Primary Percutaneous Coronary Intervention in Saphenous Vein Grafts: A Visualization Strategy to Improve Outcome with New Uses f

Percutaneous revascularization of diseased saphenous vein bypass grafts (SVGs) remains a difficult challenge for the interventional cardiologist despite major advances in catheter-based reperfusion therapies, adjunctive pharmacology and stent technology. Primary percutaneous coronary intervention (PCI) to SVGs has lower rates of TIMI 3 flow after PCI in the range of 70.2–80.7% as compared to 92–97.4% in native vessels.^1,2 This reduced short-term success rate is consistently associated with sustained poor long-term results with increased 1-month,³ 6-month^1,3 and 10-year² mortality rates.

SVGs requiring primary PCI often have complex morphology such as a long, less predictable and sometimes extensively diseased course that may contain substantial amounts of friable thrombus and atherosclerosis. These factors predispose the patient to complications such as occlusive thrombus, extensive dissection and distal embolization that lead to a high incidence of poor flow. A number of treatment options are available for the percutaneous management of such graft lesions including thrombus removal, covered stents⁴ and distal protection.⁵ However, while evidence suggests that distal protection improves PCI in elective, non-occluded SVGs,⁵ none have been conclusively beneficial in acute SVG occlusion causing ST-elevation myocardial infarction (MI) and, additionally, such devices cannot be safely used in vessels that are occluded or have poor flow. Furthermore, in an era where jump grafts are used for multiple anastamoses, distal protection devices may fail to completely protect all the vessels involved.

The Medtronic Export aspiration catheter (EAC) (Medtronic, Inc., Minneapolis, Minnesota) is a 4 Fr monorail system that has a 1 mm (0.041”) lumen that ends at an end-hole which is marked fluoroscopically by a radio-opaque marker situated 2 mm from the tip. It is relatively atraumatic, as it is a flexible system and uses only hand-powered suction. Aspiration catheters have been shown to be effective at removing intracoronary debris in acute settings^6,7 and are flexible or supple enough to reach distal parts of the coronary tree.⁶

This report describes the ability of such a system to aid diagnosis by delivering intracoronary X-ray contrast which helps to visualize the problem and to identify the mechanism. The catheter can then be used for aspiration to remove intracoronary debris or for the delivery of therapeutic medication. This report is the first description of a coherent strategy in acutely occluded SVGs to discriminate between the different causes of poor flow by targeted contrast delivery, and then use the information obtained to initiate treatment. In addition, this over-the-wire device can be used in conjunction with other distal protection devices such as the Filterwire Ex (Boston Scientific, Natick, Massachusetts) if it can be safely deployed.⁸

Case 1. A 53-year-old male who had undergone coronary artery bypass graft surgery (CABG) in 1998 with a left internal mammary artery (LIMA) to the left anterior descending (LAD) artery, a jump SVG to the diagonal and obtuse marginal, and a SVG to the right coronary artery, presented with an inferior MI. The time from onset of pain to catheterization was 2.5 hours. His electrocardiogram (ECG) showed ST-elevation in leads II, III and aVf (sum of 4 mm) with inverted T-waves and ST-depression in the anterior chest leads. Angiography showed severe native vessel disease. The proximal end of a graft was identified, but dye was held up proximally with only mild to-and-fro eddying of contrast. This lack of dye progression down the graft persisted despite repeated injections and the use of nitroglycerin via the guiding catheter. A Galeo wire (Biotronik, Berlin, Germany) passed easily in an appropriate downward direction but then curled distally. We decided to use an aspiration catheter to aspirate along the trajectory in case of thrombus within the graft. However, the pattern of dye stasis remained unchanged with no indication as to where the occlusion might be or the state of the graft or distal vessels (Figure 1A). The aspiration catheter was removed and flushed. The EAC was thenplaced distally in the graft and a syringe with 50:50 contrast/saline was attached and aspiration performed until blood came back easily into the clear 50:50 mix to ensure there was no air in the catheter. Once the operator was satisfied that there was an absence of air and that the backflow was good (in order to check that the catheter had not migrated into dissection or aspirated a large piece of intracoronary debris), the syringe with 50:50 contrast/saline mix was injected with X-ray acquisition. This delineated a long thrombus-filled graft with a tapering stump that served as a target (Figure 1B).

With the identification of an appropriate stump, the wire passed through easily, and injection via the guiding catheter showed the restoration of TIMI 1 flow (Figure 1C). Aspiration was performed immediately with the EAC and 2 overlapping 3.5 x 32 Liberté stents (Boston Scientific) produced TIMI 3 flow in a large inferior territory (Figure 1D), with resolution of the patient’s chest pain and ECG changes.

Case 2. A 90-year-old male had undergone previous CABG with single SVGs to the LAD, OM1, OM2 and RDP in 1989. He presented with severe chest pain and his ECG showed ST-elevation in leads V1–V4 (sum of 7 mm). The time from the onset of chest pain to catheterization was 1.5 hours. Angiography revealed a stump with TIMI 0 flow (Figure 2A). A wire passed easily in an apical direction and aspiration was performed with the EAC. Despite aspiration and balloon inflations with a 2 x 30 Maverick along the length of the graft, there was no reflow (Figure 2B).

The EAC was flushed and passed distally with ease. A 50:50 contrast injection showed a severely diseased proximal section and further severe disease at the site of the anastomosis (Figure 2C).

A 2.5 x 18 MicroDriver (Medtronic) was deployed distally (Figure 2D) and TIMI 2 flow was restored. Flow improved furtherwith the use of nitrates and adenosine (Figure 2E).

Case 3. A 71-year-old male presented with an acute anterior MI. He had previously had 2 CABGs in relatively quick succession. The first in 1986 had placed a jump SVG on the LAD and D2 and a jump SVG to the OM, RPL and RDP. In 1987, he received a single jump SVG from the D to the OM and RPL, as the previous graft to that territory had failed.

Angiography showed TIMI 1 flow (Figure 3A). Use of the EAC produced TIMI 2 flow and uncovered 2 extensive lesions in the graft (Figure 3B). A 3.5 x 32 Liberté stent was deployed distally and 2 stents, a 4 x 30 mm Driver and a 4 x 18 mm Driver, were overlapped proximally. However, there was no re-flow despite the use of nitrates and adenosine via the guiding catheter (Figure 3C). The EAC was used to aspirate again, with no improvement. The EAC was flushed and passed to the region of the second anastomosis and a 50:50 contrast/saline injection showed that the graft and distal vessel were widely patent (Figure 3D).

The EAC was then used to deliver nitrates and adenosine to the native LAD just distally to the graft anastomosis. This was performed by attaching the diluted medication, aspirating to obtain good blood flow to ensure no air was in the system and injecting the medication. The result was good and brisk TIMI 3 flow was established (Figure 3E).

Discussion. Primary PCI of SVGs has a higher risk and poorer outcome when compared with primary PCI on native arteries. The higher incidence of distal embolization and noreflow suggest that removal of thrombus and atherosclerotic debris may be especially important in this group. This case series identifies a number of scenarios where the EAC performed functions that were additional to thrombus aspiration and proved crucial in obtaining a successful angiographic result.

The first case demonstrated stasis at the proximal end of a long graft. Contrast injection via the EAC delineated theocclusion and gave a target for wire placement. Thrombus aspiration was immediately applied and promptly restored flow. Visualization proved crucial in the second case with the identification of dissection distal to the occlusion site. This indicated that stent placement would be the appropriate strategy and resulted in the prompt restoration of TIMI 3 flow. In the third case, a diffusely diseased SVG that had been treated with 2 stents had no-reflow. Opacification with contrast injected down the EAC did not identify an obstructive lesion and, while there was stasis in the proximal end of the graft that did not respond to nitrates via the guiding catheter, injection of nitrates to the native LAD just distally to the graft anastomosis resulted in the restoration of TIMI 3 flow.

Poor flow is seen in a large proportion of SVG PCI, as demonstrated in the above cases, all of which benefited from the delivery of contrast deep within the coronary conduit. The results of this diagnostic action then determined their further management. Well-recognized thrombectomy systems such as the X-Sizer (ev3, Inc., Plymouth, Minnesota) have no possibility of contrast injection. While the use of contrast injection through an over-the-wire balloon is feasible, it has several disadvantages. Wire position must be sacrificed to allow contrast injection, the smaller lumen restricts contrast injection and gives a more concentrated and therefore potentially more damaging jet, and forward movement of the balloon to adjust position without the wire predisposes the vessel to the risk of perforation. In contrast, the EAC has a separate and larger lumen for injection that allows both more contrast as well as a less powerful jet, and therefore can be used to opacify any point along the trajectory of a wire that remains in situ. Additionally, suction can be immediately performed to remove intracoronary debris. While each of the functions are possible with other equipment such as over-the-wire balloons, multifunction probing catheters and thrombectomy devices, the EAC is a single device that can perform all these functions.

These cases identify a coherent two-step strategy that relies on distal visualization by contrast injection at any site that the wire has reached. Subsequently, a decision can be made as to further management, a situation that benefits from the fact that the EAC is in place for therapeutic maneuvers such as aspiration or delivery of medication. Alternatively, stenoses or dissections can be treated with stent placement. These functions allow an improvement on standard techniques in a logical and staged manner.

References

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