Following implantation, re-epithelialization of the stent reduces the risk of in-stent thrombosis. However, this takes time and we protect the patient by placing them on therapy to reduce the risk of thrombosis prior to re-epithelialization. Due to the cytotoxic nature of the DES, re-epithelialization is prolonged compared to BMS. (3-6 months for BMS vs ??? for DES, some say 21 months)
Current ACC/AHA guidelines (the ones we should go by) recommend DAT (dual antiplatelet therapy ie plavix and aspirin) for at least 1 month after bare metal stent implantation and 12 months after drug eluting stent implantation. They also recommend 12 months of DAT in patients who receive bare metal stents and are at low risk for bleeding.
The European Society of Cardiology recommends 6-12 months of DAT following routine placement of a stent and 9-12 months if the placement of the stent was for an acute coronary syndrome.
Current data is fairly weak with conflicting results. More importantly, the question of "net clinical benefit" i.e. a composite endpoint of risk of bleeding combined with benefit from reduced restenosis (
Byrne et al) has not been addressed.
Two large ongoing studies may further elucidate optimal duration.
The big one is the
DAPT study. 15,000 DES patients and 5,000 BMS patients. comparing 12 months of DAT with 30 months of DAT. With a budget of some $100 million and industry support from all the major players, this is a key study to watch for. Results should be available in 2014.
Since I always love the iconoclast, the more interesting study is
ISAR-SAFE. This one is looking at six months vs twelve months of dual therapy. They plan to enroll 6000 individuals and results should be available in 2013. Surprisingly they do not seem to have any industry support.
Preliminary data from Korea was presented at the ACC conference this past April that suggests that a six-month duration of treatment is non-inferior to 12 months of therapy.
Then there is the question of interrupting DAT for surgery.
AHA/ACC guidelines are as follows.
- Aspirin therapy should not be interrupted.
- Surgery with low bleeding risk should be performed without interrupting the second antiplatelet agent if possible.
- Patients with BMS should not have disruption of antiplatelet agents for a minimum of 4-6 weeks after implantation.
- Patients with DES should not have disruption of antiplatelet agents for a minimum of 12 months after implantation
- Consideration of heparin bridging should be given to all high-risk patients with stents.
If one is undergoing PTCA with the foreknowledge of imminent surgery, then balloon angioplasty without stenting can be performed. There should be a 2-week window between balloon angioplasty and surgery.
Hope that helps someone
- pod
