摘要: Conclusions— Carotid arteries are smaller in women even after adjusting for body and neck size, age, and blood pressure。 Sonography of Carotid Arteries Four experienced investigators performed carotid ultrasound examinations using a 7。 Diameters of the ICA and CCA were significantly greater in......
the Department of Radiology (J.K., J.W., R.W.H.), University of Pennsylvania, Philadelphia
Department of Radiology (J.K.), Medical University of Gdansk, Poland
Medical University of Bialystok, Poland (A.U.)
Department of Neurology, Ageing, Degenerative, and Cerebrovascular Diseases (M.A.), Silesian Medical University, Katowice, Poland
Department of Neurology (S.E.K., B.L.C., S.R.M.), University of Pennsylvania, Philadelphia.
Background and Purpose— To explore relationships among gender, body size, neck size, and the diameters of the common carotid artery (CCA) and internal carotid artery (ICA).
Methods— Using multivariate regression, the best predictors of sonographic diameters of CCA and ICA were determined based on age, height, weight, body mass index, body surface area, neck circumference, neck length, and blood pressure.
Results— Measurements were obtained in 500 consecutive patients (age 52±15 years; 61% women). Mean diameters of ICA (4.66±0.78 mm) and CCA (6.10±0.80 mm) in women were significantly smaller than in men: 5.11±0.87 mm and 6.52±0.98 mm, respectively. Sex significantly influenced the diameters after controlling for body size, neck size, age, and blood pressure.
Conclusions— Carotid arteries are smaller in women even after adjusting for body and neck size, age, and blood pressure.
Key Words: carotid arteries carotid endarterectomy ultrasonography
Women appear to be at higher risk of early complications associated with carotid endarterectomy (CEA) and lower risk of stroke for any degree of stenosis compared with men.1–4 This may negate the potential benefit of carotid intervention in women, particularly in the setting of an asymptomatic stenosis.1,4
Body size may confound the effect of gender in carotid surgery because the procedure may be more difficult in smaller patients who may have proportionally smaller arteries.1,2,5 Smaller patients also likely have shorter necks, which may limit surgical access to the arteries. This study explored relationships among sex, body size, neck size, and the diameters of carotid arteries.
Patients and Methods
Patients were eligible if they gave informed consent and underwent routine cerebral angiographic and neurosonographic examinations for the purpose of a larger trial comparing the 2 methods. The institutional review board approved the study protocol. A total of 306 women and 194 men (mean 52±15 years; range 14 to 103) were prospectively studied over 17 months. Clinical history about atherosclerotic risk factors was obtained from the patient or medical record.
Sonography of Carotid Arteries
Four experienced investigators performed carotid ultrasound examinations using a 7.5-MHz probe (Aplio 80; Toshiba Medical System). On longitudinal high-resolution harmonic gray-scale images, internal diameters were measured at the most distal plaque-free portion of the internal carotid artery (ICA) above the carotid bulb and at the common carotid artery (CCA) &15 to 20 mm below the bifurcation.6
Height and weight were obtained from the medical record or patient interview. Body mass index (BMI) and body surface area (BSA) were calculated as: BMI=weight/height2 and BSA (m2)=0.20247x height (m)0.7256xweight (kg)0.425. Neck circumference was measured midway between the sternoclavicular notch and the jaw, whereas neck length was measured bilaterally from the sternoclavicular notch to the mastoid process and averaged between sides.
Heart rate (HR), cuff systolic blood pressure (SBP), diastolic blood pressure (DBP), and mean blood pressure (MBP) were measured using an automated sphygmomanometer.
Normal distribution of data were verified by the probability plot method. Measurements from both sides were compared using a paired 2-sided t test and averaged. Sex differences were analyzed with nonpaired 2-sided t test. Effects of body and neck size on diameters of ICA or CCA were determined using univariate and multivariate linear regression analysis and these variables, adjusting for blood pressure, heart rate, and age. The relationships between diameters and clinical parameters were derived by maximizing the F statistic in multivariate regression models (SYSTAT for Windows ; SYSTAT). This method simultaneously incorporates multiple variables, and the model with the maximum F statistic best fits the existing data. A P value <0.05 indicated statistical significance.
Women had lower values of height, weight, BSA, neck circumference, and neck length as well as slightly lower mean blood pressure and diastolic blood pressure than men (Table 1). Diameters of the ICA and CCA were significantly greater in men than in women (Table 1). The right CCA (6.15±0.91) was slightly larger than the left (6.05±0.87; P<0.05) in women, but there was no side-to-side difference of the CCA in men. There were no side-to-side differences in the ICA diameter. Carotid diameters increased with male sex, height, weight, BMI, BSA, neck circumference, and blood pressure, predominantly with SBP (Table 2).
The relationships between ICA and CCA diameters and the clinical parameters were derived as follows (both models F=13; R2=0.17; P<0.001): ICA diameter (mm)=0.449 (sex, male=1)+0.813(BSA, 0.1 m2)–0.113 (neck length, cm)+0.003(age, years)+0.007 (SBP, mm Hg)+4.36 mm and CCA diameter (mm)=0.26 (sex, male=1)+1.21(BSA, 0.1 m2)–0.05 (neck length, cm)+0.003 (age, years)+0.004 (SBP, mm Hg)+0.789 mm.
This study demonstrates that carotid arteries are smaller in women, even after adjusting for body and neck size, age, and blood pressure. An association between sex and carotid artery diameter has been reported previously,7–12 but these studies did not investigate combined effects of these potential confounders. In contrast to previous reports,8–10,12 no significant relationships between carotid artery size and age were found, most likely because of the relatively young patient population in our study. As expected, carotid artery diameter was influenced by blood pressure.
CCA diameter was related to body height and weight independent of sex.9–12 However, blood pressure, which is usually lower in women, was not controlled for in most studies.7,8 Moreover, BMI was the body size parameter that was most often controlled for,11,12 whereas BSA, height, and neck size appeared to better predict carotid artery diameter in our patients, presumably because BMI is a marker for nutritional and conditioning status.
The relationships between neck size and carotid size have not been explored previously. Neck circumference was found to be a stronger predictor of carotid artery diameter than neck length; however, only the latter was included in our regression models because of weaker correlation with BSA.
It has been reported that body size contributes to the risk of CEA,5 suggesting that greater surgical risk may be attributable in part to smaller patient size. This study demonstrates that women have smaller carotid arteries even after adjusting for body size. This finding may further explain the gender gap in the natural history and treatment of carotid artery disease. Further analyses are needed in CEA or stenting studies to more directly address the issue of whether women have higher complication rates related to reduced arterial diameter.
This work was supported by American Heart Association established investigator award grant 044099N to J.K. We express our thanks to Dr Oleg Bronov for his help with diagnostic studies.
Goldstein LB, Samsa GP, Matchar DB, Oddone EZ. Multicenter review of preoperative risk factors for endarterectomy for asymptomatic carotid artery stenosis. Stroke. 1998; 29: 750–753.
Sternbach DY, Perler BA. The influence of female gender on the outcome of carotid endarterectomy: a challenge to the ACAS findings. Surgery. 2000; 127: 272–275.
Rothwell PM, Eliasziw M, Gutnikov SA, Warlow CP, Barnett HJM. Endarterectomy for symptomatic carotid stenosis in relation to clinical subgroups and timing of surgery. Lancet. 2004; 363: 915–924.
Dick P, Sherif C, Sabeti S, Amighi J, Minar E, Schillinger M. Gender differences in outcome of conservatively treated patients with asymptomatic high grade carotid stenosis. Stroke. 2005; 36: 1178–1183.
Messe SR, Kasner SE, Mehta Z, Warlow CP, Rothwell PM, and for the European Carotid Surgery Trialists. Effect of body size on operative risk of carotid endarterectomy. J Neurol Neurosurg Psychiatry. 2004; 75: 1759–1761.
Foretza AM, Krejza J, Koch S, Babikian VL. Ultrasound imaging of cerebrovascular disease. In: Babikian VL, Wechsler L, Higashida RT, eds. Imaging Cerebrovascular Disease. Philadelphia, Pa: Butterworth-Heinemann; 2003: 3–35.
Schulz UGR, Rothwell PM. Sex differences in carotid bifurcation anatomy and the distribution of atherosclerotic plaque. Stroke. 2001; 32: 1525–1531.
Denarie N, Gariepy J, Chironi G, Massonneau M, Laskri F, Salomon J, Levenson J, Simon A. Distribution of ultrasonographically assessed dimensions of common carotid arteries in healthy adults of both sexes. Atherosclerosis. 2000; 148: 297–302.
Polak JF, Kronmal RA, Tell GS, Oleary DH, Savage PJ, Gardin JM, Rutan GH, Borhani NO. Compensatory increase in common carotid artery diameter - Relation to blood pressure and artery intima-media thickness in older adults. Stroke. 1996; 27: 2012–2015.
BonithonKopp C, Touboul PJ, Berr C, Magne C, Ducimetiere P. Factors of carotid arterial enlargement in a population aged 59 to 71 years—the EVA study. Stroke. 1996; 27: 654–660.
Crouse JR, Goldbourt U, Evans G, Pinsky J, Sharrett AR, Sorlie P, Riley W, Heiss G. Risk factors and segment-specific carotid arterial enlargement in the atherosclerosis risk in communities (ARIC) cohort. Stroke. 1996; 27: 69–75.
Mannami T, Baba S, Ogata J. Potential of carotid enlargement as a useful indicator affected by high blood pressure in a large general population of a Japanese city: the Suita Study. Stroke. 2000; 31: 2958–2965.