Assessment of the contractile reserve in patients with intermediate coronary lesions: a strain rate imaging study validated by invasive myocardial fractional flow reserve

Abstract

The present study aims to compare the change of left ventricular deformation during dobutamine stress echocardiography (DSE) with the reference standard of invasive myocardial fractional flow reserve (FFR) to assess the haemodynamic significance of intermediate coronary lesions. In 30 patients with an intermediate coronary artery stenosis in one epicardial coronary artery, FFR measurements were performed during coronary catheterization. In case of an FFR < 0.75 after intracoronary adenosine administration, the stenosis was considered significant, indicating ischaemia. In addition, during DSE, peak systolic strain rate and systolic strain of the region of interest (supplied by the stenotic vessel) and of a non-ischaemic remote region were assessed at baseline and at peak stress. Thirteen patients had an FFR >or= 0.75, indicating normal flow reserve (non-ischaemic group). The remaining 17 patients with an FFR < 0.75 comprised the ischaemic group. At baseline DSE, mean values of strain rate (-1.2 +/- 0.3 s(-1)) and strain (-17 +/- 8%) were not significantly different between both groups. In the ischaemic group, in the target region, strain at peak stress decreased to - 10 +/- 8%, whereas strain rate remained unchanged. In contrast, in the non-ischaemic group, strain at peak stress remained unchanged (-18 +/- 7%), whereas strain rate increased to - 2.5 +/- 1.1 s(-1). The receiver operating characteristic curve analysis revealed the change in strain rate as the best parameter to detect ischaemia, with a sensitivity of 89% and a specificity of 86%. In the remote region, in both groups, strain rate (-1.4 +/- 0.4 s(-1)) and strain values (-20 +/- 7%) were not significantly different at baseline, and strain rate doubled and strain remained unchanged at DSE peak stress. Non-invasive evaluation of regional deformation, using strain rate imaging during DSE, predicted the relevance of intermediate coronary stenosis. In this context, strain rate is superior to strain measurements for the quantification of the contractile reserve.