**2.5 Balloons and angioplasty**

Multiple balloons with different designs from multiple companies are available. Main important characteristics for balloons are: balloon diameter, length, compliance, rupture pressure, tip designs, crossing profile, shaft diameter and length. Standard diameter for coronary interventions starts from 1.2 mm and goes up. However, there are commercially available smaller balloons: nano-balloon 0.85 and 1 mm balloons (Sapphire Pro, Ikazuchi Zero, Ryurel). If necessary, even large diameter peripheral balloons can be used.

Selection of Balloons: after wiring the target vessel and lesion, balloon can be advanced and inflated to perform angioplasty. The goal of pre-dilatation of lesion is to prepare lesion for stenting and assess whether the lesion/plaque would response to balloon and stenting afterwards would have a good results or further plaque

modification is needed. Balloons are also used for post stenting optimization of stents size and assuring stent well apposition. Inflation should always be started at the target lesion and monitored under fluoroscopy.

atherosclerosis where the stent struts are not close to the lumen. Other instent restenosis mechanisms where the stent struts are close to the lumen, it is not

Withdrawing balloons should be performed after full deflation and confirmed

There are several stents from several medical companies with variable designs and engineering. Operator should be familiar with the basics of stent design, engineering, and generations. Stent design's topic is extensive, and reader is referred to

Similar to balloons: crossing profiles, stents design/generation, struts characteristics, stent drug, presence of polymer, sizes (diameter and length), clinical safety data and outcome all factors that affect operator choice of stent. Smallest stent diameter is 2 mm. Stenting vessel <2 mm size is not recommended as the value and long-term outcome is significantly questionable. However, balloon angioplasty of small vessels is recommended especially when these vessels supply a significant territory of the myocardium and when their occlusion cause significant symptoms or hemodynamic effect such as in cases of some septal perforators and right ventricular branch which could cause right ventricular infarction, shock and even death. These branches could shut down when jailed by stents and so it is recommended to avoid multiple layers of stents or stents overlap when jailing a branch vessel. In cases where multiple stents are needed in the main vessel, operator

should plan to avoid multiple layers of stents jailing the branch vessel.

In coronary world, all available stents are rapid exchange balloon expanded design. In rare cases, it is necessary to use a peripheral size or self-expandable stent such in very large coronaries >6 mm or in cases of complications like perforations in a large coronary. Balloon expandable stents are semi-compliant balloons that can expand by increasing inflation pressure but there a max stent size for each design. As in balloons, each stent has a table for inflation pressure and correlating diameter

The old and still active role is to use stent length that covers the lesion with both proximal and distal stent edges at normal segment of the coronary. This is the role that current evidence support. However, with rapid progress in coronary stents design, wide spread of stent use, and expansion of stent indications such in diabetic patients with diffuse coronary disease, this role might not be applicable anymore. Stent size topic is more complicated than balloon. The technical goal of stenting is to achieve a good coverage of the plaque, restore the vessel lumen, allow covering of struts with endothelium and prevent restenosis by using stent with strong radial force to prevent recoil and assuring well apposed struts. Operator should be knowledgeable of available stent sizes and design that allow them to expand beyond their original size by inflating the balloon beyond the design pressure or by post dilatation using larger balloon. For example: if an operator used a 3.0 mm stent that is designed to expand only to 3.5 mm and tried to expanded the stent to match the vessel size of 4 mm, that might be unsuccessful, cause struts fracture, significant recoil and restenosis. At the same time, using inappropriately large stent size, can cause edge dissection, perforation, rapid atherosclerosis at the edges due to inflammation and under expansion of the stent and restenosis. Stent size should be based on the size of reference vessel diameter RVD proximal and distal to the lesion to match the vessel size as close as possible. Operator can use several techniques to choose the appropriate stent size: using the balloon size used to prepare the lesion, compare vessel size to the guide catheter diameter, performing angiogram after

recommended to use cutting balloons.

*Coronary Artery Intervention Techniques DOI: http://dx.doi.org/10.5772/intechopen.93458*

**2.6 Stents**

dedicated stent chapter.

as part of their design.

**229**

re-wrapping of the balloon using fluoroscopy.

There are two general balloons designs: one over the wire and would require long wire and one referred to as rapid exchange which allows loading over the wire without long wire. Rapid exchange balloon is the first choice usually and considered the workhorse balloon design. Regular balloons have two radio-opaque markers at both ends. Smaller balloons ≤1.2 mm diameter and ≤ 8 mm have a single marker in the middle.

Balloon compliance: compliance is one of the most important factors to select the appropriate balloon. More compliance allows for more adoption to vessel morphology without damaging normal vessel. Compliant balloons can extend as much as it is inflated till they reach rupture pressure so they are limited by pressure range that can be used safely without rupture, whereas less compliant balloons can take high pressure and technically they are not supposed to expand beyond the size they are designed for (limited by diameter). Still, even noncompliant balloons can rupture if inflated beyond their rupture pressure. Operators develop experience and remember rupture pressure so they anticipate rupture based on the balloons and avoid it. Each balloon comes with instructions about inflation pressures and diameters and rupture pressure. Rupture should be avoided unless it is intentional (in some CTO techniques) as the rapid release in pressure can cause dissections, perforations, and air embolism. Risk of rupture increases with calcified tortuous severe lesions and using high inflation pressures. Operator can recognize rupture easily by feeling sudden drop in balloon pressure and can be seen on fluoroscopy. If balloon rupture occurs, negative pressure should be applied rapidly, and balloon should be withdrawn. Follow up angiogram and assessing for complication should be performed. Semi-compliant balloons are mostly used for pre-dilatation and preparation of the lesion.

Balloon length is determined mainly by the lesion length (should match). It is usually shorter than the final stent which covers the proximal and distal edge of the lesion. Shorter balloons can be considered for resistant lesions. For post stenting dilation, balloon length matches the stent length.

Balloon diameter: for pre-dilatation, balloon diameters are based on the target vessel. The role is 0.9–1.1 balloon to vessel ratio. However, there are multiple exceptions to the role. Resistance lesion does not allow using this role. Starting with small balloon and escalating diameter is necessary. This approach is also helpful to avoid complications in cases of total occlusion of the vessel and especially if vessel trajectory is not clear and suspicion of being in small branch.

Best balloons for pre-dilatation are balloons with the lowest crossing profiles: crossing profile has direct effect on a balloon's ability to cross the lesion. It is related to specific balloon design, balloon tip diameter in addition to diameter (balloon and shaft), and length. Shorter, smaller balloons have lower crossing profiles.

Plain Old Balloon Angioplasty POBA is still performed even with rapid development of stents. The indication for POBA is limited to recurrent instent restenosis in small vessel and especially in diabetic patient where the risk of restenosis is very high in case of adding additional layer of stent. In rare indication, pre op POBA is performed for severe stenosis to avoid stenting and the need for dual anti-platelets therapy.

Cutting or scoring balloons are noncompliant balloons surrounded by metal wires or microtomes that can help in preparation resistance calcified lesions. Several designs are available. In general, cutting balloons are available in limited sizes and lengths. They have high crossing profile which make their use challenging especially where they are needed the most. This makes their use not common and mainly indicated in ostial lesions. Some operators use it for resistant lesions not amendable to other adjunct lesion modifications and instent restenosis due to new

#### *Coronary Artery Intervention Techniques DOI: http://dx.doi.org/10.5772/intechopen.93458*

atherosclerosis where the stent struts are not close to the lumen. Other instent restenosis mechanisms where the stent struts are close to the lumen, it is not recommended to use cutting balloons.

Withdrawing balloons should be performed after full deflation and confirmed re-wrapping of the balloon using fluoroscopy.

### **2.6 Stents**

modification is needed. Balloons are also used for post stenting optimization of stents size and assuring stent well apposition. Inflation should always be started at

There are two general balloons designs: one over the wire and would require long wire and one referred to as rapid exchange which allows loading over the wire without long wire. Rapid exchange balloon is the first choice usually and considered the workhorse balloon design. Regular balloons have two radio-opaque markers at both ends. Smaller balloons ≤1.2 mm diameter and ≤ 8 mm have a single marker in

*Cardiac Diseases - Novel Aspects of Cardiac Risk, Cardiorenal Pathology and Cardiac Interventions*

Balloon compliance: compliance is one of the most important factors to select the appropriate balloon. More compliance allows for more adoption to vessel morphology without damaging normal vessel. Compliant balloons can extend as much as it is inflated till they reach rupture pressure so they are limited by pressure range that can be used safely without rupture, whereas less compliant balloons can take high pressure and technically they are not supposed to expand beyond the size they are designed for (limited by diameter). Still, even noncompliant balloons can rupture if inflated beyond their rupture pressure. Operators develop experience and remember rupture pressure so they anticipate rupture based on the balloons and avoid it. Each balloon comes with instructions about inflation pressures and diameters and rupture pressure. Rupture should be avoided unless it is intentional (in some CTO techniques) as the rapid release in pressure can cause dissections, perforations, and air embolism. Risk of rupture increases with calcified tortuous severe lesions and using high inflation pressures. Operator can recognize rupture easily by feeling sudden drop in balloon pressure and can be seen on fluoroscopy. If balloon rupture occurs, negative pressure should be applied rapidly, and balloon should be withdrawn. Follow up angiogram and assessing for complication should be performed. Semi-compliant

balloons are mostly used for pre-dilatation and preparation of the lesion.

dilation, balloon length matches the stent length.

trajectory is not clear and suspicion of being in small branch.

Balloon length is determined mainly by the lesion length (should match). It is usually shorter than the final stent which covers the proximal and distal edge of the lesion. Shorter balloons can be considered for resistant lesions. For post stenting

Balloon diameter: for pre-dilatation, balloon diameters are based on the target vessel. The role is 0.9–1.1 balloon to vessel ratio. However, there are multiple exceptions to the role. Resistance lesion does not allow using this role. Starting with small balloon and escalating diameter is necessary. This approach is also helpful to avoid complications in cases of total occlusion of the vessel and especially if vessel

Best balloons for pre-dilatation are balloons with the lowest crossing profiles: crossing profile has direct effect on a balloon's ability to cross the lesion. It is related to specific balloon design, balloon tip diameter in addition to diameter (balloon and

Plain Old Balloon Angioplasty POBA is still performed even with rapid development of stents. The indication for POBA is limited to recurrent instent restenosis in small vessel and especially in diabetic patient where the risk of restenosis is very high in case of adding additional layer of stent. In rare indication, pre op POBA is performed for severe stenosis to avoid stenting and the need for dual anti-platelets therapy.

Cutting or scoring balloons are noncompliant balloons surrounded by metal wires or microtomes that can help in preparation resistance calcified lesions. Several designs are available. In general, cutting balloons are available in limited sizes and lengths. They have high crossing profile which make their use challenging especially where they are needed the most. This makes their use not common and mainly indicated in ostial lesions. Some operators use it for resistant lesions not amendable

shaft), and length. Shorter, smaller balloons have lower crossing profiles.

to other adjunct lesion modifications and instent restenosis due to new

the target lesion and monitored under fluoroscopy.

the middle.

**228**

There are several stents from several medical companies with variable designs and engineering. Operator should be familiar with the basics of stent design, engineering, and generations. Stent design's topic is extensive, and reader is referred to dedicated stent chapter.

Similar to balloons: crossing profiles, stents design/generation, struts characteristics, stent drug, presence of polymer, sizes (diameter and length), clinical safety data and outcome all factors that affect operator choice of stent. Smallest stent diameter is 2 mm. Stenting vessel <2 mm size is not recommended as the value and long-term outcome is significantly questionable. However, balloon angioplasty of small vessels is recommended especially when these vessels supply a significant territory of the myocardium and when their occlusion cause significant symptoms or hemodynamic effect such as in cases of some septal perforators and right ventricular branch which could cause right ventricular infarction, shock and even death. These branches could shut down when jailed by stents and so it is recommended to avoid multiple layers of stents or stents overlap when jailing a branch vessel. In cases where multiple stents are needed in the main vessel, operator should plan to avoid multiple layers of stents jailing the branch vessel.

In coronary world, all available stents are rapid exchange balloon expanded design. In rare cases, it is necessary to use a peripheral size or self-expandable stent such in very large coronaries >6 mm or in cases of complications like perforations in a large coronary. Balloon expandable stents are semi-compliant balloons that can expand by increasing inflation pressure but there a max stent size for each design. As in balloons, each stent has a table for inflation pressure and correlating diameter as part of their design.

The old and still active role is to use stent length that covers the lesion with both proximal and distal stent edges at normal segment of the coronary. This is the role that current evidence support. However, with rapid progress in coronary stents design, wide spread of stent use, and expansion of stent indications such in diabetic patients with diffuse coronary disease, this role might not be applicable anymore.

Stent size topic is more complicated than balloon. The technical goal of stenting is to achieve a good coverage of the plaque, restore the vessel lumen, allow covering of struts with endothelium and prevent restenosis by using stent with strong radial force to prevent recoil and assuring well apposed struts. Operator should be knowledgeable of available stent sizes and design that allow them to expand beyond their original size by inflating the balloon beyond the design pressure or by post dilatation using larger balloon. For example: if an operator used a 3.0 mm stent that is designed to expand only to 3.5 mm and tried to expanded the stent to match the vessel size of 4 mm, that might be unsuccessful, cause struts fracture, significant recoil and restenosis. At the same time, using inappropriately large stent size, can cause edge dissection, perforation, rapid atherosclerosis at the edges due to inflammation and under expansion of the stent and restenosis. Stent size should be based on the size of reference vessel diameter RVD proximal and distal to the lesion to match the vessel size as close as possible. Operator can use several techniques to choose the appropriate stent size: using the balloon size used to prepare the lesion, compare vessel size to the guide catheter diameter, performing angiogram after

lesion preparation and intra-coronary Nitroglycerin, fluoroscopy based quantitative measurement and using intravascular imaging (IVUS or OCT).

slowly toward till the tip of the wire engage the target vessel. This technique is helpful to wire a jailed branch vessel and assuring the wire is not between stent

First step to recognize if the difficulty is related to the lesion itself or difficulty

Use a wire with strong shaft (Grandslam, ironman, mailman) that provide more support. If not able to deliver such wire, use special wire that can navigate tortuous vessels (Suoh, Sion blue or Black, Samurai) and exchange for stiffer

Use a guide extension: guide extensions should be advanced carefully over a balloon or stent using balloon-assisted tracking technique to avoid vessel injury especially at vessel bends. Guide extension shaft is to one side (not centered like balloons or stents) and their lumen is on the other side which make them biased to one side and that's the reason the tip can damage the intima and cause dissection while advancing them. Guide extensions will cause pressure dampening and can increase ischemia as they get advanced within the coronary. Operator should avoid advancing them to a target vessel smaller than the size of guide extension to avoid vessel injury. Contrast injection with

Using anchor balloon. A small compliant balloon in a proximal branch is usually

Grenadoplasty: intentionally inflating small balloon to rupture which could

Wire cutting technique: using two wires across the lesion, passing small balloon over one wire, and performing tugging and pushing on the balloon or the other

Use lesion modification techniques such as atherectomy, LASER, Intra vascular

Administration of Rota glide/Viper glide while advancing the stent toward the

Aorto-ostial lesions (RCA, left main, and bypass grafts) can be challenging for

More aggressive techniques involve sub-intimal access to perform external

Combination of above techniques is needed in difficult cases.

and vessel wall (under stent).

*Coronary Artery Intervention Techniques DOI: http://dx.doi.org/10.5772/intechopen.93458*

Use a buddy wire technique.

Deep guide intubation.

Use glide balloon.

used to provide support.

affect the lesion integrity.

lithotripsy, brachytherapy.

crush or distal anchoring.

**3.3 Difficulty with stent delivery**

lesion.

several reasons:

**231**

**4.1 Aorto-ostial lesions**

In addition to techniques above: Use shorter stent with smaller struts.

**4. Special challenging cases of PCIs**

*If the* difficulty *is more related to the lesion itself:* Use simultaneous two small balloons inflations.

wire that can act as a saw cutting the lesion.

**3.2 Difficulty delivering balloons and stents**

due to the target vessel (severe tortuosity or calcifications)

wire using over the wire balloon or micro-catheter.

high pressure through a guide extension can cause dissection.

To assure good results, operator can use stent imaging enhancement technology (Available on Phillips Fluoroscopy system) and intravascular imaging. Most operators use post dilatation with balloon to achieve good angiographic results. This step has been shown to improve angiographic results. Clinically, the benefit and long-term outcome of this step is a complex question to answer as it has multiple variables and cofounders. It is related to the clinical presentation acute myocardial infarction vs. stable angina, type of lesion and stent generation. Best data support this step for bare metal stents and first-generation drug eluting stents. For second and third generation DES, the data are controversial [11–13]. Significant evidence supports this step [14]. However, some question it as it might lead to microvascular injury or distal embolization in the setting of acute myocardial infarction. It is best to make individual decision to perform post dilatation in acute myocardial infarction cases.

Operator should minimize the number of stents used by using single stent and avoid stents overlap. This can be challenging in long lesions with significant discrepancy between proximal and distal vessel size or in challenging distal lesion in tortuous vessel. Using shorter and multiple stents might be required if other techniques for increasing support for delivery are not successful.

Stent restenosis is related to target vessel size (smaller have higher risk), stent length (longer higher risk), small diameter stents, undersized stent, stent drug type and body response (inflammation), ostial lesions, venous grafts lesions especially distal anastomosis to target vessel, presence of diabetes mellitus and calcifications. Appropriate oversizing might have beneficial results and reduce target lesion revascularization.

Stents thrombosis risk increases with premature stopping of anti-platelets therapy, stents overlap, bifurcation lesions, stent edge dissection, stent's struts malapposition, time from implantation, poor distal flow post intervention, presence of diabetes mellitus and chronic kidney disease, reduced left ventricular systolic function. There are some data to subject larger vessel and especially RCA has more risk of thrombosis.
