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Ann Thorac Surg 2005;79:99-103
© 2005 The Society of Thoracic Surgeons

Original article: Cardiovascular

Intravascular Ultrasound Analysis of the Radial Artery for Coronary Artery Bypass Grafting

Akio Oshima, MDa, Satoshi Takeshita, MDb,*, Ken Kozuma, MDa, Naoyuki Yokoyama, MDa, Kentaro Motoyoshi, MDa, Shuichi Ishikawa, MDa, Mitsuyoshi Honda, MDa, Koji Oga, MDa, Masahiko Ochiai, MDa, Takaaki Isshiki, MDa

a Department of Medicine (Cardiology), Teikyo University School of Medicine
b Department of Medicine (Cardiology), International Medical Center of Japan, Tokyo, Japan

Accepted for publication June 25, 2004.

* Address reprint requests to Dr Takeshita, Department of Medicine (Cardiology), International Medical Center of Japan, 1–21–1 Toyama, Shinjuku-ku, Tokyo 162–8655, Japan (E-mail: stake{at}muse.ocn.ne.jp).


   Abstract
Top
 Abstract
Introduction
 Patients and Methods
 Results
 Comment
 References
 
BACKGROUND: The radial artery has become a popular conduit for coronary artery bypass surgery. However, limited information has been provided regarding the atherosclerotic nature of this artery, which may affect both the immediate intraoperative difficulties and long-term graft patency.

METHODS: We examined intravascular ultrasound (IVUS) images of the radial artery in patients with coronary artery diseases. Cross sections of the radial artery were assessed using the following factors: lumen diameter, lumen area, vessel diameter, vessel area, plaque area, percent plaque area, and extent of calcium deposition.

RESULTS: The IVUS images were obtained from radial arteries of 58 patients (47 men, average 67 ± 9 years) during transradial procedures; ie, transradial coronary angiography and/or transradial coronary intervention. Mean luminal diameter was 3.28 ± 0.69 mm and 3.00 ± 0.70 mm at the proximal and distal segments, respectively, and 2.58 ± 0.73 mm at the minimal lumen cross section. A percent plaque area greater than 50% was seen in five radial arteries (8.6%) whose average plaque length was 26.4 ± 30.8 mm. Of these, one showed a plaque length greater than 50 mm, and another showed vessel caliber less than 2.0 mm. Five of 58 radial arteries (8.6%) showed calcium deposition, two of which showed diffuse calcification (> 50 mm). Thus, among 58 radial arteries, four (6.9%: one with diffuse arteriosclerosis, one small radial artery, two with diffuse calcification) were considered unsuitable for bypass conduit.

CONCLUSIONS: Preoperative evaluation of the radial artery is recommended in order to prevent unnecessary exploration of the forearm and to improve graft patency.


   Introduction
Top
 Abstract
 Introduction
Patients and Methods
 Results
 Comment
 References
 
The use of the radial artery for coronary artery bypass surgery (CABG) was first introduced over three decades ago by the pioneering work of Carpentier and colleagues [1]. However, subsequent postoperative studies, which followed up patients by means of angiography, documented frequent graft failure, and the use of this conduit was therefore completely abandoned after 1976. Nevertheless, in the early 1990s, interest in the use of the radial artery in this surgical procedure was revived [2–4]. With the advent of improved harvesting techniques, the use of postoperative aspirin, and the introduction of calcium-channel-blockers, results of radial artery grafting have been improved. Recent studies have indicated that 5-year patency rate of radial artery graft yields approximating 85% [2, 5], which is higher than that of the venous grafts reported in the literature [6].

Despite this resurgence in the popularity of the radial artery as a CABG conduit, only limited information is currently available regarding its anatomic characteristics. In order to further improve operative results, such information, including the prevalence of preexisting arteriosclerosis, is needed because it could affect both the immediate intraoperative difficulties as well as long-term graft patency.

Intravascular ultrasound (IVUS) can accurately depict the absolute luminal area, the structure of the arterial wall, and the presence and extent of atherosclerotic plaque, which have been shown to have good correlation with histopathologic findings [7, 8]. In the current study, we examined the IVUS images of the radial artery in patients with coronary artery diseases, and sought to clarify the anatomic characteristics and the prevalence of arteriosclerosis of the radial artery as a conduit for CABG.


   Patients and Methods
Top
 Abstract
 Introduction
 Patients and Methods
Results
 Comment
 References
 
The investigation conforms to the principles outlined in the Declaration of Helsinki. Written informed consent was obtained from all patients before enrollment.

The right radial arteries from 58 consecutive patients with coronary artery diseases were analyzed by means of IVUS, during transradial procedures; ie, transradial coronary angiography (TRA) and/or transradial coronary intervention (TRI). None of these patients had received transradial procedures previously. All IVUS examinations were performed before any devices went through the radial artery.

After insertion of the partial sheath (3 to 5 cm) into the distal radial artery, the IVUS catheter, a single-element 40 MHz transducer within a 2.6F imaging sheath (CVIS/Boston Scientific Corp, San Jose, CA), was advanced into the brachial artery and positioned approximately 10 mm beyond the bifurcation of the radial and ulnar arteries. Following the intraarterial administration of 2.5 mg of verapamil through the arterial sheath, automated pullback, over an overall length of 150 mm, was employed at a constant speed of 1.0 mm/s from the distal brachial artery to the distal radial artery (Fig 1). For off-line analysis, IVUS images were recorded on half-inch, high resolution super video home system (S-VHS) videotape.



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  		Fig 1. Intravascular ultrasound measurements. Intravascular ultrasound catheter was advanced into the brachial artery and positioned approximately 10 mm beyond the bifurcation of the radial and the ulnar arteries. Automated pullback (overall length 150 mm) was employed at a constant speed of 1.0 mm/s from the distal brachial artery to the distal radial artery. Arrows indicate (A) 10 mm distal to the bifurcation of the radial and the ulnar arteries (proximal point), (B) 100 mm distal to the bifurcation (distal point), and (C) the minimal lumen cross section throughout the pullback.

 
The IVUS cross-sectional images were analyzed offline using a semiautomated IVUS image analysis system (Netra IVUS; ScImage, Los Altos, CA) as described previously [9]. Briefly, this program constructed three-dimensional (3D) longitudinal sections from the data set and identified the contours corresponding to the lumen and media boundaries. Checking and editing of the contours of the planar images were performed by an independent experienced analyst. The cross sections of the entire radial artery were assessed using the following factors: lumen diameter, lumen area, vessel diameter, vessel area, plaque area, and percent plaque area (Fig 2A). The radial artery was defined as small if the proximal cross section showed a vessel diameter less than 2.0 mm. Diffuse arteriosclerosis was defined when significant arteriosclerosis (percent plaque area > 50%) was distributed greater than 50 mm longitudinally throughout IVUS pullback.



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  		Fig 2. Intravascular ultrasound images. (A) Normal radial artery. Minimal amount of atherosclerotic plaque is seen. Lumen diameter is 3.5 mm and percent plaque area is only 8%. No plaque accumulation was observed along the entire length of the radial artery. (B) Atherosclerotic radial artery. Plaque encroaches on the vessel. Lumen diameter is reduced to 2.0 mm and percent plaque area is increased to 55%. The plaque extended 8 mm long along the radial artery. (C) Calcified radial artery. Lumen diameter is reduced to 1.9 mm and the maximum calcium arc is 270 degrees. Calcified plaque extends to 50 mm in length.

 
Plaque calcification, defined as bright and dense structure with acoustic shadowing, was also assessed by IVUS. The intimal circumference of a calcified lesion (the calcium arc) was measured in degrees, using a protractor centered in the middle of the vessel. The longitudinal length of the calcified lesion (calcium length) was also determined. Diffuse calcification was defined as a calcium length greater than 50 mm. All quantitative data were expressed as the mean ± the standard deviation, and qualitative data were expressed as frequency of occurrence.


   Results
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 Abstract
 Introduction
 Patients and Methods
 Results
Comment
 References
 
Study Patients
The clinical characteristics of the 58 patients are summarized in Table 1. The study population comprised 47 men (81.0%) and 11 women (19.0%), with age range from 52 to 85 years (average 67 ± 9 years). Fifty-seven patients (98.3%) underwent IVUS examination during TRI, and one (1.3%) during TRA. Thirty-two patients (55.2%) were active smokers, 28 (48.3%) had hyperlipidemia (total cholesterol ≥ 220 mg/dL), and 24 (41.4%) had diabetes. Thirty-six patients (62.1%) presented with multivessel disease.


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  		Table 1. Patient Characteristics
 
IVUS Findings
The results of the IVUS measurements of the radial artery are summarized in Table 2. Data in this table represent measurements 10 mm distal to the bifurcation of the radial and ulnar arteries (proximal point), 100 mm distal to the bifurcation (distal point), and the minimal lumen cross section throughout the pullback (Fig 1). Mean luminal diameter of the radial artery was 3.28 ± 0.69 mm at the proximal point, 3.00 ± 0.70 mm at the distal point, and 2.58 ± 0.73 mm at the minimal lumen cross section.


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  		Table 2. Results of Intravascular Ultrasound Measurements
 
Percent plaque area greater than 50%, at the minimal lumen cross section, was observed in five out of the 58 (8.6%) radial arteries, in which no calcium deposition was observed (Fig 2B). The average percent plaque area of these five radial arteries was 62.6 ± 10.5%, and the plaque length was 26.4 ± 30.8 mm. Diffuse arteriosclerosis (percent plaque area of > 50% distributed > 50 mm longitudinally) was seen in only one of these five radial arteries (lesion length: 80 mm). Among four radial arteries with discrete lesions (lesion length < 50 mm), one showed small vessel caliber (1.59 mm at the proximal and 1.97 mm at the distal points). In this vessel, focal plaque deposition was seen proximally (lesion length: 10 mm) and the percent plaque area was 58.7% at the proximal, and 26.7% at the distal cross sections. Overall, among the five radial arteries with significant arteriosclerosis, two (one classified as diffusely diseased and the other as a small radial artery) were considered unsuitable for CABG conduit.

Calcium deposition was observed in five of the 58 (8.6%) radial arteries (Fig 2C); all five showed a percent plaque area of less than 50% throughout the pullback. The average percent plaque area at the minimal cross section of the five calcified radial arteries was 28.2 ± 11.6%, the average calcium arc was 167.8 ± 98.8 degrees, and the average calcium length was 25.0 ± 27.6 mm. In three of the five radial arteries, calcium deposition was discrete (5 mm in length for all) and the calcium arc was 47, 119, and 133 degrees, respectively. In contrast, the remaining two calcified radial arteries showed diffuse calcium deposition (calcium length > 50 mm) of 60 and 50 mm, respectively. In both cases, the calcium arc was 270 degrees. Therefore, these two radial arteries were not considered to be suitable for CABG conduit.


   Comment
Top
 Abstract
 Introduction
 Patients and Methods
 Results
 Comment
References
 
Vessel Diameter of the Radial Artery
Because of a trend towards the use of arterial conduit in CABG, radial arteries have again become a popular choice for many cardiac surgeons [2–4]. One of the major features of the radial artery is that it provides an ideal vessel caliber as a bypass conduit. Horning and colleagues [10], for example, reported that the mean diameter of the radial artery 15 cm proximal to the wrist was 2.8 mm in healthy volunteers. Similarly, in the current study, average luminal diameter of the radial artery was 3.28 mm at the proximal and 3.00 mm at the distal points. Even at the minimal lumen cross section, average luminal diameter was 2.58 mm. It must be remembered, however, that one patient (1.7%) in our study had a small radial artery (vessel diameter < 2.0 mm at the proximal point), which was considered to be unsuitable for CABG conduit. This low incidence of small radial artery is consistent with our previous observations that 1.7% of patients undergoing TRI presented with small radial arteries as assessed by conventional two-dimensional and color-Doppler ultrasound [11]. Since excluding those patients with small radial arteries by physical examination (ie, radial pulsation) is often misleading [11], preoperative imaging by means of IVUS or conventional ultrasound may prove more reliable.

Arteriosclerosis of the Radial Artery
Radial arteries have been shown to be associated with a higher degree of arteriosclerosis than the internal thoracic artery, and this may limit their use as a bypass conduit [12, 13]. Ruengsakulrach and colleagues [12], for example, examined histologically a total of 110 radial artery specimens, and found arteriosclerosis in 5% and medial calcifications in 13%. Similarly, in the current study, atherosclerotic radial arteries were not uncommon, as we found a plaque encroachment of greater than 50% of the lumen in five of 58 radial arteries (8.6%). Nevertheless, it must be noted that, in most cases, these lesions were discrete, and most of the atherosclerotic radial arteries were considered usable as a conduit. In fact, only one out of the five atherosclerotic radial arteries was diffusely diseased, and therefore rejected.

Calcification of the Radial Artery
The presence of vessel calcification, the most common pathology of radial arteries [14], would also preclude its use for CABG. The incidence of calcified radial arteries has been previously reported as about 10% of patients. Rodriguez and colleagues [14] performed preoperative ultrasound examination in patients receiving CABG and found calcified radial arteries in 8.7% of patients, while Ruengsakulrach and colleagues [12] reported an incidence of 13%. In our study, vessel calcification was seen in five radial arteries (8.6%), including extensive calcification in two (3.4%). A heavily calcified radial artery is difficult to handle, and the long-term patency of such conduit is questionable [15]. We therefore considered that these two radial arteries were not suitable for use as bypass conduits. This meant that in our study the incidence of ungraftable calcified radial arteries was 3.4%, which was within the range reported by other investigators [2, 15].

Clinical Implications
The various pathologies of radial arteries, such as diffuse arteriosclerosis, diffuse calcification, and/or small vessel caliber should not be discounted since they could have an effect on immediate intraoperative difficulties and the long-term patency of the graft. In the current study, four out of the 58 (6.9%) radial arteries showed pathology (one diffusely atherosclerotic, two diffusely calcified, one small caliber). Although other investigators have suggested that the atherosclerotic changes of radial arteries, including calcified lesions, were significantly related to certain clinical factors such as smoking, age, and diabetes [12, 16], no significant correlations were observed in our study (data not shown). Preoperative imaging may thus be recommended to prevent unnecessary forearm exploration and inadvertent use of a diseased conduit.

In this respect, IVUS may be a useful tool in assessing the pathology of radial arteries, as it can accurately depict vascular dimensions, plaque morphology, and distribution in vivo. It should also be noted that such anatomical information obtained from IVUS shows a good correlation with the vessel’s histopathology, especially in calcified plaque [7, 8]. Moreover, through the use of the 3D reconstruction program, we can detect, objectively, the site of minimal lumen area. However, as the use of IVUS is expensive and requires an invasive procedure, alternative approaches such as ultrasound examination [11] and forearm soft tissue radiography [15] may also be considered. In this regard, standard ultrasound is a powerful tool in measuring the vessel size of the radial artery [11], although it is less sensitive than IVUS in evaluating precise vessel pathologies, including calcification. Soft tissue radiography is sensitive in identifying vessel calcification, although it lacks qualitative aspects of evaluation, including the extent of calcified plaque within the vessel wall. Whether these noninvasive-inexpensive alternatives can be as effective as IVUS in detecting the pathology of the radial artery remains to be determined.

Study Limitations
First, performance of IVUS requires insertion of a sheath into the distal radial artery, where IVUS examination cannot be performed. Thus, the incidence of the arteriosclerosis and/or calcification assessed by IVUS did not reflect the pathology of the distal radial artery. Second, follow-up angiography of radial artery grafts was not performed in the current study. Whether the exclusion of diseased radial arteries will improve and whether the use of lightly diseased radial arteries will not affect the immediate as well as the long-term patency of the graft needs to be determined.


   References
Top
 Abstract
 Introduction
 Patients and Methods
 Results
 Comment
 References
 

  1. Carpentier A, Guermonprez JL, Deloche A, Frechette CM, DuBost C. The aorta-to-coronary radial artery bypass graft: a technique avoiding pathological changes in grafts Ann Thorac Surg 1973;16:111-121.[Medline]
  2. Acar C, Ramsheyi A, Pagny JY, et al. The radial artery for coronary artery bypass grafting: clinical and angiographic results at five years J Thorac Cardiovasc Surg 1998;116:981-989.[Abstract/Free Full Text]
  3. Brodman RF, Frame R, Camacho M, Hu E, Chen A, Hollinger I. Routine use of unilateral and bilateral radial arteries for coronary artery bypass graft surgery J Am Coll Cardiol 1996;28:959-963.[Abstract]
  4. Chen AH, Nakao T, Brodman RF, et al. Early postoperative angiographic assessment of radial grafts used for coronary artery bypass grafting J Thorac Cardiovasc Surg 1996;111:1208-1212.[Abstract/Free Full Text]
  5. Possati G, Gaudino M, Alessandrini F, et al. Midterm clinical and angiographic results of radial artery grafts used for myocardial revascularization J Thorac Cardiovasc Surg 1998;116:1015-1021.[Abstract/Free Full Text]
  6. Lytle BW, Loop FD, Cosgrove DM, Ratliff NB, Easley K, Taylor PC. Long-term (5 to 12 years) serial studies of internal mammary artery and saphenous vein coronary bypass grafts J Thorac Cardiovasc Surg 1985;89:248-258.[Abstract]
  7. Nishimura RA, Edwards WD, Warnes CA, et al. Intravascular ultrasound imaging: in vitro validation and pathologic correlation J Am Coll Cardiol 1990;16:145-154.[Abstract]
  8. Potkin BN, Bartorelli AL, Gessert JM, et al. Coronary artery imaging with intravascular high-frequency ultrasound Circulation 1990;81:1575-1585.[Abstract/Free Full Text]
  9. Oshima A, Ochiai M, Takeshita S, et al. Serial automated three-dimensional intravascular ultrasound analysis of the self-expanding radius stent Am J Cardiol 2000;85:388-391A9.[Medline]
  10. Horning B, Arakawa N, Kohler C, Drexler H. Vitamin C improves endothelial function of conduit arteries in patients with chronic heart failure Circulation 1998;97:363-368.[Abstract/Free Full Text]
  11. Yokoyama N, Takeshita S, Ochiai M, et al. Anatomic variations of the radial artery in patients undergoing transradial coronary intervention Catheter Cardiovasc Interv 2000;49:357-362.[Medline]
  12. Ruengsakulrach P, Sinclair R, Komeda M, Raman J, Gordon I, Buxton B. Comparative histopathology of radial artery versus internal thoracic artery and risk factors for development of intimal hyperplasia and atherosclerosis Circulation 1999;100:II139-144.
  13. Kaufer E, Factor SM, Frame R, Brodman RF. Pathology of the radial and internal thoracic arteries used as coronary artery bypass grafts Ann Thorac Surg 1997;63:1118-1122.[Abstract/Free Full Text]
  14. Rodriguez E, Ormont ML, Lambert EH, et al. The role of preoperative radial artery ultrasound and digital plethysmography prior to coronary artery bypass grafting Eur J Cardiothorac Surg 2001;19:135-139.[Abstract/Free Full Text]
  15. Deshpande RP, Chukwuemeka A, Iqbal A, Desai JB. Dystrophic calcification of the radial artery Ann Thorac Surg 2000;69:1939-1940.[Abstract/Free Full Text]
  16. Nicolosi AC, Pohl LL, Parsons P, Cambria RA, Olinger GN. Increased incidence of radial artery calcification in patients with diabetes mellitus J Surg Res 2002;102:1-5.[Medline]



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