Follow-up for more than 10 years attests to the safety of the first-in-man fully biodegradable coronary stents made of poly-l-lactic acid (PLLA), Japanese and Dutch researchers say.
"I believe that our study strongly guarantees the future of the biodegradable drug-eluting stent (DES)," Dr Kunihiko Kosuga said.
But obviously, as Dr Kosuga of the Shiga Medical Centre for Adults and colleagues noted in an online paper in Circulation, "Before putting the biodegradable drug-eluting PLLA stent into routine clinical practise, we need to confirm that PLLA does not cause any critical adverse events during the whole process of biodegradation."
Their new data are from an observational study of 50 patients with 63 lesions treated electively during 57 procedures with 84 Igaki-Tamai biodegradable non-drug-eluting PLLA coronary stents between 1998 and 2000.
In 48 patients followed for a mean of more than 10 years, there was one cardiac death, six non-cardiac deaths and four myocardial infarctions.
High cardiac survival demonstrate safety
This high cardiac survival rate, say the investigators, demonstrates the long-term safety of this stent and although "many non-cardiac death cases were reported in this study, they have no relation to the Igaki-Tamai stents."
During the process of biodegradation, which takes one to three years, target lesion/vessel revascularisation reached a near plateau, suggesting that the process of PLLA biodegradation does not correlate with an increased risk of clinical events.
At five years, the target lesion/vessel revascularization rate was 18%, which is comparable to results with bare metal stents (BMS). This rose to 28% at 10 years but may have been due to new atherosclerotic progression.
There were two cases of definite scaffold thromboses, but one was related to sirolimus-eluting stent, which was implanted for a lesion proximal to an Igaki-Tamai stent.
Stents can disappear
In conclusion, say the investigators "acceptable major adverse cardiac event rates similar to those of BMS and scaffold thrombosis rates without stent recoil and vessel remodelling suggested the long-term safety of the Igaki-Tamai stent."
"Although the mechanism of vessel healing in a chronic phase may not be the same between Igaki-Tamai stents and bioabsorbable drug-eluting PLLA stents," they add, "our study is essential in paving the way for a bioabsorbable drug-eluting PLLA stent, especially from the standpoint of long-term safety."
Commenting on the findings, Dr Ron Waksman, of Washington Hospital Center, Washington, DC told Reuters Health by email, "The next wave of DES will be including bioabsorbable technology." He added that the 10 years of follow-up "proves that the stents can indeed disappear without safety issues."
In an editorial, he also pointed out that "restenosis rates seen with PLLA stents... are similar to those reported with bare metal stents." Thus, "in order to obtain efficacy similar to DES, the PLLA polymer-based scaffold requires the addition of an antiproliferative drug."
(David Douglas, Reuters Health, June 2012)
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