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Calcification
CTO Manual Online cases: 1 , 5 , 17 , 18 , 27 , 39 , 40 , 46 , 49 , 65 , 85 , 133 , 134 , 136 , 142 , 145 , 147 , 148 , 149 , 150
PCI Manual Online cases: 3 , 6 , 8 , 17 , 20 , 21 , 22 , 24 , 32 , 45 , 46 , 47 , 60 , 62 , 64 , 71 , 85
Severe calcification is usually defined angiographically as radioopacities noted without cardiac motion before contrast injection, involving both sides of the arterial wall. Moderate calcification is defined by densities involving <50% of the reference lesion diameter, often noted only during cardiac movement before contrast injection. However, coronary angiography underestimates the degree of calcification: in a study of 1,155 lesions, calcification was seen in 38% of lesions by angiography and in 73% via IVUS . Imaging with IVUS or OCT can also better quantify the arc of calcification. Greater than 270° arc of calcification is considered severe, 180°–270° arc is considered moderate, and less than 180° arc is considered mild.
Performing PCI of heavily calcified lesions can be challenging due to: (1) difficulty assessing lesion severity; (2) difficulty delivering equipment; (3) difficulty expanding the lesion and stent; and (4) increased risk of complications, both acute (such as dissection, perforation, and equipment loss or entrapment) and late (such as restenosis).
19.1
Planning
Knowing that the target lesion(s) are heavily calcified has important implications for procedural planning. Treatment of heavily calcified lesions can be facilitated by use of large guide catheters, techniques to increase guide catheter support, intravascular imaging, atherectomy, and other plaque modification strategies, such as intracoronary lithotripsy.
19.2
Monitoring
Monitoring is performed as described in Chapter 2 : Monitoring.
19.3
Medications
Standard medications (anticoagulation and antiplatelet therapy) are used for PCI of heavily calcified lesions, as described in Chapter 3 : Medications. PCI of calcified lesions may have long duration, hence anticoagulation should be carefully monitored.
If atherectomy is performed in the artery that supplies the AV node (usually the right coronary artery), bradycardia may occur. Aminophylline (250–300 mg intravenously over 10 min or 20–40 mg intracoronary injection ) may be used to prevent bradycardia. Aminophylline is an A1 adenosine receptor antagonist that blocks the effect of adenosine, which is released from red blood cells injured during atherectomy. Alternatively atropine (0.5–1.0 mg) can be administered intravenously prior to performing atherectomy.
Vasodilators, such as nicardipine (100–300 mcg intracoronary) or nitroprusside (100–300 mcg intracoronary) can also be used before atherectomy to facilitate passage of particles released during atherectomy through the microcirculation.
19.4
Access
Most calcified lesions can be successfully treated via radial access (ideally using 7 French low-profile sheaths or sheathless guide catheters), however femoral access can provide superior support that can facilitate treatment of particularly complex calcified lesions.
19.5
Engagement
Strong guide catheter support should be obtained when treating heavily calcified lesions. Consider utilizing large guide catheters (7 or 8 French) with supportive shapes (AL1 or 3D Right for the RCA and XB or EBU for the left main). Techniques to improve guide catheter support should be used early and coaxial guide catheter alignment should be maintained during atherectomy.
19.6
Angiography
Multiple views may be needed to assess heavily calcified lesions. Calcification can hinder angiographic interpretation, hence physiologic assessment and intracoronary imaging with IVUS or OCT are encouraged .
19.7
Selecting target lesion(s)
Selection of target lesion(s) is performed as discussed in Chapter 7 : Selecting Target Lesion(s).
19.8
Wiring
Wiring of calcified lesions is performed as discussed in Chapter 8 : Wiring. Use of microcatheters and hydrophilic or polymer-jacketed guidewires may be required for wiring heavily calcified lesions, especially if they are also tortuous. A microcatheter can also be used to exchange the initially used guidewire for an atherectomy wire. Alternatively, a microcatheter can be used to insert a support guidewire ( Section 30.7.4 ) that can facilitate equipment delivery across calcified and tortuous lesions.
19.9
Lesion preparation
Primary stenting should never be performed in heavily calcified lesions, as failure to completely dilate the lesion and expand the stent can result in stent underexpansion that increases the risk of restenosis and stent thrombosis ( Fig. 19.1 ).
Adequate lesion preparation can facilitate both equipment delivery and stent expansion, but carries risks in itself. The following options exist for treating severely calcified lesions ( Fig. 19.2 ):
- 1.
Balloon angioplasty (ideally using noncompliant balloons at high pressure, Chapter 9 : Lesion Preparation).
- 2.
Plaque modification balloons (Angiosculpt, Cutting balloon, Chocolate balloon, Section 30.9.3 ), although delivery can be challenging through heavily calcified lesions.
- 3.
Atherectomy (orbital and rotational; laser is not very effective in severely calcified lesions, but can be used, especially for treating underexpanded stents) ( Section 30.10 ).
- 4.
Novel treatments, not clinically available in the United States as of 2020: intravascular lithoptripsy ( Section 30.9.8 ) and the SIS OPN high-pressure balloon ( Section 30.9.7 ).
19.9.1
Balloon angioplasty versus atherectomy
The key question when performing PCI of severely calcified lesions is whether and when to perform coronary atherectomy in addition to balloon angioplasty.
There are two approaches: (1) upfront or primary atherectomy; and (2) “secondary” atherectomy if the target lesion fails to expand with balloon angioplasty (using standard or plaque modification balloons) ( Fig. 19.3 ).
The advantage of upfront atherectomy is better vessel preparation with lower likelihood of stent loss (which occurred in 2.5% of patients randomized to no rotational atherectomy in the ROTAXUS trial ) or stent underexpansion. The disadvantage of upfront atherectomy is the risk of complications and more time and cost. Initial balloon angioplasty may be faster but can lead to false impression of adequate vessel preparation and can cause dissections or perforations that may hinder performing atherectomy. In addition, stent delivery may still be difficult. In the PREPARE-CALC study that randomized severely calcified lesions to a plaque modification balloon or rotational atherectomy, cross-over from the plaque modification balloon group to rotational atherectomy was required in 16% . The ongoing 2,000 patient ECLIPSE trial is comparing both acute and long-term outcomes of balloon angioplasty versus orbital atherectomy.
Coronary atherectomy should be performed when the anticipated benefits exceed the potential risks.
The potential benefits of atherectomy are higher when treating severely calcified and long lesions. The presence of circumferential superficial calcification, obstructive nodular calcium, or thick calcium, as assessed by intravascular imaging, suggests high likelihood of needing atherectomy to modify the plaque and facilitate adequate stent expansion. OCT is particularly useful in determining the arc and depth of calcification ( Fig. 13.7 ).
The risks of atherectomy (dissection, embolization, perforation, equipment loss, or entrapment) increase with increasing tortuosity (relative contraindication) and in the setting of thrombus, dissections (relative contraindication), and bypass grafts. Atherectomy should generally not be performed in bypass grafts, although rare cases of heavily calcified old saphenous vein graft (SVG) lesions have been successfully treated with atherectomy after failure to expand the lesion with other techniques . Atherectomy is also usually avoided in dissected coronary segments, although it has been performed in this setting to treat chronic total occlusions and balloon undilatable lesions .
Intravascular imaging can assist with deciding about whether to perform atherectomy depending on arc of calcium, calcium thickness, and calcium length, as described in Section 13.3.6.2 , part C.
19.9.2
Orbital versus rotational atherectomy
( Fig. 19.4 )
- 1.
Orbital atherectomy should NOT be done within recently placed stents due to risk of entrapment, but has been successfully performed in stents that have endothelialized. Rotational atherectomy can be done in old stents, but has also been performed within stents placed immediately prior, after they failed to expand. Rotational atherectomy through recently placed stents carries risk of distal embolization, burr entrapment and stent distortion and should be followed in most cases by repeat stent implantation due to disruption of the previously placed stents. When performing rotational atherectomy in recently deployed stents higher speeds should be used to avoid burr and stent entrapment.
- 2.
Rotational atherectomy may be preferred for balloon uncrossable lesions due to its forward ablation (vs side ablation in orbital atherectomy) mechanism of action, although orbital atherectomy has also been successfully used in this setting.
- 3.
Orbital atherectomy may be preferred in larger vessels, as it can provide effective ablation with a single crown, whereas increasingly larger burrs may be needed when performing rotational atherectomy in large diameter vessels.
19.9.3
Balloon angioplasty for severely calcified lesions
Balloon type
Balloon angioplasty is reasonable in deep wall calcification, although superficial and nodular calcification is likely best treated with atherectomy. Balloon angioplasty can be performed with standard noncompliant or plaque modification balloons (Angiosculpt, Chocolate, cutting balloon). Plaque modification balloons facilitate lesion expansion, but are less deliverable than standard balloons. The decision on whether to start with a standard or a plaque modification balloon depends on the severity of calcification (with more severe calcification favoring upfront use of plaque modification balloons) and the likelihood of successful balloon delivery (lower for plaque modification balloons). In most cases, standard balloons are used first, followed by plaque modification balloons if standard balloons fail to expand the lesion. Noncompliant (NC) balloons are preferred over compliant balloons, as higher pressures can be achieved with lower risk of dissection or rupture, but NC balloons have a higher crossing profile and are less flexible which makes them harder to deliver. Balloon rupture leading to vessel dissection is more likely to happen in heavily calcified vessels, particularly with nodular calcification.
The efficacy of balloon inflation in expanding a calcified lesion may be enhanced by the following :
- 1.
High pressure (≥20 atm).
- 2.
Prolonged inflation time (1–2 min).
- 3.
Using one or more buddy wires that can score the vessel.
- 4.
Monitoring the inflation device pressure: decreasing pressure suggests that the lesion is expanding, hence longer balloon inflation is needed .
Cutting balloon
In contrast to Angiosculpt and Chocolate, the cutting balloon requires slow inflation and deflation (1 atm every 5 sec) to allow enough time for the blades to exit the balloon folds and rewrap .
What to observe ?
- 1.
Balloon expansion : the balloon (sized 1:1) needs to be fully expanded before stents are implanted to prevent stent underexpansion, which is much harder to treat than balloon undilatable de novo lesions.
- 2.
Balloon movement : after inflation the winged balloon can be advanced back and forth through the lesion to determine whether adequate lesion modification has been achieved or whether additional predilation is needed to facilitate subsequent stent delivery.
- 3.
Intravascular imaging: after balloon angioplasty circumferential superficial calcification will ideally have “cracked” in some sectors, which are identifiable on imaging. This provides the operator confidence that the stent will expand adequately.
What can go wrong ?
- 1.
Balloon rupture . Rapid loss of pressure suggests balloon rupture. The balloon should be immediately deflated and removed, followed by coronary angiography to determine whether balloon rupture caused vessel dissection, perforation, and/or no reflow. If perforation is confirmed, a new balloon is rapidly deployed proximal to the perforation to stop pericardial bleeding and facilitate subsequent treatment steps ( Chapter 26 : Perforation). Moreover, if the balloon had not been adequately prepared, there is a risk of air embolization ( Section 25.2.3.3 ).
- 2.
Vessel perforation . High-pressure balloon inflation can cause perforation, especially in heavily calcified lesions and with use of oversized balloons.
- 3.
Vessel dissection . Dissection is part of the mechanism of action of balloon angioplasty, however extensive dissections may compromise antegrade flow or result in side branch occlusion.
- 4.
Balloon entrapment , especially in cases of balloon rupture.
19.9.4
Preparation for atherectomy
Two key questions need to be answered before proceeding with atherectomy (orbital or rotational):
- 1.
Need for temporary pacemaker ( Fig. 19.5 )
A temporary pacemaker is not routinely needed for LAD and non-dominant circumflex artery PCI.
For RCA or dominant circumflex: can use temporary pacemaker, or aminophylline (250–300 mg IV over 10 min or 20–40 mg intracoronary bolus ), or do brief test runs to determine if the patient develops bradycardia. The advantage of the latter approach (not using pacemaker or aminophylline) is that atherectomy runs can be tailored (atherectomy stops when patient develops bradycardia) and there is no risk of right ventricular perforation from the temporary pacemaker lead. Orbital atherectomy may be less likely to cause bradycardia than rotational atherectomy.
Bigger burrs and longer runs are more likely to cause bradycardia, than smaller burrs and shorter runs.
- 2.
Need for hemodynamic support ?
Atherectomy may lead to complications, hence prophylactic hemodynamic support should be considered, especially in patients with poor baseline hemodynamics, low ejection fraction, large area of myocardium at risk, severe concomitant valve disease and severe pulmonary hypertension.
19.9.5
Rotational atherectomy
19.9.5.1
Step 1. Select burr size
There are multiple size burrs, ranging from 1.25 mm to 2.5 mm. Most times the 1.5 mm burr is preferred, as it may be less likely to get entrapped as compared with the 1.25 mm burr. Larger burrs (1.75 mm or larger) are infrequently used except for left main lesions, as the goal is to modify the vessel enough to allow balloon expansion rather than full calcium debulking. A burr to artery diameter ratio of 0.5 is usually selected. The minimum guide size required for each burr size is shown in Table 19.1 :
Table 19.1
Compatibility of various size Rotablator burrs with various guide sizes.
| Burr size | Guide size |
|---|---|
| 1.25–1.75 mm | ≥6 French |
| 2.0 mm | ≥7 French |
| 2.15–2.25 mm | ≥8 French |
19.9.5.2
Step 2. Engage the target vessel
-
Engagement is performed as described in Chapter 5 : Coronary and Graft Engagement.
-
Supportive guide catheters should be used, ensuring coaxial alignment. However, advancement of the Rotablator burr can be challenging through guide catheters with significant bends, such as Amplatz Left.
-
Avoid pressure dampening, as it will increase the likelihood of no-reflow or slow flow.
-
Ensure coaxial guide catheter orientation with the target vessel.
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