Inaccurate Ultrasound Assessment of Internal Carotid Disease in Patients with Carotid Artery Disease and Aortic Valve Stenosis C

Introduction

The association of internal carotid artery disease (ICAD) with aortic valve stenosis (AVS) constitutes a very high-risk clinical occurrence of which surgical management is still unclear, because the rate of death and stroke for combined suergry is 3%.¹ Carotid stenting before or after cardiac surgery may be a valuable option in such high-risk patients. An accurate diagnosis of any significant carotid artery stenosis is of paramount importance for a proper combined or staged surgical or endovascular repair, and for immediate results after cardiac valve surgery.² Unfortunately, in patients with AVS, the evaluation of carotid arteries by Doppler ultrasound (DUS) may be inaccurate.³ The present retrospective study is aimed to evaluate the pitfalls of DUS and the role of carotid angiography, before carotid stenting, in evaluating ICAD in patients with AVS.

Methods

We analyzed the clinical, hemodynamic and angiographic findings of 200 patients with moderate to severe AVS (aortic valve area index DUS protocol DUS examinations were performed with a Hewlett Packard SONOS 2500 color-coded duplex ultrasound system, according to the good-quality criteria described by the Society of Radiologists in Ultrasound,⁴ including grayscale, color Doppler, spectral DUS and using an angle of insonation of 60°.5 All studies included measurements of arterial peak systolic velocity (PSV), end-diastolic velocity, the ratio of the internal to common carotid artery velocities, and a planimetric estimation of the stenosis.

Angiographic film analysis

Angiograms were obtained by a transfemoral approach on imaging systems manufactured by Siemens Coroscope Plus (Malvern, PA). Two vessels were catheterized in each patient — common carotid arteries bilaterally. Digital subtraction angiographic images were also collected for each patient. Ipsilateral diagnostic images of the extracranial carotid arteries were obtained. An investigator, blinded to the clinical and Doppler ultrasound data, measured the stenosis in the internal carotid artery using fine calipers. Measurements were performed on the angiographic view that demonstrated the maximum severity of stenosis. The diameters of stenosis and of the distal internal carotid artery were then measured. Lesion severity was assessed following the European Carotid Surgery Trial (ECST) criteria³ for carotid arteries, using quantitative coronary angiography (QCA) analysis. A stensosis > 50% has been identified as significant stenosis.

Statistical analysis

Data are expressed by mean + SD and as percentage. A student t-test and chi-square test have been used to compare quantitative data and percentages, respectively; significance was set to p Results Seventy patients with moderate to severe AVS and doubtful carotid ultrasonography underwent coincident carotid angiography. The use of suboptimal Doppler ultrasonographic examinations are related to the anatomical or difficult evaluation of Doppler flow due to hemodynamic influences of aortic valve stenosis. On carotid angiography, 20 patients (28.5%, male/female: 8/12, mean age 72.1 + 5.1 years) were diagnosed with critical stenosis of one (16 patients) or both (4 patients) internal carotid artery arteries. In 5 patients, a significant ICAD was not diagnosed by DUS, whereas in 7 patients, the stenosis was underestimated by DUS (mean luminal narrowing 58 + 12.7 % versus 76.7 + 19.3 %, p Discussion Carotid artery screening by means of DUS examination makes sense in patients undergoing major vascular and cardiac surgery, but the prevalence of the association of AVS and ICAD may be understimated. Because the standard approach for screening of such patients has limitations due to technical difficulties, overestimation of lesions in cases of bilateral disease⁵, as well as difficult appreciation of occlusion and complex anatomy^6-7 may be particularly exacerbated by the characteristic abnormalities in flow velocity pattern due to aortic valve stenosis. In the only previous report on this issue, O’Boyle et al3 showed that patients with critical or severe stenosis had a mean acceleration time that was significantly longer than that in the control subjects (p = 0.008–0.0001). Peak velocities were decreased in all cases of aortic stenosis, regardless of severity only in the common carotid arteries. And finally, all 13 patients with critical aortic stenosis had delayed upstrokes and rounded waveforms in the common, internal and external carotid arteries. The presence or absence of a second systolic peak or a dicrotic notch was not different among patients with aortic stenosis and control subjects, such as the increased acceleration time, the decreased peak velocity and a delayed upstroke. Angiographically, our report suggests that DUS may be inconclusive in evaluating ICAD in patients with moderate to severe AVS. Carotid angiography may be proposed at the time of cardiac catheterization in patients with inconlusive DUS examination without increasing risk, avoiding the costs of other noninvasive techniques such as magnetic resonance angiography. This strategy may be effective endovascularly. The low frequency of bifurcation and ulcerated lesions, and high prevalence of focal stenosis reported in our study may be attractive characteristics for an endovascular management. Recently, the technique has been successfully applied to a patient with severe AVS⁸ and in patients undergoing major cardiac surgery.^9-10

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