Disappearing bracket: Don't let the propaganda blind your eyes

Release date: 2016-08-02

Recently, the US Food and Drug Administration (FDA) approved the Absorb GT1 bioabsorbable vascular stent (BVS) system. This led the author to start thinking about a modern medical problem—the tension between progress and safety. Embracing new things and insisting on trying is a risky act. Interventional cardiologists are always known for their pioneering spirit, and these pioneers must also take risks and sometimes even pay a price. We allow new equipment to have room for improvement, as iterations of new equipment are more beneficial. Overall, the latest generation of drug-coated stents (DES) is superior to previous generations.

But the update is not necessarily better. For example, the implantable cardioverter defibrillator (ICD) wire (Medical's Sprint Fidelis), which was accepted by the American Heart Rhythm Association, has had disastrous consequences for patients.

Do we need a new type of stand?

Most interventional cardiologists believe that current DES performs well. Of course, the new atherosclerosis problem in the metal stent site will continue to affect the long-term outcome of PCI, but less than 1 in 500 patients with standard DES will develop advanced stent thrombosis, which is the case for any new stent. It's a daunting challenge – whether it's an absorbable stand or another stand.

The approval of bioresorbable stents has caused a lot of sensation among doctors and patients. The Wall Street Journal reported the first BVS implant in the United States, and patients and their doctors were attracted by the potential benefits of this new technology. Of course, in the whole story we have to recognize a keyword - potential.

Before delving into the real BVS evidence, let's review the case of patients with stable coronary heart disease who are treated with stents. The story is slightly shorter, and the highest quality evidence suggests that PCI does not reduce the likelihood of myocardial infarction or death; until 3 years, treatment still does not show the advantage of relieving angina.

Evidence of BVS vs DES

ABSORB III: The approval of BVS depends on this large study. This multicenter randomized trial implanted BVS (n = 1322) or standard DES (n = 686) in more than 2,000 patients with stable or unstable angina. The primary endpoint was the failure rate of the target lesion at 1 year, ie, cardiac death due to cardiac death, target vessel obstruction, or ischemia. The trial included only patients with relatively stable symptoms and simple coronary lesions. Results The target lesion failure rate in the BVS group was slightly higher than that in the DES group (7.8% vs 6.1%), and the 1.7% increase was within the 95% confidence interval for non-inferiority (−0.5~ 3.9, P=0.007). . The stent thrombosis rates in the BVS and DES groups were 1.5% and 0.7%, respectively. The authors conclude that this study is not sufficient to account for the occurrence of low-frequency events such as stent thrombosis, but data from subacute stents can be seen in other data sets (0.9 vs 0.1, P=0.04).

The lancet meta-analysis: A meta-analysis performed by German and Japanese researchers (6 trials, n=3738) found similar rates of target lesion failure, revascularization, and death in patients with DES and BVS. The most worrying observation was that the risk of stent thrombosis nearly doubled, and subacute stent thrombosis tripled (OR 3.11; 95% CI 1.24–7.82, P=0.02).

Systematic review and meta-analysis: Investigators from the Medius Cardiovascular Research Network conducted a systematic review of patients with different BVS indications, including registration studies and retrospective studies involving more than 10,500 patients ( BVS 8351, DES 2159). Similar to the lancet meta-analysis, BVS doubled the risk of stent thrombosis (OR 2.06; 95% CI 1.07–3.98).

BVS in the real world

ISAR-ABSORB registration study: 419 patients who were implanted with BVS were studied by doctors from Munich. At 12 months, the subject's death, myocardial infarction, or target lesion failure rate was 13.1%. The clear stent thrombosis rate was 2.6%, almost twice that of clinical trials. The authors believe that longer follow-up and larger studies are needed to clarify the role of these devices in clinical practice.

German/Swiss registration study: Of the 2 German and 2 Swiss hospitals, 1305 patients were implanted with 1870 BVS. The investigators found that stent thrombosis occurred in 42 patients, 40 of whom were ACS or sudden death. The rate of stent thrombosis at 30 days and 12 months was 1.8% and 3%.

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BVS supporters cited the potential benefits of this new device, such as the ability of absorbable stents to reduce new blood vessel formation at the stent site and return arterial motion to normal, all of which can improve clinical outcomes. The animal model suggests that the stent can be completely absorbed at 36 months. However, the problem is that there is currently no clinical data for more than one year of follow-up. Despite this, BVS passed the approval in 2011. Supporters also said that this is only the first generation of brackets, so there may be room for improvement.

I think there are many reasons why BVS is worrying. The first is the published evidence. The studies I have seen suggest that the number of BVS complications is significantly higher, such as myocardial infarction. Secondly, the problem of stent thrombosis, marketing, treatment optimism and the pioneering spirit of cardiologists have prompted people to ignore the problem of stent thrombosis. This may cause acute damage to the heart of a chronically ill patient. You can think that the author has said anything, but the author of the German/Swedish registered study believes that stent thrombosis is a malignant disease.

The second problem is that the surgical procedure of BVS is more complicated, and patient and lesion selection are key – and this also applies to the inclusion criteria for clinical trials. The third problem is cost. Now, both new devices and drugs must pass the test of economic efficiency. BVS is priced higher than DES, and surgery is more complicated.

Finally, there is doubt about the approval of the US device: I am not sure that the FDA's decision is correct. The FDA Advisory Committee highly praised BVS, but given the current data does not suggest the superiority of BVS, I can't understand why they are so optimistic.

医脉通 compiled from: Dissolving Coronary Stents: The Fog of Hype. Medscape. July 21, 2016

Source: Medical Pulse Compilation

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