| Lesion-Specific Characteristics
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| Type A lesions (minimally complex)
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| Discrete (length <10 mm)
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| Concentric
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| Readily accessible
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| Nonangulated segment (<45°)
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| Smooth contour
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| Little or no calcification
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| Less than totally occlusive
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| Not ostial in location
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| No major side branch involvement
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| Absence of thrombus
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| Type B lesions (moderately complex)∗
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| Tubular (length 10 to 20 mm)
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| Eccentric
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| Moderate tortuosity of proximal segment
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| Moderately angulated segment (>45°, <90°)
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| Irregular contour
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| Moderate or heavy calcification
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| Total occlusions <3 mo old
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| Ostial in location
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| Bifurcation lesions requiring double guide wires
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| Some thrombus present
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| Type C lesions (severely complex)
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| Diffuse (length >2 cm)
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| Excessive tortuosity of proximal segment
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| Extremely angulated segments >90°
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| Total occlusions >3 mo old and/or bridging collaterals
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| Inability to protect major side branches
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| Degenerated vein grafts with friable lesions
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- ∗ Although the risk of abrupt vessel closure may be moderately high with Type B lesions, the likelihood of a major complication may be low in certain instances such as in the dilation of total occlusions <3 mo old or when abundant collateral channels supply the distal vessel.
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