Goal : To deliver and adequately expand a stent, completely covering the target lesion.
10.1
When to stent?
Stenting (in most cases with drug-eluting stents [DES]) is performed in the vast majority of coronary lesions because stenting:
- 1.
Prevents vessel recoil and reduces the risk of acute closure, especially in lesions with dissection, rupture, and thrombus.
- 2.
Reduces the risk of restenosis.
Stenting should not be performed in the following scenarios:
- 1.
Poor antegrade flow (unless poor flow is caused by a dissection). Stenting in the setting of no reflow will worsen it.
- 2.
Inability to expand the target lesion with a balloon.
- 3.
High risk of compromising an important coronary branch that cannot be protected.
- 4.
Very small target vessel and target lesion [although 2.0 mm stents are currently available (Resolute Onyx, Medtronic) that could be used in some of those lesions].
Stenting should not be performed until after successful wiring of the lesion (as described in Chapter 8 : Wiring) and (in most cases) successful lesion preparation (as described in Chapter 9 : Lesion Preparation). Optimal distal wire position should be confirmed prior to stenting.
10.2
How to stent
Several of the stenting steps are similar to the balloon angioplasty steps, which are described in Chapter 9 : Lesion Preparation.
10.2.1. Step 1. Confirm that a guidewire is advanced through the target lesion and optimally positioned distally (Section 9.5.1).
10.2.2. Step 2. Confirm that the guide catheter is aspirated and flushed (Section 9.5.2).
10.2.3. Step 3. Select stent type and size.
10.2.3.1. Goal : To choose optimal stent type and size.
10.2.3.2. How ?
10.2.3.2.1. Stent type
DES vs. bare metal stents (BMS) : Newer generation drug-eluting stents are currently used in the vast majority of patients, due to better efficacy (less restenosis) and safety (stent thrombosis) as compared with bare metal stents with the exception of saphenous vein grafts, where DES and BMS have similar outcomes .
Stent implantation (DES or BMS) should be avoided if possible, if noncardiac surgery is needed within 6–12 months .
Stent brand : Thinner strut stents have higher deliverability, which is often achieved at the cost of lower visibility. Stent brand selection depends on the associated clinical studies results, the target lesion characteristics and local availability and cost.
10.2.3.2.2. Stent size
Stent diameter :
Stent diameter can be selected using coronary angiography and/or intravascular imaging ( Section 13.3.6, Section 13.4.4.2 ). Intravascular imaging significantly facilitates accurate stent size selection and can also confirm the adequacy of lesion preparation.
The stent diameter should match the distal reference vessel diameter (as assessed by angiography and/or intravascular imaging). Sizing stents based on the proximal vessel may result in distal vessel dissection or perforation, as the proximal vessel is usually larger than the distal vessel due to normal vessel tapering; it can also lead to side branch occlusion due to carina shift. After implantation, the proximal portion of the stent should be postdilated with a larger balloon to match the proximal reference vessel diameter [proximal optimization technique (POT), Section 16.1.10.1.3]. When the proximal vessel diameter is much larger than the distal vessel diameter (e.g., in left main lesions or in aneurysmal coronary vessels) it is important to know the limits of expansion of the various stents ( Fig. 10.1 ). Peripheral stents can be used in very large (≥6 mm) vessels.
When intravascular imaging is used for stent sizing, it can be based on distal reference vessel diameter, or if the media is visible, on media to media measurements (selected stent diameter should be 85% of media to media dimension) ( Section 13.1.2 ).
Stent length : the stent should be long enough to cover the entire target lesion, including coronary artery segments proximal or distal to the lesion that were injured with balloon angioplasty. Failure to cover the entire lesion/predilated segment is called “geographic miss” and increases the risk of restenosis. Long stents (40 mm in the United States and 60 mm in Europe) are currently available.
The desired stent length can be estimated angiographically by using a known length balloon to predilate the lesion. It can also be measured using intravascular imaging with automated pullback (IVUS or OCT).
Long stents can be challenging to deliver, especially through tortuous and calcified segments. In such lesions, delivering >1 shorter stents may be easier. Alternatively better lesion preparation, and increased guide catheter support can be used to facilitate delivery.
10.2.3.3. What can go wrong ?
Poor stent size selection may not result in complications until the time of stent delivery and deployment, as follows:
- 1.
Inability to deliver stent to the target lesion (see step 8).
- 2.
Perforation (if stent diameter is too big for the target vessel) (see step 13).
- 3.
Geographic miss (if stent is too short for the target lesion) (see step 13).
10.2.4. Step 4. Prepare stent balloon.
10.2.4.1. Goal : To remove the air from the stent balloon, fill the stent balloon lumen with a contrast solution, and connect to an indeflator.
10.2.4.2. How ?
- 1.
The stent is removed from its packaging.
- 2.
A luer-lock syringe is filled usually with 50% contrast/50% saline solution. Lower concentration of contrast will speed up the inflation/deflation of the balloon but will also decrease the stent balloon visibility.
- 3.
The syringe is connected with the stent balloon proximal hub.
- 4.
Suction is performed with the syringe positioned upside down to remove the air from the balloon.
- 5.
The stent balloon is connected with the indeflator.
- 6.
Many operators do NOT apply suction through the indeflator (to minimize the risk of stent dislodgement from the delivery balloon). However, with contemporary stents, the risk of dislodgement and stent loss is very low, and suction with the indeflator can usually be applied.
10.2.5. Step 5. Load the stent on the guidewire (Section 9.5.5).
10.2.6. Step 6. Advance the stent balloon monorail segment through the Y-connector (Section 9.5.6).
10.2.7. Step 7. Advance the stent to the tip of the guide catheter (Section 9.5.7).
10.2.8. Step 8. Advance the stent to the target lesion.
10.2.8.1. Goal : To advance the stent to target lesion.
10.2.8.2. How ?
- 1.
The stent is advanced toward the target lesion using the “independent-hand” or “two-hand” technique ( Fig. 9.5 ).
“Two-hand technique”. The left hand fixes the guidewire while the right hand pushes the balloon.
“Independent technique” (preferred): The right hand is holding the touhy, the stent balloon shaft and the guidewire. This frees the left hand that can push the guide catheter forward to increase the guide catheter support.
- 2.
The position of the stent is confirmed using X-ray landmarks (such as clips, previous stents, etc.) and/or contrast injection ( Fig. 10.2 ). Contrast injections should be minimized in patients with chronic kidney disease. Angiographic coregistration with intravascular imaging or physiology systems can be utilized to assist in optimal stent positioning.
Figure 10.2
Use of a surgical clip (panels A and B) as a landmark for balloon (panel C) and stent (panel D) positioning.
10.2.8.3. Challenges
- 10.2.8.3.1.
Failure to reach the lesion with the stent ( stent shaft is not long enough )
Causes:
- •
Very distal lesion location, especially in patients with prior coronary bypass grafts and lesions distal to bypass graft anastomoses.
- •
Prevention:
- •
Use short (or shortened) guide catheters when treating very distal coronary lesions.
- •
Use stents with the longest available shaft (Xience: 145 cm, Promus/Synergy: 144 cm, Resolute/Elunir/Orsiro: 140 cm).
- •
Use guide extensions that may allow safer deep intubation and better align the guide catheter.
- •
Treatment:
- •
Use short (or shortened) guide catheters when treating very distal coronary lesions.
- •
Use stents with the longest available shafts.
- •
- 10.2.8.3.2.
Failure to reach the lesion or cross the lesion with the stent
Causes:
- •
Proximal vessel: significant disease, tortuosity, and/or calcification.
- •
Severe lesion tortuosity.
- •
Severe lesion calcification.
- •
Tight lesion.
- •
Poor lesion preparation.
- •
Prevention:
- •
If there is proximal disease, treat the proximal vessel.
- •
Good lesion preparation.
- •
Treatment:
