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J Thorac Cardiovasc Surg 2004;127:1139-1144
© 2004 The American Association for Thoracic Surgery

Surgery for acquired cardiovascular disease

Composite Y internal thoracic artery–saphenous vein grafts: Short-term angiographic results and vasoreactive profile

^a Department of Cardiac Surgery, Catholic University, Rome, Italy
^b Department of Cardiology, Catholic University, Rome, Italy

Received for publication May 13, 2003; revisions received June 27, 2003; accepted for publication July 7, 2003.

^* Address for reprints: Mario Gaudino, MD, Divisione di Cardiochirurgia, Policlinico Universitario A. Gemelli, Largo A. Gemelli 8, 00168 Rome, Italy
mgaudino{at}tiscali.it

	Abstract

Top Abstract Patients and methods Results Discussion References

 
BACKGROUND: The angiographic patency of composite Y internal thoracic artery–saphenous vein grafts has not been investigated in detail.

METHODS: Twenty-five patients who received composite Y internal thoracic artery–saphenous vein grafts had control angiography and vasoactive challenges with serotonin, acetylcholine, and isosorbide dinitrate at a mean of 2.5 ± 1.2 years after surgery.

RESULTS: The perfect patency rate of composite Y internal thoracic artery–saphenous vein grafts was 72% (18/25). The distal portion of the internal thoracic artery was stringed in 4 patients and occluded in 2. The saphenous branch of the composite Y internal thoracic artery–saphenous vein grafts was found patent in all patients except 1. No failures were reported in the proximal tract of the internal thoracic artery. The distal tract of the internal thoracic artery showed reduced capacity of endothelium-mediated relaxation.

CONCLUSION: The short-term patency of composite Y internal thoracic artery–saphenous vein grafts is suboptimal and markedly influenced by distal runoff and native flow competition.

During the past 48 months we adopted this type of graft configuration in 28 patients. As YITA-SV can represent an interesting model of internal thoracic artery flow diversion and "hybrid" vascular architecture, and due to the limited information available on this issue, we decided to ask all our patients to undergo control angiography and to try to elucidate the vasoreactive characteristics of YITA-SV by means of endovascular vasoactive challenges.

	Patients and methods

Top Abstract Patients and methods Results Discussion References

 
Patient population
From January 1999 to December 2002 YITA-SVs were used in 28 consecutive patients. These patients represent 0.7% of all coronary artery bypass (CABG) procedures performed during that period. The decision to adopt this unusual type of conduit was based on the necessity to avoid aortic manipulation (due to severe ascending aorta atherosclerosis, too short ascending aorta, or presence of an ascending aorta prosthesis) coupled with the impossibility of using the additional arterial conduits in use at our institution: the right internal thoracic and the radial artery. All patients survived surgery and were discharged from the hospital in good condition. Twenty-five of these patients agreed to undergo control angiography and represent the objects of this study. The main preoperative features of the patients and the contraindications to use additional arterial conduits are reported in Tables 1 and 2. Patients were in their eighth decade, had poor left ventricular function and limited functional capacity, and had a high incidence of associated pathologies.

In all patients 2 coronary anastomoses were performed; myocardial revascularization was complete in 13 patients (52%) and incomplete in the remaining 12. In consideration of the poor systemic and cardiac status of these patients and of the considerable operative risk (see Table 1), this high degree of incomplete revascularization was judged acceptable.

Angiographic protocol
Patients were studied in a fasting state, after premedication with oral diazepam (10 mg). Selective YITA-SV angiography was performed by percutaneous left radial (n = 24) or right femoral approach (n = 1). Thoracic artery catheters (5F or 6F; Boston Scientific, Natick, Mass) were used as appropriate to obtain optimal YITA-SV visualization and selective contrast medium injection. Multiple angiographic views were obtained to detect significant stenosis at any YITA-SV level; Thrombosis in Myocardial Infarction flow grade was visually estimated separately by 2 different observers.

Pharmacological stimulation was then started according to a previously described protocol,⁵ using serotonin, isosorbide dinitrate, acetylcholine, and isosorbide dinitrate, as follows.

Serotonin hydrochloride 10^–5 mol/L (ICN Pharmaceuticals Inc, Costa Mesa, Calif) was selectively injected into the YITA-SV graft at a rate of 3 mL/min for 3 minutes; at the end of the serotonin challenge 2 mg of isosorbide dinitrate was injected into the conduit. After a 20-minute period acetylcholine chloride 10^–6 mol/L (Miovisin, Farmigea, Italy) was selectively injected into the YITA-SV at a rate of 1.5 mL/min for 3 minutes; again at the end of the acetylcholine infusion 2 mg of isosorbide dinitrate was injected into the graft. Drug infusion was always performed under electrocardiogram and invasive blood pressure monitoring. At the end of each step of the protocol a cine run was performed, keeping fixed angiographic view.

Digital angiograms were then analyzed using computerized quantitative angiography (Medis, Neuen, The Netherlands). Due to the complex vascular architecture of the graft and for a more detailed angiographic analysis of the conduit, the YITA-SV was divided in 3 vascular segments: proximal ITA (proximal to the saphenous vein anastomosis), distal ITA (distal to the saphenous vein anastomosis), and SV graft. The 3 segments were measured in end-diastolic frames after proper catheter calibration as follows:

• proximal ITA: 10 to 15 mm proximal to the SV anastomosis;
  
• distal ITA: 10 to 15 mm distal to the SV anastomosis;
  
• SV graft: 10 to 20 mm distal to anastomosis with the ITA.
  

Patients did not received vasoactive medications in the 24 hours before the procedure. Written informed consent was obtained from each patient.

Statistical analysis
Chi-square or Fisher exact tests were used to compare discrete parameters. Analysis of Variance (ANOVA) for repeated measures was used to test differences after vasoactive challenges; post hoc comparison was performed by Neuman-Keuls test. Analysis was conducted using the software Statistica for Windows 4.1 (Statsoft, Inc, Tulsa, Okla).

	Results

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Angiographic patency
Control angiography was performed at a mean of 2.5 ± 1.2 years after surgery. Eighteen of the 25 grafts were perfectly patent (72%); the distal portion of the ITA was stringed in 4 patients (Figure 1) and occluded in 2 (Figure 2). The saphenous branch of the YITA-SV was found patent in all patients except 1. No failures were reported in the proximal tract of the ITA. Overall, the short-term YITA-SV graft patency was 22/25 (88%).

View larger version (117K): [in this window] [in a new window]   Figure 1. Stringed distal internal thoracic artery in a Y internal thoracic artery–saphenous vein graft. The internal thoracic artery shows diffuse narrowing of its distal portion. Arrow indicates thoracic artery–saphenous vein anastomosis. GSV, Great saphenous vein; LAD, left anterior descending artery; LITA prox, proximal left internal thoracic artery; LITA dist, distal left internal thoracic artery.

View larger version (118K): [in this window] [in a new window]   Figure 2. Occluded distal internal thoracic artery in a Y internal thoracic artery–saphenous vein graft. The distal tract of the internal thoracic artery results occluded; of note, injection in the left coronary system consents visualization of the distal part of the internal thoracic artery indicating a patent distal anastomosis. Large arrow indicates the presumed level of thoracic artery–saphenous vein anastomosis, whereas small arrows indicate clips on the occluded portion of the internal thoracic artery. GSV, Great saphenous vein; LITA prox, proximal left internal thoracic artery.

Distal (but not proximal) ITA graft diameter was significantly influenced by target vessel stenosis (Figure 3). Mean proximal ITA diameter was 2.71 ± 0.21 mm for patients with <70% LAD stenosis versus 2.67 ± 0.18 mm in patients with >70% lesion (P = .47); in contrast, distal ITA diameter was 1.78 ± 0.18 mm for patients with <70% LAD stenosis versus 2.25 ± 0.09 mm in patients with >70% lesion (P < .001).

View larger version (127K): [in this window] [in a new window]   Figure 3. Caliber reduction between proximal and distal tract of the internal thoracic artery in an Y internal thoracic artery–saphenous vein graft. Marked reduction of internal thoracic artery diameter is evident between the portion of the artery proximal and distal to the saphenous vein anastomosis. Arrow indicates thoracic artery–saphenous vein anastomosis. GSV, Great saphenous vein; LAD, left anterior descending artery; LITA prox, proximal left internal thoracic artery; LITA dist, distal left internal thoracic artery.

Vasoreactivity
YITA-SV reactions to endovascular vasoactive challenges are summarized in Table 3. Proximal and distal ITAs did not significantly react to serotonin infusion and showed significant dilatation after the administration of isosorbide dinitrate. The proximal part of the ITA also showed significant capacity of endothelium-dependent vasodilatation, whereas the distal tract of the artery dilated only slightly following acetylcholine challenge. The SV branch reacted to both serotonin and isosorbide dinitrate but did not show significant endothelium-mediated relaxation.

	Discussion

Top Abstract Patients and methods Results Discussion References

Our series reports the angiographic results and vasoreactive profile of 25 YITA-SVs at a mean interval of 2.5 years from surgery. We found that the overall patency (22/25 = 88%) was lower than that reported for single ITA and for composite all-arterial conduits.^6,7 The great majority of graft malfunctions (string or occlusion) were localized in the portion of the ITA distal to the SV anastomosis and were reported when the artery was used to revascularize target vessels with a moderate (<70%) stenosis.

Theoretically YITA-SV represent an interesting model of ITA flow diversion. The SV graft can be regarded as a major ITA collateral branch whose caliber is significantly larger than that of the main artery itself. This situation creates the possibility of a significant flow diversion from the ITA to the SV; flow steal is even enhanced when the ITA is anastomosed to a coronary vessel with moderate stenosis. ITA side branch flow steal has been denied in single ITA grafts^8,9; however, the diameter and length of the SV grafts proximally anastomosed to the artery are larger than those of the ITA side branches, and the YITA-SV represents a hemodynamic model that cannot be compared with the single ITA with its natural side branches.

Although in more physiologic situations the ITA is able to adapt to a wide flow range without occlusion, the hemodynamic condition created by the anastomosis of a large conduit to the proximal part of the artery renders YITA-SV more susceptible to the detrimental effect of chronic native competitive flow. It is interesting to note that this dependence of Y graft patency from flow competition has not been reported in angiographic series where the graft was constructed by anastomosing 2 arterial conduits (usually 2 ITAs or the ITA and a radial artery).^6,7 It must be considered that the SV is larger and less reactive than all arterial conduits and is likely to offer less resistance to flow. It is then conceivable that flow diversion from the main stem of the Y graft is higher when the side branch is represented by an SV instead of a right ITA or a radial artery, rendering YITA-SV more vulnerable to native competitive flow.

The portion of the ITA distal to the SV also exhibited a lower capacity of endothelium-dependent vasodilatation (see Table 3); as it is well known that flow and shear stress are major determinant of nitric oxide (NO) production and endothelium-mediated dilatation,¹⁰ it seems highly likely that reduced NO synthesis due to low flow in the distal ITA could have played a causal role in graft malfunction and occlusion.

YITA-SV have been proposed for complex technical settings and in high-risk patients and, in this view, the suboptimal patency rate that we have found could be considered acceptable. However, our findings show that this type of graft configuration jeopardizes the distal tract of the ITA, placing at risk the most important myocardial territory. When adopting this type of conduit surgeons must be aware of this possibility and consider eventual alternative technical solutions.

In our institution after evaluation of the present data we have abandoned the use of these composite grafts. In the situations where we used YITA-SV we now adopt 2 different solutions:

• performance of an all-arterial Y graft using alternative arterial conduits such as the inferior epigastric or gastroepiploic arteries or even the radial or right ITAs if the risk associated with their use is judged less important than the possibility of performing 1 additional graft;
  
• incomplete revascularization by a single ITA graft on the LAD with eventual successive percutaneous treatment of the non-LAD vessels.¹¹
  

	References

Top Abstract Patients and methods Results Discussion References

 

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9. Cohn WE, Ruel M, Zhang JP, Sellke FW, Johnson RG. Internal thoracic artery flow competition: studies in a canine H-graft model. Eur J Cardiothorac Surg. 2003;23:56–59[Abstract/Free Full Text]
   
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This Article Abstract Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Add to Personal Folders Download to citation manager Author home page(s): Mario Gaudino Francesco Alessandrini Claudio Pragliola Nicola Luciani Giuseppe Nasso Giovanni Guarini Gianfederico Possati Permission Requests Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Gaudino, M. Articles by Possati, G. Search for Related Content PubMed PubMed Citation Articles by Gaudino, M. Articles by Possati, G. Related Collections Coronary disease