Reliability of new and old Doppler echocardiographic indexes of the severity of aortic stenosis in patients with a low cardiac output.

BACKGROUND

In addition to the conventional "flow-corrected" parameters (continuity equation and aortic valve resistance), new and simpler Doppler echocardiographic indexes of the severity of aortic stenosis have recently been introduced. These measures can be classified as "function-corrected" indexes (fractional shortening-velocity ratio and ejection fraction-velocity ratio) and "pressure-corrected" indexes (percent stroke work loss). Little information however is available about the diagnostic accuracy of each of these parameters in identifying patients with severe aortic stenosis in low-flow states, in which the diagnosis and clinical decision-making are more difficult and challenging.

METHODS

We analyzed 161 patients with aortic stenosis (96 males, 65 females, mean age 68 +/- 9 years) and a low cardiac output (thermodilution cardiac index < or = 2.5 l/min/m2). All patients underwent both cardiac catheterization and echocardiography within 48 hours one of the other. The invasive Gorlin valve area was used as gold standard (severe aortic stenosis = Gorlin < or = 0.8 cm2). Echocardiographic indexes were assessed by an investigator who was unaware of the hemodynamic findings.

RESULTS

The mean Gorlin aortic valve area was 0.7 +/- 0.3 cm2; cardiac catheterization allowed the identification of 129 patients with severe aortic stenosis and of 32 with mild-to-moderate aortic stenosis. The diagnostic accuracy of the Doppler gradient alone was low (sensitivity 55%). The best linear correlation with the Gorlin value was found using the "function-corrected" ejection fraction-velocity ratio (r = 0.85). Similarly, the best combination of sensitivity and specificity in identifying patients with severe aortic stenosis, as assessed by cardiac catheterization, was observed using the ejection fraction-velocity ratio (sensitivity 87%, specificity 88%).

CONCLUSIONS

In patients with aortic stenosis and a low cardiac output, the "function-corrected" ejection fraction-velocity ratio offers the better diagnostic accuracy, as compared with the cardiac catheterization valve area calculation.