MMCTS
(March 15, 2006). doi:10.1510/mmcts.2004.000828
Copyright © 2006 European Association for Cardio-thoracic Surgery
Procedure
Conventional surgery with aortic cross-clamping
Massimo Caputo,
Pradeep Narayan and
Gianni D. Angelini*
Bristol Heart Institute, Bristol Royal Infirmary, Bristol BS2 8HW, UK
* Corresponding author: * Tel.: +44-117-928 3145; fax: +44-117-929 9737. E-mail: g.d.angelini{at}bristol.ac.uk
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Summary
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This article provides a brief description of how to perform proximal and distal anastomosis on the arrested empty heart along with the grafting strategy and utilisation of different conduits in coronary artery revascularisation. Sequential grafting and indications of coronary artery revascularisation has also been described.
Key Words: Cardiopulmonary bypass • Coronary anastomosis • Coronary surgery • Myocardial revascularisation
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Introduction
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Coronary artery disease represents a substantial health problem in the developed world and is associated with a reduction in 10-year survival and significant morbidity with increasing health costs. Revascularisation by coronary artery bypass grafting (CABG) surgery has been shown to offer symptomatic and prognostic benefits. In the following sections we describe the technique of performing distal and proximal anastomosis in the arrested, empty heart.
Operative indications
The indications for operative myocardial revascularisation are based on anatomic criteria such as left main coronary artery disease, multivessel coronary disease, and double-vessel coronary disease with proximal left anterior descending artery involvement, and with or without symptoms and signs of acute ischaemia, myocardial infarction, and left ventricular dysfunction [1,2]. In general, only coronary arteries with significant (>70%) stenoses are bypassed, because graft patency is otherwise severely limited by competitive native coronary flow. Nevertheless, the indications for surgical revascularisation in coronary artery disease are evolving from criteria based on simple angiographic criteria. In patients with challenging coronary disease, that is not amenable to equivalent revascularisation by a percutaneous coronary intervention (PCI) approach and those patients in whom the success of PCI is difficult to obtain (occluded vessels or bifurcation lesions), CABG surgery still remains the treatment of choice [1,2].
Different conduits in coronary surgery
A wide choice of conduits can be used to construct coronary artery bypass grafts. These include venous (long and short saphenous veins and cephalic vein) and arterial conduits (left and right internal thoracic, radial, gastroepiploic and inferior epigastric arteries) – See Photo 1, Schematics 1,2,3, Photo 2, Schematics 4,5,6 and Ref. [3], and Photo 3.
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Schematic 1 When a pedicle LITA is found to be of insufficient length to provide a tension-free anastomosis, the conduit can be lengthened significantly by skeletonising short segments of the artery, dividing the fascia, muscle, and accompanying veins.
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Schematic 2 The right internal thoracic artery (RITA) can be used as a pedicle or as a free graft. As a pedicle graft, it can be brought anterior to the aorta or posteriorly through the transverse sinus to graft the circumflex artery, or it can be brought anteriorly to supply the LAD with the pedicle LITA used to supply the circumflex artery.
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Schematic 3 The RITA can be used as a free graft, attached proximally to the aorta directly or at times with a venous hood when the aortic wall is unsuitable for direct suture. More commonly it is used as a Y-graft to the LITA.
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Schematic 4 The gastroepiploic artery (GEA) is another type of arterial conduit, which can be used as a pedicle graft to bypass mainly the postero-lateral coronary vessels (Main Right, PDA and circumflex arteries) and occasionally the LAD [3].
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Schematic 5 The GEA pedicle can reach the pericardial space by traversing the anterior surface of stomach and liver (anterior route) or the posterior surface of stomach and liver (posterior route). The anterior route is used more frequently because it is easier to check for twisting and bleeding of the pedicle following completion of the anastomosis.
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Schematic 6 The inferior epigastric artery (IEA) originates from the external iliac artery almost immediately posterior to the inguinal ligament. This conduit is used as a free graft, but reported experience is much less than with other arterial grafts, and its use limited by the availability of the other more frequently used arterial conduits.
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The early and long-term behaviour of these conduits is judged in terms of graft patency (catheter-based contrast angiography, CT or MRI scans) and clinical outcomes (mortality and cardiac-related events including myocardial infarction, congestive cardiac failure, further coronary revascularisation procedure and recurrence of angina). Both graft patency and clinical outcomes can be measured at specific time points following surgery, enabling the comparison between conduits.
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Surgical technique
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Proximal anastomosis
See Video 1 and Refs. [4,5,6,7].
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Video 1 Proximal anastomoses of the free bypass conduits can be performed onto the ascending aorta before or after the distal anastomoses, with the cross-clamp or with side-biting aortic clamp, or can be done as "Y" or "T" anastomoses on pedicle mammary arteries or saphenous veins [4,5]. The partial occlusion clamp is probably still the most common method of completing proximal anastomosis. While the single cross-clamp technique offers the advantage of avoiding additional aortic manipulation and risk of neurological injury [6,7], the main disadvantage is the longer ischaemic time and possibly the need for de-airing the heart.
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Composite grafts
Various configurations of Y- and T-grafts can be used with both venous and arterial conduits [8]. The rationale behind composite grafts is to perform an increased number of distal anastomoses and at the same time minimise aortic proximal anastomoses and therefore aortic manipulation and avoiding the marked mismatch between aortic wall thickness and conduit size (Schematics 7 and 8; Refs. [9,10,11]).
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Schematic 7 When composite grafts are used using bilateral thoracic arteries or the RA to the in situ LITA, our preferred strategy consists of directing the LITA to the LAD-diagonal area [9], and the free RITA or the RA to the circumflex territory as a Y-graft attached to the LITA. The RITA can also be used as a pedicle graft (through the transverse sinus) to the circumflex territory [10].
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Schematic 8 Alternatively, the LITA can be directed to the circumflex vessels and the RITA as a pedicle graft to the LAD area [11].
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Proximal anastomotic devices
Sutureless proximal anastomotic devices not requiring clamping of the aorta have been recently developed in order to minimise embolisation during construction of proximal anastomoses. These devices are used for creating an aortotomy and subsequently attaching a vein graft to the aorta with a circular wire appliance (Photos 4 and 5). The early results from several studies are controversial regarding the patency rate of such devices [11,13,14,15], and no definite answer regarding their clinical benefits compared to the standard anastomotic technique is yet available.
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Photo 4 Courtesy of St. Jude Medical Inc.
The first device to market was the SymmetryTM device from St. Jude. There have been more than 50,000 implants performed.
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Photo 5 Courtesy of Cardica Inc.
The Pass-PortTM, from Cardica is another automatic proximal device that consists of an integrated system which performs the aortotomy, delivers the graft to the aorta and deploys a stainless steel connector end-to-side the graft using one delivery device.
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Distal anastomosis
Visual inspection and epicardial examination of the target coronary vessels is generally performed after starting CPB with the heart still beating, in order to formulate a strategy for the sequence of anastomosis and reducing the cross-clamp time. This examination also allows choosing an anastomotic site free from atherosclerotic plaques, and reducing the need for endoarterectomies (Videos 2 and 3).
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Video 2 Silastic tapes or Prolene stitches (MMCTSLink 27) can be placed through the epicardium, around the proximal and distal coronary artery target, to help with visualisation and stabilisation of the planned arteriotomy site.
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Video 3 Care is taken to keep the opening into the conduit somewhat longer than that into the coronary vessel. The ‘parachute’ technique and a running stitch of 8/0 Prolene suture.
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Grafts to the right, posterior descending and postero-lateral left ventricular branches are usually routed along the right atrioventricular groove. Grafts to the obtuse marginal branches of the circumflex coronary artery or to intermediate vessels lie best when brought anterior to the pulmonary artery to the left lateral aspect of the ascending aorta. Generally, our practice is to graft the right side of the heart first, the circumflex territory second and finally the LAD/diagonal vessels (Schematics 9 and 10).
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Schematic 9 Sequential grafting permits the performance of additional distal anastomoses while sparing conduit and additional proximal anastomosis. A proximal side-to-side and a distal end-to-side anastomosis is normally performed. The length of the coronary arteriotomy should not exceed the diameter of the conduit (LITA) to avoid flattening of the anastomotic site. The anastomoses may be constructed as side-to-side (A) or end-to-side anastomosis (B).
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Schematic 10 Sequential grafting can also be carried out as a diamond shaped intermediate sequential anastomosis and a T-shaped distal anastomosis.
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Grafting strategy
The LITA graft to the LAD coronary artery has been well described, particularly with respect to long-term survival, cardiac event-free survival, and conduit patency rates, when compared with saphenous vein grafts [16]. This has led to the widespread use of arterial coronary revascularisation, and several options exist for additional arterial conduits. The use of the RITA as a second arterial graft has been shown to be beneficial compared to saphenous vein in observational studies [16,17]. Clinical data suggest that bilateral mammary artery in patients <70 years who had a first time myocardial revascularisation gives a better clinical outcome even 10 years after the operation [18].
The radial artery (RA) is an alternative arterial conduit that is often used instead of the RITA. After the first disappointing experience more than two decades ago, the use of the RA in coronary artery bypass grafting was again proposed by Acar and colleagues in 1992 [19]. Since then many groups have reported encouraging short and mid-term clinical and angiographic results with this alternative arterial conduit [20]. The RA presents some advantages when compared to the RITA: it is easy to harvest with minimal incidence of arm complications reported in the literature [11]; because of its length (>20 cm), the RA can be used to bypass any coronary artery; it can be used in patients with (a) diabetes or (b) chronic obstructive airway disease while the RITA in these patient populations is associated with an increased risk of deep sternal wound infection and there is the potential risk of graft compromise by hyperinflated lungs.
The RA, being a free graft, can be used as a conventional aorto-coronary bypass or, in order to extend as much as possible the number of distal anastomoses, it can be proximally placed on the LITA as a Y graft. Late RA patency rate can be adversely affected if placed in a coronary artery with moderate stenosis (<70%).
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Results
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According to the United Kingdom Cardiac Surgical Register the overall mortality of isolated coronary artery bypass graft is around 2%. In our centre, the overall mortality was 1.4%. Usage of bilateral internal thoracic artery is associated with significantly better survival than single internal thoracic artery, risk of re-operation, and angioplasty [16,17]. With regards to usage of radial artery there is no consensus at present. The final results obtained after 10 years of follow-up should help clarify the long-term RA patency rates and whether the use of this graft in CABG is superior to the RITA or SV.
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Conclusions
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- Careful planning of anastomotic coronary targets and sequence of anastomosis before aortic cross-clamping helps in reducing the ischaemic time and avoiding diseased coronary plaques.
- Two arterial conduits should be used whenever possible, with the LIMA to the LAD/diagonal territory and the second conduit to the other territory supplying most of the remaining myocardium.
- Avoiding touching the ascending aorta for proximal anastomoses with the use of composite graft is recommended particularly in high-risk patients with diffuse atherosclerotic disease.
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References
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Summary
Introduction
