Chronic total occlusions
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Editors-In-Chief: Duane Pinto, M.D. Brian C. Bigelow, M.D. Joanna J. Wykrzykowska, M.D., Roger J. Laham, MD and C. Michael Gibson, M.S., M.D.
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Goals of Treatment
- Epicardial & myocardial reperfusion in acute total occlusion
- Improving anginal status: collaterals may maintain viability but collateral insufficiency may lead to anginal sx during times of increased myocardial demand
- Increase exercise capacity
- Reduce need for late bypass surgery
- Favorably impact ventricular remodeling
- Promote electrical stability in border/watershed zones
Patient selection
Contraindications to treatment:
- Small area of viability
- No clinical evidence of ischemia
- Low likelihood of procedural success based on angiographic predictors (failed intervention patients tend to have higher mortality but also higher procedural complication rate such as perforations and dissections)
Assessment of viability prior to procedures:
- Low dose Dobutamine echocardiography
- Delayed-enhancement cardiac magnetic resonance
- Thalium/Myoview PET scanning
Clincal predictors of success are very poor. Angiographic predictors of failure include:
- Vessel length > 15 mm
- Moderate to severe calcifications
- Undefined stump morphology
- Presence of bridging collaterals
- Tortuosity Side branch at the occlusion site
These predictors may be more clearly assessed with MDCT, especially occlusion length. This may aid in choosing retrograde approach via collaterals (CART and reverse CART technique) rather than the traditional antegrade approach.
Technique
- Choices for crossing lesion:
- Standard PTCA wire
- Fixed wire-balloon system
- Laserwire
- Ultrasound probe
- Rotational atherectomy
- Blunt dissection (Lumend Frontrunner)
- Choices for dilation of lesion:
- PTCA
- Atherectomy
- Stenting
- Lasers
- Advantages of Each Choice:
- Conventional guidewires usually sufficient to cross >90% of acute total occlusions
- There are a variety of wire properties to consider:
- Non-hydrophilic wires are a good first choice as they are less likely to lead to a subintimal position than a hydrophilic wire & may have additional advantages in crossing the proximal cap of the occlusion.
- Hydrophilic wires may track better after the proximal cap of the occlusion has been crossed.
- Stiffer wire tips will allow for a greater chance of crossing the proximal cap of the occlusion at the cost of an increased risk of vessel dissection or perforation.
- Tapered-tip wires are occasionally better at navigating into a smaller channel than on 0.014” wire.
- It is frequently necessary to use multiple wires to successfully navigate through a chronic total occlusion.
- Monorail systems inferior to over-the-wire systems in this setting, because of inferior balloon tracking & difficulty exchanging guidewires
- Fixed wire-balloon systems lack track ability & steer ability; over-the-wire systems usually favored. These systems may, however, occasionally be useful because their low profile may allow passage across small channels.
- Devices such as laser wires, vibrational energy, blunt dissection & ultrasound catheters used w/ variable success to recanalize chronic total occlusions resistant to standard wires
- Stent placement reduces restenosis, revascularization, & reocclusion rates
More tips
- Good guiding catheter support facilitates wire passage:
- for native arteries, left Amplatz guides are useful for the native right coronary system & extra backup (XB) guides are useful for the left coronary system in 7-8 Fr size
- Guides with side-wholes are usually very useful for the RCA
- Determine duration of occlusion:
- if duration of occlusion <3 mo, standard PTCA wires usually sufficient
- A non-hydrophilic wire with a medium-stiffness tip is a good first choice to interrogate a lesion with a progression to stiffer wires or hydrophilic wires at the operator’s discretion.
- The usual progression would be:
1. Non-hydrophilic wires with intermediate stiffness (Miracle 3 or Asahi ntermediate) 2. Intermediate stiffness hydrophilic wires: Choice PT XS, Pilot or PT Graphix 3. Stiff non-hydrophilic wires: Miracle 6, 9 and 12, Cross-IT, Confienza, Persuader 4. Stiff and hydrophilic (most aggressive): Pilot 200 and Shinobi
- Laserwires rarely used because they are limited to short lesions where distal vessel can be visualized via collaterals
- Ultrasound probes & vibrational angioplasty not often used for lesions resistant to standard guidewires
- Ball-tipped guidewires have not demonstrated clear superiority over conventional wires in observational & randomized trials.
- Blunt dissection may be considered if conventional wires fail to cross the occlusion.
- Debulking calcified or rigid lesions w/ rotational atherectomy can facilitate distal delivery of stents or PTCA balloons.
- If there is good collateral flow to the vessel distal to the stenosis, the use of two catheters for dual injections may be considered.
Advanced approaches to chronic total occlusions include
- Anchor balloon technique Mother-child catheter (5Fr within an 8 Fr guide)
- Parallel wire and seesaw wiring
- IVUS guidance to look for the true lumen Retrograde approach (especially in previous antegrade failures)
- Cotrolled antegrade and retrograde technique (CART)
Outcomes
- Anticipate >90% angiographic success rate if occlusion <3 mo
- Patients w/ total occlusions >3 mo have lower success rate of 70%, & higher acute closure rates
- 80% of failures due to inability to cross lesion; 15% due to inability for balloon to cross; 5% of lesions cannot be dilated adequately (>30% residual stenosis); calcifications are often a major obstacle to crossing the lesion
- Integration of several angiographic factors helps determine likelihood of success (see above); no single factor should preclude revascularization attempt
Long-term outcomes
- Most (70%) patients angina-free 1-4 y after successful PTCA
- Revascularization may prevent ventricular dilation & some studies suggest improvement in global ventricular function
- Successful PTCA reduces need for CABG by 50-75% but does not reduce total mortality or late MI
- Restenosis rates high (40-75%); stents reduce restenosis rates
Trouble-shooting
- Difficult guidewire rotation, difficulty advancing wire or balloon, or guidewire buckling may signify extraluminal position of wire
- Intraluminal position of crossing wire may be verified by distal injection through central lumen of PTCA balloon or distal injection (Ultrafuse) catheter
- If difficulty encountered crossing w/ standard PTCA wires, progressively stiffer wires w/ flexible tips may be used; alternatively, hydrophilic guidewires may be substituted
- If intraluminal guidewire position cannot be confirmed, balloon inflation should not be performed
- If balloon cannot be inserted all the way across lesion, an inflation in proximal part of lesion can be performed to favorably alter anatomy & potentially facilitate eventual crossing • Consider aborting procedure if, despite multiple attempts w/ various guidewires, lesion cannot be crossed or successfully dilated; risk of dissection or perforation may outweigh benefit