Management of the thrombotic lesion: Difference between revisions
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* In the setting of [[ST segment elevation MI]], the goal is to achieve greater than 70% ST segment resolution. | * In the setting of [[ST segment elevation MI]], the goal is to achieve greater than 70% ST segment resolution. | ||
== | == Step-By-Step Strategy in the Management of the Thrombotic Lesion== | ||
* The first strategy is to prevent the occurrence of thrombus through the use of upstream antiplatelet and antithrombotic pharmacotherapies including [[aspirin]], [[thienopyridine]]s, and glycoprotein 2b3a inhibition. | * The first strategy is to prevent the occurrence of thrombus through the use of upstream antiplatelet and antithrombotic pharmacotherapies including [[aspirin]], [[thienopyridine]]s, and glycoprotein 2b3a inhibition. | ||
* The second strategy is to mechanically aspirate thrombus. | |||
* The third strategy is to direct stent the lesion without pre-dilation to minimize distal embolization. | |||
* The fourth strategy is to utilize intracoronary fibrinolytic therapy to dissolve clot that is refractory to other forms of treatment and dissolve clot inside branches that may be accessible to mechanical devices. | |||
* Alternate strategies include the use of distal protection and saphenous vein grafts to minimize distal embolization. | |||
==Treatment Choices== | ==Treatment Choices== | ||
===Pharmacologic Therapy=== | ===Pharmacologic Therapy=== | ||
Revision as of 11:33, 25 October 2011
Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editors-In-Chief: Brian C. Bigelow, M.D.
Overview
The presence of angiographically apparent thrombus is associated with poorer outcomes in patients undergoing PCI. Thrombus often embolizes distally and causes no reflow and associated myonecrosis. There are two broad strategies to reduce thrombus burden: mechanical strategies and pharmacologic strategies.
Goals of Treatment
Goals in the management of the thrombotic lesion include:
- Restoration of normal antegrade flow in the epicardial artery (TIMI Grade 3 Flow)
- Maintenance of normal perfusion in the downstream capillary bed or microvasculature (TIMI Myocardial Perfusion Grade 3)
- Resolution of thrombus burden
- Avoid distal embolization with abrupt cutoff of distal branches and side branches
- Avoid / reduce thrombotic major adverse cardiac events (MACE) which includes death, MI, recurrent ischemia, urgent target vessel revascularization (TVR).
- In the setting of ST segment elevation MI, the goal is to achieve greater than 70% ST segment resolution.
Step-By-Step Strategy in the Management of the Thrombotic Lesion
- The first strategy is to prevent the occurrence of thrombus through the use of upstream antiplatelet and antithrombotic pharmacotherapies including aspirin, thienopyridines, and glycoprotein 2b3a inhibition.
- The second strategy is to mechanically aspirate thrombus.
- The third strategy is to direct stent the lesion without pre-dilation to minimize distal embolization.
- The fourth strategy is to utilize intracoronary fibrinolytic therapy to dissolve clot that is refractory to other forms of treatment and dissolve clot inside branches that may be accessible to mechanical devices.
- Alternate strategies include the use of distal protection and saphenous vein grafts to minimize distal embolization.
Treatment Choices
Pharmacologic Therapy
- Antiplatelet therapy: Aspirin, platelet glycoprotein IIb/IIIa receptor (GP IIb/IIIa) antagonists (abciximab, eptifibatide, tirofiban), ADP receptor/P2Y12 inhibitors (plavix, ticagrelor, prasugrel)
- Antithrombin Therapy: Ufractionated heparin (UFH), low molecular weight heparin (LMWH). Fondaparinux is not recommended in primary PCI.
- Direct Thrombin Inhibitors: Hirudin, bivalirudin, argatroban
- Thrombolytic Therapy: Urokinase (UK), tissue plasminogen activator (tPA) for STEMI when other pharmacologic and mechanical treatments are not successful
It is an "off label" the use of these agents (this mode of administration is not been approved by the FDA), but fibrinolytic agents and glycoprotein 2b3a inhibitors can be administered by the intracoronary route. The total dose of TPA is 20 mg which is approximately the 1/5 of that generally used for systemic fibrinolysis. TPA can it be administered 2 mg at a time to evaluate its efficacy.
Mechanical Therapy
- Aspiration Catheter: (Export, Pronto) is the choice prior to the other interventions listed below
- Percutaneous Coronary Intervention (PCI): Bare metal or drug-eluting stent, particularly direct stenting without pre-dilation by conventional balloon angioplasty
- Distal Protection: (Percusurge guardwire, Triactive, Spider wire, Proxis), particularly in saphenous vein grafts
- Directional Atherectomy
- Transluminal Extraction Catheter (TEC)
- Rheolytic Thrombectomy (Possis Angiojet)
Advantages of Each Choice
- Aspirin is a conventional therapy that reduces ischemic complications after PCI.
- GP IIb/IIIa antagonists are used adjunctively to treat and prevent thrombus formation and decreases ischemic complications post-PCI in patients with angiographic evidence of or suspected thrombus. In patients with STEMI undergoing primary PCI, GP IIb/IIIa antagonists have been shown to reduce mortality in meta-analyses. There is an ongoing debate as to the optimal timing of their administration (upstream vs in-lab administration).
- UFH is a conventionally used thrombin inhibitor that prevents arterial thrombus formation at the site of a vessel wall injury, on catheters, and on equipment during PCI.
- LMWH: ExTRACT-TIMI 25[1] demonstrated that there were improved clinical outcomes with LMWH in patients with STEMI undergoing fibrinolysis and subsequent PCI.
- Direct thrombin inhibitors (DTI) may be used as an alternative to heparin and GP IIb/IIIa. The optimal strategy is to pre-load with clopidogrel if a DTI is used, which is the drug of choice in patients with a history of heparin-induced thrombocytopenia.
- Thrombus aspiration is the preferred treatment and has been associated with improved myocardial perfusion and mortality. Care should be exercised in very proximal lesions in the LAD and the circumflex, as the clot may embolize into the other artery.
- After aspiration, direct stenting is associated with improved rates of recurrent MI in meta-analyses, improved myocardial perfusion, and improved ST segment resolution. Stenting reduces the risk of abrupt closure.
- Rheolytic thrombectomy with Possis Angiojet was not found to have any benefit in the setting of STEMI in native coronary arteries in the AIMI trial. Infarct sizes were larger and mortality was higher.
- Distal protection
- Occlusive (Percusurge guardwire, Triactive) and filter (Filterwire) methods may improve safety and efficacy of PCI in patients with thrombotic lesions in SVG; SAFER study of Percusurge device demonstrated lower rate of death/MI
- Distal embolic protection has not shown to be efficacious in the setting of STEMI in native coronary arteries with either Percusurge (EMERALD trial[2]) or Filterwire (PROMISE trial[3]).
Making a Selection
Proper management of thrombotic lesions depends on the thrombus size, location, underlying severity of stenosis, clinical stablility, age of thrombus, and candidacy for antithrombotic or thrombolytic therapy. The treatment should be stratified according to thrombus burden. Standard therapy includes: ASA, UFH, and a GP IIb/IIIa antagonist with the addition of a thienopyridine as soon as possible after the anatomy is defined.
Consider using direct thrombin inhibitors in the setting of heparin-induced thrombocytopenia. Furthermore, avoid GP IIb/IIIa antagonists in patients with a high risk of bleeding complications.
When to Change Treatment
If thrombus persists despite aspirin, glycoprotein inhibition, thienopyridine administration, mechanical aspiration, and stenting, consider trying intracoronary fibrinolytic administration (2 mg of IC tPA at a time to a total dose of 20 mg. This is an off-label use of an approved drug.). You should also treat the patient for potential spasm or no-reflow with a calcium channel blocker, adenosine (100 mcg IC) or nitroprusside (100 mcg IC). You should also consider the presence of a dissection in the differential diagnosis.
- ↑ White HD, Braunwald E, Murphy SA; et al. (2007). "Enoxaparin vs. unfractionated heparin with fibrinolysis for ST-elevation myocardial infarction in elderly and younger patients: results from ExTRACT-TIMI 25". Eur. Heart J. 28 (9): 1066–71. doi:10.1093/eurheartj/ehm081. PMID 17456482. Unknown parameter
|month=ignored (help) - ↑ Nikolsky E, Stone GW, Lee E; et al. (2009). "Correlations between epicardial flow, microvascular reperfusion, infarct size and clinical outcomes in patients with anterior versus non-anterior myocardial infarction treated with primary or rescue angioplasty: analysis from the EMERALD trial". EuroIntervention. 5 (4): 417–24. PMID 19755327. Unknown parameter
|month=ignored (help) - ↑ Gick M, Jander N, Bestehorn HP; et al. (2005). "Randomized evaluation of the effects of filter-based distal protection on myocardial perfusion and infarct size after primary percutaneous catheter intervention in myocardial infarction with and without ST-segment elevation". Circulation. 112 (10): 1462–9. doi:10.1161/CIRCULATIONAHA.105.545178. PMID 16129793. Unknown parameter
|month=ignored (help)