Comparative study on the histomorphology and molecular biology of radial artery conduits in patients with diabetes mellitus who underwent coronary bypass surgery

We studied the impact of diabetes mellitus (DM) on the radial artery (RA) in 30 patients with DM and 30 non-diabetic patients undergoing coronary artery bypass grafting with autologous RA. RAs were recorded as normal if there was no cellular or stromal tissue between the endothelium and the internal elastic lamina. The RA was normal in 26.7% of diabetic and 76.7% of non-diabetic patients (p = 0.000298). Intimal thickness index and intima:media ratio were higher in the former than in the latter (p < 0.05; p < 0.05), with no significant difference in luminal narrowing (p > 0.05). Electron microscopy scores were lower in the non-diabetic group (p < 0.001); endothelial nitric oxide synthase (eNOS) protein expression and optical density were higher (p < 0.001). Von Willebrand factor and endothelin-1 messenger RNA (mRNA) levels were higher in the DM patients (p < 0.001). The quality of the RA in patients with DM was thus inferior to that in non-diabetic patients. Care should be taken when selecting RA as a conduit in patients with DM.

[Comparative study on the ultrastructure of radial artery in elderly patients underwent coronary artery bypass grafting with diabetes mellitus]

OBJECTIVE

To explore the impact of age and diabetes mellitus (DM) on the ultrastructure of radial artery (RA).

METHODS

From June 2009 to December 2010, 64 patients underwent coronary artery bypass grafting (CABG) with autologous RA: 14 patients aged beyond 65 years without DM [9 male patients and 5 female patients, age (70 ± 4) years] and 18 patients aged beyond 65 years with DM [11 male patients and 7 female patients, age (68 ± 5) years], 20 patients aged under 60 years without DM [13 male patients and 7 female patients, age (53 ± 5) years] and 12 patients aged under 60 years with DM [7 male patients and 5 female patients, age (51 ± 6) years]. Four groups were subjected to routine electron microscopic examination and transmission electron microscopic examination.

RESULTS

There were significant differences in percentage of endothelial denudation among four groups according to scanning electron microscopic evaluation (χ² = 18.082, P = 0.000). To compare with each other, there were significant differences between DM elderly patients and non-DM elderly patients, also between DM young patients and non-DM young patients according to scanning electron microscopic evaluation. There were no significant differences between DM elderly patients and DM young patients, also between non-DM elderly patients and non-DM young patients. Foam cells and the tendency of smooth muscle cells moving to intima could be visualized in DM patients according to transmission electron microscope. According to semiquantitative electron microscopic evaluation, non-DM young patients got the lower total scores than DM young patients (1.32 ± 0.20 vs. 4.38 ± 0.30) while non-DM elderly patients got the lower total scores than DM elderly patients (1.43 ± 0.20 vs. 4.67 ± 0.30). According to factorial design, there were significant differences between DM patients and non-DM patients (F = 41.22, P = 0.000). There were no differences between elderly patients and young patients (F = 1.24, P = 0.270). There is no interaction (F = 1.05, P = 0.309) between age and DM.

CONCLUSIONS

After preoperative assessment with modified Allen's test and Doppler analysis, RA used as graft in the elderly has similar quality and function with young patients, and it may lead to a high patency in long term. However, the quality of RA in patients with DM is in bad condition, and further research on patency needs to be done.

Comparison of the pretreatment effects of mixed vasodilators (3-D solution) on radial and internal thoracic arteries by using a 3-dimensional anaglyph electron microscope technique

OBJECTIVE

Currently, internal thoracic arteries (ITA) and radial arteries (RA) are the first choice of conduits for coronary artery bypass grafts (CABG). Because the perioperative vasospasm continues to be a major problem, a number of pharmacologic agents such as papaverine, calcium receptor blockers, nitroglycerine, and phenoxybenzamine have been suggested as topical antispasmodics that may be used in the pre- and postoperative periods. In the present study, we investigated the quantitative efficacies of the mixed solution, which included verapamil, nitroglycerin, and papaverine, on RA and ITA using a scanning electron microscope with a 3-dimensional anaglyph technique.

METHODS

Diameter changes of RA and ITA in response to clinically important vasodilators were measured on 40 RA and 40 ITA rings from patients who had been subjected to coronary artery bypass procedure after 20 minutes of ex vivo incubation with verapamil (45 microg/L), nitroglycerin (45 microg/L), papaverine solution (266 micromol/L or 0.1 micro/mL), and 30 mL autologous heparinized whole blood (individual patient's blood obtained before cardiopulmonary bypass contained 100 IU of heparin per kg of patient weight). The pretreatment action was assessed by measuring the response to vasodilators.

RESULTS

In all cases, we did not observe graft vasospasm in any of the conduits during the intraoperative period between postanastomosis and sternal closure. In the postoperative period, we did not record any evidence of ischemic change in patients' electrocardiographic and myocardial enzyme analyses. None of the cases required inotropic support after the operation. The diameters of the pretreated RA and ITA were: minimum, 2.1 mm; maximum, 4.0 mm; and mean value, 2.80 +/- 0.46 mm. The diameters of the pretreated ITA were: minimum, 1.2 mm; maximum, 2.5 mm; and mean value, 1.76 +/- 0.35 mm. Incubated arterial segment diameters for the RA were: minimum, 2.8 mm; maximum, 5.2 mm; and mean value, 3.95 +/- 0.65 mm. These values for the ITA were: minimum, 1.5 mm; maximum, 3.9 mm; and mean value, 2.37 +/- 0.50 mm. These findings were statistically significant for both arterial grafts (P <.05).

CONCLUSIONS

According to our study findings, the mixed solution demonstrates a broad range of efficacy. We conclude that the described vasodilator solution with heparinized autologous blood seems to be very effective and may be used as a pretreatment agent in CABG conduits. Although papaverine has the shortest duration of action, its efficiency is increased by verapamil and nitroglycerin, in our opinion. To the best of our knowledge, high-quality imaging of CABG conduits with the 3-D anaglyph technique using a scanning electron microscope was a first in the literature. This technical approach may be used for confirming the ultrastructural anatomy and the quantitative vasodilator effects of arterial conduits. We believe that valuable anatomo-pathologic details of the CABG conduit can be obtained by this technique.

The choice of the technique for harvesting and preparation of the radial artery for coronary artery bypass grafting

At present coronary artery disease (CAD) is a most frequently occurring cause of the lethality and disability of patients. One of the basic methods for CAD treatment is coronary artery bypass grafting (CABG). Actuality of the problem of applying the radial artery (RA) for CABG is determined by the proven advantage of arterial grafts versus vein grafts in myocardial revascularization. Today the RA ranks second in frequency of using the arterial graft subsequently to the internal thoracic artery (ITA). The RA may be harvested by two techniques: skeletization and in a case with surrounding tissue. However, to this day there is no unanimous opinion as regards the advantages of one or another approach. Of importance is conduit conservation from the time of harvesting to implantation into the coronary artery position. Despite a great number of conservants offered for conservation before implantation, comparative analysis of their effect on the conduit endothelium was not carried out. The problem of the safety of the RA conduit also remains open to discussion.

Implantation in coronary circulation induces morphofunctional transformation of radial grafts from muscular to elastomuscular

BACKGROUND

The purpose of this research was to investigate the in vivo morphofunctional changes induced in the radial artery (RA) by its use as coronary artery bypass conduit by comparing the morphological features and vasoreactivity of the native RA versus the coronary RA graft in the same patient.

METHODS AND RESULTS

Ten years after surgery, 10 patients were submitted to intravascular ultrasound examination of the RA graft of the controlateral (in situ) RA and of the internal thoracic artery (ITA) graft and to vasoactive challenges with acetylcholine and serotonin. Quantitative angiographic assessment showed that the mean diameter of the RA coronary grafts was significantly larger than that of the in situ RA and of the ITA (2.89+/-0.40 mm RA grafts, 2.14+/-0.52 mm in situ RA, 2.25+/-0.53 mm ITA grafts; P<0.001). The in situ RA demonstrated a typical muscular architecture, whereas RA coronary grafts showed a clear reduction of the thickness of the medial layer and had a less well-defined muscular component of the media with interposition of elastic tissue. Serotonin endovascular infusion elicited a strong spastic reaction in in situ RAs; the same challenge induced only moderate constriction in RA and ITA coronary grafts.

CONCLUSIONS

Implantation in the coronary circulation leads to major anatomic and vasoreactive modifications of the RAs that tend to lose the morphofunctional features of a muscular conduit and assume those of an elastomuscular artery, such as the ITA.

[Comparative study on the ultrastructures of radial and internal mammary arteries used for coronary artery bypass grafting]

OBJECTIVE

The radial artery differs from internal mammary artery in its vascular biology and long-term patency after coronary artery bypass grafting (CABG). This study was designed to investigate their ultrastructural differences that may have implications in arterial remodeling and graft failure.

METHODS

Thirty-four radial artery and 11 internal mammary artery samples were obtained from patients underwent CABG, and subjected to routine electron microscopic examination. A semi-quantitative method was used to evaluate secretary endothelial cells, endothelial denudation, synthetic smooth muscle cells (SMCs), matrix accumulation, lipid deposition and medial submicroscopic calcification.

RESULTS

Compared with internal mammary arteries, the radial arteries had more secretory endothelial cells (47.1%, 16/34 vs 27.2%, 3/ 11) and synthetic type SMCs in a background (14.4% vs 0.9%) that had more intimal lipid deposition and matrix accumulation (14.7%, 5/34 vs 9.1%, 1/11). Matrix vesicles and calcifications were frequently present in the media of both types of arteries. The calcifications, however, could not be visualized by routine histological stains, and therefore, named as submicroscopic calcification in this study. Fewer endothelial denudations were observed in the radial arteries, but no differences in medial lipid deposition and submicroscopic calcification were observed between these two types of arteries. The ultrastructural features and the arrangement of medial SMCs in radial arteries were similar to those of internal mammary arteries.

CONCLUSIONS

Radial arteries have a higher SMC proliferative potential and more actively secretory status of endothelial cells, which may enhance the remodeling process and correlate with a decreased long-term patency. Better preservation of endothelial cells in radial arteries could be attributed to the "no touch" technique utilized in surgical harvesting. The significance of submicroscopic medial calcification during graft remodeling requires further investigations.

Harvesting Techniques Affect the Integrity of the Radial Artery: An Electron Microscopic Evaluation

BACKGROUND

Four methods of radial artery harvesting were evaluated with transmission electron microscopy and tissue lipid peroxidation to determine the degree of damage to the artery.

METHODS

Radial artery samples from 4 groups of patients (10 samples from each group) who underwent coronary artery surgery were evaluated. In groups I and II, radial arteries were stored in a solution containing 100 mL patients' own heparinized oxygenated blood and 5 mg nitroglycerine. The grafts were distended in group II. In groups III and IV, side branches of the grafts were occluded and left in situ until the coronary anastomosis. In group III, the distal end of the graft was also occluded, while in group IV, both ends were open.

RESULTS

The least degree of endothelial damage and disruption of arterial wall integrity were in group IV according to electron microscopic evaluation. The grafts in group III were relatively in good condition compared to groups I and II. Tissue lipid peroxidation was also lowest in group IV. Tissue lipid peroxide levels correlated with ischemic preservation period of the radial artery (r = 0.426). Total semiquantitative transmission electron microscopic scores of the radial artery samples correlated with the lipid peroxide levels (r = 0.581) and ischemia times (r = 0.734).

CONCLUSIONS

All arterial grafts, including the radial artery that will be used for coronary artery surgery should not be left ischemic during harvesting to prevent endothelial damage. Ischemia of the conduits for coronary artery grafting can be prevented by leaving them in their anatomic position until the distal coronary artery anastomosis.

Arterial endothelial denudation by intraluminal use of papaverine-NaCl solution in coronary bypass surgery

OBJECTIVES

Preservation of endothelial integrity during coronary artery bypass grafting is considered important for short- and long-term patency of the graft. In current literature there are controversial data about the safety of papaverine, a vasorelaxant widely used in coronary artery bypass grafting. Accordingly, we examined the immediate effects of papaverine on the endothelial morphology of arterial grafts and on viability of cultured human coronary artery endothelial cells.

METHODS

Totally 22 segments of the radial artery were collected from 11 patients undergoing coronary artery bypass grafting. The segments were cut from the distal redundant parts of the arteries, which were not required for bypass grafting. A small distal segment of the artery was excised and placed into autologous heparinized whole blood (control segment). The rest of the graft, still remaining proximally attached to the circulation, was treated intraluminally with papaverine-NaCl solution (pH 4.2) for 5 min, after which another small distal segment was excised for the study (papaverine-treated segment). Segments were then perfusion-fixed and the endothelial surface was examined by scanning electron microscopy. Endothelial denudation was assessed and its severity graded. Additionally, viability of cultured human coronary artery endothelial cells after treatment with papaverine was assessed with trypan blue staining.

RESULTS

Treatment with papaverine solution markedly increased the endothelial denudation (grades from 6.2+/-1.7 to 10.0+/-3.5; mean+/-SD; P=0.004). Papaverine-treatment increased trypan blue staining of cultured human coronary artery endothelial cells regardless of papaverine diluent (normal saline of pH 4.5 or 7.4 or blood).

CONCLUSIONS

Treatment of arterial grafts with papaverine solutions apparently damages endothelial cells. Thus, the clinical practice of dilating arterial bypass grafts with papaverine should be reassessed, and alternative methods of vasodilatation should be considered.

Skeletonization versus pedicle preparation of the radial artery with and without the ultrasonic scalpel

BACKGROUND

The radial artery (RA) is increasingly used for myocardial revascularization because of its presumed advantageous long-term patency rates. The vessel can be harvested as a pedicle or skeletonized. The aim of this study was to compare the skeletonization technique with pedicle preparation using either an ultrasonic scalpel or scissors.

METHODS

Forty consecutive patients with coronary artery disease undergoing complete arterial revascularization were included in the study. In 20 patients the RAs were prepared using scissors and clips (group 1: skeletonization; group 2: pedicle). In another 20 patients the arteries harvested were prepared using an ultrasonic scalpel (group 3: skeletonization; group 4: pedicle). The RA was treated with papaverine to prevent spasm of the vessel during and after harvesting. Tissue specimens of each RA were taken to analyze endothelial morphology by scanning electron microscopy. After implantation of the RA, graft perfusion was measured with a flow probe.

RESULTS

Harvesting the RA as a skeletonized vessel took more time as compared with pedicle preparation (group 1 vs group 2: 37.1 +/- 3.5 minutes vs 24.4 +/- 3.9 minutes; p < 0.001 and group 3 vs group 4: 31.1 +/- 3.5 minutes vs 25.6 +/- 3.7 minutes; p < 0.01). The number of hemostatic titanium clips was similarly higher in group 1 as opposed to group 2 (58.7 +/- 7.1 vs 38.7 +/- 7.1; p < 0.01). However, there was no difference between groups 3 and 4 (p = 0.086). The length of the RA after skeletonization with scissors and clips was 20.8 +/- 1.5 cm in contrast with 19.1 +/- 0.9 cm (p < 0.01) after dissection as a pedicle. In the groups using the ultrasonic scalpel, there was no difference in graft length (p = 0.062). Mean blood flow through the graft after establishing the proximal anastomosis was similar among all groups (groups 1, 2, 3, and 4: 50 +/- 20.1 mL/min, 53.8 +/- 24.3 mL/min, 56.3 +/- 25.1 mL/min, and 51.8 +/- 23 mL/min, respectively). Scanning electron microscopy demonstrated endothelial damage in all patients in groups 1, 2, and 3 and in 7 patients of group 4. Most endothelial lesions were minor except in group 3 in which 1 of 5 endothelial lesions were severe. Statistically significant differences was found between groups 1 and 2, and 3 and 4 with respect to the degree of endothelial damage (p < 0.01).

CONCLUSIONS

Skeletonization using scissors and clips is more time consuming and technically more difficult, but yield significantly longer grafts. Skeletonization with an ultrasonic scalpel did not result in additional length and was more frequently associated with severe endothelial damage. Pedicle preparation using scissors or an ultrasonic scalpel is much simpler and faster, and does not jeopardize endothelial integrity.