DYNAMITE (DYNAMx bioadaptor ImplanTation for the trEeatment of complex CAD) is an observational, prospective, single-arm cohort study including patients with CAD treated with implantation of the sirolimus-eluting DynamX bioadaptor system at a single center in Italy (IRCCS Humanitas Research Hospital, Rozzano, Italy) between September 2021 and August 2023 (NCT05464147, Figure 1 ). Follow-up clinical assessments were scheduled at 9, 12, and 24 months, and angiographic and optical coherence tomography (OCT) follow-up at 9 months. This study complied with the Declaration of Helsinki and was approved by the local ethics committee. All patients provided written informed consent for the procedure and subsequent data collection based on local institutional review board approval. The full list of inclusion and exclusion criteria is provided in Supplementary Table 1 . In brief, patients were included if presenting with complex CAD, defined as such in presence of one or more of the following criteria: (1) long lesions (>28 mm), (2) chronic total occlusion (CTO), that is, a total occlusion more than 3 months old, (3) bifurcation lesion, defined as a division with a side branch >2.25 mm, and (4) patients with CAD that would require implantation of 4 or more devices. Moderate or severe calcification was not an inclusion criterion but was recorded as a descriptive angiographic characteristic. Lesions had to be present in vessels with reference diameters of ≥2.25 and ≤4.0 mm. Patients with in-stent restenosis, lesions in saphenous vein grafts, and CTO with subintimal tracking >20 mm were excluded. Enrollment occurred if a subject satisfied any of the predefined inclusion criteria and met none of the exclusion criteria, after evidence of optimal lesion preparation as per standard practice, that is, a residual stenosis of <30%, and Thrombolysis In Myocardial Infarction flow of ≥2.

Study design. Flow diagram outlining patient enrollment, timing of optical coherence tomography and clinical follow-up.

The DynamX sirolimus-eluting coronary bioadaptor system is a novel coronary implant featuring a 71 μm cobalt-chromium platform composed of 3 helical sinusoidal strands connected axially by 3 S-links and 3 uncaging elements positioned at equal distances in low-stress regions of the struts. The device is circumferentially coated with a thin, conformal, bilayer biodegradable polymer similar to that used on previous platforms. Specifically, the outer poly-lactic-co-glycolic acid-based top coat releases sirolimus, present at approximately 7 μg per mm of device length, over 3 months. The inner base coat is a 6-μm poly-L-lactic-acid-based bioresorbable polymer resorbing over 6 months, which temporarily holds the uncaging elements and helical strands together. After bioresorption of the polymer base coat, the axial connections between rings are released, allowing the 3 cobalt-chromium helical strands to unlock and separate from each other, and leaving each helical strand embedded within the vessel wall to enable adaptive remodeling of the vessel. The DynamX bioadaptor received Conformité Européenne mark approval in September 2019.

Intravenous injection of 100 U/kg unfractionated heparin to maintain an activated clotting time of >250 seconds was administered during the procedure. Sirolimus-eluting coronary bioadaptor implantation (implanted in a similar manner to a traditional DES) was conducted as per DES implantation standards, with the only exception of avoiding overdilation of the stent to >1 mm above the nominal diameter of the bioadaptor implanted. The study device was available in diameters of 2.5, 3.0, and 3.5 mm and lengths of 14, 18, 28, and 38 mm. All patients received a loading dose of acetylsalicylic acid and a P2Y ₁₂ inhibitor preprocedure, followed by dual antiplatelet therapy, with a duration as suggested by current European guidelines. OCT was performed at the end of the index procedure and at 9-month follow-up. It was acquired by means of OPTIS imaging system and Dragonfly OPTIS imaging catheter (Abbott, Abbott Park, Illinois) with a nonocclusive technique according to a standardized method. ^, OCT assessment of bioadaptor implantation was performed on the basis of expert consensus. ^,, Imaging analyses were performed at an independent core laboratory (Cardiovascular Department, San Giovanni Addolorata Hospital, Rome, Italy) by experienced operators blinded to procedural data and clinical outcomes. Further information is provided in Supplementary Table 2 .

OCT follow-up was scheduled 9 months after the index procedure for each enrolled patient. Patients underwent clinical follow-up via inpatient/outpatient clinic visits or direct telephone contact 9, 12, and 24 months following the index procedure. The primary end point was the change in mean device area and mean in-device lumen area from postprocedure to 9 months, as measured by OCT. Mean device area was defined as the mean cross-sectional area of the bioadaptor across all analyzable frames. Mean in-device lumen area was defined as the mean cross-sectional lumen area within the device-treated segment, as traced by the luminal border, irrespective of strut apposition. Secondary end points included minimum and maximum bioadaptor diameter as measured by OCT, and incidence of major adverse cardiac events (MACE, a composite of cardiac death, myocardial infarction [MI], and clinically-driven target lesion revascularization [TLR]) and each of its single components at 9-month, 12-month, and 24-month follow-up. End points were defined according to the Academic Research Consortium-2 criteria.

Continuous variables were reported as mean ± standard deviation or median ± interquartile range, and pairwise comparisons between postprocedure and follow-up were performed by Student’s t test or the Wilcoxon signed-rank test in case of 2-group comparisons on the basis of normality of data distribution, verified using the Shapiro–Wilk test. Categorical variables were reported as numbers (percentages). Survival curves were constructed with the use of Kaplan–Meier estimates. Clinical follow-up was censored at the latest available follow-up. Data for patients lost to follow-up were censored at the time of the last contact. A 2-sided p value <0.05 was considered statistically significant. Statistical analyses were performed using Stata version 14.0 (StataCorp, College Station, Texas).

A total of 55 patients were enrolled. The mean age of the study population was 67 ± 10 years, and 4 females were included (7.3%). Sixteen patients (29%) had diabetes mellitus, of whom 8 (14%) were insulin-dependent. A history of previous PCI was reported in 27 patients (49%), previous coronary artery bypass grafting in 4 (7%), and previous MI in 14 (25%). Chronic kidney disease was present in 7 patients (13%), and the mean left ventricular ejection fraction was preserved at 55 ± 6%.

With respect to clinical presentation, most patients (85%) presented with chronic coronary syndrome, while 3 patients (5%) had unstable angina, and 5 patients (9%) were admitted with non-ST-segment elevation MI. No patients presented with ST-segment elevation MI at the time of the index procedure ( Table 1 ).

Lesions were most commonly located in the left anterior descending artery (53%), followed by the right coronary artery (36%) and the left circumflex artery (11%). All lesions were classified as American College of Cardiology/American Heart Association type B2/C (n = 55 [100%]). Moderate-to-severe angiographic calcification was observed in 64% of lesions. A total of 42 patients had a lesion >28 mm (76%), chronic total occlusions were present in 12 cases (22%, Figure 2 ), bifurcation lesions in 9 (16%), and 1 patient underwent implantation of 4 or more devices (2%). The mean SYNTAX (SYNergy between PCI with TAXus and cardiac surgery) score was 16 ± 8.

Right coronary artery chronic total occlusion (CTO) treated with DynamX bioadaptor implantation. A CTO in the mid-segment of the right coronary artery ( A ) treated with 3.0 × 38 mm DynamX bioadaptor implantation ( B ), followed by hig- pressure noncompliant balloon postdilation and kissing balloon inflation ( C ). An optimal angiographic result was evident at the end of the procedure ( D ), with a minimal stent area on optical coherence tomography of 4.86 mm ² ( E ). At 9-month follow-up, the minimal lumen area measured 5.50 mm ² ( F and G ). Of note, the minimal lumen area was found distal to the second acute marginal branch at follow-up, and positive vessel remodeling was evident at the site of postprocedural minimal stent area (top left inset of panel F ). The white arrowhead with light blue borders identifies the same (first) acute marginal branch at postprocedural and 9-month follow-up imaging. The white arrowhead with light green borders identifies the same (second) acute marginal branch at postprocedural and 9-month follow-up imaging.

Radial access was adopted in 53 patients (96%). Predilation was performed in nearly all cases (96%) using a mean balloon diameter of 3.0 ± 0.4 mm inflated to 17 ± 4 atm. Calcium-dedicated devices were used in 25% of lesions, including cutting balloon in 8 (14%), rotational atherectomy in 3 (5%), orbital atherectomy in 2 (4%), and intravascular lithotripsy in 1 (2%). The mean implanted device diameter was 3.2 ± 0.3 mm with an average length of 28 ± 7 mm. On average, 1.6 ± 0.8 devices were used per patient. Postdilation was performed in all cases (n = 55 [100%]) using a balloon diameter of 3.6 ± 0.5 mm at 19 ± 3 atm ( Table 2 ).

Postprocedural OCT and follow-up OCT at 9 months were available in 50 of 55 patients (91%). Mean device area increased from 8.15 ± 0.64 mm² postprocedure to 8.53 ± 1.71 mm² at 9 months (absolute difference: 0.37 ± 0.99 mm²; relative difference: 5.52 ± 14.8%, p = 0.010, Central Illustration ). Minimum device diameter increased from 3.04 [2.66–3.23] mm to 3.15 [2.88–3.32] mm (p < 0.001, Table 3 ), while maximum device diameter was 3.52 [3.21–3.72] mm at postprocedure and 3.57 [3.28–3.78] mm at 9-month follow-up (p = 0.771). The mean in-device lumen area decreased from 8.27 ± 1.78 mm² postprocedure to 7.57 ± 1.86 mm² at 9 months (absolute difference: −0.70 ± 1.09 mm²; relative difference: −7.98 ± 14.9%, p < 0.001). Minimum lumen diameter decreased from 3.04 [2.66–3.23] mm to 2.83 [2.54–3.00] mm (p < 0.001), and maximum lumen diameter changed from 3.60 [3.21–3.81] mm postprocedure to 3.40 [3.07–3.62] mm (p = 0.005). Intradevice tissue area increased from 0.04 [0.02–0.08] mm² postprocedure to 1.01 [0.80–1.25] mm² at 9 months (p < 0.001), that is 0.66 [0.25–1.22] % of device area to 12.7 [9.80–15.9] % (p < 0.001). Malapposition area decreased from 0.08 [0.02–0.29] mm² postprocedure to 0.00 [0.00–0.07] mm² at 9 months (p < 0.001), corresponding to a reduction from 1.02 [0.30–2.60] % to 0.01 [0.00–0.59] % of device area (p < 0.001). Postprocedural OCT and follow-up OCT measurements at the minimum lumen area site are reported in Supplementary Table 3 .

Table 3

Optical coherence tomography characteristics at postprocedure versus 9-month follow-up.

Characteristic	Postprocedure (n = 50)	9 months (n = 50)	p Value
Lumen area, mm 2	8.27 ± 1.78	7.57 ± 1.86	<0.001
Minimum lumen diameter, mm	3.03 [2.66– 3.20]	2.83 [2.54–3.00]	<0.001
Maximum lumen diameter, mm	3.60 [3.21– 3.81]	3.40 [3.07–3.62]	0.005
Device area, mm 2	8.15 ± 0.64	8.53 ± 1.71	0.010
Minimum device diameter, mm	3.04 [2.66–3.23]	3.15 [2.88–3.32]	<0.001
Maximum device diameter, mm	3.52 [3.21–3.72]	3.57 [3.28–3.78]	0.771
Intradevice tissue area, mm 2	0.04 [0.02–0.08]	1.01 [0.80–1.25]	<0.001
Intradevice tissue area, %	0.66 [0.25–1.22]	12.7 [9.80–15.9]	<0.001
Malapposition area, mm 2	0.08 [0.02–0.29]	0.00 [0.00–0.07]	<0.001
Malapposition area, %	1.02 [0.30–2.60]	0.01 [0.00–0.59]	<0.001

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