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J Invasive Cardiol. 2016 Oct;28(10):391-396.

Impact of Proximal Cap Ambiguity on Outcomes of Chronic Total Occlusion Percutaneous Coronary Intervention: Insights From a Multicenter US Registry.

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Dallas VA Medical Center (111A), 4500 South Lancaster Road, Dallas, TX 75216 USA.



We sought to determine the impact of proximal cap ambiguity on procedural techniques and outcomes for coronary chronic total occlusion (CTO) percutaneous coronary intervention (PCI).


We examined the clinical and angiographic characteristics and outcomes of 1021 CTO-PCIs performed between 2012 and 2015 at 11 United States centers.


Proximal cap ambiguity was present in 31% of target lesions and was associated with increased clinical and angiographic complexity (prior coronary artery bypass graft surgery: 43% vs 33%; P=.01; moderate/severe calcification 66% vs 51%; P<.001) and lower technical success (85% vs 93%; P<.001) and procedural success (84% vs 91%; P=.01), but similar incidence of major adverse cardiac events (3.2% vs 2.9%; P=.77). A retrograde approach was more commonly utilized among cases with proximal cap ambiguity (68% vs 33%; P<.001), and was more likely to be the initial (39% vs 13%; P<.001) and successful approach (42% vs 20%; P<.001). Proximal cap ambiguity was associated with increased use of intravascular ultrasound (49% vs 36%; P=.01) and contrast (281 mL vs 250 mL; P<.001), higher air kerma radiation dose (4.0 Gy vs 3.0 Gy; P<.001), and longer procedure time (161 min vs 119 min; P<.001).


Proximal cap ambiguity is present in one-third of CTO-PCI target lesions and is associated with lower success rates, higher utilization of the retrograde approach, and lower procedural efficiency, but no significant difference in the incidence of major adverse cardiac events.

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