What are the findings and implications of the Orbit 2 trial?

ORBIT II Trial: Orbital Atherectomy for Severely Calcified Coronary Lesions

Overview and Primary Findings

The ORBIT II trial demonstrated that orbital atherectomy using the Diamondback 360° Coronary Orbital Atherectomy System is a safe and effective strategy for treating de novo, severely calcified coronary lesions prior to stenting, with a 3-year MACE rate of 23.5%. 1

Trial Design and Population

• ORBIT II was a single-arm, prospective, multicenter trial that enrolled 443 patients at 49 U.S. sites 1
• All patients had de novo, severely calcified coronary lesions requiring treatment with orbital atherectomy before stent implantation 1
• Patients with chronic total occlusions were excluded from the trial 2
• The majority of subjects (88.2%) underwent PCI with drug-eluting stents after orbital atherectomy 1

Primary Endpoints and Results

Procedural Success

• The primary efficacy endpoint was procedural success: stent delivery with residual stenosis <50% without in-hospital MACE 1
• High procedural success rates were achieved even in complex lesions with ≥95% stenosis (94.5%) 2

Safety Outcomes

• The primary safety endpoint was 30-day MACE (composite of cardiac death, MI, and TVR) 1
• At 3 years, the overall cumulative MACE rate was 23.5%, including cardiac death (6.7%), MI (11.2%), and TVR (10.2%) 1
• The 3-year target lesion revascularization rate was 7.8% 1
• Severe angiographic complications occurred in 6.7% of patients 2

Subgroup Analyses Revealing Important Nuances

Impact of Stent Type

• Second-generation drug-eluting stents significantly outperformed bare metal stents, with 2-year target lesion revascularization rates of 5.0% versus 15.3% respectively 3
• First-generation DES also showed superior outcomes (6.3% TLR at 2 years) compared to BMS 3
• Higher diameter stenosis and use of BMS were independently associated with increased MACE and TVR at 2 years 3

Tight Subtotal Occlusions (≥95% Stenosis)

• Lesions with ≥95% stenosis had similar procedural success (94.5% vs. 88.3%, p=0.120) compared to less severe stenoses 2
• The 3-year MACE rates were comparable (27.1% vs. 22.5%, p=0.548) 2
• However, the TVR rate was significantly higher in the ≥95% stenosis group (19.1% vs. 7.5%, p=0.004), which is expected given the complexity of these lesions 2

Long Lesions (≥25-40 mm)

• Patients with long calcified lesions (≥25-40 mm) had higher 3-year MACE rates compared to shorter lesions (29.9% vs. 21.1%, p=0.055) 4
• The rate of MI was significantly higher in long lesions (17.0% vs. 9.0%, p=0.024), with most occurring in-hospital (13.6% vs. 7.0%, p=0.037) 4
• When using the contemporary SCAI definition of MI, there was no significant difference in MI rates between short and long lesion groups 4
• Cardiac death and TVR rates did not significantly differ between groups 4

Clinical Implications and Recommendations

When to Use Orbital Atherectomy

• Orbital atherectomy represents a reasonable revascularization strategy for patients with severely calcified coronary lesions that require lesion modification prior to stenting 1
• It is particularly effective for tight subtotal occlusions (≥95% stenosis) where traversing with traditional equipment may be challenging 2
• Long calcified lesions (≥25-40 mm) can be safely treated, though operators should anticipate higher in-hospital MI rates using older definitions 4

Stent Selection Strategy

• Always prioritize second-generation drug-eluting stents over bare metal stents following orbital atherectomy to minimize target lesion revascularization 3
• Avoid BMS unless there are compelling contraindications to DES, as BMS use independently predicts worse outcomes 3

Critical Pitfalls to Avoid

• Do not assume that severely calcified lesions with ≥95% stenosis are unsuitable for orbital atherectomy; procedural success rates remain high 2
• Do not use bare metal stents routinely after orbital atherectomy, as this significantly increases revascularization rates 3
• When treating long lesions (≥25-40 mm), anticipate higher periprocedural enzyme elevations, but recognize these do not translate to increased long-term mortality or cardiac death 4
• Recognize that the higher TVR rate in tight subtotal occlusions (≥95% stenosis) reflects lesion complexity rather than device failure 2

Comparison to Historical Controls

The 3-year outcomes from ORBIT II demonstrate a low rate of adverse ischemic events compared with historical controls for severely calcified lesions 1, establishing orbital atherectomy as a viable alternative to other lesion modification strategies like rotational atherectomy or focal force balloon angioplasty 4.