Ann Thorac Surg 1999;67:120-123
© 1999 The Society of Thoracic Surgeons
Original Articles
Temporary luminal arteriotomy seal: III. Postmortem arteriosclerotic human coronary artery
Robin H. Heijmen, MDa,
Cornelius Borst, MD, PhDa,
Chantal M. Mouës, MDa,
Yvonne J.M. van der Helm, MDa,
Paul F. Gründeman, MD, PhDa,
Gerard Pasterkamp, MD, PhDb
a Department of Cardiology, Utrecht University Hospital, Utrecht, The Netherlands
b Department of Functional Anatomy, Utrecht University Hospital, Utrecht, the Netherlands
Accepted for publication June 23, 1998.
Address reprint requests to Dr Borst, Utrecht University Hospital (Room G02.523), P.O. Box 85500, 3508 GA Utrecht, the Netherlands
e-mail: exp.cardio{at}hli.azu.nl
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Abstract
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Background. Recently, we described a temporary luminal arteriotomy seal that provided a bloodless arteriotomy without obstructing recipient artery blood flow during bypass grafting in nonarteriosclerotic porcine arteries. This postmortem study assessed the sealing properties in irregular arteriosclerotic human coronary arteries.
Methods. Three hearts were obtained from donated corpses within 24 hours of death. The coronary arteries were pressure-perfused at 60 mm Hg with citrated porcine blood. At 15 anastomosis sites in four different coronary arteries, an end-to-side anastomosis was created using a 200-µm-thick polyurethane seal. Adequacy of sealing was determined at perfusion pressures of 60, 40, and 20 mm Hg.
Results. After insertion, the arteriotomy was sealed instantaneously in 10 of 15 anastomoses. After repositioning, complete sealing with a bloodless operative field was obtained in all cases. Low intracoronary transmural pressure did not impede sealing. In 8 of 15 anastomoses, minor leakage without obscuring the arteriotomy edges was observed during anastomotic suturing. Histologic examination revealed no intimal tear or dissection caused by the anastomotic procedure.
Conclusions. In postmortem-obtained arteriosclerotic human coronary arteries, the temporary luminal arteriotomy seal provided optimal visualization of the coronary anastomosis site in combination with persistent distal perfusion.
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Introduction
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Coronary artery bypass grafting (CABG) without cardiopulmonary bypass has emerged as an alternative treatment for selected patients with coronary artery disease [1, 2]. Off-pump, beating-heart CABG requires temporary interruption of recipient coronary blood flow to provide optimal visualization of the distal anastomosis site. Interruption of coronary flow, however, may result in regional myocardial ischemia. Furthermore, perforating branches located in the isolated coronary segment often produce retrograde blood flow into the arteriotomy.
To circumvent these two concerns about off-pump CABG, ie, blood in the arteriotomy and regional myocardial ischemia, we developed a briefly occlusive, end-to-side anastomosis technique by means of a temporary luminal arteriotomy seal (TLAS) [3, 4]. Previously, we demonstrated that in both the nonarteriosclerotic porcine carotid [3] and coronary arteries [4], the 200-µm-thick polyurethane seal enabled bloodless suturing of the anastomosis without obstructing the recipient artery blood flow. The TLAS was easily and effectively applied and retrieved, with a minimum of arterial wall damage. However, the sealing properties of the TLAS in the case of arteriosclerotic luminal wall surface irregularities or decreased transmural pressure remained to be established.
The aim of this study was to assess the efficacy of the TLAS during end-to-side anastomosis suturing in postmortem-obtained irregular arteriosclerotic human coronary arteries at physiologic and low transmural pressures.
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Material and methods
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Experimental set-up
Three hearts were obtained from donated corpses (1 male, 2 females, age 70, 70, and 79 years, respectively) within 24 hours after death. After direct coronary ostial cannulation, the coronary arteries were flushed with saline to remove adherent blood and postmortem thrombi, and subsequently visualized by angiography (C-arm BV27, Philips, Eindhoven, the Netherlands) to identify and localize luminal stenoses and irregularities and to determine the anastomotic sites. The angiographic diameter of the target coronary arteries varied between 1.7 and 2.5 mm.
Fifteen anastomotic sites in four different coronary arteries (left anterior descending, n = 4; diagonal, n = 6; obtuse marginal, n = 2; posterior descending artery, n = 3) were selected for end-to-side anastomotic suturing using the TLAS [3, 4]. The anastomotic sites were intentionally located either distal to (n = 12) or in (n = 3) angiographically determined luminal stenoses.
The coronary ostial cannulas were connected to a continuous-flow roller-pump, and the coronary arteries were pressure-perfused at 60 mm Hg with citrated porcine blood (whole blood mixed with sodium citrate 3.2%, at a ratio of 8:2) at room temperature. The coronary arteries were transected distally to establish coronary blood flow.
Anastomotic technique
A segment of human saphenous vein or porcine internal mammary artery was used as a graft to create the end-to-side anastomosis using the TLAS. The oval shape of the 200-µm-thick polyurethane seal was slightly modified from the coronary artery seal reported previously [4], and measured 7.5 mm in length and 4.5 mm in width. After interruption of coronary flow by switching off the roller-pump, the seal was inserted through a 3- to 4-mm longitudinal arteriotomy. After positioning the seal correctly inside the artery, blood flow was restored (Fig 1A).
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Fig 1. (A) After insertion, the temporary luminal arteriotomy seal completely covered the arteriotomy and provided a bloodless operative field without obstructing recipient artery flow (B) During suturing, the flimsy seal gave way when a needle was inserted between the seal and the arterial wall.
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Adequacy of sealing was determined at stepwise decreasing perfusion pressures of 60, 40, and 20 mm Hg.
The arteries were connected in the usual fashion (Fig 1B) with a continuous 8-0 polypropylene suture (Ethicon, Somerville, NJ) under the operating microscope (Wild M680, Leica AG, Heerbrugg, Switzerland) at 60 mm Hg perfusion pressure. At the toe of the anastomosis, the suture loops were loosely applied, creating a funnel-shaped exit in the length direction [3, 4]. After finishing the suturing, the TLAS was taken hold of and withdrawn from the artery past the suture, which subsequently was tightened to complete the anastomosis.
Histologic examination
To preserve anastomotic geometry, the coronary arteries were pressure-fixed with 4% formalin for 30 minutes at 60 mm Hg. After the heart had been submerged in 4% formalin for 3 days, the anastomotic segments, including the graft hood, suture line, and proximal and distal outflow tracts, were excised and decalcified in 10% EDTA for 3 days. Ten anastomotic segments were embedded in paraffin and subsequently sectioned in the longitudinal plane. From five anastomotic segments, the floor of the recipient coronary artery was cut and subsequently unfolded to enable longitudinal sectioning throughout the circumference of the coronary artery. Sections were stained with hematoxylin and eosin, and with elastin van Gieson. Light microscopy was used to identify and localize arteriosclerotic luminal wall surface irregularities.
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Results
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Coronary arteriography
Coronary arteriography (Fig 2) revealed the presence of multiple eccentric and concentric stenotic lesions. The arterial lesions were mainly located proximally in the coronary arteries and at side-branch takeoffs. No apparent luminal irregularities were observed peripherally.
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Fig 2. Coronary arteriography revealing stenotic lesions throughout the left coronary artery. The anastomotic sites were intentionally located either distal to (closed arrows) or in (open arrow) an arteriosclerotic lesion.
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Anastomotic procedure
Only at the three anastomotic sites that were located in an angiographic luminal stenosis, multiple arteriosclerotic spots in the coronary arterial wall and apparent luminal wall irregularities were observed after dissection and arteriotomy, respectively. Before insertion of the seal, the coronary lumen could be clearly identified in all arteries. After insertion, instantaneous complete sealing of the arteriotomy was obtained in 10 of 15 anastomoses (Table 1). In four anastomoses, the seal was successfully repositioned intravascularly, whereas in one anastomosis, which was located in an atherosclerotic lesion (Fig 2), the seal needed to be reinserted. Once properly positioned, the seal provided a bloodless arteriotomy in all cases. In nine anastomoses, the sealed arteriotomy was extended with a microsurgical knife (Sharppoint; Surgical Specialties Corporation, Reading, PA), to approximately 5 mm in length, without producing a leak.
Irrespective of the coronary perfusion pressure (60, 40, and 20 mm Hg), and consequently, the intraarterial transmural pressure, the TLAS continued to provide a dry operative field in all cases.
In 12 of 15 anastomoses, pressurizing the coronary artery to 60 mm Hg after insertion of the seal resulted in an elliptic arteriotomy of 1 to 1.5 mm in width (Fig 3A). In the remaining three anastomoses, however, the arteriotomy widened to approximately 2.5 mm in width (Fig 3B). Placement of a suture needle at the side of the anastomosis resulted in advertent expulsion of the seal in one of the latter three. After reinsertion of a larger seal (9 x 6 mm), anastomotic suturing could be continued.
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Fig 3. Pressurizing the arteriosclerotic human coronary artery to 60 mm Hg after insertion of the seal resulted usually in an elliptical arteriotomy of only 1 to 1.5 mm in width (A), but sometimes in a much wider opening (B). The latter resembles our earlier observations in the healthy porcine coronary artery [4], in which the longitudinal incision widened to an almost round arteriotomy (C).
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In 8 of 15 anastomoses, suturing resulted in minor leakage of the seal at some stitches, without obscuring the arteriotomy edges. In none of the anastomoses was the seal inadvertently transferred downstream.
Histologic examination
The extent of intimal thickening varied widely in the different anastomotic segments. In 8 of 15 anastomoses, the thickness of the intima ranged from 25 to 150 µm, without apparent wall surface irregularities. In seven anastomoses, however, the thickness of the intimal layer ranged from 250 to 1,000 µm, which resulted in an irregular wall surface adjacent to the suture line (Fig 4). In five of these, a calcified arteriosclerotic plaque was observed that partially obstructed the coronary lumen proximal to the anastomosis. No apparent difference in instantaneous complete sealing and leakage during suturing was observed between the two groups (Table 1).
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Fig 4. Longitudinal cross-section of an end-to-side anastomosis at the diagonal branch of the left anterior descending coronary artery, distal to an arteriosclerotic lesion. The thickened intimal layer resulted in an irregular wall surface adjacent to the suture line. The temporary luminal arteriotomy seal (dotted line) provided an instant dry operative field without producing a leak during suturing of the anastomosis. (Elastin van Gieson stain.) (Original magnification x10 before 48% reduction).
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In all anastomotic segments, the extent of intimal thickening and plaque formation, and hence luminal wall irregularity, was considerably more pronounced at the floor of the coronary artery compared with its ceiling.
In none of the anastomoses was an intimal tear or dissection observed that could be ascribed to insertion, manipulation, or retrieval of the seal or to anastomotic suturing. Apposition of the intima of the graft to the intima of the coronary artery was adequate in all cases.
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Comment
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In perfused postmortem arteriosclerotic human coronary arteries, the TLAS provided a bloodless operative field in all anastomoses. A stepwise decrease in intraarterial transmural pressure to 20 mm Hg did not impair the sealing properties of the TLAS.
In the present study, three hearts were obtained from donated corpses of advanced age. Both coronary arteriography and histologic examination revealed the presence of irregular arteriosclerotic lesions. Irrespective of the extent of luminal wall irregularities, the seal, once properly positioned, provided a bloodless arteriotomy, even in an arteriosclerotic lesion, and hence optimal visualization of the coronary anastomotic site.
In contrast to our earlier observations in nonarteriosclerotic porcine carotid [3] and coronary arteries [4], in 8 of 15 anastomoses, insertion of a suture needle between the seal and the arterial wall resulted in minor leakage of the seal at some stitches without hampering anastomotic suturing. Leakage could not be related to perfusion pressure and coronary anatomy. It is conceivable that for perfect sealing, both the seal (see Fig 1B) and the arterial wall need to give way to the suture needle to maintain a completely bloodless arteriotomy. The latter, however, may have been frustrated locally by the diseased, stiff human coronary arterial wall.
The TLAS was made from a polyurethane balloon skin material [3]. Placement of the suture needle, therefore, requires a careful approach to prevent accidental catching and dislocating of the seal. By slightly impressing the seal with the convex, blunt side of the needle, a space is created between the seal and coronary arterial wall in which the needle can be forwarded intraluminally. In our hands, using the operating microscope, none of the anastomotic procedures was complicated by accidental catching of the seal during suturing or retrieval [3, 4].
In concordance with our previous findings in the porcine carotid artery [3] (32 consecutive anastomoses; internal diameter, approximately 3.5 mm; TLAS, 12 x 7 mm) and in the porcine coronary artery [4] (18 consecutive anastomoses; internal diameter, approximately 2.5 mm; TLAS, 9 x 6 mm), a single-sized temporary luminal arteriotomy seal (7.5 x 4.5 mm) provided a bloodless arteriotomy in 15 of 15 consecutive postmortem arteriosclerotic human coronary arteries (internal diameter, 1.7 to 2.5 mm). Which size of the seal eventually will meet the variably sized human coronary arteries in clinical practice remains to be established. The present device, however, has proved the potential of "one size fits most" recipient arteries. In one anastomosis with a 2.5-mm-wide arteriotomy, however, the 1-mm overlap of the seal and arterial wall at both sides of the arteriotomy was insufficient to prevent expulsion of the seal when a suture needle was pulled through the coronary wall. After reinsertion of a larger seal, anastomotic suturing was continued uneventfully.
In conclusion, in postmortem arteriosclerotic human coronary arteries, the temporary luminal arteriotomy seal provided a bloodless operative field at all 15 anastomotic sites. Irregular luminal wall surface and low transmural pressure did not impede sealing. After extensive experimental evaluation [3, 4], the seal holds promise for clinical application. Its reliable functioning, however, in less optimally exposed and presented coronary anastomotic sites remains to be addressed in the clinical arena.
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Acknowledgments
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We acknowledge the contributions of Rob van Dalen, Hendricus J. Mansvelt Beck, Cees W. J. Verlaan, Simon Klomp, and Willem van Wolveren.
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References
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Calafiore A.M., Di Giammarco G., Teodori G., et al. Midterm results after minimally invasive coronary surgery (LAST operation). J Thorac Cardiovasc Surg 1998;115:763-771.[Abstract/Free Full Text]
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Buffolo E., Andrade J.C.S., Branco J.N.R., Teles C.A., Aguiar L.F., Gomes W.J. Coronary artery bypass grafting without cardiopulmonary bypass. Ann Thorac Surg 1996;61:63-66.[Abstract/Free Full Text]
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Heijmen R.H., Borst C., van Dalen R., Gründeman P.F., Verlaan C.W.J. Temporary luminal arteriotomy seal for bypass grafting. Ann Thorac Surg 1998;65:1093-1099.[Abstract/Free Full Text]
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Heijmen R.H., Borst C., van Dalen R., et al. Temporary luminal arteriotomy seal: II. Coronary artery bypass grafting on the beating heart. Ann Thorac Surg 1998;66:471-476.[Abstract/Free Full Text]
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Abstract
Introduction
