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The basics of percutaneous coronary interventions
Key points
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Percutaneous coronary intervention (PCI) procedures in today’s cath lab require assimilating numerous details regarding a patient’s clinical history, testing before catheterization with anatomic information provided from the diagnostic angiogram.
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PCI requires an understanding of anticoagulation therapy, guide catheters, guidewires, balloons, coronary physiology, and intravascular imaging procedures, before and after stent implantation.
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Appropriate selection of patients and coronary lesions for PCI, weighing the risk of complications against long-term clinical benefits remains the key to quality coronary interventional procedures.
Introduction
On September 16, 1977, Andreas Grüentzig performed the first human percutaneous transluminal coronary angioplasty (PTCA) in Zurich, Switzerland. Until then, coronary artery bypass surgery was the only alternative to medicine for the treatment of coronary artery disease (CAD). Since that time, PTCA has rapidly evolved into more sophisticated techniques involving predominantly stenting and other nonballoon devices and is now called percutaneous coronary intervention (PCI). PCI is a highly successful method of coronary revascularization with more than 1.5 million procedures done in the United States annually. Because of significant technical advances in treating chronic total occlusions (CTOs), mechanical left ventricular (LV) support, and novel atherectomy devices, to name just a few, PCI operators have taken on more complex patients and lesions than the initial PTCA substrate of discrete single- and double-vessel coronary stenoses. It is now routine to see many PCI centers treating cases of complex multivessel CAD, including significant left main stenosis. High-risk PCI, including the treatment of patients with depressed LV function, requires a Heart Team approach, much like that convened before many structural heart disease interventions.
PCI encompasses various mechanical approaches to addressing coronary stenoses, such as balloons, stents, cutters, lasers, grinders, aspirators, filters, and other tools. The term percutaneous transluminal coronary angioplasty or PTCA may be used when describing balloon catheter techniques and older studies related to use of the original balloon catheter first employed by Grüentzig. Percutaneous coronary and structural heart disease interventional techniques are commonly performed after diagnostic angiography for patients with ischemic and structural heart disease. Table 1.1 lists diagnostic and therapeutic interventional procedures performed in the catheterization laboratory.
Table 1.1
Diagnostic and Therapeutic Procedures in Cardiac Catheterization Laboratory
| Diagnostic Procedures | Therapeutic Procedures |
|---|---|
| Coronary angiography | Percutaneous coronary interventions (balloon, stents, rotoblator, etc.) |
| Ventriculography | Valvuloplasty, TAVR, mitral clip |
| Hemodynamics | ASD, PFO, PDA, VSD Shunt closure |
| Shunt detection | Thrombolysis, thromboaspiration |
| Aortic and peripheral angio | Coil embolization |
| Pulmonary angio | Pericardiocentesis, window |
| Coronary hemodynamics | |
| Endomyocardial biopsy |
Angio, Angiography; ASD , atrial septal defect; PDA , patent ductus arteriosus; PFO , patent foramen ovale; Rx , treatment, TAVR , transaortic valve replacement; VSD, ventricular septal defect.
This chapter, an expansion of the chapter from Kern’s Cardiac Catheterization Handbook, 7e (2019), will present the basic method and mechanisms of coronary angioplasty and stenting, as well as many of the fundamental techniques associated with the practice of interventional cardiology. An overview of the various devices of PCI used for specific applications is provided in Table 1.2 . The interventions used for peripheral vascular and structural heart disease will be discussed in their corresponding chapters herein.
Table 1.2
Niche Applications of Percutaneous Coronary Intervention Devices
| Lesion Type | Stent | CB | RA | Thr Asp | Special Devices |
|---|---|---|---|---|---|
| Type A | +++ | + | ± | − | − |
| Complex | ++ | ++ | ++ | − | Guideliners |
| Ostial | ++ | ++ | + | − | − |
| Diffuse | + | − | ++ | − | − |
| CTO | ++ | − | ± | − | Special equip a |
| Ca ++ | ± | ++ | +++ | − | (orbital ath, IV lithotripsy) |
| SVG focal | +++ | ± | ± | − | Filters, |
| SVG diffuse | + | ± | − | − | − |
| SVG thrombotic | ± | − | − | ++ | Filters, |
| Dissection | +++ | − | ± | ± | imaging catheters |
| Acute occlusion | ++ | − | − | ± | − |
| Thrombosis | + | − | − | +++ | − |
| Perforation | ± | − | − | − | Covered stent |
| Device embol | − | − | − | − | Snares, forceps |
+++, highly applicable; ++, somewhat helpful; +, applicable; ±, marginal depending on status; −, not applicable.
Ca ++ , Calcified; CB; cutting balloon; CTO , chronic total occlusion; embol , emboli; RA , rotational or orbital atherectomy; SVG , saphenous vein graft; Thr Asp , thrombus aspiration.
a Specialized equipment includes unique guidewires, balloons with reentry ports, and transport catheters for antegrade or retrograde access.
PCI overview
The technique of PCI is an extension of the basic methods used for diagnostic cardiac catheterization and coronary angiography. Obviously, one should master the basic techniques, concepts, and knowledge of diagnostic cardiac catheterization before moving into the specialty of interventional cardiology.
After the required clinical evaluation to establish an appropriate indication for revascularization, PCI is often performed either as a separate procedure or as an add-on, ad hoc procedure after the diagnostic study.
Fig. 1.1 shows how a stent is implanted during PCI. In brief, a guiding catheter is seated in the coronary ostium. A thin, steerable angioplasty guidewire is introduced through the guide catheter to the coronary artery, crossing the stenosis and positioned in the distal aspect of the artery. A balloon angioplasty catheter, which is considerably smaller than the guiding catheter, is inserted through the guiding catheter, tracking over the guidewire, and is then positioned, spanning the narrowed stenotic area. After correct positioning within the stenosis, the balloon catheter is inflated; repeat inflations are often required. The inflation and deflation of the balloon in the blocked artery restores blood flow to the deprived myocardium supplied by the stenosed artery. After balloon dilation, a stent is implanted in the same fashion as balloon dilation. Full stent deployment is should be confirmed with intravascular imaging (e.g., intravascular ultrasound [IVUS]). After successful stent implantation, patients may be discharged the same day or may need to stay overnight in the hospital to be discharged the following morning. Patients can usually resume their normal routine within days.
Decision points in the PCI procedure
For all catheterization procedures, but particularly PCI, the type of vascular access is one of the most important decisions. The techniques for the placement of an arterial sheath through the arm (radial, ulnar, or distal radial artery) or leg (femoral artery) are described in detail in Chapter 2 , Vascular Access. In contrast to diagnostic catheters, PCI requires larger lumen, specialized “guiding” catheters, and often larger vascular access sheaths. The risk of access site bleeding must be carefully considered for the individual patient. The bleeding risk for radial artery access is significantly lower than femoral access. Currently, the most common guide catheter and sheath size is 6F. Larger-sized (>7F) PCI equipment often requires femoral access.
After vascular access, the next decision is selecting an effective guide catheter that will remain well seated in the coronary ostium and support the passage of a balloon catheter and stent. The operator will then review the angiographic vessel anatomy and select an angioplasty guidewire and balloon dilation catheter. Both the guidewire and the guide catheter have specific characteristics to manage difficult guide support and negotiate vessel tortuosity and complex lesions.
The choice of an angioplasty balloon to dilate the target lesion is based on the diameter of the unaffected reference segment of the target vessel and the length of the stenosis. Specialized balloons to score or cut the lesion are available. Calcified lesions may require additional treatment with grinding burr catheters (called rotablation or rotational atherectomy or most recently, an intrvascular lithotripsy balloon system, Shockwave) before stent placement (see Chapter 6 ).
After the initial balloon dilation of the stenosis, the next decision is which stent to use. There are several manufacturers and types of stents but the most common are balloon expandable, thin metal mesh-like designs, which are selected based on characteristics of the stent as a scaffold, the type of drug coating, diameter of the artery, and length of the stenosis to be treated. The stent is positioned in the dilated stenosis and deployed by balloon inflation. Optimal stent implantation after high-pressure inflations with a noncompliant (NC) balloon is confirmed not only by angiographic images of the stent but also by specialized imaging catheters (intravascular ultra sound [IVUS] or optical coherence tomography [OCT]) to see appropriate vessel/stent matching and full stent strut expansion and apposition (contact without space against the wall), features required to give the best short- and long-term results (see Chapter 5 ).
The last decision point is the type of arterial hemostasis to be used after sheath removal. Radial artery access uses a pressure band. Femoral artery access hemostasis can be achieved with one of several different vascular closure devices. For uncomplicated PCI, same-day discharge is now routine. Decisions for timing of discharge depend on the clinical situation and potential of a late complication. The patient commonly returns to work shortly (<2 days) thereafter.
Indications, contraindications, and complications of PCI
The American Heart Association (AHA), American College of Cardiology (ACC), and Society for Cardiac Angiography and Interventions (SCAI) PCI Updated Guidelines of 2015 provide recommendations for the performance of PCI. Specific anatomic and clinical features for each patient should be considered for the likelihood of success; failure; and risk for complications, morbidity, mortality, and restenosis. Restenosis and incomplete revascularization must also be weighed against the outcome anticipated for coronary artery bypass grafting (CABG). The indications, contraindications, and complications of PCI are listed in Table 1.3 . There are no absolute contraindications to emergency life-saving interventions except for patient refusal and malfunctioning equipment. There are several anatomic factors that are associated with poor stent outcomes and may be considered relative contraindications. These include:
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Small coronary vessels of less than 2.5 mm
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Vessels with poor distal runoff or severe diffuse disease
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Vessels supplying poorly functional or nonfunctional myocardium
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Extensive and heavily calcified vessels
Table 1.3
Indications, Contraindications, and Complications of Percutaneous Coronary Intervention (PCI)
| Indications for PCI |
|
| Contraindications for PCI |
|
| Complications Associated With PCI |
|
Complex or high-risk PCI
Stenting for patients with complex and high-risk anatomy or clinical presentations should be carefully considered. Anatomic concerns include the following:
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Long lesions requiring more than one stent per lesion
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Small coronary artery reference vessel diameters (<2.5 mm)
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Significant thrombus at the lesion site
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Lesions in saphenous vein grafts, the left main artery, ostial locations, or bifurcated lesions
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Restenotic lesions
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Diffuse disease or poor outflow distal to the identified lesion
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Very tortuous vessels in the region of the obstruction or proximal to the lesion
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Complex CAD with significant impairment of LV function
It should be noted that some patients with contraindications may have no options regarding coronary revascularization, and PCI becomes their only alternative to failed medical therapy.
Complications of PCI
For more information, see Chapter 12 . For most elective procedures:
- 1.
Death (0.1%)
- 2.
Myocardial infarction (MI; 1%–3%)
- 3.
Emergency CABG (0.5%–2%)
Of course, any complications that can occur during diagnostic cardiac catheterizations can also occur during PCI, such as femoral access site bleeding, especially with larger sheaths and prolonged anticoagulation (1:250 patients), contrast-medium reactions, cerebral vascular accident, MI, and vascular injury (e.g., pseudoaneurysm of femoral artery, radial artery occlusion).
Restenosis is a biological effect that is not considered a complication but rather a clinical response to angioplasty. Restenosis occurs in 5% to 10% of cases with drug-eluting stents (DES), and 10% to 20% of cases with bare metal stents. Restenosis within the stent or at the edges of the stent occurs in approximately 10% of patients, even with DES, and may lead to recurrence of anginal symptoms. Typically, restenosis occurs most frequently within the initial 12 months after PCI.
Stent thrombosis is the abrupt formation of a blood clot inside the stent and is a potentially catastrophic event that can lead to MI or death. The incidence of stent thrombosis is 1% to 2%. It is more likely to occur if dual antiplatelet therapy (i.e., aspirin and clopidogrel or other P2Y12 platelet inhibitors) is prematurely discontinued or if the stent is suboptimally expanded.
PCI equipment
Every PCI starts with three basic pieces of equipment: a guiding catheter, a coronary guidewire, and a balloon/stent catheter system ( Fig. 1.2 ). Each piece of PCI equipment is designed to facilitate three major procedural challenges: (1) provide a stable platform (the guide catheter) from which the delivery of the guidewire and balloon/stent catheter can be accomplished; (2) navigate arteries and cross stenoses to deliver the balloon/stent system; (3) expand/implant the stent to the correct vessel size for all plaque types. A large variety of specialized guide catheters, accessories, and lesion modification tools are available to achieve the goal of opening a stenotic vessel. The technique of PCI requires the operator to control all three of the principal movable components (guide catheter, guidewire, and balloon/stent catheter system) simultaneously.
The guiding catheter
For more detail, see Chapter 4 .
A special large-lumen catheter is used to deliver and help guide the balloon catheter to the stenosis ( Fig. 1.3 ). Compared with a diagnostic catheter, a guiding catheter has a thinner wall and larger lumen, which allows contrast injections with the balloon catheter inside. A large catheter lumen is achieved at the expense of catheter wall thickness and thus may result in decreased catheter wall strength, increased catheter kinking, or less torque control. A guiding catheter is stiffer than a diagnostic catheter to provide support for advancing the balloon/stent catheters into the coronary artery. It responds differently to manipulation than a diagnostic catheter. Unlike diagnostic catheters, guiding catheters have relatively shorter, nontapered tips of softer material to decrease catheter-induced trauma.
Use of 6F (or, in some patients, 7F) guide catheters from the radial artery approach is now common practice for most routine PCI. Smaller (<5F) guide catheters may not permit adequate visualization with some stent systems. 7F or 8F guide catheters are used for complex procedures requiring larger PCI devices (e.g., rotoblator) or simultaneous positioning of two stents for treatment of bifurcation lesions. Guiding catheters come in many different shapes for both femoral and radial approaches to meet the need of the numerous anatomic variations encountered in daily practice.
Functions of the guiding catheter
The three major functions of a guiding catheter during PCI include balloon/stent catheter delivery, contrast injection, and pressure monitoring:
- 1.
Balloon/stent catheter delivery: The guiding catheter is the delivery device of the coronary guidewire, balloon catheter, or any other equipment needed for the coronary artery. If the guiding catheter is not seated properly in a coaxial manner, it may not be possible to advance the balloon/stent across the stenotic area. The guiding catheter “sits” in the coronary ostium (a technique called cannulation) and provides backup support or a “platform” to push the balloon/stent catheter across the stenosis. Several important terms are commonly used when referring to guiding catheters:
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Backing out: The guiding catheter moves out of the coronary ostium into the aortic root when pressure is applied to the balloon to cross the lesion. This is caused by an insufficient support position or a vessel or stenosis producing considerable resistance or friction to the balloon or stent movement.
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Deep seating: The guiding catheter moves deeply into the ostium or into the proximal portion of the coronary vessel. This maneuver increases backup support and is typically used as a last resort because of the increased risk for guiding catheter–induced dissection. A guide catheter extension (see later) obviates this maneuver and currently is the preferred approach.
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Coaxial alignment: Good backup support is best achieved when the catheter tip is aligned parallel (i.e., coaxial) to the axis of the ostial part of the left main coronary artery, right coronary artery (RCA), or bypass conduit. Coaxial alignment permits efficient transmission of the force needed to advance the balloon/stent across a stenosis. Alignment may require guide catheter repositioning or occasionally deep seating into the artery. A specialized guide-within-a-guide or guide extension catheter (e.g., guideliner, also called mother-and-child guides; Fig. 1.4 ) may be required for support in some difficult situations. Although safer than deep guide catheter intubation, use of the guide extension is associated with an increased chance of proximal vessel dissection.
-
- 2.
Contrast injection: The guiding catheter permits visualization of the target by contrast administration with or without the balloon catheter in place. Reliable visualization of the vessel and stenosis before, during, and after intervention is critical to correct positioning and to success of the balloon/stent systems. Good visualization may be particularly difficult when the lumen is occupied by the PCI devices inside. Large nonballoon PCI devices (e.g., rotoblators, thrombus aspiration catheters) in small guide catheters may not allow adequate contrast delivery and vessel visualization. This problem has been overcome with larger lumen catheters and contrast media power injectors.
- 3.
Pressure monitoring: The guiding catheter allows the operator to continually assess aortic pressure during the procedure, an essential monitor for patient safety (e.g., avoiding hypotension from vagal episode or ischemia because of guide catheter obstruction). Pressure wave damping may occur if the guide catheter blocks the coronary ostium; if there is noncoaxial seating; or if equipment, clot, or plaque obstructs flow through the coronary ostium. Guide catheter coronary occlusion is noted by the change in the arterial pressure waveform to one of “damping,” which shows a flattened diastolic portion or ventricular-like pattern ( Fig. 1.5 ). Guiding catheters with small side holes near the tip permit blood to enter the coronary artery when the ostium is blocked by the guide catheter and can reduce damping when the catheter is deeply seated and the tip is obstructing flow. Side holes are used when the guide catheter either partially or totally occludes blood flow into the coronary artery; however, side holes may lead to inadequate artery visualization from loss of contrast media exiting the catheter before entering the artery. Although side holes may provide reliable aortic pressure, coronary flow can still be compromised during the procedure. These catheters should be used with caution and are not suitable for hemodynamic lesion assessment (i.e., fractional flow reserve [FFR]) because of the creation of a pseudostenosis through the side holes (more detail found in Chapter 5 ).
Balloon catheter systems
There are two types of PCI balloon catheters: over-the-wire (OTW; Fig. 1.6 ) and monorail or rapid-exchange catheters ( Fig. 1.7 ).
OTW angioplasty balloon catheters
An OTW balloon/stent catheter has two lumens: one that runs the length of the catheter, ending in the balloon for inflation/deflation, and a second lumen that runs the entire length of the catheter and serves as the channel for the guidewire. These balloons are approximately 145 to 155 cm long and are designed to be used with guidewires of various dimensions (<0.014 in). The major advantage of OTW catheters is their ability to maintain distal artery access with the balloon beyond the lesion while exchanging one guidewire for another or using the distal lumen to give contrast or administer drugs (e.g., nitrates, thrombolytics, after the guidewire is removed, of course). The OTW system tracks very well because the whole balloon length has a wire in the lumen. Nevertheless, it requires long (300 cm) guidewire exchanges.
To exchange OTW catheters, the balloon is advanced over the wire to a distal position. Although a standard short (145 cm) wire can be used with an OTW balloon/stent, typically an exchange length guidewire (300 cm) is preferred. Guidewire extension devices or magnets can facilitate exchange of OTW balloons/stents if the operator prefers to use a short wire. OTW catheters can accept multiple guidewires, which allows for the exchange of additional devices that may require stronger, stiffer, or specialized guidewires.
The limitations of OTW systems include the slightly larger catheter diameter than the rapid-exchange (monorail) catheters and the need for additional personnel to help with long guidewire catheter exchanges.
Rapid-exchange (monorail) catheters
Rapid-exchange catheters, also called monorail catheters, were developed to permit the exchange of balloon catheters by a single operator. Rapid-exchange catheters have one long lumen to inflate the balloon and a short (30–40 cm) length of the distal catheter shaft, which contains two lumens. The second lumen holds the guidewire over which the catheter travels through the guide and into the vessel. Because only a limited portion of the catheter requires two lumens, rapid-exchange catheters are smaller in diameter than OTW balloon catheters.
Rapid-exchange balloon catheters obviate the need for long exchange wires to change OTW catheters and two operators to participate in the exchange (although one can certainly be used if the operator prefers). The smaller diameter monorail design may also have some advantage.
Limitations of monorail catheters include that it requires more care in manipulation of the guidewire, balloon/stent catheter, and guiding catheter. For example, if the monorail balloon is advanced beyond the distal end of the guidewire, the wire may come out of its short lumen, necessitating catheter withdrawal and reassembly of the balloon and guidewire. This is especially true when with catheters that have relatively short (<2 cm) “rail” segments (e.g., some IVUS catheter systems). Additionally, if the balloon catheter requires substantial force during advancement, a loop of guidewire may form outside the guide catheter in the aorta. This loop is nearly invisible but should be considered if the operator advances the catheter without seeing motion at the balloon tip.
Characteristics of balloon catheters
The plastic material of the balloon determines its compliance (defined as the amount of expansion or diameter size for a given amount of pressure), stiffness, and strength. Compliance is the main differentiating feature among balloon catheters. Inflation of a moderately compliant balloon above factory-determined mean inflation pressure (also called nominal pressure to achieve a known balloon size) will lead to approximately a 10% to 20% balloon size over the predicted diameter. NC balloons, on the other hand, remain very close to their rated diameter even when inflated several atmospheres above nominal pressure.
A compliant balloon may result in balloon oversizing, particularly after several high-pressure inflations, and possibly cause a dissection. After stent deployment, high-pressure inflations are routinely performed with NC balloons to assure that the stent struts firmly and completely into the vessel wall and fully expanded.
Operators should understand that there is balloon overinflation at balloon ends beyond the stent. According to Laplace’s law, wall stress increases with radius. Artery sites adjacent to the lesion may be traumatized by inflations at high pressures. When inflating a balloon above the rated burst pressure, consider limiting the number and duration of inflations.
Balloon diameters always increase with increasing pressure. Even NC balloons will grow in diameter (usually by <10% over nominal) with high pressure. Compliant balloons may increase by more than 20%. Table 1.4 lists the advantages and limitations of angioplasty balloon catheters.
Table 1.4
Advantages and Limitations of Angioplasty Balloon Catheters
| Advantages | Limitations | |
|---|---|---|
| Over the wire (OTW) | Distal wire position | Needs two people for exchanging balloon catheter/stent |
| Accepts multiple wires Distal port for pressure, contrast injection |
||
| Rapid exchange (monorail) | Ease of use, single-operator system | Needs good guide support |
| Enhanced visualization | Blood loss at Y valve during exchanges | |
| Unable to change wire |
Selection of balloon size (diameter and length)
In general, select a balloon size to achieve a less than 1 to 1 size match with the vessel so that some part of the lesion is visible for stent positioning (e.g., use of a 2.5-mm balloon in a 3.0-mm vessel so that a remnant of the lesion will mark the area for stent positioning). Balloon-to-artery ratios of more than 1.2 to 1 are associated with increased complications. Longer balloons (30–40 mm) are useful for dilating long and diffuse narrowings. Short (10–15 mm) balloons are used for stent expansion to avoid stretching the vessel wall outside the stent.
The balloon/stent size is determined using the distal arterial reference segment diameter compared with the size of the guiding catheter (conversion of 1 French = 0.33 mm; 6F x 0.33 = 1.98 mm or approximately 2 mm, which is useful as a gauge of artery diameter or distance on the angiogram). Visual estimation of artery diameter is less accurate than quantitative angiographic and intravascular imaging (IVUS or OCT) approaches, but it is the method used by nearly all interventionalists during the procedure. From IVUS studies, most stents selected by visual sizing are 0.5 mm smaller than true vessel dimensions.
Although some consider various technical features of stent systems, including device profile, ease of delivery, and restenosis and acute thrombosis rates, when making a decision, there appears to be only a small difference between different modern balloon and stent systems. Stent profile alone is not the only factor in facilitating a stent to cross a lesion. Resistance to balloon/stent catheter forward motion may also occur because of vessel tortuosity or calcification with the guidewire or friction within the guide catheter.
Balloon/stent inflation strategies
Stenosis resolution occurs when the balloon/stent pressure eliminates the balloon indentation caused by the stenosis (called the waist ). Unstable or thrombotic lesions are generally soft and are associated with a lower balloon inflation pressure than are chronic, stable, or calcific lesions. Because stenting is now routine, issues regarding optimal balloon inflation strategies (namely, inflation time or pressure) are relatively unimportant. Balloon inflations are generally brief (<60 sec) but should be inflated long enough to permit elastic tissue to relax and stretch and permit some stent metal to expand to its nominal diameter.
PCI guidewires
PCI guidewires are small-caliber (0.010–0.014 in), steerable wires advanced into the coronary artery branches over which the balloon/stent/device is tracked to address the lesion. The operator imparts a slight bend to the tip, which allows for steering across side branches and through tortuous artery curves.
Guidewires are made with an inner core wire and an outer spring tip. The shorter the distance between the end of the central core and the spring tip, the stiffer and more maneuverable the wire. Differences in core construction affect guidewire handling. Important considerations when selecting a guidewire include diameter, coating, torque control, flexibility, malleability, radio-opacity, and trackability. The most used coronary guidewires are 0.014 in, but a family of specialized guidewires and microcatheters (See Chapters 4 and 8 for further details) are available for crossing and treating CTOs.
Several guidewire characteristics should be considered in their selection. Stiffness of the guidewire determines specific performance. Soft wires may be easier to advance through tortuous artery branches. Stiff wires torque better and are often useful for crossing difficult or total chronic occlusions. Extrastiff guidewires provide better support for difficult stent placement in highly tortuous arteries. “Steerability,” “flexibility,” and “malleability” are terms used to differentiate various guidewires ( Table 1.5 ).
Table 1.5
General Categories of Guidewires
| Category | Use | Features | Example |
|---|---|---|---|
| Workhorse | First-line wire for majority of percutaneous coronary interventions (PCIs) | Safety, 1:1 torque, Good tip shape retention | HT Balance Middleweight Universal |
| Finesse | Tortuosity | Lubricity, moderate support | HT Pilot 50 |
| Extra-Support | Tortuosity, distal lesions | Soft gentle tip, High-level of support, Does not “spring back” | HT Iron Man |
| Specialty | Multiple | Depends on need | Sion |
Radio-opacity, marker bands, and special coatings
Visualization of the guidewire is improved by a radio-opaque coating usually applied only to the distal 3 cm of the wire. The limited radio-opaque segment permits lesion visualization without obscuring useful angiographic detail, such as small dissections. Calibrated radio-opaque marker bands on some wires are used to gauge lesion length.
Stent/balloon catheters usually have two markers, one at each end of the balloon. Small balloons (e.g., 1.5 mm in diameter) have one central marker. These markers may be confused for the markers on some marker guidewires.
A variety of different wire coatings increase ease of wire movement within the balloon catheter and artery. Some coated plastic-tipped wires, especially those with hydrophilic tips, have a higher likelihood of dissecting or perforating the arterial wall. With the emergence of the special approaches to CTO, families of specialized guidewires have been developed that increase procedure success (see Chapter 8 on CTO).
An exchange guidewire is like the standard wires previously mentioned except for its length (280–300 cm). This long wire replaces the initial 140-cm wire when an exchange of the OTW balloon catheter is necessary (e.g., upsizing balloon or insertion of stent). Alternatively, a 120- to 145-cm extension wire can be connected to a companion 145-cm guidewire, thus creating a long exchange guidewire to allow balloon catheter exchanges. Some regular-length guidewires can accept an extension wire and thus become an exchange wire.
Accessory equipment
See Fig. 1.8 .
Adjustable hemostatic rotating Y-connector valves
The Y-connector is attached to the guide catheter to permit introduction of PCI equipment into the guide while allowing contrast injection and pressure measurement through the guide catheter. The end of the Y-connector has a rotating hub and a valve. The valve minimizes back bleeding while the PCI catheter is inserted or removed from the guide catheter.
Balloon inflation devices
A disposable syringe device is used to inflate the PCI balloon. A pressure gauge or digital display indicates the precise inflation pressure in atmospheres (atm or torr) or pounds/square inch (psi). Typically, the balloon is inflated with sufficient pressure (4–12 atm) to fully expand the stenosis indentation (“dumbbell” or “waist”) of the partially inflated balloon. Occasionally, some calcified or highly fibrotic lesions require very high inflation pressures (>18 atm) to expand and eliminate the “dumbbell” appearance of the balloon.
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