Ann Thorac Surg 2008;86:828-831. doi:10.1016/j.athoracsur.2008.04.086
© 2008 The Society of Thoracic Surgeons
Original Articles: Adult Cardiac
Radial Artery Harvesting for Coronary Artery Bypass Grafting: A Stepwise-Made Decision
Petar M. Vukovi
, MD*,
Sandra S. Radak, MD,
Miodrag S. Peri, MD, PhD,
Du
ko G. Ne
i, MD, PhD,
Aleksandar M. Kneevi, MD
Department of Cardiac Surgery, Dedinje Cardiovascular Institute, Belgrade, Serbia
Accepted for publication April 24, 2008.
* Address correspondence to Dr Vukovi, Milana Tepia 1, Belgrade, 11040, Serbia (Email: petarvuk{at}eunet.yu).
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Abstract
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Background: The purpose of this study was to propose a safe, stepwise, testing system to select radial arteries that are suitable for conduits on the basis of their morphologies and characteristics of the collateral circulation.
Methods: Before operation, 113 patients underwent the modified Allen test, Doppler ultrasonography, and pulse oximetry testing. Morphologic criteria used for radial artery exclusion were small size of radial or ulnar artery (< 2 mm in inner diameter), diffuse calcifications, and congenital anomalies of forearm arteries. Collateral circulation was interpreted as insufficient if the reverse flow in the anatomic snuffbox was absent or if the increase of the ulnar peak systolic flow velocity was less than 20%.
Results: A positive modified Allen test was found in 10.6% of patients. As assessed by Doppler ultrasonography, 27 patients (23.9%) were not candidates for radial artery harvesting according to morphologic and functional abnormalities of forearm and hand circulation. Pulse oximetry test results were abnormal in 6.2%. After a follow-up period of 8.9 ± 1.8 months, 23 patients (29.1% of operated patients) were controlled for Doppler ultrasonographic changes in the ulnar artery. The mean peak systolic flow velocity was significantly higher than the preoperative value measured at rest (p < 0 .001).
Conclusions: After preoperative tests, including the modified Allen test, Doppler ultrasonography, and pulse oximetry, 30.1% of patients were not considered candidates for radial artery harvesting. This method provides preoperative radial artery selection according to its morphologies, compensatory capacity of collateral circulation, and anatomic properties of ulnar artery.
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Introduction
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The radial artery (RA) is widely used as a conduit for coronary artery bypass grafting (CABG). The renewed interest in the use of the RA in coronary procedures has been supported by the results of several angiographic studies that have shown excellent short-, medium-, and long-term patency of RA grafts [1–3].
The RA is one of the two major arteries supporting the circulation of the hand. Safe RA harvesting is possible only when a sufficient ulnar artery (UA) collateral blood supply exists; therefore, reliable tests of collateral hand circulation are mandatory. Traditionally, the Allen test is the first and often the only preoperative screening procedure for adequacy of collateral circulation of the hand. Although it is cost-free and very easy to perform, its reliability has been doubted [4, 5]. In some cases, RA removal on the basis of Allen test results alone has led to postoperative hand ischemia [6, 7].
Several studies advocate the importance of Doppler ultrasonographic (US) assessment of hand circulation, but no criteria have been established for normal and abnormal US results [8–11]. Digital oximetry has also been described as a simple and reliable method for candidate selection for RA harvesting [12, 13].
The aim of this study was to evaluate noninvasive tests for assessment of the collateral hand circulation before RA harvesting. It was conducted with an intention to propose a safe, stepwise, testing system to select RAs that are suitable for conduits on the basis of their morphology and characteristics of the collateral circulation.
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Patients and Methods
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Between August 2004 to December 2007, the study enrolled 113 patients who were considered candidates for CABG using RA as one of the grafts. The patients were aged 58.9 ± 7.4 years; 17 (15%) were women, and 96 (85%) were men. The study protocol was approved by the local ethics committee. Informed consent was obtained from each patient.
Patients underwent the modified Allen test, Doppler US, and the pulse oximetry testing before operation. Three observers conducted the tests, where each of them consistently performed one of three tests and were blinded to the results of other tests. The results were reported to the surgeon. If abnormalities were found by any of the tests, the surgeon decided not to use RA as a conduit, and a saphenous vein graft was harvested. The tests were applied in the following order:
- 1 The modified Allen test: The patient's nondominant hand was examined in supinated position. The patient was asked to clench the fist for 1 minute. The RA and UA were located by their pulses and compressed with the examiner's fingers. The patient was instructed to open the hand and the UA was released. The return of the color to the hand was noted. A recovery time of more than 10 seconds was defined as a positive (abnormal) Allen test.
- 2 Doppler US: The study was performed with the HDL 3500 linear transducer (5 to 12 MHz.; Philips ATL, Bothell, WA). Morphologic and functional characteristics of forearm and hand circulation were assessed. The inner diameter of RA and UA, diffuse calcifications, and anatomic abnormalities of the forearm vessels were the morphologic properties that were recorded. RA measurements were made in proximal, middle, and distal segments of the artery. The functional status of the hand collateral circulation was assessed by detecting the reversal of flow in the anatomic snuffbox after RA compression in the wrist [14]. In addition, change in UA peak systolic flow velocity (PSFV) after RA compression was measured.
Morphologic criteria that were used to exclude RA were small size of RA (< 2 mm in inner diameter), diffuse calcifications (diffusely increased echogenicity of the vessel wall with luminal narrowing), agenesis of RA, high bifurcation of the brachial artery, and a small UA (< 2 mm inner diameter) [10].
Collateral circulation was interpreted as insufficient if the reverse flow in the anatomic snuffbox was absent or if the increase of the ulnar PSFV was less than 20% [8, 10, 14]. The increase in PSFV was calculated by the formula: Increase in PSVF (%) = (PSVF2 –PSFV1) x 100/PSFV1, where PSFV1 is the PSFV at rest, and PSFV2 is the PSFV during RA compression.
- 3 Pulse oximetry: An oxygen saturation monitor was attached to the thumb and baseline oxygen saturation was measured. The RA and UA were occluded until the oxygen saturation reading fell to zero. If the oxygen saturation level did not return to the baseline within 10 seconds of decompressing the UA, the RA was not harvested. A portable pulse oximeter was used for preoperative screening, and a standard intraoperative monitoring system was used for continuous measurement of the oxygen saturation level while the RA was harvested. Before the RA was removed from the hand circulation, a vascular clamp was placed on the most distal part of the RA for 1 minute to assess the capacity of the collateral circulation for the last time. If any reduction occurred in the oxygen saturation level, the RA was not harvested.
Patients underwent a postoperative Doppler US control. Changes in the UA circulation and morphology on the operated-on side were analyzed. Minimum follow-up was 6 months.
Statistical analysis was performed using SPSS 11.0 software (SPSS, Chicago, IL). A paired samples t test was used to compare mean PSFV and mean inner diameter of the UA.
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Results
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A positive modified Allen test was found in 10.6% of patients. Twenty-seven patients (23.9%) were not candidates for RA artery harvesting according to morphologic or functional abnormalities of the forearm and hand circulation assessed by Doppler US. Morphologic abnormalities were found in 21 patients (18.6%): 10 patients (8.8%) had calcified RA, in 4 (3.5%) the inner diameter of RA was less than 2 mm, 3 patients (2.6%) had high bifurcation of the brachial artery, and 9 (8%) had small ulnar arteries (the inner diameter was < 2 mm). Five patients had multiple morphologic abnormalities (2 or 3 abnormalities found concurrently). There was no RA or UA agenesis in our patient population. Doppler US findings of RA are reported in Table 1.
Functional circulatory abnormalities, noted during RA compression, were present in 9 patients (7.9%): nonreversal of RA flow measured in the snuffbox in 3.5%, and increase in ulnar PSFV of less than 20% was present in 4.4% (Fig 1). Morphologic abnormalities were also present in 3 of these patients.
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Fig 1. Distribution of the increase in peak systolic flow velocity (PSFV) during radial artery compression.
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Pulse oximetry testing showed that in 6.2% of patients, the oxygen saturation level did not return to the baseline within 10 seconds of the UA decompression.
Positive results of the modified Allen test were compared with abnormal Doppler US findings where abnormalities of the collateral hand circulation were detected. The modified Allen test had sensitivity of 66.6% and specificity of 94.2%.
When the pulse oximetry was compared with Doppler US, the pulse oximetry had sensitivity of 66.6% and specificity of 99%. Comparison between results of the modified Allen test and the pulse oximetry showed that the sensitivity of the modified Allen test was 71.4% and the specificity was 93.4%.
A positive Allen test, abnormalities found by Doppler US, or a positive finding on pulse oximetry testing resulted in 34 patients (30.1%) being excluded from RA harvesting. In the remaining 79 patients, the nondominant RA was harvested. No additional morphologic changes were noted by the surgeons during the operation. None of the patients had any ischemic complication. A subcutaneous hematoma developed in 1 patient. There were no wound infections.
After 8.9 ± 1.8 months after operation, 23 patients (29.1% of operated patients) returned for a Doppler US follow-up. The mean PSFV in the UA was significantly higher than the preoperative value measured at rest—before RA compression (p < 0 .001). PSFV measured during RA compression increased once again at follow-up compared with preoperative PSFV (Fig 2). This increase of 7.1%, from 80.30 ± 15.77 to 86 ± 17.45 cm/s, did not reach statistical significance (p = 0.209). There was no difference in the inner diameter of the UA between the preoperative and follow-up values: 3.11 ± 0.35 vs 3.13 ± 0.41 mm (p > 0.8). Significant atherosclerotic plaque formation was not found at follow-up measurements.
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Fig 2. The mean peak systolic flow velocity (PSFV) in the ulnar artery measured preoperatively at rest and during radial artery (RA) compression, as well as on control, at 8.9 ± 1.8 months after operation. Error bars show the standard deviation.
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Comment
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Two major concerns related to RA harvesting are whether long-term patency of RA grafts is better than the patency of the saphenous vein grafts and whether RA harvesting compromises the blood supply of the hand. In most publications that reported good patency rates of RA conduits, RA placement was restricted to patients with high-grade stenosis and good distal runoff [1–3]. In our study, as well as in our clinical practice, this principle was adopted as the first step in the decision-making process towards RA harvesting.
Not all of the angiographic follow-up studies have shown better patency rates of RA grafts compared with saphenous vein grafts [15, 16]. The differences in angiographic outcomes may result from a variety of factors, including variations in harvesting and preservation techniques, as well as preoperative selection of RA suitable for conduits. We hypothesize that good anatomic properties of the RA could be favorable for its long-term patency, which led us to conduct US screenings to exclude RA with diffuse calcifications and small size (< 2 mm in inner diameter). These criteria were proposed by Rodrigues and colleagues [10] and used as exclusion criteria for RA harvest in studies conducted later [11, 17].
The second major concern when the RA is harvested is hand ischemia. The results of studies in which the Allen test was evaluated are heterogenous and sometimes contradictory. A study comparing results of the Allen test with those of Doppler US suggested that at no cutoff point was the Allen test able to accurately identify the patients with and without an adequate UA collateral blood supply to the hand. The authors concluded that it should be replaced by more objective tests, such as Doppler US [5]. The range of positive results found by Allen test varied from 0% (cutoff point was not mentioned) and 5.6% (10-second cutoff) to 23% (6-second cutoff) [9, 11, 17]. In our study, the Allen test was positive in 10.6% of patients at the cutoff of 10 seconds. Similar to the other studies, we conducted additional, more objective tests on which to base the decision whether the RA was safe to harvest. Because Doppler US was used to exclude the RA with unfavorable morphologic features, the functional status of collateral circulation was assessed by the same instrument.
The Doppler US examination of the RA in the anatomic snuffbox was described by Kochi and colleagues [14]. The anatomic snuffbox is the most distal area of the RA that remains after RA harvesting. A backward flow direction in the snuffbox after RA compression is evidence of good collateral hand circulation.
Meharawal and colleagues [13] harvested the RA in 3977 patients using pulse oximetry as the single preoperative screening method. None of the patients had acute ischemic injury of the hand, and only minor complications were observed. In our study, pulse oximetry was used as an additional test for assessment of RA harvesting safety.
When RA harvesting is considered, the fate of the residual UA artery is often disregarded. The prospective circulation of the hand depends on one artery that is undergoing changes over time. We therefore decided to exclude the patients with small UA (< 2 mm) from RA harvesting. Three of 9 UAs from this category were described as even hypoplastic. These UAs showed an increase of peak systolic flow velocity (PSV) of less then 20% during RA compression. Chronic atherosclerotic changes in small UAs after RA harvesting could additionally reduce their lumen so the blood supply to the hand could be insufficient.
In our study, a significant increase in UA PSFV was found at follow-up compared with the preoperative value measured at rest. Gaudino and colleagues [18] referred to a chronic compensatory increase in UA flow accompanied with accelerated atherosclerosis after RA harvesting in a group of 25 patients who underwent a series of Doppler US evaluations. The difference in intimal thickness of the UA reached statistical significance at the 10-year follow-up, as did the prevalence of atherosclerotic plaques. It can be concluded that removal of the RA leads to an immediate significant increase in the UA flow velocity. This higher level of flow velocity increases slowly over time and is accompanied by faster progression of atherosclerosis in the UA.
We realize that our ultraconservative approach resulted in a considerably higher rejection rate than would have occurred using the modified Allen test alone. We believe that additional tests made RA harvesting safer and also enabled selection of RAs with favorable morphologic characteristics. We hope that this approach can be of value for surgeons who are uncomfortable with even a small chance of hand ischemia as well as for those who believe that only the best RA grafts should be harvested.
After undergoing a series of preoperative tests including the modified Allen test, Doppler US, and pulse oximetry, 30.1% of the patients we studied were not considered candidates for RA harvesting. This method provides preoperative RA selection according to its morphologies, compensatory capacity of collateral circulation, and anatomic properties of the UA.
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References
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Abstract
Introduction
