Prediction of severity of aortic stenosis: Accuracy of multiple noninvasive parameters

PURPOSE: As newer non-medical techniques are developed to treat older patients with severe aortic stenosis, reliable noninvasive diagnosis of the condition will become increasingly important. For this reason, the accuracy of multiple noninvasive indexes for quantitation of the severity of aortic stenosis was evaluated, relative to catheterization-determined aortic valve area. PATIENTS AND METHODS: To evaluate the accuracy of multiple noninvasive parameters in assessing the presence and extent of aortic valve narrowing, noninvasive and catheterization correlations of the severity of aortic stenosis were obtained on 121 occasions in 81 patients (mean age, 76 +/- 11 years). Forty patients had studies performed before and after valvuloplasty. Noninvasive studies included the time to one-half carotid upstroke and carotid ejection time, corrected for heart rate, measured from a carotid pulse tracing; M-mode echocardiographic aortic valve excursion; mean pressure gradient across the aortic valve assessed by Doppler technique; the ratio of the peak to mean pressure gradient by Doppler; and Doppler aortic valve area assessed using the following continuity equation: aortic valve area = A X V/V1, where A = left ventricular outflow tract area, V = peak left ventricular outflow tract velocity, and V1 = peak velocity in the aortic stenotic jet. Mean aortic valve gradients and area (calculated using the Gorlin formula) were also assessed at cardiac catheterization. RESULTS: The correlations between the catheterization measurement of aortic valve area and the various noninvasive measurements were as follows: time to one-half carotid upstroke (r = -0.32, p less than 0.001); corrected left ventricular ejection time (r = -0.24, p less than 0.05); aortic valve excursion (r = 0.51, p less than 0.001); mean gradient by Doppler study (r = -0.44, p less than 0.001); mean gradient by catheterization analysis (r = -0.55, p less than 0.001); peak to mean gradient ratio measured by continuous wave Doppler (r = 0.38, p less than 0.001); and aortic valve area assessed using the Doppler continuity equation (r = 0.85, p less than 0.001). CONCLUSION: Noninvasive determination of aortic valve area using the continuity equation is an accurate means of assessing the severity of aortic stenosis. Although multiple other noninvasive parameters also correlate with aortic valve area measured at catheterization, there is too much scatter of data points to permit accurate prediction of catheterization aortic valve area in any given patient.