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Ann Thorac Surg 2005;80:559-563
© 2005 The Society of Thoracic Surgeons

Original article: Cardiovascular

Radial Artery Grafts in Women: Utilization and Results

Jennifer S. Lawton, MD * , Hendrick B. Barner, MD, Marci S. Bailey, RN, Tracey J. Guthrie, RN, BSN, Nader Moazami, MD, Michael K. Pasque, MD, Marc R. Moon, MD, Ralph J. Damiano, Jr, MD

Department of Surgery, Division of Cardiothoracic Surgery, Washington University School of Medicine, St. Louis, Missouri

Accepted for publication February 14, 2005.

* Address reprint requests to Dr Lawton, Washington University School of Medicine, 660 S. Euclid Ave, Campus Box 8234, St. Louis, MO 63110 (Email: lawtonj{at}msnotes.wustl.edu).


   Abstract
Top
 Abstract
Introduction
 Patients and Methods
 Results
 Comment
 References
 
BACKGROUND: Despite a known survival benefit with the use of the left internal mammary artery, it is used less frequently in women when compared with men. This study evaluated the hypotheses that the radial artery graft is used less frequently in women compared with men, that the radial artery is smaller in women compared with men, and that the use of the radial artery influences operative mortality and long-term survival in women.

METHODS: The use of a radial artery graft was evaluated in 2,633 patients who underwent isolated coronary artery bypass. Radial artery size and flow were compared in 207 patients who had intraoperative radial artery diameter and flow measurements. Propensity scoring was utilized to compare short- and long-term outcomes in a matched cohort of 588 women.

RESULTS: Of 862 women (33%) who had isolated coronary artery bypass grafting, only 301 (35%) received a radial artery graft versus 44% of men (786 of 1,771, p < 0.001). Radial artery size and flow were significantly less in women. Operative mortality was not different between women with a radial artery graft and women without; however, 5-year survival was significantly better in women with a radial artery graft than in those without.

CONCLUSIONS: Women received fewer radial artery grafts than men. Radial artery size and flow were significantly less in women than in men. Use of a radial artery graft did not influence operative mortality among women. However, 5-year survival among women who received a radial artery graft was significantly better than among women who did not.


   Introduction
Top
 Abstract
 Introduction
Patients and Methods
 Results
 Comment
 References
 
The operative mortality rate of women undergoing coronary artery bypass graf (CABG) surgery has been reported to be twice that of men [1]. Despite a known survival benefit associated with the use of the left internal mammary artery (LIMA), this arterial graft is used less frequently in women [2, 3]. In fact, in analysis of data from the Bypass Angioplasty Revascularization Investigation (BARI), logistic regression analysis identified female sex as an independent predictor of the nonuse of a LIMA graft [4]. It has been suggested that the use of the radial artery as a conduit is protective against early mortality and morbidity after CABG [5]. Therefore, underutilization of arterial grafts may be one of a myriad of factors related to an increased operative mortality rate for women undergoing CABG. The use of the radial artery graft has not specifically been evaluated in women. This study evaluated the following hypotheses: the radial artery graft is used less frequently in women compared with men, the radial artery is smaller in size in women compared with men, and the use of the radial artery influences operative mortality and long-term survival in women.


   Patients and Methods
Top
 Abstract
 Introduction
 Patients and Methods
Results
 Comment
 References
 
Demographic data, radial artery graft utilization, and outcome were retrospectively evaluated in all patients undergoing isolated CABG procedures (n = 2,633) and specifically those patients with a radial artery graft (n = 1,087) between 1997 and 2001 at one institution. No patients were excluded. Approval for this study was granted by the Institutional Review Board at the Washington University School of Medicine.

Prospective radial artery size and flow measurements were obtained intraoperatively in 207 patients undergoing isolated CABG with the use of a radial artery for conduit. In all patients with radial artery size and flow data, the radial artery was utilized as a T graft originating on the LIMA graft as has been previously described [6]. All of these procedures were performed with cardiopulmonary bypass. Radial artery size (internal diameter, proximal and distal) was measured after its harvest and removal using calibrated dilators with the artery in a nondilated state. Radial artery free flow was measured after its anastomosis to the LIMA in a T fashion (before any distal anastomosis and with the distal LIMA occluded beyond the T anastomosis). The lumen of the radial artery was injected with 2 mg/mL papaverine in 30 mL heparinized blood, and 10 minutes later, free flow into a beaker was measured for 30 seconds. Radial artery transonic flow (mL/min.) was measured 10 to 20 minutes after discontinuation of cardiopulmonary bypass in the radial limb using a Transonic flow probe (Transonic Systems, Ithaca, NY) with flow occluded in the LIMA limb. A stable mean blood pressure was maintained in a normal physiologic range during all flow measurements.

Follow-up was conducted by phone interview, mailed questionnaire, and analysis of mortality data using available federal databases.

The decision to utilize the radial artery for grafting was made by the operating surgeon. The resulting selection bias to use a radial artery graft or not was addressed by propensity matching. In 862 women who underwent isolated CABG at one institution between 1997 and 2002, women who received a radial artery graft were compared with women who did not receive a radial artery graft. Logistic regression analysis was used to identify covariates among 18 baseline patient variables that were imbalanced in the two groups of interest (SPSS 11.0 for Windows; SPSS, Chicago, Illinois). Thirteen variables were not significant in the logistic regression analysis, including race, current smoking status, diabetes mellitus, hypercholesterolemia, chronic renal insufficiency, hypertension, chronic obstructive pulmonary disease, peripheral vascular disease, history of myocardial infarction, unstable angina, New York Heart Association (NHYA) classification, number of diseased vessels, and cardiogenic shock. In contrast, the logistic regression analysis identified five variables as significant predictors for the use of a radial artery graft: younger age, nonurgent/emergent operative status, no current dialysis requirement, previous coronary artery bypass procedure, and a higher left ventricular ejection fraction.

Using the significant regression coefficients, a propensity score was calculated for all 862 female patients. The total population was ranked by propensity score, and the patients were closely matched on the basis of this score [7, 8]. The short- and long-term outcome of the patients was blinded during the matching process. This process matched 294 of the 301 female patients who underwent a CABG with the use of a radial artery graft with 294 of the 561 female patients who underwent a CABG without the use of a radial artery graft. Six of the 301 radial artery patients were not able to be matched with the nonradial artery patients because their propensity scores were extreme outliers. The resulting 588 patients form the focus of the outcomes analysis for the study.

Descriptive statistics were expressed as mean ± SD unless otherwise specified. Categorical data were expressed as counts and proportions. Comparisons were done with paired, two-tailed t tests for means of normally distributed continuous variables and the Wilcoxon rank-sum tests for skewed data. Chi-square or Fisher’s exact tests were used to analyze differences among the categorical data. Kaplan-Meier estimate was used to depict survival. A p value of less than 0.05 was considered significant.


   Results
Top
 Abstract
 Introduction
 Patients and Methods
 Results
Comment
 References
 
Between January 1997 and December 2002, 2,633 patients (862 women and 1,771 men) underwent isolated CABG at Barnes Jewish Hospital. Of those 2,633 patients, 1,087 patients (301 women and 786 men) had at least one radial artery used as a conduit. Radial arteries were utilized for 1.6 ± 0.7 anastomoses in women and 1.7 ± 0.7 anastomoses in men. The radial artery was utilized as a T graft in 578 patients and as a free graft in 509 patients. Significantly more men (44%) received a radial artery graft compared with women (35%, p < 0.001).

Between February 1999 and November 2001, 207 patients (62 women and 145 men) underwent CABG with prospective collection of intraoperative radial artery diameter and flow measurements. The intraoperative measurements obtained in these 207 patients are listed in Table 1. Radial artery diameter (proximal and distal) and flow (transonic and free flow) were significantly less in women than in men. In addition, the radial artery diameters and flows were significantly less in women than in men even when indexed to body mass index.


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  		Table 1. Intraoperative Radial Artery Measurements in 207 Male and Female Patients
 
Of 862 women who underwent isolated CABG, 301 received a radial artery graft and 561 did not. Propensity scoring matched 294 patients in each group (Table 2). Women who received a radial artery graft had a significantly longer cross-clamp time, a significantly higher rate of LIMA graft utilization, a shorter length of mechanical ventilation, a shorter intensive care unit stay, and improved long-term survival when compared with women who did not receive a radial artery graft (Table 2, Fig 1). Operative mortality was not different between the two groups (Table 2).


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  		Table 2. Propensity Score Matched Women (n = 588)
 


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  		Fig 1. Estimated Kaplan-Meier survival for 588 women who did receive (n = 294; black line) or did not receive (n = 294; gray line) a radial artery graft for coronary artery bypass graft surgery between 1997 and 2002 (p = 0.003 at 5 years). The number of patients remaining is shown at 1, 3, and 5 years.

 

   Comment
Top
 Abstract
 Introduction
 Patients and Methods
 Results
 Comment
References
 
The long-term patency of the radial artery as a conduit for CABG has been demonstrated to be superior to that of saphenous vein grafts [9]. Its ease of use and associated favorable outcomes have led to its widespread utilization as a conduit. However, despite the fact that approximately 33% of all CABG procedures yearly are performed on women, a much smaller percentage of women (12–27%) appear to receive a radial artery graft or all arterial grafting in published reports [5, 9–15]. This is consistent with the findings of this study in that only 35% of women received a radial artery graft whereas 44% of men benefited from a radial artery graft. This is similar to the trend noted in several retrospective studies of less frequent use of proven efficacious therapies (ß-blockers, aspirin, heparin, thrombolytics, use of LIMA) in women after myocardial infarction when compared with men [3, 16]. These factors may contribute to the increased mortality noted in women after CABG. However, in this series, the use of a radial artery graft alone did not improve operative mortality among women.

Several factors may influence conduit selection for CABG. The use of the radial artery graft is determined solely by surgeon preference at our institution. Factors involved in the decision to utilize the radial artery as a conduit could include the following: the result of an Allen test, surgeon preference, perceived patient life span, emergent nature of surgery, patient’s occupation (if manual dexterity is vital), presence of severe diabetes or peripheral vascular disease, patient preference, and the patient’s desire to avoid a visible arm scar. In this study, logistic regression demonstrated that five variables were associated with the use of a radial artery graft in women (younger age, nonurgent/emergent operative status, no current dialysis requirement, previous CABG, and higher left ventricular ejection fraction). Intuitively, these variables seem obvious, as younger patients would benefit more from an arterial conduit, more staff and time are needed to prepare the radial artery conduit making its use in an emergency less likely, patients on dialysis often do not have radial artery grafts available for use due to the need for arm shunts or fistulas, patients with previous CABG may have limited conduit available making the use of the radial artery necessary, and patients with a better ejection fraction would also be more likely to live longer and benefit from an arterial conduit. It is also interesting to note that the patients who received a radial artery graft also had a significantly higher rate of LIMA graft utilization, perhaps for many of the same reasons.

Many surgeons may hesitate to use the radial artery in women due to its feared smaller size. In this study, radial artery flow and size were significantly less in women. This is consistent with the fact that women often have a smaller body surface area and have been documented to have smaller coronary artery size [17, 18]. When the flow and size were indexed to body mass index, however, they were still statistically different between women and men (Table 1).

The reduced use of a radial artery graft in women compared with men at our institution may be partially explained by more women (20.2%) than men (16.8%) undergoing emergent surgery (p = 0.04). In addition, we found that nonurgent/elective operative status was a predictor of use of a radial artery graft in women. This finding is consistent with other series that have indicated that women are more likely to undergo emergent CABG when compared with men [1].

Radial artery conduits were used less in women at our institution over a 5-year period when compared with men. Radial artery grafts were found to be significantly smaller and to have significantly less flow in women compared with men. In this study, younger age, nonurgent/emergent operative status, no current dialysis requirement, previous CABG, and higher left ventricular ejection fraction predicted the use of a radial artery as CABG conduit in women; and women who received a radial artery graft had improved 5-year survival compared with women who did not. These data raise awareness with regard to the use of radial artery grafting in women, as its use, along with other proven efficacious therapies, may influence long-term survival after CABG in women.

Study Limitations
It is not possible to comment on the influence of radial artery size on long-term patency as only 17 patients of the 207 patients with radial artery size and flow measurements underwent postoperative cardiac catheterization. The long-term radial artery patency is therefore unknown and cannot be compared between women and men in this series. This represents a limitation of this study, and the answer to this question would require a large prospective, randomized clinical trial in which patients would agree to undergo postoperative cardiac catheterization. In addition, it is not possible to determine the potential differences in radial artery patency that may exist between women and men in other published studies for comparison, as follow-up patency data have not been specifically reported with regard to sex.

Radial artery flow (free flow and transonic) may be influenced by many factors, including vessel size, target vessel run-off, systemic blood pressure, and the presence of vasoactive medications. It was not possible to rigorously control and normalize all of these variables in comparisons made, and this represents a limitation of this study. In addition, although propensity scoring was utilized to limit baseline differences in the two groups of women that were compared, this study has all of the inherent limitations of a retrospective study.


   References
Top
 Abstract
 Introduction
 Patients and Methods
 Results
 Comment
 References
 

  1. Vaccarino V, Abramso JL, Veledar E, Weintraub WS. Sex differences in hospital mortality after coronary artery bypass surgery Circulation 2002;105:1176-1181.[Abstract/Free Full Text]
  2. Loop FD, Lytle BW, Cosgrove DM, et al. Influence of the internal-mammary-graft on 10-year survival and other cardiac events N Engl J Med 1986;314:1-6.[Abstract]
  3. Jacobs AK, Kelsey SF, Brooks MM, et al. Better outcome for women compared with men undergoing coronary revascularizationa report from the Bypass Angioplasty Revascularization Investigation (BARI). Circulation 1998;98:1279-1285.[Abstract/Free Full Text]
  4. Schaff HV, Rosen AD, Shemin RJ, et al. Clinical and operative characteristics of patients randomized to coronary artery bypass surgery in the Bypass Angioplasty Revascularization Investigation (BARI) Am J Cardiol 1995;75(Suppl):18C-26C.[Medline]
  5. Cohen G, Tamariz MG, Sever JY, et al. The radial artery versus the saphenous vein graft in contemporary CABGa case-matched study. Ann Thorac Surg 2001;71:180-186.[Abstract/Free Full Text]
  6. Barner HB, Sundt TM, Bailey M, Zang Y. Midterm results of complete arterial revascularization in more than 1,000 patients using an internal thoracic artery/radial artery T graft Ann Surg 2001;234:447-453.[Medline]
  7. Blackstone EH. Comparing apples and oranges J Thorac Cardiovasc Surg 2002;123:8-15.[Free Full Text]
  8. Grunkemeier GL, Payne N, Jin R, Handy Jr JR. Propensity score analysis of stroke after off-pump coronary artery bypass grafting Ann Thorac Surg 2002;74:301-305.[Free Full Text]
  9. Possati G, Gaudino M, Prati F, et al. Long-term results of the radial artery used for myocardial revascularization Circulation 2003;108:1350-1354.[Abstract/Free Full Text]
  10. Legare JF, Buth KJ, Sullivan JA, Hirsch GM. Composite arterial grafts versus conventional grafting for coronary artery bypass grafting J Thorac Cardiovasc Surg 2004;127:160-166.[Abstract/Free Full Text]
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  12. Singh SK, Mishra SK, Kumar D, Yadave RD, Agarw R, Sinha SK. Total arterial revascularization on beating heartexperience in 803 cases. Asian Cardiovasc Thorac Ann 2003;11:107-112.[Abstract/Free Full Text]
  13. Beghi C, Nicolini F, Budillon AM, Borrello B, Ballore Reverberi C, Gherli T. Midterm clinical results in myocardial revascularization using the radial artery Chest 2002;122:2075-2079.[Abstract/Free Full Text]
  14. Modine T, Al-Ruzzeh S, Mazrani W, et al. Use of radial artery graft reduces the morbidity of coronary artery bypass surgery in patients aged 65 years and older Ann Thorac Surg 2002;74:1144-1147.[Abstract/Free Full Text]
  15. Tatoulis J, Royse AG, Buxton BF, et al. The radial artery in coronary surgerya 5-year experience—clinical and angiographic results. Ann Thorac Surg 2002;73:143-147.[Abstract/Free Full Text]
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