Prediction of the severity of aortic stenosis by Doppler aortic valve area determination: prospective Doppler-catheterization correlation in 100 patients

Two-dimensional and Doppler echocardiography was performed prospectively in 100 patients with aortic stenosis who were undergoing clinically indicated cardiac catheterization. The purpose of this study procedure was to determine various Doppler variables predictive of the severity of aortic stenosis and to compare Doppler- and catheterization-derived aortic valve areas. Doppler-derived mean gradient correlated well with corresponding gradient by catheterization (r = 0.86). Peak Doppler aortic flow velocity greater than or equal to 4.5 m/s and Doppler-derived mean aortic gradient greater than or equal to 50 mm Hg were specific (93 and 94%, respectively) for severe aortic stenosis (defined as catheterization-derived aortic valve area less than or equal to 0.75 cm2) but were not sensitive (44 and 48%, respectively). Doppler-derived aortic valve area calculated by the continuity equation correlated well with catheterization-derived aortic valve area calculated by the Gorlin equation when either the time-velocity integral ratio (r = 0.83) or the peak flow velocity ratio (r = 0.80) between the left ventricular outflow tract and the aortic valve was used in the continuity equation. A velocity ratio of less than or equal to 0.25 alone was sensitive (92%) in detecting severe aortic stenosis. Therefore, use of various Doppler-derived values allows reliable noninvasive estimation of the severity of aortic stenosis.     

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.     

Valvular aortic stenosis: disease severity and timing of intervention

Standard echocardiographic evaluation of aortic stenosis (AS) severity includes measurement of aortic velocity, mean transaortic pressure gradient, and continuity equation valve area. Although these measures are adequate for decision making in most patients, there is no single value that defines severe stenosis. Aortic stenosis affects not just the valve, but the entire vascular system, including the left ventricle (LV) and systemic vasculature. More sophisticated measures of disease severity might explain the apparent overlap in hemodynamic severity between symptomatic and asymptomatic patients and might better predict the optimal timing of valve replacement. There have been several approaches to evaluation of stenosis severity based on valve hemodynamics, the ventricular response to increased afterload, ventricular-vascular coupling, or the systemic functional consequences of valve obstruction, such as exercise testing and serum brain natriuretic peptide levels. Aortic valve replacement is indicated when symptoms due to severe AS are present. In most asymptomatic patients, the risk of surgery is greater than the risk of watchful waiting so that management includes patient education, periodic echocardiography, and cardiac risk factor modification. Many adults with AS have comorbid conditions that affect both the diagnosis and management of the valve disease, including aortic regurgitation, aortic root dilation, hypertension, coronary artery disease, LV dysfunction, and atrial fibrillation. Comorbid conditions should be evaluated and treated based on established guidelines, although awareness of the potential effects of therapy in the presence of valve obstruction is needed.     

Clinical and noninvasive hemodynamic results after aortic balloon valvuloplasty for aortic stenosis

Balloon valvuloplasty has been shown to be an effective treatment for adults with aortic stenosis, typically providing a 50 to 80% increase in aortic valve area and marked improvement in exertional dyspnea, angina and syncope. However, the duration of this hemodynamic and clinical improvement is uncertain. Forty-two patients were followed for 10.2 +/- 0.5 months. Balloon valvuloplasty caused dramatic immediate reduction in the number of patients with moderate or severe dyspnea (80 to 14%), moderate or severe angina (39 to 2%) and syncope (30 to 2%). Furthermore, this improvement in symptoms continued for the duration of the follow-up period in most patients. Echocardiographic aortic valve mean gradient and area determined at 3-month intervals, however, showed a trend toward or return to prevalvuloplasty levels by 9 months' follow-up in 13 of 25 patients (52%), whereas 12 of 25 patients showed no deterioration in their hemodynamic parameters. This trend toward restenosis was accompanied by symptomatic deterioration in 5 of 13 patients (38%). This tendency toward restenosis in greater than 50% of patients by 9 months underscores the need for further technical improvements if balloon valvuloplasty is to be widely applied. Even with these limitations, however, balloon valvuloplasty seems to provide a significant improvement in actuarial survival compared with the natural history of elderly patients with severe aortic stenosis.     

Usefulness of noninvasive assessment of aortic stenosis before and after percutaneous aortic valvuloplasty

Noninvasive and catheterization studies were performed in 40 patients (mean age 76 +/- 12 years) before and after percutaneous aortic valvuloplasty. Measurements included time to 1/2 carotid upstroke, left ventricular ejection time, aortic valve excursion, mean aortic valve gradient and aortic valve area assessed using the continuity equation: aortic valve area = A X V/V1, where A = left ventricular outflow tract area, V = maximal left ventricular outflow tract velocity assessed by pulsed Doppler echocardiography and V1 = peak velocity in the aortic stenotic jet assessed using continuous-wave echocardiography. In addition, mitral regurgitation was assessed by pulsed Doppler mapping techniques. Mean aortic valve gradient, cardiac output and aortic valve area, calculated using the Gorlin formula, were determined at cardiac catheterization. There were significant correlations between Doppler and catheterization measurements of aortic valve area both before (r = 0.71, p less than 0.001) and after (r = 0.85, p less than 0.0001) valvuloplasty. The relations were demonstrated to be linear by F test and met criteria for identity. There were significant increases (all p less than 0.0005) after valvuloplasty in catheterization valve area (0.60 +/- 0.21 to 0.95 +/- 0.39 cm2), Doppler valve area (0.64 +/- 0.22 to 0.91 +/- 0.37 cm2), valve excursion (0.5 +/- 0.3 to 0.8 +/- 0.3 cm) and cardiac output (4.5 +/- 1.6 to 4.9 +/- 1.7 liter/min).(ABSTRACT TRUNCATED AT 250 WORDS)     

Valvular aortic stenosis: disease severity and timing of intervention.

Standard echocardiographic evaluation of aortic stenosis (AS) severity includes measurement of aortic velocity, mean transaortic pressure gradient, and continuity equation valve area. Although these measures are adequate for decision making in most patients, there is no single value that defines severe stenosis. Aortic stenosis affects not just the valve, but the entire vascular system, including the left ventricle (LV) and systemic vasculature. More sophisticated measures of disease severity might explain the apparent overlap in hemodynamic severity between symptomatic and asymptomatic patients and might better predict the optimal timing of valve replacement. There have been several approaches to evaluation of stenosis severity based on valve hemodynamics, the ventricular response to increased afterload, ventricular-vascular coupling, or the systemic functional consequences of valve obstruction, such as exercise testing and serum brain natriuretic peptide levels. Aortic valve replacement is indicated when symptoms due to severe AS are present. In most asymptomatic patients, the risk of surgery is greater than the risk of watchful waiting so that management includes patient education, periodic echocardiography, and cardiac risk factor modification. Many adults with AS have comorbid conditions that affect both the diagnosis and management of the valve disease, including aortic regurgitation, aortic root dilation, hypertension, coronary artery disease, LV dysfunction, and atrial fibrillation. Comorbid conditions should be evaluated and treated based on established guidelines, although awareness of the potential effects of therapy in the presence of valve obstruction is needed.     

Value of noninvasive testing in adults with suspected aortic stenosis

To determine the predictors of surgically correctable aortic stenosis in patients with systolic murmurs, 231 patients were evaluated. Five variables (carotid upstroke timing, carotid upstroke volume, aortic valve calcification on chest radiography, single or absent second heart sound, and a murmur with its maximal intensity at the right upper stemal border) were significant multivariate correlates. Two echocardiographic factors (a maximal aortic valve leaflet separation of 7 mm or less and hypertrophy of the posterior wall of the left ventricle to 12 mm or more) and one systolic time interval factor (a rate-corrected ejection time of more than 340 msec) added significant incremental information. When prospectively tested on an independent set of 86 patients with suspected aortic outflow obstruction, the combined clinical and noninvasive information correctly placed 10 patients (12 percent) into a low-risk group in which catheterization may not be indicated and 15 patients (17 percent) into a high-risk group in which it might be avoided or limited to coronary arteriography. This approach to predicting aortic stenosis deserves wider prospective testing.     

Improving accuracy in diagnosing aortic stenosis severity: An in-depth analysis of echocardiographic measurement error through literature review and simulation study

Aims

The present guidelines advise replacing the aortic valve for individuals with severe aortic stenosis (AS) based on various echocardiographic parameters. Accurate measurements are essential to avoid misclassification and unnecessary interventions. The objective of this study was to evaluate the influence of measurement error on the echocardiographic evaluation of the severity of AS.

Methods and results

A systematic review was performed to examine whether measurement errors are reported in studies focusing on the prognostic value of peak aortic jet velocity (V_max), mean pressure gradient (MPG), and effective orifice area (EOA) in asymptomatic patients with AS. Out of the 37 studies reviewed, 17 (46%) acknowledged the existence of measurement errors, but none of them utilized methods to address them. Secondly, the magnitude of potential errors was collected from available literature for use in clinical simulations. Interobserver variability ranged between 0.9% and 8.3% for V_max and MPG but was higher for EOA (range 7.7%-12.7%), indicating lower reliability. Assuming a circular left ventricular outflow tract area led to a median underestimation of EOA by 23% compared to planimetry by other modalities. A clinical simulation resulted in the reclassification of 42% of patients, shifting them from a diagnosis of severe AS to moderate AS.

Conclusions

Measurement errors are underreported in studies on echocardiographic assessment of AS severity. These errors can lead to misclassification and misdiagnosis. Clinicians and scientists should be aware of the implications for accurate clinical decision-making and assuring research validity.