Left main intervention
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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]
Associate Editors-In-Chief: Neil M. Gheewala, M.D.; Anthony Smeglin, M.D.
Background
Approximately 5% of all patient undergoing coronary angiography have significant (> 50%) left main coronary artery (LMCA) stenosis. The ACC/AHA recommends coronary artery bypass grafting (CABG) in patient with significant LMCA disease who have angina and ACS. However, not all patients are operative candidates. In selected patients, LM PCI can safely and effectively treat patients in whom coronary artery bypass grafting (CABG) is suboptimal, or have prior CABG with a ‘protected’ LMCA. ‘Protected’ left main in patients with prior CABG is defined as at least one patent graft to left anterior descending or circumflex artery.
Goals of Treatment
The main goal of treatment is to provide a treatment option in patients who would otherwise be poor surgical candidates, declined by surgery, or refuse CABG. It is essential to properly select patients based on their anatomy who would be better candidates for DES vs BMS vs bifurcation stents.
Treatment Choices
Medical Therapy
Treating a patient with non-surgical methods include smoking cessation and risk factor modification. If a stent is placed, the patient is placed on prolonged dual antiplatelet therapy.
Appropriate Candidate Selection
CABG has generally been accepted as the standard of care for patients with LMCA disease. Left main intervention is considered a high risk subset of PCI, but it may be necessary for certain patients.
Candidates for LMCA PCI include:
- Poor operative candidates
- Low-risk patients who refuse CABG
- Patients with 'protected' left main disease (see above)
- Syntax score less than or equal to 22 is considered reasonable based on the Syntax trial (remains subject to debate)
High-risk features in patients with left main disease PCI include:
- Absence of internal mammary artery, radial artery, or saphenous vein grafts distally leading to an ‘unprotected’ left main.
- Concomitant right coronary artery (RCA) disease and/or lack of collaterals from RCA
- Left ventricular dysfunction
Hemodynamic Monitoring and Support
Hemodynamic support is not mandatory, but should be considered for high-risk patients who have refractory angina or are awaiting CABG with persistent angina on maximal medical therapy. Options include Intra-aortic balloon pump (IABP), Impella, and Tandom Heart. Also, [pulmonary artery (PA) line monitoring may be helpful.
Pre-interventional Preparation: Clearly Define Relevant Anatomy
Characterizing the patient's anatomy may reduce complications and the duration of the intervention. This can be done in several different methods:
- Intravascular ultrasound (IVUS): IVUS allows you to characterize the extent of the plaque, and identify any calcification.
- Multiple angiographic views: A layout of the anatomy can help characterize any disease in the LMCA ostium, the distal/bifurcation lesion, and the extent of the lesion.
- Guiding catheter selection: Larger guiding catheters (i.e.: 7 or 8 French) can be used in the event that distal bifurcation intervention becomes necessary, as they provide good support and do not occlude the ostium. If necessary, you can use side hole guiding catheters.
In addition to characterizing the patient's anatomy, it's essential to have all stents and balloons on the table, prepped, and ready to be deployed so that no time is wasted.
Antiplatelet Regimen
Aspirin is a one part of an antiplatelet regimen.
Clopidogrel is another part, for which you load with 600 mg, then administer 150 mg PO qd for one week, and then 75 mg daily. Prasugrel could also be used if the patient is under age 75, over 60 kg, has no history of stroke or TIA, and is at low risk of bleeding.
GP IIb/IIIa inhibitors are typically used to prevent thrombotic closure.
Reduce Ischemic Time
Besides selecting and prepping the equipment in advance, other methods can be employed to reduce ischemic time. You may use a rapid exchange system, or dilute the contrast in an indeflator to allow faster deflation. For conventional angioplasty balloon inflations, consider using a perfusion balloon in the left anterior descending artery (if this is dominant territory).
Appropriate Stent Selection
Consider using a BMS if the vessel diameter is 3.5mm or greater, and consider using a DES if the vessel diameter is small or if the lesion is long. If there is an ostial lesion, assure that the aorto-ostial region is covered by a stent.
Making a Selection
Stent Selection
There is increasing evidence for better PCI outcomes using DES instead of BMS because of lower angiographic rates of restenosis and significant reductions in major adverse events[1]. There are unclear benefits of using one DES over another based on their design (open/closed cell, modular), strut thickness/radial strength, and type of drug/polymer.
Approach Dictated by Lesion Morphology
Outcome differences have been observed according to the location of the LMCA stenosis. For instance, distal left main involvement (~75%) lesions have worse outcomes compared to more proximal lesions.
Distal bifurcation involvement has poorer results when treated with a two stent approach (i.e. kissing stents, culotte, T, etc). The approach is similar to other bifurcation therapies, but it has a higher risk:
- Directional coronary atherectomy (DCA) alone
- DCA plus stenting of the principal vessel
- Stenting of the principal vessel (which is usually the LAD) and rescuing circumflex. Bifurcation stenting (Crush, Culotte, T) have been shown to be non-inferior to each other and yield reasonable angiographic and clinical outcomes.
Calcified lesions can be treated with rotational atherectomy or stenting.
Bulky plaque can be treated with directional atherectomy and stenting, or stenting alone.
Anticipated Outcomes
An achieve excellent angiographic result is anticipated. Once initial treatment is complete, it is important to aggressively screen for restenosis.
Other Concerns
One concern is that a left main restenosis may present as sudden death rather than recurrent angina. As restenosis is a possible complication, it is recommended to relook at the angiography generally 2-3 months post-procedure, even in the absence of symptoms so that early restenosis can be caught. Some recommend additional angiography at 6 months to identify late restenosis.
Further studies need to be done to assess the outcomes for bifurcation stenting in distal LMCA disease. In countries where it is available, implantation of an ischemia monitoring device, such as the AngelMed Guardian device[2], may permit ongoing surveillance for early detection of ischemia in these high risk patients
References
- ↑ Price MJ, Cristea E, Sawhney N; et al. (2006). "Serial angiographic follow-up of sirolimus-eluting stents for unprotected left main coronary artery revascularization". J. Am. Coll. Cardiol. 47 (4): 871–7. doi:10.1016/j.jacc.2005.12.015. PMID 16487858. Unknown parameter
|month=ignored (help) - ↑ Hopenfeld B, John MS, Fischell DR, Medeiros P, Guimarães HP, Piegas LS (2009). "The Guardian: an implantable system for chronic ambulatory monitoring of acute myocardial infarction". J Electrocardiol. 42 (6): 481–6. doi:10.1016/j.jelectrocard.2009.06.017. PMID 19631947.