Antiplatelet Therapy And Elective Surgery
Antiplatelet therapy reduces the risk of ischaemic events but increase the risk of bleeding. When a cardiac patient on dual antiplatelet therapy (DAPT) requires surgery a decision should be made whether or not to discontinue APT.
What is DAPT?
Dual antiplatelet therapy is combination of two drugs namely aspirin and clopidogrel for primary or secondary prevention of arterial or venous thrombosis.
How does it act?
Aspirin irreversibly inhibits platelets by blocking the formation of thromboxane A2, a potent platelet activator. Clopidogrel is a theinopyridine acts as a adenosine diphosphate (ADP) P2Y12 receptor antagonist. It reduces platelet granule release,thromboxane A2 formation and ultimately inhibits platelet aggregation mediated by binding of fibrinogen to activated glycoprotein 2b/3a receptors on platelets.There are no antidotes available for them.
When to stop DAPT?
Aspirin should be continued preoperatively when prescribed as secondary prevention of cardiovascular disease or stroke. Clopidogrel should be stopped 5 to 7 days prior unless recent stent insertion.
Stopping is advised 7 days prior to surgery as effect of these drugs lasts for the lifespan of a platelet which is 7 to 10 days.
What is the risk?
Risk of perioperative bleeding if DAPT continued. Risk of thrombosis if DAPT stopped more so in patients with stent in situ.
Which patients are at high risk?
Recent or recurrent ACS with DAPT
lVEF < 30> Triple vessel disease
Stent length > 25mm
Drug eluting stents
H/O thrombosis in a vessel of diameter < 2> Incomplete revascularisation
APT after a coronary event….till when?
Aspirin is given lifelong.
Clopidogrel (DAPT) is given for following period as per the cardiac status
• • Simple angioplasty without stunting | 2-4 weeks
• • PCI and bare metal stents | 6 weeks
• • Acute coronary syndrome | 3-6 months
• • PCI and drug eluting stents | Minimum of 12 months
Why so many days?
DAPT is mandatory after ACS or stent implantation as coronary lesions and stents behave like unstable plaques as long as they are not fully covered by cellular layer.
Metal frame of BMS is covered by smooth muscle cells in 6 weeks and by normal endothelium in 3 months.
DES have slow endothelialization rate :13% at 3 months and 56% at 3 years.
Which procedures are safe with DAPT?
Dental, dermatological, ophthalmological, endoscopy procedures.
How much is bleeding risk and in whom?
Low risk – peripheral and wall surgery,minor ENT and orthopaedics,endoscopy without biopsy or resection,eye anterior chamber or dentistry.
Transfusion not required.
Intermediate risk - visceral and vascular surgery,major ENT and orthopaedics,urology,endoscopy with biopsy or resection
Transfusion may be required
High risk - cardiac surgery,surgery with massive bleeding,surgery in closed space (intracranial, intramedullary, posterior eye chamber)
How much is cardiac risk and in whom?
Low risk – more than 3 months after PCI ,Bare metal stent ( BMS),CABG; more than 6 months after ACS or MI ; more than 12 months after drug eluting stent (DES).
Intermediate risk - 6-12 weeks after PCI,BMS or CABG; 6-24 weeks after ACS or MI,more than 12 months after DES.
High risk - less than 6 weeks after PCI,BMS,CABG,ACS or MI(less than 3 months if complications), less than 12 months after DES.
What is bridging therapy?
After stopping of APT anticoagulant therapy is started with heparin or low molecular heparin.
Heparin has no antiplatelet action so is not an adequate substitute for aspirin or clopidogrel because stent thrombosis is a platelet mediated phenomenon.
Short acting platelet glycoprotein inhibitor like eptifibatide,tirofiban can be used as a substitute for clopidogrel while aspirin is continued.
When to resume APT after operation?
APT is resumed within 6 – 24 hours of the procedure.
What is the treatment of bleeding if it occurs?
Same principles of managing major bleeding should be followed
Platelet transfusion carries the RISK of thrombotic events
rFVII may be helpful but carries risk of thrombosis.
Guidelines made easy
• 1. Risk factors for bleeding should be screened as soon as possible for patients requiring cardiovascular procedures. Class 1 (B).
• 2. POC Platelet function tests should be done to limit blood transfusion. Class 2b (B).
• 3. Discontinuation of clopidogrel before cardiovascular operations is recommended to reduce bleeding and blood transfusion. Class1 (B).
• 4. Stopping APT before operation is associated with reduced bleeding,blood transfusion,and reoperation but not with increased post operative death,MI or stroke. Class 1(B).
• 5. Discontinuation of aspirin in certain high risk patients who refuse transfusion for religious reasons (Jehovah’s witness) is reasonable. Class 2a (B).
• 6. Aspirin discontinuation before elective operations in patients without ACS is reasonable to decrease risk of bleeding. Class 2a (A).
• 7. Continue APT monotherapy with either aspirin or clopidogrel is reasonable in non cardiac operations,regardless of procedure urgency. Class 2a (B).
• 8. APT should be discontinued in patients with high risk bleeding eg intracranial procedures or expected major bleeding. Class 2a (b).
• 9. In patients with coronary stents for non cardiac operations continuation of DAPTcan be reasonable until bleeding risk is prohibitive. Class 2b(C).
• 10. APT for cardiac operations
For stable non bleeding patients aspirin should be started 6 to 24 hours of CABG to optimize vein graft patency. Class 1 (A)
In patients of CABG after ACS, DAPT should be restarted when bleeding risk is decreased. Class 1(A).
• 11. If urgent operations
If patient on DAPT requires urgent operation delay of even a day or two will decrease bleeding and decrease thrombotic risk in patients with ACS.Class 2a (B)
If patients on high thrombotic risk are for urgent surgery, bridging therapy with short acting antiplatelet agents might be helpful.Class 2b (C).