1. BRS Summit – Scaffold Fractures
Stephen G. Ellis, MD
Section Head of Invasive/Interventional Cardiology
Professor of Medicine, Cleveland Clinic Lerner College of Medicine

2. Potential Conflicts of Interest
Research Support Abbott Vascular Consultant Abbott Vascular Boston Scientific Medtronic Stock Options/Royalties Keystone

3. BVS Strut Fracture
When is it normal to see a “strut fracture” after BVS implantation?
Proposed nomenclature
How often are we seeing abnormal strut fracture?
What are the clinical consequences?
How to avoid strut fracture

4. SGE; , 1

5. Classification of Stent Fractures
I II III IV V
I = single strut, II = 2 or more struts fracture without deformation, III = 2 or more struts fracture with deformation, IV = multiple fractures with acquired transection without gap, V = multiple fractures with acquired transections with gap
Nakazawa, JACC 2009
SGE; , 29

6. Impact of DES Fracture Associated with fracture 0 0 0 0 6 (67)* NA
Grade I
N = 10
Grade II
N = 14
Grade
III
N = 12
Grade IV
N = 6
Grade V
N = 9
Adverse
Pathologic
Findings
Fracture (-)
N = 121
Associated with fracture (67)* NA
Event rate, % 4 (40) 3 (21) 3 (25) 1(17) 7 (78)** 46 (37) Restenosis (11) 5 (4) Thrombosis 4 (40) 3 (21) 3 (25) 1(17) 6 (67) 42 (33)
*p< vs Grade I to IV, ** p = 0.03 vs fracture (-) group
Nakazawa, JACC 2009
SGE; , 33

7. Chakravarty et al., Am J Cardiol 2010;106:1075-80
SGE; , 38

8. Bioresorbable Vascular Scaffolds
Loss of Continuity
Basic design concept is rings joined by links
Ring
Link
Design decouples radial support and axial flexibility
Rings provide resistance to radial loads
Links provide flexibility to navigate tortuous paths and conformability to match vessel curvature
It is acceptable for links become discontinuous prior to rings, because they are not necessary for support
Images are on file at Abbott Vascular.
SGE; , 9

9. Strut Disruption or Discontinuity
Metallic DES
BRS
Detectable best by high
resolution cine OCT
Repeated flexing, stent overlap Overexpansion
Maintenance of strut continuity over time is a design requirement
Unintended event
Result of fatigue over time
Loss of strut continuity over time is a design requirement
Programmed and expected event
Result of fatigue and polymer degradation (≥3M)
SGE; , 4

10. OCT Findings and Definitions
Overlaid struts: – two struts that overlay each other in the same angular sector of the lumen perimeter
Overhung struts –overlaid struts without close contact
Stacked struts– overlaid struts with direct contact in at least 1 frame
Incomplete apposition (isolated, intraluminal) – struts with visible separation from the arterial wall

11. Cumulative Risk of 3.0 mm Scaffold Fracture Comparison of Cohort B to Absorb (final design)
SGE; , 14

12. ABSORB Cohort B Experience
SGE; , 13

13. QCAVessel Sizing of the Target Lesion ABSORB Cohort B Group 1 (L=52, N=45)
Dmax >3.3 mm: 9 lesions
Dmax: mm: 30 lesions
Dmax <2.5 mm: 13 lesions
Message: with limited scaffold sizes available, 20-25% of scaffolds were oversized, and 10% would have had to be overstretched to match reference diameter
Gomez-Lara J, et al, Eurointervention 2012; 8:
SGE; , 15 18

14. Case #1 78y male with recent onset angina, culprit lesion in the OM
Predilated with a 2.5 mm balloon
Implanted with 3.0 x 18 mm Absorb at 16 atm
Post-dilated with 3.25 mm NC balloon at 24 atm
Malapposition in proximal half of scaffold by OCT
Post-dilated with 3.5 mm compliant balloon at 16 atm
IVUS and OCT showed persistent strut malapposition
At 1 month, patient reported with confirmed ischemia and treated with 3.0 x 18 mm XIENCE V stent
Event free since
Ormiston J A et al. Circ Cardiovasc Interv. 2011;4:

15. Day 33 Ischemia Confirmed
RVD=3.26 mm
Dmax
Deployment with malapposition
Post-dil up to 3.96 mm. Overhung struts,
malapposed
Figure 4. Coronary angiography and OCT of a patient with scaffold pattern irregularity at post-implantation. Patient affected of a moderate lesion in the obtuse marginal. The interpolated-RVD was 3.26 mm (A) and the proximal and distal Dmax of the scaffolded segment (prior to the implantation) were 4.09 and 3.34 mm respectively (B). After the BVS implantation the OCT imaging showed severe malapposition of the scaffold (C); and the operator decided to post-dilate with a compliance balloon up to 3.96 mm of predicted diameter. A second OCT pullback showed scaffold pattern irregularities highly suggestive of fracture (D) that were untreated. At day 33, the patient presented with ischaemia and was re-catheterised (E). A new OCT (F) showed scaffold pattern irregularities with attached thrombi (arrow).
Day 33, patient with angina and dx ischemia. OCT shows overhung and stacked struts
Gomez-Lara J, et al, Eurointervention 2012; 8:
SGE; , 17 20

16. ABSORB Cohort B-1 Experience
TLR No
Clinical Event
Signs of scaffold resorption
Ormiston J, et al., CCI 2012; 5:
SGE; , 20

17. Acute Disruption, Case #2
2.5 mm BVS implanted in 2.4 mm ramus branch (A,B)
Followed by 3.0 NC post-dil at 24 ATM
Overhung struts are seen by OCT but not IVUS
Onuma et al. JACC2014;7:1406
SGE; , 7

18. Acute Disruption, Case #2
At 6 months w/o symptoms cath and IVUS
Look fine
But operator had difficulty crossing lesion
With OCT device
After rewiring, disrupted struts are seen (J)
Onuma et al. JACC2014;7:1406
SGE; , 8

19. Acute Disruption, Case #2
At 2 yrs patient remains asymptomatic. Angiogram looks good. OCT shows struts
Covered by neointima
Onuma et al. JACC2014;7:1406
SGE; , 9

20. Recommendations for Implantation 5 Ps for Optimal Implantation of Absorb
Prepare the Lesion
Properly Size the Vessel
Pay Attention to Expansion Limits
Post-Dilate with a Non-Compliant Balloon
Prescribing and maintaining DAPT therapy
SGE; , 21

21. #2 Properly Size the Vessel Vessel Sizing Technique Limitations
Angiography
(Visual Estimate)
Actual
Vessel Size
OCT
IVUS
QCA
3.0 mm
3.0 mm
3.1 mm
2.8 mm
2.7 – 3.3 mm
Most Accurate
Over-Estimates
Under-Estimates
Inter/Intra-Observer Variability
Margin of Error* 
Recognize the risk of under-estimating vessel size by visual estimation
*Margin of error estimates based on resolution for each imaging modality: Resolution of OCT and IVUS: Bezerra, H.G., J Am Coll Cardiol.: Cardiovasc Interv. 2009; 2: 1035.
Resolution of QCA: Dahm, J. and van Buuren, F. Int J Vasc Med
Offset and variability of visual estimate: data on file at Abbott Vascular.
SGE; , 27

22. #3 Pay Attention to Expansion Limits
Scaffold expansion limits are nominal scaffold diameter mm
It is important to stay within the expansion limits of the device
Nominal Scaffold
Diameter
Maximum Scaffold Expansion Limit
2.50 mm
+ 0.5 mm
3.00 mm
3.00 mm
+ 0.5 mm
3.50 mm
3.50 mm
+ 0.5 mm
4.00 mm
SGE; , 29 29

23. #3 Pay Attention to Expansion Limits Delivery Balloon Inflation
The delivery balloon can be safely inflated up to 16 atm – rated burst pressure (RBP) – without damaging the scaffold
Deploy the scaffold slowly by pressurizing the delivery system in 2 atm increments every 5 seconds, until the scaffold is completely expanded
Maintain target deployment pressure for 30 seconds
2.5 mm
3.0 mm
3.5 mm
Clinical Trial
Average
Deployment
Pressure*
*Average Absorb scaffold deployment balloon pressures from pooled ABSORB II and ABSORB EXTEND clinical trial data. Data on file at Abbott Vascular:
2.5 mm diameter Absorb scaffolds (n = 125) = atm
3.0 mm diameter Absorb scaffolds (n = 798) = atm
3.5 mm diameter Absorb scaffolds (n = 89) = atm
SGE; , 30

24. Conclusions Timing of the fracture/discontinuity is important:
Metallic – fracture unintended, not allowed
BRS – at deployment no fracture allowed, <3M link allowed, >6M both ring and link allowed by design
Nature of fracture are likely different
Clinical experience from Cohort B is insufficient to answer the question “Are the clinical consequences of a fracture in DES vs BRS the same?”