Bypass Graft – Case 2
- 75-year-old female who presented with chest pain (CCS Class IV).
Past Medical History
- HTN, HLD, DM, Former Tobacco Use, CAD s/p 3-Vessel CABG and Multiple PCI’s, CKD, PAD
- LVEF 40%
- Stress MPI: Moderate ischemia involving the anterolateral and inferolateral segments of the myocardium.
- Home Medications: Aspirin, Atorvastatin, Diltiazem, Lisinopril, Furosemide, Insulin
- Adjunct Pharmacotherapy: Clopidogrel, Bivalirudin
- total occlusion of the proximal left anterior descending (LAD) artery filling via LIMA
- subtotal occlusion of the left circumflex (LCx)
- total occlusion of the first obtuse marginal (OM1) branch filling via SVG.
- Underwent intervention of the SVG to OM1 bypass graft.
- SVG was directly stented with procedure being complicated by slow flow.
- Intra-graft vasodilators administered with minimal improvement in flow.
- Aspiration thrombectomy was performed using an Export catheter, restoring flow (TIMI 2).
- Patient continued to have refractory chest pain with EKG showing diffuse ST-T wave changes, and an IABP was placed.
- Troponin-I peaked at 9.2 ng/mL and CK-MB peaked at 29.3 ng/mL.
- Patient was discharged 2 days later without further sequelae.
- What is the likely explanation or reason why the complication occurred?
- SVG’s which are of older age (usually >2 years since time of implantation), degenerative, or with severe plaque burden are more predisposed to extensive thrombotic burden and distal embolization during coronary graft interventions, resulting in no-reflow phenomenon and periprocedural MI.
- How could the complication have been prevented?
- Embolic protection devices (EPDs) should be used during a SVG intervention when technically feasible (AHA/ACC class 1 recommendation).
- Avoid pre-dilatation and post-dilatation of vein graft lesions as much as possible. Severe stenosis require may require SVG lesion pre-dilatation with a small balloon to facilitate delivery of devices, a stent should be sized one to one, and high pressure inflation should be avoided (balloon inflation pressure should be kept <16 atm) to prevent a “cheesegrater” effect, increasing risk of distal embolization of debris/thrombi.
- Assure patient is given adequate antithrombotic therapy (antiplatelets and anticoagulants).
- Anticoagulants used in SVG interventions include heparin or bivalirudin (lower risk for bleeding complications).
- Glycoprotein IIb/III inhibitor administration has not been shown to provide benefit in SVG interventions and should not be used (class III recommendation in the 2011 ACC/AHA PCI guidelines).
- Is there an alternate strategy that could have been used to manage the complication?
- The initial step in management of slow flow/no-reflow in a vein graft involves administration of intra-graft vasodilators through the guide catheter. If this fails it is recommended to use a dual-lumen microcatheter (Twinpass is the only dual lumen microcatheter available in the USA) to deliver intra-coronary medications to the native distal vessel and microvasculature.
- If slow flow/no-reflow occurs during intervention using a EPD, then perform aspiration thrombectomy to clear the debris obstructing the filter. If this fails, the filter should likely be removed to restore antegrade flow, and if further intervention is required a new filter should be placed prior to proceeding forward with intervention.
- What are the important learning points?
- EPDs have been shown to be beneficial in SVG interventions but not in native coronary artery interventions.
- Currently, there are 3 types of EPDs: the distal balloon occlusion/aspiration system; distal filter system; and the proximal occlusion/aspiration system.
- Distal occlusion/aspiration system. SAFER trial showed a remarkable 42% reduction in 30-day MACE and a marked decrease in the no-reflow phenomenon with utilization of EPD (PercuSurge GuardWire system). TriActiv system was proven to be noninferior to the GuardWire system in the PRIDE trial.
- Distal filtration system. FIRE trial showed noninferiority of the FilterWire EX System to the GuardWire system. BLAZE I and II study showed decease in MACE with the FilterWire EZ, and SPIDER trial showed noninferiority of the Spider Rx filtration device to GuardWire and FilterWire. AMEthyst trial showed the Interceptor PLUS device to be noninferior to the GuardWire and FilterWire EZ.
- Proximal occlusion/aspiration system. PROXIMAL trial showed the Proxis system to be noninferior to distal EPD’s.
- Location of the stenosis determines the type of EPD that may be utilized.
- Ostial lesions require a distal EPD as proximal device use is contraindicated.
- Lesions in the body of the graft can be served either by a proximal or distal device.
- Distal lesions can only be proximally protected.
- Embolic protection should be used in all SVG interventions with the following exceptions:
- ISR lesions, which are composed of fibrous tissue and have low embolization risk
- Recently implanted (<2 year-old SVG, that have not had enough time to develop significant degeneration predisposing to embolization
- EPD use is not technically feasible (which at present applies mostly to distal or anastomotic lesions, since proximal embolic protection devices are no longer available for clinical use in the United States).
- The best treatment for slow flow/no-reflow is to prevent it from happening.
- The exact mechanism of the no-reflow phenomenon is unclear, but it is thought to be associated with endothelial swelling, neutrophil infiltration, and platelet aggregation causing obstruction and spasm in the microvasculature.
- Important to have multiple vasodilators readily available during a procedure. We use the following agents and administer them intra-graft.
- Nitroprusside 50-200 mcg, Adenosine 30-40 mcg, Verapamil 100-200 mcg, Nicardipine 100-200 mcg
- Nitroglycerin 100-200 mcg (we use NTG for slow flow/no-reflow when it involved the epicardial vessels and not the coronary microvasculature)
- If the patient is hypotensive and this impedes the administration of intra-coronary or intra-graft vasodilators to treat slow flow/no-reflow, we recommend administration of IV phenylephrine 100-200 mcg as needed (may result in reflex bradycardia) to increase blood pressure, and then administer intra-coronary/intra-graft vasodilators.
- If there is refractory slow flow/no reflow then consider placement of an IABP. This helps with reduction in afterload, and improves coronary perfusion pressure by increasing coronary blood flow during diastole, and reduction in LVEDP.
- Additional stent implantation should not be performed until normal antegrade flow is restored.