bioresorbable scaffolds ( brs ) have been designed to overcome problems related to the long - term persistence of metallic stents implanted in coronary arteries .
several randomized controlled trials ( rcts ) comparing polymeric brs with new - generation drug - eluting stents ( des ) found similar clinical outcomes at 1 year . a recent meta - analysis , though , showed an increased risk of definite or probable scaffold thrombosis for brs ( 1.3% compared with 0.5% ) .
as the true benefit of brs is expected to ensue later , long - term data of rcts are awaited .
absorbable metal scaffolds constitute an attractive alternative to polymeric brs , as they conform more to the technique of percutaneous coronary intervention with des .
we assessed a novel second - generation drug - eluting absorbable metal scaffold ( dreams 2 g ) , which has been redesigned iteratively by ( i ) improving the design of the magnesium backbone of its previous version and ( ii ) using the same drug  polymer combination ( sirolimus / poly - l - lactide ) as the new - generation biodegradable polymer stent orsiro ( biotronik ag , buelach , switzerland ) .
six - month outcomes were recently published , showing favourable angiographic and clinical outcomes with a low rate of target lesion failure ( tlf ) and no definite or probable scaffold thrombosis .
we aimed to evaluate if those results are sustained at 12 months , a time point when the magnesium scaffold is expected to be degraded .
a detailed description of the study has been recently published . in brief , biosolve - ii is a prospective , multi - centre , first - in - man study to evaluate the safety and performance of dreams 2 g ( biotronik ag , buelach , switzerland ) .
the study is in compliance with the declaration of helsinki , good clinical practice , iso14155 , and was approved by the institutional ethics committees at the participating 13 institutions in europe , south america , and asia .
eligible patients had stable or unstable angina or documented silent ischaemia , a maximum of two single de novo lesions in two separate coronary arteries , with a reference vessel diameter between 2.2 and 3.7 mm , a lesion length of 21 mm , and a diameter stenosis between 50 and 99% .
exclusion criteria included thrombus in the target vessel , severe calcification , three - vessel disease , ostial lesion , bifurcation lesion involving a side branch > 2.0 mm in diameter , target lesion located in or supplied by an arterial or venous bypass graft , and unsuccessful pre - dilatation .
the full list of inclusion and exclusion criteria can be accessed at clinicaltrials.gov ( nct01960504 ) .
clinical follow - up was planned at 1 , 6 , 12 , 24 , and 36 months .
angiographic follow - up was scheduled at 6 months for all patients , an additional pre - specified imaging follow - up was scheduled at 12 months if subjects consented .
a subgroup of 30 patients underwent intravascular ultrasound ( ivus ) , optical coherence tomography ( oct ) , and vasomotion testing at 6 months . at this time point , these patients were also asked to consent for voluntary ivus , oct , and vasomotion assessment at 12 months .
only patients without target lesion revascularization ( tlr ) were asked for additional 12-month imaging assessment .
dreams 2 g is a drug - eluting absorbable metal scaffold system comprising of an absorbable magnesium scaffold pre - mounted on a balloon - expandable delivery system .
the scaffold is laser - polished and its surface is completely coated with bioresorbable poly - l - lactide , which incorporates sirolimus .
the primary endpoint was in - segment late lumen loss ( lll ) at 6-month follow - up .
secondary endpoints at 12 months were tlf , a composite of cardiac death , target - vessel myocardial infarction , and clinically tlr ; scaffold thrombosis ; in - scaffold and in - segment binary restenosis ; diameter stenosis ; and in - scaffold lll .
a clinical event committee adjudicated all adverse events , and an independent core laboratory ( cardialysis b.v .
, rotterdam , the netherlands ) performed the quantitative coronary angiography ( qca ) , ivus , and oct analyses .
the device was available to operators in sizes 2.5 mm  20 mm , 3.0 mm  20 mm , or 3.5 mm  25 mm .
pre - dilatation was mandatory ; post - dilatation was left to the operator 's discretion .
only one study device per lesion was allowed , although in bailout situations , a second dreams 2 g could be used , and , in case of failure , an orsiro des .
the sample size was calculated based on the primary endpoint in - segment lll at 6 months and has been previously reported .
the null hypothesis was a mean in - segment lll at 6 months of 0.5 mm .
an overall of 121 ( 101 + 20 ) subjects were scheduled to be enrolled , assuming an expected in - segment lll mean of 0.45 mm , standard deviation of 0.2 mm , one - sided , significance level of 0.05 , and 80% power .
the intention - to - treat analysis population was defined as patients for whom an investigational scaffold entered the guide catheter following the diagnostic angiogram .
patients not receiving a study device were included in the calculation of procedural success , but excluded from further analysis as defined in the study protocol . for serial imaging analysis , paired data were used .
means and standard deviations , medians and interquartile ranges ( iqr ) , and 95% cis were calculated as appropriate . for categorical data , absolute and relative frequencies were calculated and 95% cis for proportions .
p - values were calculated using paired t - test , fisher 's exact test ,  test , and wilcoxon signed - rank test , where applicable .
the sponsor was involved in the design and conduction of the study , data collection , monitoring , and data analysis .
a detailed description of the study has been recently published . in brief , biosolve - ii is a prospective , multi - centre , first - in - man study to evaluate the safety and performance of dreams 2 g ( biotronik ag , buelach , switzerland ) .
the study is in compliance with the declaration of helsinki , good clinical practice , iso14155 , and was approved by the institutional ethics committees at the participating 13 institutions in europe , south america , and asia .
eligible patients had stable or unstable angina or documented silent ischaemia , a maximum of two single de novo lesions in two separate coronary arteries , with a reference vessel diameter between 2.2 and 3.7 mm , a lesion length of 21 mm , and a diameter stenosis between 50 and 99% .
exclusion criteria included thrombus in the target vessel , severe calcification , three - vessel disease , ostial lesion , bifurcation lesion involving a side branch > 2.0 mm in diameter , target lesion located in or supplied by an arterial or venous bypass graft , and unsuccessful pre - dilatation .
the full list of inclusion and exclusion criteria can be accessed at clinicaltrials.gov ( nct01960504 ) .
clinical follow - up was planned at 1 , 6 , 12 , 24 , and 36 months .
angiographic follow - up was scheduled at 6 months for all patients , an additional pre - specified imaging follow - up was scheduled at 12 months if subjects consented .
a subgroup of 30 patients underwent intravascular ultrasound ( ivus ) , optical coherence tomography ( oct ) , and vasomotion testing at 6 months . at this time point , these patients were also asked to consent for voluntary ivus , oct , and vasomotion assessment at 12 months .
only patients without target lesion revascularization ( tlr ) were asked for additional 12-month imaging assessment .
dreams 2 g is a drug - eluting absorbable metal scaffold system comprising of an absorbable magnesium scaffold pre - mounted on a balloon - expandable delivery system .
the scaffold is laser - polished and its surface is completely coated with bioresorbable poly - l - lactide , which incorporates sirolimus .
the primary endpoint was in - segment late lumen loss ( lll ) at 6-month follow - up .
secondary endpoints at 12 months were tlf , a composite of cardiac death , target - vessel myocardial infarction , and clinically tlr ; scaffold thrombosis ; in - scaffold and in - segment binary restenosis ; diameter stenosis ; and in - scaffold lll .
a clinical event committee adjudicated all adverse events , and an independent core laboratory ( cardialysis b.v . ,
rotterdam , the netherlands ) performed the quantitative coronary angiography ( qca ) , ivus , and oct analyses .
the device was available to operators in sizes 2.5 mm  20 mm , 3.0 mm  20 mm , or 3.5 mm  25 mm .
pre - dilatation was mandatory ; post - dilatation was left to the operator 's discretion .
only one study device per lesion was allowed , although in bailout situations , a second dreams 2 g could be used , and , in case of failure , an orsiro des .
the sample size was calculated based on the primary endpoint in - segment lll at 6 months and has been previously reported .
the null hypothesis was a mean in - segment lll at 6 months of 0.5 mm .
an overall of 121 ( 101 + 20 ) subjects were scheduled to be enrolled , assuming an expected in - segment lll mean of 0.45 mm , standard deviation of 0.2 mm , one - sided , significance level of 0.05 , and 80% power .
the intention - to - treat analysis population was defined as patients for whom an investigational scaffold entered the guide catheter following the diagnostic angiogram .
patients not receiving a study device were included in the calculation of procedural success , but excluded from further analysis as defined in the study protocol . for serial imaging analysis , paired data were used .
means and standard deviations , medians and interquartile ranges ( iqr ) , and 95% cis were calculated as appropriate . for categorical data ,
p - values were calculated using paired t - test , fisher 's exact test ,  test , and wilcoxon signed - rank test , where applicable .
the sponsor was involved in the design and conduction of the study , data collection , monitoring , and data analysis .
a comparison of baseline parameters of the angiographic and ivus / oct subgroups with serial 6- and 12-month evaluation compared with the overall population is provided in the supplementary material online , table s1 . in two lesions ,
dreams 2 g could not be implanted due to insufficient pre - dilatation ; follow - up of these two subjects was consequently not included in this analysis . 

= 123mean age , years65.2  10.3male gender78 ( 63.4)hypertension101 ( 82.1)hyperlipidaemia74 ( 60.2)diabetes36 ( 29.3)history of smoking67 ( 54.5)previous percutaneous coronary interventions44 ( 35.8)cabg8 ( 6.5)history of myocardial infarction29 ( 23.6)renal failure4 ( 3.3)congestive heart failure8 ( 6.5)history of stroke or tia7 ( 5.7)mean lesion length , mm12.61  4.53mean reference vessel diameter , mm2.68  0.40aha / acc classification type b2/c53 ( 43.4)moderate - to - severe calcification13 ( 10.6)thrombus3 ( 2.4)data are shown as mean  sd or n ( % ) .aha
/ acc , american heart association / american college of cardiology ; cabg , coronary artery bypass graft ; tia , transient ischaemic attack.n = 120 , in 3 subjects , images were not analysable.n = 122 , 1 subject not analysable . 

two patients who did not receive an implant were used for calculation of device and procedural success only .
forty - five angiographic assessments of which two were excluded as they did not have matched projections recorded , one did not have a 6-month but only 12-month angiography .
baseline clinical and lesion characteristics data are shown as mean  sd or n ( % ) .
aha / acc , american heart association / american college of cardiology ; cabg , coronary artery bypass graft ; tia , transient ischaemic attack .
two patients who did not receive an implant were used for calculation of device and procedural success only .
forty - five angiographic assessments of which two were excluded as they did not have matched projections recorded , one did not have a 6-month but only 12-month angiography . at baseline , 88 ( 71.5% )
patients had stable angina , 17 ( 13.8% ) unstable angina , and 18 ( 14.6% ) silent ischaemia . at 12-month follow - up , 100 ( 86.2% )
patients were symptom - free , 14 ( 12.1% ) had stable angina ( 9 ccs class i and 5 ccs class ii ) , 1 ( 0.9% ) had silent ischaemia , and none had unstable angina .
fifty - seven patients ( 48.3% ) were still on dual antiplatelet therapy at 12 months .
paired qca data could be obtained in 42 patients from seven centres at a mean follow - up time of 181  17 days and 367  17 days for 6- and 12-month assessments , respectively .
paired in - segment lll at 6 and 12 months was 0.20  0.21 mm ( 95% ci : 0.13;0.26 ) and 0.25  0.22 mm ( 95% ci : 0.18;0.32 ) , p = 0.117 ,  0.05  0.21 mm ( 95% ci : 0.01;0.12 ) , and in - scaffold lll 0.37  0.25 mm ( 95% ci : 0.29;0.45 ) and 0.39  0.27 mm ( 95% ci : 0.31;0.48 ) , p = 0.446 ,  0.03  0.22 mm ( 95% ci : 0.04;0.10 ) ( table  2 , figure  2 ) .
the in - segment and in - scaffold lll of the overall population at 6 months were 0.27  0.37 and 0.44  0.36 mm for the overall population ( 0.21  0.28 and 0.37  0.28 mm in patients without tlr ) .
there was no statistically significant difference in baseline characteristics between this subgroup and the overall patient population . 

table  2quantitative coronary angiographic analysis ( paired data , n = 42)pre - procedurepost - procedure6 months12 monthsreference vessel diameter in - segment2.74  0.352.75  0.352.60  0.382.60  0.41reference vessel diameter in - scaffoldna2.84  0.372.66  0.342.64  0.44minimum lumen diameter in - segment1.22  0.332.25  0.412.01  0.381.96  0.41minimum lumen diameter in - scaffoldna2.54  0.332.14  0.382.10  0.41acute gain in - segmentna1.00  0.38nanaacute gain in - scaffoldna1.29  0.34nanadiameter stenosis in - segment55.2  10.918.7  6.822.6  9.224.7  10.6diameter stenosis in - scaffoldna10.4  6.019.6  8.420.4
 8.6binary restenosis in - segment , % nana0 ( 0)2 ( 4.8)binary restenosis in - scaffold , % nana0 ( 0)0 ( 0)late lumen loss in - segmentnana0.20  0.210.25  0.22late lumen loss in - scaffoldnana0.37  0.250.39  0.27data are shown as mean  sd or n ( % ) .
there was no significant difference in outcomes between 6 and 12 months.na , not applicable . 

figure  2cumulative frequency curves for in - segment ( a ) and in - scaffold ( b ) late lumen loss .
six- and twelve - month serial analysis of late lumen loss observed in biosolve - ii compared with biosolve - i using the precursor device dreams first generation
. quantitative coronary angiographic analysis ( paired data , n = 42 ) data are shown as mean  sd or n ( % ) .
cumulative frequency curves for in - segment ( a ) and in - scaffold ( b ) late lumen loss .
six- and twelve - month serial analysis of late lumen loss observed in biosolve - ii compared with biosolve - i using the precursor device dreams first generation .
serial ivus and oct analyses at 6 and 12 months were performed in 11 patients ( respective data listings are provided in the supplementary material online , tables s2 and s3 ) .
paired ivus parameters did not differ significantly between 6 and 12 months ( median minimum lumen area of 4.80 vs. 4.69 mm , p = 0.700 ) , except for the number of patients with incomplete strut apposition , which was reduced to zero at 12 months ( supplementary material online , table s4 ; figure  3 ) . by oct ,
the median minimal lumen area decreased from 4.58 mm at 6 months to 4.19 mm at 12 months , p = 0.032 . no intraluminal mass
figure  4 shows that at 6 and 12 months , strut - like remnants are only visible by ivus but not by oct . 

only a very small neo - intimal hyperplasia area is visible ( 7 o'clock ) .
 indicates the difference between follow - ups in mm [ 95% ci ] . 

figure  4serial angiographic , optical coherence tomography , intravascular ultrasound , and virtual histology of a patient implanted with dreams 2 g . matched images show that at 6 months , struts are hardly discernible by optical coherence tomography and the scaffold strut that had covered the side branch post - procedure ( 12 o'clock ) had disappeared .
at 12 months , the vessel surface appears even smoother than at 6 months ( 2 o'clock ) . on intravascular ultrasound ,
assessed by virtual histology , the white colour coding of the scaffold struts disappears over time demonstrating the absorption process .
only a very small neo - intimal hyperplasia area is visible ( 7 o'clock ) .
serial angiographic , optical coherence tomography , intravascular ultrasound , and virtual histology of a patient implanted with dreams 2 g . matched images show that at 6 months , struts are hardly discernible by optical coherence tomography and the scaffold strut that had covered the side branch post - procedure ( 12 o'clock ) had disappeared .
at 12 months , the vessel surface appears even smoother than at 6 months ( 2 o'clock ) . on intravascular ultrasound , strut remnants
assessed by virtual histology , the white colour coding of the scaffold struts disappears over time demonstrating the absorption process .
serial vasomotion at 6 and 12 months was tested in 14 patients ; thereof 11 ( 79% ) had a change of > 3% to the mean lumen diameter after infusion or injection of acetylcholine ( figure  5 ) . the median percentage change in mean lumen diameter between pre - and post - acetylcholine was 2.6% ( iqr : 6.4 to 0.6% ,
mean 5.1  7.7% ) at 6 months and 3.4% ( iqr : 9.4 to 3.2% , mean 3.4  11.0% ) at 12 months ; the percentage change in mean lumen diameter between post - acetylcholine and nitroglycerine was 3.4% ( iqr : 1.19.2% , mean 5.8  6.4% ) and 6.7% ( iqr : 0.017.4% , mean 8.2  10.6% ) , respectively . 

percentage change in mean lumen diameter after acetylcholine and after subsequent intracoronary injection of nitroglycerine at 6 and 12 months in 14 patients .
the ends of the boxes represent the first and third quartiles , the band the median , and the crystal the mean .
there was no statistical significant difference between 6 and 12 months ( p = 0.808 for acetylcholine and p = 0.626 for nitroglycerine ) .
percentage change in mean lumen diameter after acetylcholine and after subsequent intracoronary injection of nitroglycerine at 6 and 12 months in 14 patients .
the ends of the boxes represent the first and third quartiles , the band the median , and the crystal the mean .
there was no statistical significant difference between 6 and 12 months ( p = 0.808 for acetylcholine and p = 0.626 for nitroglycerine ) .
ach , acetylcholine ; nitro , nitroglycerine . target lesion failure at 12 months was observed in 4/118 patients ( 3.4% , 95% ci : 0.98.4 ) .
no events beyond 6 months occurred . specifically , one death ( 0.8% ) of unknown cause on day 134
one target - vessel myocardial infarction ( 0.8% ) was due to temporary no - reflow after scaffold implantation .
the main findings of our study are stability of the angiographic and clinical outcomes of the second - generation device dreams 2 g between 6 and 12 months .
there was no definite or probable scaffold thrombosis up to 12 months and no tlf beyond 6 months .
these findings are relevant as 95% of the magnesium scaffold is expected to be absorbed within 12 months . the importance of this time point for dreams 2 g is reflected in the recently published european society of cardiology 
european association of percutaneous cardiovascular interventions report on the evaluation on coronary stents , which states that  for bioresorbable stents , critical time points of follow - up will depend on the pace of biodegradation and should cover complete resorption. compared with the first generation , dreams 2 g has markedly improved angiographic performance parameters also at 12 months ( in - segment lll of 0.25  0.22 mm vs. 0.39  0.33 mm and in - scaffold lll of 0.39  0.27 vs. 0.52  0.39 mm ) .
there are reports that found a significant relationship between lll and tlr even in patients with a lll of < 0.5 mm , but to a lesser extent than above 0.5 mm .
in other studies with permanent metallic stents , an in - segment lll of 0.5 mm has been associated with a maximal tlr rate of 5% and a binary restenosis rate of 5% .
furthermore , in an evaluation from 11 rcts , pocock et al . pointed out that a 12-month in - segment lll of < 0.3 mm and in - stent lll of < 0.4 mm were associated with very low tlr rates and that further reductions in lll are unlikely to reduce clinical restenosis .
correspondingly , a meta - analysis of rcts showed that brs had similar 12-month tlr rates as new - generation des despite inferior lll .
this might also explain the good clinical outcomes in our series despite a higher lll .
specifically , compared with recently established objective performance criteria for coronary stent trials at 912 months , our series had inferior lll [ mean in - scaffold lll of 0.39  0.27 mm compared with a median of 0.18 mm ( iqr : 0.130.25 ) for new - generation des ] , but comparable clinical outcomes [ tlr of 1.7% compared with 2.91% ( iqr : 1.675.94 ) for new - generation des , definitive stent thrombosis of 0.0% compared with 0.47% ( iqr:0.28 to 0.72 ) , respectively ] .
one of the encouraging finding is the persisting absence of definite or probable scaffold thrombosis in this trial and any other trial with precursor devices of dreams 2 g , tested in the progress or biosolve - i study .
however , this has to be interpreted with the caveat that ( i ) only 123 patients were enrolled , ( ii ) the results were not obtained in an all - comers patient population , ( iii ) randomized controlled data are missing yet , and ( iv ) dual antiplatelet therapy was recommended for at least 6 months , and nearly half of the patients were still on dual antiplatelet therapy at 12 months . still , these results are promising in the context of a recent meta - analyses where higher scaffold thrombosis rates ( mostly acute and subacute ) were reported for patients treated with polymeric brs compared with des . notably , in absorb cohort a and b , there was also no scaffold thrombosis except one iatrogenic scaffold thrombosis with subsequent myocardial infarction .
nevertheless , there are several factors indicating that dreams 2 g might have a reduced risk for thrombosis : 
 in 30 patients assessed up to 6 months and 11 up to 12 months , no intraluminal mass was detected by oct . at 6 months ,
no mal - apposed struts were present , because the scaffold struts were already embedded into the vessel wall .
furthermore , in the presence of nearly full absorption of the magnesium scaffold at 12 months , late acquired mal - apposition appears to be impossible .
this is important since recent observations found four very late scaffold thrombosis in 171 patients treated with a polymeric brs with a longer degradation time compared with dreams 2 g .
all of those were associated with scaffold discontinuity , mal - apposed , and/or uncovered scaffold struts potentially promoting thrombotic events.magnesium has a negatively charged surface promoting anti - thrombotic properties in vivo . however
, this advantage might be hypothetical as the scaffold has been shown to be covered and embedded in the vessel prior to the absorption of the drug  polymer coating.dreams 2 g is laser - polished , leading to a very smooth surface.while struts of absorbable scaffolds are thicker than des struts , the strut cross section of dreams 2 g is rectangular with rounded edges , which might result in better embedding into the vessel wall.dreams
2 g does not require stepwise inflation as required with polymeric scaffolds , which may result in better expansion and apposition.at 12 months , struts were not discernible by oct , but ivus showed strut - like remnants . in the case example of figure  4 , the white colour coding of the scaffold struts disappears over time demonstrating the absorption process .
, the biodegradation of magnesium occurs by means of anions and cations exchange , magnesium hydroxide is formed , and in a second step , magnesium hydroxide is converted to amorphous calcium phosphate .
hence , at 12 months , elution of magnesium from the metallic backbone is usually completed , and the strut areas are mostly filled by amorphous calcium phosphate with high water content , which is not discernible by oct but to some extent by ivus .
amorphous calcium phosphate should not be misinterpreted as calcification that is associated with an echo shadowing that was not documented behind the scaffold remnants in ivus . in 30 patients assessed up to 6 months and 11 up to 12 months ,
no mal - apposed struts were present , because the scaffold struts were already embedded into the vessel wall .
furthermore , in the presence of nearly full absorption of the magnesium scaffold at 12 months , late acquired mal - apposition appears to be impossible .
this is important since recent observations found four very late scaffold thrombosis in 171 patients treated with a polymeric brs with a longer degradation time compared with dreams 2 g .
all of those were associated with scaffold discontinuity , mal - apposed , and/or uncovered scaffold struts potentially promoting thrombotic events .
however , this advantage might be hypothetical as the scaffold has been shown to be covered and embedded in the vessel prior to the absorption of the drug  polymer coating .
while struts of absorbable scaffolds are thicker than des struts , the strut cross section of dreams 2 g is rectangular with rounded edges , which might result in better embedding into the vessel wall .
dreams 2 g does not require stepwise inflation as required with polymeric scaffolds , which may result in better expansion and apposition .
vasodilatation or vasoconstriction > 3% was already observed at 6 months , and continued to increase at 12 months . in general ,
angiographic , ivus , and oct parameters remained stable between 6 and 12 months , yet there was a small , but significant decrease in median minimal lumen area when serially measured by oct in 11 patients ( 0.25 mm , iqr : 0.64 to 0.09 , p = 0.032 ) .
given the very small number of patients included in the intracoronary imaging sub - study , these findings should be interpreted with caution .
since dreams 2 g was designed to provide a longer scaffolding time compared with dreams 1 g , it may be assumed that late lumen enlargement is postponed and unlikely to be seen as early as after 1 year .
additional longer - term follow - up evaluation is required to confirm luminal enlargement , as shown for other polymeric scaffolds or previous versions of the magnesium scaffold implanted in the progress and biosolve - i studies . as with most first - in - man trials , biosolve - ii was not randomized and
the clinical follow - up rate was high , but  attributed to the fact that it was voluntary per protocol  only a relatively small cohort was available for serial qca , ivus , and oct assessments .
the demographics of these patients were comparable to those of the overall study cohort , but nevertheless 
 the data were only powered for in - segment lll at 6 month , eventually , a bias is introduced as symptomatic patients may be more prone to agree to 12-month imaging assessments than asymptomatic patients , and12-month imaging assessments were not performed in all participating centres.a further limitation is that long - term data are pending to document lumen enlargement  as seen in biosolve - i at 3 years . finally , the favourable outcomes of biosolve - ii need to be confirmed in more complex patient and lesion scenarios .
the data were only powered for in - segment lll at 6 month , eventually , a bias is introduced as symptomatic patients may be more prone to agree to 12-month imaging assessments than asymptomatic patients , and 12-month imaging assessments were not performed in all participating centres .
as with most first - in - man trials , biosolve - ii was not randomized and included a limited population with simple lesions . consequently , comparisons with other devices have to be interpreted with caution .
the clinical follow - up rate was high , but  attributed to the fact that it was voluntary per protocol  only a relatively small cohort was available for serial qca , ivus , and oct assessments .
the demographics of these patients were comparable to those of the overall study cohort , but nevertheless 
 the data were only powered for in - segment lll at 6 month , eventually , a bias is introduced as symptomatic patients may be more prone to agree to 12-month imaging assessments than asymptomatic patients , and12-month imaging assessments were not performed in all participating centres.a further limitation is that long - term data are pending to document lumen enlargement  as seen in biosolve - i at 3 years . finally
, the favourable outcomes of biosolve - ii need to be confirmed in more complex patient and lesion scenarios .
the data were only powered for in - segment lll at 6 month , eventually , a bias is introduced as symptomatic patients may be more prone to agree to 12-month imaging assessments than asymptomatic patients , and 12-month imaging assessments were not performed in all participating centres .
this novel absorbable metal scaffold showed a sustained favourable safety profile up to 12 months and no increase in lll between 6 and 12 months in a subgroup of 42 patients .
these findings suggest that dreams 2 g can be considered as an alternative to current polymeric brs .
m.h . handled funding and supervision , conceived and designed the research , and drafted the manuscript .
the open access publication charges for this article was provided by biotronik ag , buelach , switzerland .
reports study grants and lecture fees from biotronik , abbott vascular , cardiac dimensions , medtronic , volcano , and lilly .
reports institutional research grants from biotronik , medtronic , boston scientific , and astrazeneca ; and personal fees from medtronic , boston scientific , and astra zeneca . w.w .
reports grants from abbott vascular , biotronik , and terumo ; and being a non - executive board member and shareholder of argonauts partners , celyad .
reports grants from biotronik ; and personal fees and non - financial support from abbott vascular , boston scientific , medtronic , and biotronik . e.e
s.t.l . reports institutional research grants from biotronik , medtronic , biosensors , bayer , and actelion ; and non - financial support from abbott vascular , orbus neich , alvimedica , philips , asahi intecc , and terumo . y.o .
reports personal fees from biotronik , medtronic , and abbott vascular ; grants and personal fees from astra zeneca and boston scientific ; and grants from the medicines company and edwards lifesciences .
 aimsmetal absorbable scaffolds constitute a conceptually attractive alternative to polymeric scaffolds . 
 promising 6-month outcomes of a second - generation drug - eluting absorbable metal scaffold ( dreams 2 g ) , consisting of an absorbable magnesium scaffold backbone , have been reported . 
 we assessed the 12-month safety and performance of this novel device.methods and resultsthe prospective , international , multi - centre , first - in - man biosolve - ii trial enrolled 123 patients with up to two de novo lesions with a reference diameter between 2.2 and 3.7 mm . 
 all patients were scheduled for angiographic follow - up at 6 months , and  if subjects consented  at 12 months . 
 dual antiplatelet therapy was recommended for 6 months . 
 quantitative coronary angiography ( qca ) parameters remained stable from 6 to 12 months [ paired data of 42 patients : in - segment late lumen loss 0.20  0.21 mm vs. 0.25  0.22 mm , p = 0.117 ,  0.05  0.21 mm ( 95% ci : 0.01;0.12 ) ; in - scaffold late lumen loss 0.37  0.25 mm vs. 0.39  0.27 mm , p = 0.446 ,  0.03  0.22 ( 95% ci : 0.04;0.10 ) , respectively ] . 
 intravascular ultrasound and optical coherence tomography findings corroborated the qca results . 
 target lesion failure occurred in four patients ( 3.4% ) , consisting of one death of unknown cause , one target - vessel myocardial infarction , and two clinically driven target lesion revascularization . 
 no additional event occurred beyond the 6-month follow - up . during the entire follow - up of 12 months 
 , none of the patients experienced a definite or probable scaffold thrombosis.conclusionthe novel drug - eluting metal absorbable scaffold dreams 2 g showed a continuous favourable safety profile up to 12 months and stable angiographic parameters between 6 and 12 months.clinicaltrials.gov identifiernct01960504 . 
ClinicalTrials.gov identifier
Introduction
Methods
Study design and population
Study device
Endpoints and definitions
Procedure
Statistical analysis
Role of the funding source
Results
Discussion
Limitations
Conclusion
Supplementary material
Authors contributions
Funding