Ann Vasc Dis Vol. 6, No. 3; 2013; pp 590–595 ©2013 Annals of Vascular Diseases
Online July 31, 2013 doi:10.3400/avd.oa.13-00053
Original Article
Usefulness of Acceleration Time for Internal Carotid Artery Origin Stenosis Hirokazu Tamura, RT,1 Yasuhisa Akaiwa, MD, PhD,2 and Kiyoshi Onda, MD, PhD3
Calcification of the internal carotid artery (ICA) hinders accurate evaluation of the stenosis by conventional ultrasonography due to acoustic shadow. We examined the relationship between acceleration time (AcT) and ICA origin stenosis. One hundred thrity seven samples (266 vessels) that enforced duplex ultrasonography in our hospital were targeted. The results have shown that there is a significant relationship between AcT and stenosis. AcT of more than 110 msec suggests that the stenosis is more than 60% by the North American Symptomatic Carotid Endarterectomy Trial (NASCET) method. AcT is thought to be useful for the diagnosis of ICA stenosis with calcification. (*English Translation of J Jpn Coll Angiol 2011; 51: 365-371) Keywords: acceleration time, internal carotid artery, ultrasonography
Introduction
T
he carotid artery stenosis is a risk factor for cerebral infarction. Recently, procedures such as carotid endarterectomy (CEA) and carotid artery stenting (CAS) have been recommended depending on the severity of stenosis.1) Ultrasonography is a simple and noninvasive examination widely used for the diagnosis of carotid artery stenosis. However, apparatus-specific artifacts are occasionally observed, and the evaluation of stenosis with calcification may be hampered by acoustic shadows. The presence of stenosis is known to make the upstroke of the blood flow velocity waveform gentler on its distal
1Department of Medical Radiology, Niigata Neurosurgical Hospital, Niigata, Niigata, Japan 2Department of Neurology, Niigata University Medical and Dental Hospital, Niigata, Niigata, Japan 3Department of Neurosurgery, Niigata Neurosurgical Hospital, Niigata, Niigata, Japan
Received: June 5, 2013; Accepted: June 5, 2013 Corresponding author: Hirokazu Tamura. Department of Medical Radiology, Niigata Neurosurgical Hospital, 3057 Yamada, Nishi-ku, Niigata, Niigata 950-1101, Japan Tel: +81-25-231-5120, Fax: +81-25-231-5130 E-mail: [email protected] *This article is English Translation of J Jpn Coll Angiol 2011; 51: 365-371.
590
side and to prolong the systolic acceleration time (AcT).2) These changes in the flow velocity waveform have been reported to be useful for the diagnosis of stenosis in perip heral arteries and the renal artery.3,4) On ultrasonography of the cervical blood vessels, the diagnosis of stenosis often depends on changes in the flow velocity waveform pattern, and prolonged AcT. In this study, we examined the relationship between AcT and the severity of stenosis at the origin of the internal carotid artery (ICA).
Materials and Methods The materials were 274 vessels of 137 patients (99 males and 38 females aged 35–90 years, with a mean of 66.4 years) who underwent ultrasonography of the cervical blood vessels between June 2007 and April 2010. Patients with a history of aortic stenosis (AS) were excluded from the subjects. Excluding 8 vessels with obstruction of the internal carotid artery, stenosis of the common carotid artery, or stenosis of the brachiocephalic artery, 266 vessels were eventually evaluated. Ultrasonography was carried out using Vivid7 Dimension (GE Healthcare, Tokyo, Japan) and a linear probe with a central frequency of 9 MHz in the supine position. The percent stenosis was evaluated by ultrasonography using the North American Symptomatic Carotid Endarterectomy
Annals of Vascular Diseases Vol. 6, No. 3 (2013)
Usefulness of Acceleration Time for Internal Carotid Artery Origin Stenosis
Fig. 1 M easurement methods of acceleration time (AcT). (A) The linear array probe was set in the internal carotid artery (ICA) at 2–3 cm above the ICA origin. The AcT was measured using the average of 3 heartbeats. (B) The normal Doppler wave-form pattern. (C) Duplex sonogram of a patient with ICA stenosis shows that upstroke is delayed and peak is rounded.
Trial (NASCET) method.5) The AcT and the flow velocity were measured using the duplex Doppler technique by avoiding curved parts of the vessel. The measurements were performed 2–3 cm above the carotid bifurcation in patients with no stenosis and 2–3 cm above the stenosed lesion in patients with stenosis (Fig. 1). The AcT was measured with the ultrasonographic apparatus, and the mean of 3 heartbeats was calculated. The sample volume was 2/3 of the vascular diameter, and the angle of incidence of ultrasound relative to the direction of the blood flow was set at 60° or less. If the flow velocity waveform showed 2 peaks, the time from the upstroke to the first peak was regarded as the AcT. Of the 266 vessels, 172 that showed no stenosis were used as a control group, and the mean + 2SD was calcu-
Annals of Vascular Diseases Vol. 6, No. 3 (2013)
lated as a normal cutoff value. Ninety-four vessels that showed 10% or more stenosis by the NASCET method were regarded as a stenosis group, and the relationship between the percent stenosis and AcT was evaluated (Fig. 2). The percent stenosis was also evaluated by angiography (angio-NASCET) in patients who were judged by the attending physician to require the examination and consented to it. Angiography was performed using Advantx UNV (GE Healthcare, Japan) and Allura Xper FD 20/10 (Royal Philips Electronics, Amsterdam, Netherlands). Correlations between 2 variables were examined using Pearson’s correlation coefficient. Comparisons between the 2 groups were made with Mann-Whitney’s U-test at the P
Online July 31, 2013 doi:10.3400/avd.oa.13-00053
Original Article
Usefulness of Acceleration Time for Internal Carotid Artery Origin Stenosis Hirokazu Tamura, RT,1 Yasuhisa Akaiwa, MD, PhD,2 and Kiyoshi Onda, MD, PhD3
Calcification of the internal carotid artery (ICA) hinders accurate evaluation of the stenosis by conventional ultrasonography due to acoustic shadow. We examined the relationship between acceleration time (AcT) and ICA origin stenosis. One hundred thrity seven samples (266 vessels) that enforced duplex ultrasonography in our hospital were targeted. The results have shown that there is a significant relationship between AcT and stenosis. AcT of more than 110 msec suggests that the stenosis is more than 60% by the North American Symptomatic Carotid Endarterectomy Trial (NASCET) method. AcT is thought to be useful for the diagnosis of ICA stenosis with calcification. (*English Translation of J Jpn Coll Angiol 2011; 51: 365-371) Keywords: acceleration time, internal carotid artery, ultrasonography
Introduction
T
he carotid artery stenosis is a risk factor for cerebral infarction. Recently, procedures such as carotid endarterectomy (CEA) and carotid artery stenting (CAS) have been recommended depending on the severity of stenosis.1) Ultrasonography is a simple and noninvasive examination widely used for the diagnosis of carotid artery stenosis. However, apparatus-specific artifacts are occasionally observed, and the evaluation of stenosis with calcification may be hampered by acoustic shadows. The presence of stenosis is known to make the upstroke of the blood flow velocity waveform gentler on its distal
1Department of Medical Radiology, Niigata Neurosurgical Hospital, Niigata, Niigata, Japan 2Department of Neurology, Niigata University Medical and Dental Hospital, Niigata, Niigata, Japan 3Department of Neurosurgery, Niigata Neurosurgical Hospital, Niigata, Niigata, Japan
Received: June 5, 2013; Accepted: June 5, 2013 Corresponding author: Hirokazu Tamura. Department of Medical Radiology, Niigata Neurosurgical Hospital, 3057 Yamada, Nishi-ku, Niigata, Niigata 950-1101, Japan Tel: +81-25-231-5120, Fax: +81-25-231-5130 E-mail: [email protected] *This article is English Translation of J Jpn Coll Angiol 2011; 51: 365-371.
590
side and to prolong the systolic acceleration time (AcT).2) These changes in the flow velocity waveform have been reported to be useful for the diagnosis of stenosis in perip heral arteries and the renal artery.3,4) On ultrasonography of the cervical blood vessels, the diagnosis of stenosis often depends on changes in the flow velocity waveform pattern, and prolonged AcT. In this study, we examined the relationship between AcT and the severity of stenosis at the origin of the internal carotid artery (ICA).
Materials and Methods The materials were 274 vessels of 137 patients (99 males and 38 females aged 35–90 years, with a mean of 66.4 years) who underwent ultrasonography of the cervical blood vessels between June 2007 and April 2010. Patients with a history of aortic stenosis (AS) were excluded from the subjects. Excluding 8 vessels with obstruction of the internal carotid artery, stenosis of the common carotid artery, or stenosis of the brachiocephalic artery, 266 vessels were eventually evaluated. Ultrasonography was carried out using Vivid7 Dimension (GE Healthcare, Tokyo, Japan) and a linear probe with a central frequency of 9 MHz in the supine position. The percent stenosis was evaluated by ultrasonography using the North American Symptomatic Carotid Endarterectomy
Annals of Vascular Diseases Vol. 6, No. 3 (2013)
Usefulness of Acceleration Time for Internal Carotid Artery Origin Stenosis
Fig. 1 M easurement methods of acceleration time (AcT). (A) The linear array probe was set in the internal carotid artery (ICA) at 2–3 cm above the ICA origin. The AcT was measured using the average of 3 heartbeats. (B) The normal Doppler wave-form pattern. (C) Duplex sonogram of a patient with ICA stenosis shows that upstroke is delayed and peak is rounded.
Trial (NASCET) method.5) The AcT and the flow velocity were measured using the duplex Doppler technique by avoiding curved parts of the vessel. The measurements were performed 2–3 cm above the carotid bifurcation in patients with no stenosis and 2–3 cm above the stenosed lesion in patients with stenosis (Fig. 1). The AcT was measured with the ultrasonographic apparatus, and the mean of 3 heartbeats was calculated. The sample volume was 2/3 of the vascular diameter, and the angle of incidence of ultrasound relative to the direction of the blood flow was set at 60° or less. If the flow velocity waveform showed 2 peaks, the time from the upstroke to the first peak was regarded as the AcT. Of the 266 vessels, 172 that showed no stenosis were used as a control group, and the mean + 2SD was calcu-
Annals of Vascular Diseases Vol. 6, No. 3 (2013)
lated as a normal cutoff value. Ninety-four vessels that showed 10% or more stenosis by the NASCET method were regarded as a stenosis group, and the relationship between the percent stenosis and AcT was evaluated (Fig. 2). The percent stenosis was also evaluated by angiography (angio-NASCET) in patients who were judged by the attending physician to require the examination and consented to it. Angiography was performed using Advantx UNV (GE Healthcare, Japan) and Allura Xper FD 20/10 (Royal Philips Electronics, Amsterdam, Netherlands). Correlations between 2 variables were examined using Pearson’s correlation coefficient. Comparisons between the 2 groups were made with Mann-Whitney’s U-test at the P
