = -0.94, SEE = 0.029). These results support the clinical use of percent stroke work loss as an easily obtained index of the severity of aortic stenosis.     

Limitations in assessing the severity of aortic stenosis by Doppler gradients

Continuous wave Doppler echocardiography was performed before cardiac catheterisation in 69 consecutive patients with suspected aortic stenosis. Agreement between the maximum and the mean Doppler gradients and catheterisation gradients was good. Doppler echocardiography, however, systematically underestimated the maximum and mean gradients, particularly in the high range. Stepwise regression analysis of the small pressure difference between the two methods showed that it could not be explained by age, sex, stroke volume, differences in heart rate, ejection fraction, the presence of coronary artery disease, or severity of aortic regurgitation. There was a negative curvilinear correlation between the maximum and mean Doppler gradients and the aortic valve areas that were measured at catheterisation in patients with pure aortic stenosis. The degree of correlation decreased when patients with concomitant aortic regurgitation were included. The scatter of gradients above and below the correlation line was large and this was caused by low and high transvalvar flow. These results show that the usefulness of Doppler gradients for judging the severity of aortic stenosis, both in relation to immediate diagnosis and follow up, is severely limited if transvalvar flow is not taken into account.     

Cross-sectional echocardiography in assessing the severity of valvular aortic stenosis.

Real-time, cross-sectional echocardiograms were recorded in 28 consecutive adult patients with valvular aortic stenosis using a high resolution, mechanical sector scanner. Using the cross-sectional technique, the aortic valve orifice diameter was recorded in each of the 28 patients. With M-mode echocardiographic examination of these same patients, this value could be estimated in only 21 of these 28 patients (75%). The maximum aortic valve diameter recorded during the cross-sectional study averaged 7.9 +/- 1.8 mm (range 4-11 mm) in 15 patients with severe aortic stenosis; 11.6 +/- 2.3 mm (range 9-15 mm) in five patients with moderate aortic stenosis; 16.9 +/- 2.0 mm (range 14-20 mm) in eight patients with mild aortic stenosis; and 20.5 +/- 2.8 mm (range 15-26 mm) in 25 patients with no evidence of aortic valve disease. Comparing the means of these groups yielded the following: severe vs moderate P less than 0.005; moderate vs mild P less than 0.001; and mild vs normal P less than 0.001. Although there was some overlap between the individual groups, a clear separation existed between patients with severe and mild aortic stenosis. In addition, the group of patients in whom surgical intervention was recommended was also separated from the other subjects. When the aortic valve orifice was recorded using the M-mode technique, there was also a good correlation with the severity of the stenosis; however, the tendency of the M-mode study to overestimate severity in individual patients with calcific aortic stenosis and to underestimate severity in congenital aortic stenosis was again demonstrated. This study suggests that real-time, high resolution, cross-sectional echocardiography should be valuable in the noninvasive assessment of patients with aortic stenosis.