Extra Topic 5.2 -- Recent Stent Placement

Question 1

What would you like to know concerning his CAD and recent stent placement?

(A 68-year-old man presents for laparoscopic cholecystectomy. He has a history of CAD and underwent angioplasty and stent placement 6 months ago.)

Answer 1

I would be interested in –

• the degree of his coronary artery disease,
• which arteries were affected,
• what type of coronary stent was used,
• his myocardial function,
• what medications he is taking (especially anticoagulants), and
• specific treatment plans.

To this end, I would –

• perform a history and physical to determine the severity of his coronary artery disease,
• ensure that treatment has been optimized, and
• to identify any signs of myocardium at risk, such as –
  
  • orthopnea,
  • ECG signs of myocardial ischemia/infarction, and
  • angina following his PTCA.

Additionally, I would also –

• ask him if he was taking all of his medications and
• review all of his previous medical records including –
  
  • the operative report,
  • hospital discharge summary, and
  • any follow up care that had been provided.

Question 2

What are the risk factors for late stent thrombosis following the placement of a DES?

(A 68-year-old man presents for laparoscopic cholecystectomy. He has a history of CAD and underwent angioplasty and stent placement 6 months ago.)

Answer 2

The risk factors for late stent thrombosis following the placement of a DES include:

1. small vessel lesions,
2. multiple lesions,
3. ostial lesions (lesions at the opening/origin of the coronary arteries),
4. bifurcation lesions,
5. long stents,
6. overlapping stents,
7. suboptimal stent results (malapposition, residual dissection, or underexpansion),
8. left main coronary artery stent,
9. stent placement in the only remaining coronary artery or graft conduit,
10. prior brachytherapy (radiotherapy used in the treatment of coronary in-stent stenosis),
11. reduced left ventricular ejection fraction,
12. hypercoagulable states (i.e. pregnancy, malignancy, diabetes),
13. advanced age,
14. major adverse cardiac events within 30 days of percutaneous coronary intervention,
15. diabetes mellitus, and
16. renal failure/insufficiency.

–

The risk for stent thrombosis is increased perioperatively due to –

• the increased catecholamine release,
• increased platelet aggregability, and
• decreased fibrinolysis associated with surgery.

However, it is important to understand that –

the cessation of dual antiplatelet therapy is the single most significant predictor of perioperative stent thrombosis.

Question 3

The patient tells you that he was told to discontinue all “blood thinners” a week ago.

You see from the chart that he had a drug-eluting stent (DES) placed 5 months ago and was subsequently prescribed aspirin and clopidogrel.

What do you think?

(A 68-year-old man presents for laparoscopic cholecystectomy. He has a history of CAD and underwent angioplasty and stent placement 6 months ago.)

Answer 3

This is concerning because, following the placement of a DES, the incidence of late stent thrombosis is significantly increased with the premature discontinuation of thienopyridine therapy within the first year.

Moreover, the inherent hypercoagulable state associated with surgery places the patient at additional risk of thrombosis.

Given the high incidence of myocardial infarction and death associated with this complication (64.4% in one analysis),

I would – notify the surgeon of my concerns and discuss with him the possibility of delaying the procedure (it is recommended that elective surgery be delayed for 365 days following DES placement to allow for adequate endothelialization of the stent struts) and restarting thienopyridine therapy (clopidogrel) as soon as the risk of bleeding had diminished (ideally within 24 hours).

If the procedure could not be delayed for an extended amount of time, I would recommend –

• administering a loading dose of clopidogrel,
• restarting his aspirin, and
• delaying the procedure for a couple of hours to allow time for the antiplatelet activity of clopidogrel to take effect
  
  • (aspirin has an onset of action of about 30 minutes).

If an extended delay of the procedure was not possible and the bleeding risk of dual therapy was unacceptable, I would start by –

• evaluating the patient for concomitant risk factors for stent thrombosis (i.e. multiple stents, bifurcation lesions, left main coronary stent, etc.). —-
• If there were no additional risk factors and aspirin could be continued perioperatively, I would –
  
  • administer aspirin, wait at least 30 minutes for the aspirin’s antiplatelet activity to take effect, and
  • proceed with surgery.
• If, on the other hand, additional risk factors were present and/or aspirin therapy could NOT be continued perioperatively, I would –
  
  • proceed with surgery without any antiplatelet medications, recognizing that thre was significant risk of perioperative stent thrombosis.
• In either case, I would ensure intensive perioperative monitoring for signs of stent thrombosis and confirm the availability of an interventional cardiologist, recognizing that emergent PCI remains the best treatment option for acute stent thrombosis.
• —*
• Clinical Notes:*
• Elective procedures –
  
  • should be delayed for 14 days following balloon angioplasty to allow for complete healing of any vessel injury.
  • When a stent is placed, elective procedures for which there is significant risk of bleeding should be delayed for at least 30 days following bare metal stent placement (BMS) and
  • for 365 days (optimally) following drug eluting stent (DES) placement.
• With newer-generation drug-eluting stents, the risk of stent thrombosis stabilizes by 6 months, making it possible to undergo elective noncardiac surgery after 180 days if the risk of further delay is considered to be greater than the anticipated risks of ischemia and stent thrombosis (Class IIb).
  
  • This should only be considered if dual antiplatelet therapy could be continued perioperatively.
• Elective surgery should NOT be performed within 12 months of DES implantation for patients in whom dual antiplatelet therapy must be discontinued perioperatively (Class III: Harm)
• The current recommendations for delaying elective surgery and continuing dual antiplatelet therapy are based on the anticipated length of time required for the stent struts to become adequately endothelialized.
• Even after 12 months following DES placement, the risk of stent thrombosis is significant (although reduced when compared to < 12 months).
• Following DES placement, dual antiplatelet therapy may be continued for longer than 1 year in patients with concomitant risk factors for stent thrombosis (due to the risk of very late stent thrombosis).

Question 4

Would it make a difference if he had a bare metal stent?

(A 68-year-old man presents for laparoscopic cholecystectomy. He has a history of CAD and underwent angioplasty and stent placement 6 months ago.)

Answer 4

It would make a difference.

Given the significantly slower rate of endothelialization associated with drug-eluting stents, the risk of late stent thrombosis is much higher for a DES when compared to a bare metal stent.

Drug-eluting stents are impregnated with drugs that inhibit the proliferation and migration of vascular smooth muscle and endothelial cells, thereby impeding re-endothelialization.

Furthermore, these same drugs may exert a prothrombogenic effect until endothelialization is complete.

If this patient’s stent were a bare metal stent, it would be acceptable to continue with the procedure even if it were elective and the risk of bleeding precluded the continuation of dual antiplatelet therapy.

However, if the bleeding risk were not unacceptable, I would still prefer to continue his aspirin to further minimize his risk of thrombosis.

• Clinical Note:*
• Elective noncardiac surgery should be delayed for 4-6 weeks following bare metal stent placement, but should not be delayed more than 12 weeks because at this point restenosis may begin to occur. (WHAT??.. this no make sense..)

Question 5

Tell me how “bridging” therapy is employed.

(A 68-year-old man presents for laparoscopic cholecystectomy. He has a history of CAD and underwent angioplasty and stent placement 6 months ago.)

Answer 5

When the bleeding risk is unacceptably high with the perioperative continuation of the patient’s thienopyridine,

“bridging” therapy may be employed by:

1. discontinuing thienopyridine therapy 5-7 days prior to surgery,
2. continuing aspirin throughout the perioperative period
   
   • (even though aspirin is a long-acting platelet inhibitor, its continuation is usually acceptable unless the risk of bleeding is high or the consequence of bleeding is catastrophic, such as may be the case when bleeding occurs in a closed space… i.e. intracranial surgery),
3. starting a short-acting platelet inhibitor, such as eptifibatide (Integrilin) or tirofiban (Aggrastat), 2-3 days before surgery,
4. giving consideration to a concomitant heparin infusion, and
5. discontinuing any “bridging” drugs 6 hours prior to surgery (the aspirin should be continued, if possible).

Clinical Notes:

• Heparin alone is insufficient to prevent stent thrombosis because the heparin-antithrombin complex’s ability to inactivate fibrin-bound thrombin and factor Xa is limited.
• Glycoprotein IIb/IIIa inhibitors act by – blocking fibrinogen-mediated cross-linking between platelets (thereby inhibiting platelet aggregation).
  
  • Platelet function is completely restored within 2-4 hours following the discontinuation of Eptifibatide (Integrilin) or Tirofiban (Aggrastat).
• When “bridging” therapy is employed and the use of aspirin places the patient at an unacceptable risk of bleeding, an NSAID or COX-1 inhibitor may be substituted.
• Even the continuation of aspirin may pose an unacceptable bleeding risk in certain cases where bleeding may be excessive or occur in a closed space, resulting in a catastrophic outcome
  
  • (i.e. intracranial neurosurgery,
  • posterior chamber eye surgery,
  • spinal canal surgery).
• _Proton pump inhibitors should be avoided in patients receiving dual antiplatelet therapy following stent placement because they may inhibit the antiplatelet effects of clopidogrel and aspirin._