Ultrasonic Evaluation of the Radial Artery Diameter in a Local Population From Texas

Abstract: Background. Radial access is the preferred route for cardiac catheterization; however, small radial arterial diameters can make complex procedures difficult. The assessment of radial artery diameters prior to intervention may be beneficial for the interventional cardiologist. Our aim was to measure the diameter of radial arteries in a study sample from our population, and to analyze the feasibility of using larger sheaths for radial interventions. Methods. The right radial artery diameter of 100 volunteers was measured using an ultrasound technique. A logistic regression analysis was performed to identify factors associated with small arterial diameters. Results. The average age of our sample was 35 years, 40% were male, and the mean body mass index (BMI) was 27 kg/m². The mean right arterial diameter for our population was 2.22 ± 0.35 mm. No strong direct association was found between diameters with age, height, weight, and body surface area. Forty-two percent of the patients had diameters larger than 5 Fr sheaths, 20% of the subjects had a diameter larger than 6 Fr sheaths, and 5% of the patients had diameters larger than 7 Fr sheaths. Logistic regression analysis revealed that female volunteers were associated with smaller arterial diameters (odds ratio [OR], 4.0; confidence interval [CI], 1.51-10.51; P=.005), while increases in BMI were associated with larger arterial diameters (OR, 0.21; CI, 0.07-0.61; P=.004). Conclusion. Six Fr sheaths can be used in a significant proportion of our population. Careful selection of male patients with a larger BMI may help the interventionist in advance for planning a radial procedure with larger sheaths.

J INVASIVE CARDIOL 2012;24(7):339-341

Key words: transradial access, body mass index

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Since the efficacy of radial access for coronary angiography was first explained by Campeau in 1989¹ and coronary angioplasty through the radial route was reported by Kiemeineij et al in 1993,² radial arteries have been increasingly utilized as an alternative access site for cardiac catheterization. A recent meta-analysis demonstrated that the radial approach was associated with a shorter hospital stay, lower costs, and a lower rate of bleeding complications than the femoral approach.³ However, due to smaller radial arterial diameters, the need to switch to another puncture site is more common in the case of complex procedures requiring larger sheaths. Registries from 2004 to 2007 show that the use of the radial approach in the United States remains low when compared to Europe, Japan, and Canada.⁴ Currently, the 5 Fr sheath is the most commonly used size for radial access in the United States. However, studies to assess the suitability for larger sheaths have not been done to the best of our knowledge. The aim of our study was to assess the diameter of radial arteries in a study sample from our local population, identify possible factors affecting it, and analyze the feasibility of using larger sheaths for radial interventions.

Methods

During December 2010 and January 2011, the radial artery diameters were measured in 100 volunteers at our Institution. Informed consent was obtained from each volunteer. The study protocol was reviewed and approved by our Institutional Review Board, conforming to the ethical guidelines of our institution and the American Physiological Society.

Right radial arteries diameters were measured using a General Electrics LOG IQ9 Probe 9L (8 MHz) ultrasound. Diameters were measured 1 to 2 cm proximal to the radial styloid process, the most common site for vascular access in radial procedures. Measurements were taken in short axis view by a single experienced operator. A horizontal and vertical diameter were obtained for each radial artery and an average of both values was considered to be the “average diameter.” The outer diameter of radial sheaths was obtained by using data from previously published studies.⁵

The SPSS version 16.0 data analysis package for Windows was used (SPSS Inc). Descriptive statistics were used to characterize our study sample; continuous variables were compared using student’s t-test. At the end, a logistic regression analysis was performed to identify smaller diameters adjusting for gender, age, and body mass index (BMI). P-values less than .05 were considered statistically significant.

Results

Baseline characteristics of the subjects are presented in Table 1. The mean age of subjects was 35 years, 40% of subjects were male, and the mean BMI was 27. Male subjects were significantly older, heavier, and taller than female subjects. The mean right arterial diameter for our entire population was 2.22 ± 0.35 mm. The diameters ranged from 1.45 to 3.0 mm. The diameters followed a normal distribution (Figure 1). The mean right diameter for males was larger (2.42 ± 0.33 mm) compared to females (2.08 ± 0.29 mm; P<.001).

Using individual linear relationships, no linear correlation was found for age, height, weight, and body surface area (BSA) with average radial artery diameters (Table 2). Subjects above age 35 had a significantly larger arterial diameter than their younger subjects; however, patients above 50 years did not have diameters larger than subjects between 35 and 50 years. When dividing subjects between BMI subgroups, those with a BMI larger than 25 kg/m2 had larger diameters (Table 3).

Forty-two percent of the patients had an arterial diameter larger than a 5 Fr arterial sheath (2.28 mm; Terumo)⁵ and 20% of the subjects have diameters larger than 6 Fr sheaths (2.62 mm). Only 5% of the subjects had a radial artery diameter larger than 7 Fr sheaths (2.95 mm). After adjusting for age, gender, and BMI using a logistic regression analysis, female subjects were 4 times more likely to have smaller diameters, (odds ratio, [OR], 4.0; confidence interval [CI], 1.51-10.51; P=.005), and subjects with a higher BMI were less likely to have smaller diameters (OR, 0.21; CI, 0.07-0.61; P=.004). Increases in age also made the subjects less likely to have small arterial diameters, but this was not statistically significant (OR, 0.67; CI, 0.43-1.03; P=.068).

Discussion

In this study sample, ultrasound (the gold standard technique) was used to measure radial arterial diameters. The mean right radial artery diameter in our study was 2.22 ± 0.35 mm. This is close to measurements taken by Ashraf et al in the Pakistani population⁶ (2.3 ± 0.4 mm for right and 2.2 ± 0.4 mm for left radial artery), but smaller than measurements in Chinese (2.38 ± 0.56 mm), Singaporean (2.45 ± 0.45 mm), and Korean populations (2.60 ± 0.41 mm).^5,7,8

No strong individual linear relationship was found between radial diameters and height, weight, or BSA, which is consistent with findings in other studies.⁹ However, from our study population, we concluded that male gender, age above 35 years, and BMI >25 kg/m² helped predict larger arterial diameters. It can be expected from our results that female patients with a low BMI may be more difficult to cannulate with larger sheaths.

Our study showed that 20% of subjects have a diameter larger than a 6 Fr sheath. Considering the elastic properties of radial arteries, this number could be actually higher. This finding may need to be interpreted with caution, as Saito et al⁹ demonstrated that a radial artery diameter/sheath-diameter ratio <1 is associated with a reduction in distal flow. A 4% occlusion occurs with a ratio >1 and 13% with a ratio <1. A study by Nagai et al showed that the risk of diffuse late stenosis has been correlated positively with the difference between the radial artery and the sheath size.¹⁰ However, the clinical significance of these findings is unknown.

The use of gender and low BMI for predicting smaller radial artery diameters may help the interventionist consider alternative access sites or anticoagulation for preventing radial artery occlusion. A recent study¹¹ suggests that radial artery occlusion remains asymptomatic in about half of the patients after catheterization, and treatment with low molecular weight heparins may increase the patency of the arteries. Hand ischemia is uncommon after radial artery occlusion due to ulnar artery blood supply; however, the presence of a patent radial artery may save an access site for future interventions.

Study limitations. The limitation in our study was our small population size and the relatively young age of our patients, who may not have the same amount of co-morbidities as patients undergoing coronary interventions. We did not analyze for other factors that could have influenced the ratio of the radial artery, such as smoking, diabetes mellitus, peripheral vascular disease, and ethnicity. We also did not perform a radial catheterization in our patients to confirm the ability of the arteries to support each sheath.

Conclusion

Our study concludes that a significant proportion of our study population has radial arterial diameters large enough for 6 Fr sheaths. When planning complex radial interventions, male subjects with a higher BMI can be expected to allow larger arterial sheaths with fewer complications. The use of ultrasound prior to radial interventions is a useful option that needs to be validated with more studies.

References

1. Campeau L. Percutaneous radial artery approach for coronary angiography. Cathet Cardiovasc Diagn. 1989;16(1):3-7.
2. Kiemeneij F, Laarman GJ, de Melker E. Transradial artery coronary angioplasty. Am Heart J. 1995;129(1):1-7.
3. Jolly SS, Amlani S, Hamon M, et al. Radial versus femoral access for coronary angiography or intervention and the impact on major bleeding and ischemic events: a systematic review and meta-analysis of randomized trials. Am Heart J. 2009;157(1):132-140.
4. Rao SV, Ou FS, Wang TY, et al. Trends in the prevalence and outcomes of radial and femoral approaches to percutaneous coronary intervention: a report from the National Cardiovascular Data Registry. JACC Cardiovasc Interv. 2008;1(4):379-386.
5. Yoo B, Yoon J, Ko JK, et al. Anatomical consideration of the radial artery for transradial coronary procedures: arterial diameter, branching anomaly and vessel tortuosity. Int J Cardiol. 2005;101(3):421-427.
6. Ashraf T, Panhwar Z, Habib S, et al. Size of radial and ulnar artery in local population. J Pak Med Assoc. 2010;60(10):817-819.
7. Loh YJ, Nakao M, Tan WD, et al. Factors influencing radial artery size. Asian Cardiovasc Thorac Ann. 2007;15(4):324-326.
8. Yan ZX, Zhou YJ, Zhao YX, et al. Anatomical study of forearm arteries with ultrasound for percutaneous coronary procedures. Circ J. 2010;74(4):686-692.
9. Saito S, Ikei H, Hosokawa G, Tanaka S. Influence of the ratio between radial artery inner diameter and sheath outer diameter on radial artery flow after transradial coronary intervention. Catheter Cardiovasc Interv. 1999;46(2):173-178.
10. Nagai S, Abe S, Sato T, et al. Ultrasonic assessment of vascular complications in coronary angiography and angioplasty after transradial approach. Am J Cardiol. 1999;83(2):180-186.
11. Zankl AR, Andrassy M, Volz C, et al. Radial artery thrombosis following transradial coronary angiography: incidence and rationale for treatment of symptomatic patients with low-molecular-weight heparins. Clin Res Cardiol. 2010;99(12):841-847.

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From the Departments of 1Internal Medicine and 2Cardiology, School of Medicine, Texas Tech University Health Sciences Center, Lubbock, Texas, and 3the Division of Biostatistics and Epidemiology, Paul L. Foster School of Medicine, Texas Tech University Health Sciences Center, El Paso, Texas.
Disclosure: The authors have completed and returned the ICMJE Form for Disclosure of Potential Conflicts of Interest. The authors report no conflicts of interest regarding the content herein.
Manuscript submitted January 30, 2012, provisional acceptance given February 20, 2012, final version accepted March 13, 2012.
Address for correspondence: Dr Alejandro Velasco, Department of Internal Medicine, School of Medicine, Texas Tech University Health Sciences Center, 3601 4th  Street, Lubbock, TX 79430. Email: alejovela@hotmail.com