Clinical application of transpulmonary contrast-enhanced Doppler technique in the assessment of severity of aortic stenosis.

ABSTRACT

OBJECTIVE: The aim of this study was to demonstrate the clinical usefulness of the transpulmonary contrast-enhanced Doppler technique by using it to assess the severity of aortic stenosis. BACKGROUND: Sonicated albumin microbubbles can pass through the pulmonary circulation after peripheral venous injection and have been reported to enhance Doppler signals from the left side of the heart. Therefore, their use to determine aortic flow velocity would facilitate the assessment of the severity of aortic stenosis. METHODS: Twenty-two patients with aortic stenosis and seven normal volunteers were examined. Aortic flow velocity was recorded with continuous wave Doppler technique from an apical window before and after injection of 2 ml of sonicated albumin. RESULTS: In 10 patients with aortic stenosis, the aortic velocity envelope was too indistinct to determine the peak velocity before sonicated albumin was injected. After injection, the aortic flow Doppler signal was enhanced in 9 of the 10 patients and the velocity envelope became clear enough to measure the peak velocity, enabling calculation of the transaortic pressure gradient. In the remaining 12 patients with aortic stenosis and in all 7 normal volunteers, the velocity envelope was clear before injection and became much clearer after injection. The calculated transaortic pressure gradient showed a good agreement with catheterization measurements (y = 1.1x-6.5, r = 0.88, p less than 0.001, SEE = 16 mm Hg, n = 13). Duration of Doppler signal enhancement was measured as the time during which the envelope was clearer than before injection throughout the ejection period. The duration was significantly shorter in patients with aortic stenosis than in normal volunteers (16 +/- 5 vs. 52 +/- 32 s, p less than 0.01). There was a significant correlation between left ventricular systolic pressure measured by catheterization and the duration of signal enhancement (r = -0.69), suggesting that albumin microbubbles were fragile at high pressure. CONCLUSIONS: The transpulmonary contrast-enhanced Doppler technique using sonicated albumin is useful for assessing the severity of aortic stenosis even in patients with poor Doppler recordings, although the duration of signal enhancement might be affected by left ventricular systolic pressure.