Introduction

A milestone in modern medicine was the introduction in 1977 by Andreas Grüntzig of percutaneous coronary intervention (PCI; this term encompasses balloon angioplasty with and without stent implantation as well as other interventions such as atherectomy; the term “percutaneous transluminal coronary angioplasty” (PTCA) is now also referred to as “plain old balloon angioplasty” (POBA)). The first nonsteerable balloon catheters were stiff and had thick walls, so that initially only proximal stenoses could be reached. The balloons, which were made from noncompliant material, would burst at an inflation pressure of only 6 atm (600 kPa). Significant problems of sole PCI balloon angioplasty were the high rates of peri-interventional acute vessel occlusions, usually due to dissection, and restenosis. Another milestone in the further development of PCI was therefore the introduction of coronary stents in the mid-1980s. However, further improvements were required for the breakthrough of the methodology: intensified pharmacological platelet inhibition, high-pressure implantation, and, to reduce the rate of restenosis, the development of drug-eluting stents (DES).

With the steady improvement in catheter and stent materials, the optimization of steerable coronary guidewires, the increasing experience of the operators, and the development of evidence-based treatment strategies, PCI has developed into the primary therapy for coronary revascularization.

Even coronary lesions that are complex or difficult to access such as bifurcations and chronic total occlusions can be treated relatively safely and with a high success rate by PCI. The use of PCI has substantially broadened over time.

The current methodologies in the interventional treatment of stable coronary artery disease are presented below.

Indications/Contraindications

The extended technical possibilities, the clinical results, and the safety of coronary angioplasty continuously change the indications for PCI versus coronary artery bypass graft (CABG) surgery. The basis for both indications is overt or inducible ischemia in the area supplied by one or more coronary arteries that can be revascularized and preserved myocardial viability in that area. Prognostic and symptomatic indications are differentiated on this basis.

The following criteria are important when considering PCI:

Due to the various manifestations of CAD, the diverse presentations of individual patients, and the ongoing evaluation of different approaches, a specific outline of the use of the therapeutic options currently considered appropriate is beyond the scope of this book. The reader is referred to current guidelines and appropriate use criteria provided by appropriate professional bodies. Nevertheless, decisions have to be made on a case-by-case basis. The immediate technical feasibility is not the crucial factor, but rather the acute and long-term prospects of success of the revascularization method to maximize patient benefit.

A catheter shape should be selected that will achieve an ideally axial orientation between guiding catheter and coronary ostium and provide a good backup against the contralateral aortic wall.

Left coronary artery. For the left coronary artery a special extra support curve (EBU, etc.) is most often used. The classic Judkins shape can also be considered, especially for LAD interventions. A good projection for coronary interventions to evaluate the origins of the LAD and LCX from the left main stem is the 40 to 50° LAO projection with caudal angulation (so-called “spider view”).

If the main stem is short and a PCI of an LAD stenosis is planned, both engagement with the guidewire and subsequent advancement of the balloon are easier when a smaller Judkins curve (JL 3.5) is selected. The same is true if the LAD takes off from the stem at a steep angle.

For the LCX a Judkins 4 curve is usually suitable, which can be directed to the LCX origin by clockwise rotation.

Improved back-up for PCI of the LCX (distal stenosis, tortuous vessel) can be obtained in particular with the left Amplatz guiding catheter, which most often selectively engages the LCX ostium.

For main stems with small diameters that are partially or completely occluded by the guiding catheter (as indicated by ventricularization of the pressure curve after seating), all guiding catheters are also available with side holes.

Right coronary artery. For the RCA the Judkins right curve is most often selected. Back-up can be increased by using the right or left Amplatz catheter. For a “shepherd’s crook” configuration of the RCA the left Amplatz catheter or an internal mammary guiding catheter are suitable. Many operators always use guiding catheters with side holes for the RCA (occlusion of the ostium by the guiding catheter is frequently more pronounced than with the LCA, longer dwelling time in the vessel compared with coronary angiography, repeated contrast media injection, which can trigger ventricular fibrillation with forceful injection).

Balloon Catheter

Drug-eluting balloons (DEBs). Balloons can also be used to locally deliver antiproliferative drugs at the time of PCI. Paclitaxel-eluting balloons are a mainstay in the interventional treatment of in-stent restenoses or POBA of small vessels that do not appear suitable for stent implantation. Different products use different carrier substances to fix paclitaxel on the balloon then deliver it to the vessel wall during longer balloon inflations of > 60 seconds.

Hydrophilic iopromide and also urea and crystalline structures such as shellac have been used as a carrier for paclitaxel. The greatest experience is available for DEBs that use hydrophilic iopromide as carrier.

On-the-wire balloon catheters and perfusion catheters. On-the-wire balloon catheters and perfusion catheters are no longer of clinical relevance.

During stent implantation we do these maneuvers only after the stent has already been advanced to the coronary artery to prevent a possible loosening of the stent from the balloon.

Coronary Guidewires

The coronary stenosis is crossed with a steerable guidewire. The flexible, shapeable tip consists of a thin beveled guidewire end, which is covered with a fine spring coil of radiopaque material. Three different wire tips are distinguished:

1. Floppy: a soft, atraumatic tip

2. Intermediate: compared with floppy it has a somewhat firmer tip and is thus more steerable

3. Standard: a firm and thus more traumatic tip, but with good steerability

Guidewires have a length of 190 cm or 300 cm and are available in three sizes (0.010 in., 0.014 in., 0.018 in.). For the 190 cm-long wire, a 122 cm-long extension wire is available. Usually a 0.014-in. wire is used for routine PCI. Guidewires with hydrophilic or hydrophobic coating as well as polymer-coated tips are available for special indications.

Special wires are used to recanalize chronically occluded arteries; their characteristics will be discussed separately.

General Requirements Prior to Coronary Interventions

Surgical Standby

With the modern procedures of interventional cardiology the immediate standby of a cardiac surgeon during PCI is no longer required. Due to improved technique and the introduction of stents, the frequency of emergent CABG has decreased substantially (0.4 – 1 %). Coronary angioplasty without direct standby of a surgical team is generally safe and has become common clinical practice.

However, ultimately even a presumably “simple” coronary angioplasty can take an unexpected course that cannot be managed interventionally. Therefore, coronary angioplasties should in general be done in close cooperation with a cardiosurgical department at a highly experienced interventional center. Ideally, though not absolutely required, cardiac surgery should be in the same location as the catheterization laboratory. If not, then it should be within 30 minutes travel.

Preparation of the dilatation syringe: about half of the syringe is filled with a 1: 1 mixture of contrast medium and normal saline; the syringe should be purged of air.

Balloon/stent selection with size determination: the balloon/stent diameter should be matched as closely as possible to the diameter of an undiseased portion in the segment of the vessel to be dilated. Either this is done using quantitative coronary angiography (QCA), or the vessel diameter is estimated from a comparison with the size of the guiding catheter placed:

– 6F = 1.98 mm diameter

– 7F = 2.31 mm diameter

– 8F = 2.64 mm diameter

– 9F = 2.97 mm diameter

Preparation of the balloon catheter: flushing of the catheter lumen with normal saline; removal of all air from the balloon by aspiration with a 20 mL syringe filled with ~3 to 4 mL of the normal saline–contrast medium mixture.

Introduction of the coronary guidewire into the balloon catheter. The tip of the guidewire is preshaped to correspond to the vessel course and then pulled back into the tip of the balloon catheter.

Balloon catheter and guidewire are introduced together via the Y-connector into the guiding catheter and advanced until shortly before the coronary ostium.

With the aid of a torque tool, the guidewire is advanced under fluoroscopy without pressure by rotational movements across the stenosis into the periphery of the stenotic vessel.

Alternatively, the wire is placed first, and only then is the balloon threaded over it and advanced.

Subsequently, the balloon catheter is advanced to the stenosis via the guidewire, which is held in place. With the aid of markings on the balloon catheter, it is placed so that it covers the diseased, stenotic segment completely.

The balloon with or without stent is slowly inflated under fluoroscopy. Usually, at the beginning of the dilatation an indentation of the balloon due to the stenosis can be seen. In general, the balloon diameter is adjusted optically to the vessel diameter. The dilatation pressure is determined by the compliance of the individual balloon—depending on the manufacturer the normal diameter is usually achieved at 8 to 12 bar (higher pressures for balloons with premounted stents).

The lower the dilatation pressure and the slower the inflation, the lower the shear forces that act on the vessel wall during POBA.

ST-segment elevation

Ventricular tachyarrhythmias (from ventricular extra-systoles to ventricular tachycardia)

Higher-degree AV block

Drop in arterial blood pressure

The individual variability in the ischemic response is substantial and ultimately cannot be accurately predicted. Some patients can tolerate dilatations up to several minutes in duration without problems, whereas others have severe complaints after only 15 seconds. Independently of this, the standard duration for dilatations can vary considerably between centers (30 seconds to 2 minutes). We usually attempt to achieve a dilatation time of 1 minute with increasing balloon pressure and thus increasing balloon diameter. This is done assuming that a somewhat longer dilatation can achieve a larger residual lumen with a lower rate of dissections (with POBA). For dilatations with DEBs, the inflation time should be at least 60 seconds

If the patient tolerates only brief dilatations, then repeated dilatations are performed with sufficiently long pauses in between (1–2 minutes). During a second inflation, patients usually tolerate longer times as a result of ischemic preconditioning.

A large area is supplied by the coronary artery to be dilated (e. g., left coronary main stem, when there is a lot of “myocardium at risk”)

Impaired ventricular function

Contralateral akinesia

Stenosis in a vessel that supplies collateral circulation

The last open coronary artery

Verification after dilatation.

After the dilatation, repeat administration of up to 0.5 mg nitroglycerin IC

After completion of the dilatation the balloon catheter is withdrawn into the guiding catheter. The primary result is verified angiographically with the guidewire still in place. A residual stenosis of ≤ 20 % without significant dissection and maintained TIMI 3 flow is currently considered acceptable. Otherwise, a repeat PCI with stent implantation is performed after POBA, whereas a dilatation with a noncompliant balloon is done after coronary stenting to achieve a complete expansion.

The coronary guidewire remains in place until the final result has been achieved.

After a brief waiting period, final angiography is performed and the primary result is evaluated with the guidewire withdrawn.

If the result is good, the intervention is concluded. The puncture site is treated with a vascular closure device or, in the case of femoral access, the sheath may remain in place for later removal and compression. With radial access, the sheath is removed immediately and a pressure bandage is applied.

The patient is transferred for monitoring.

Procedure: Direct Stent Implantation

The aims of coronary stent-implantation are

To reduce the risk of severe dissections, and

To reduce the rate of restenosis

Owing to this and to advances in stent technology, “direct stent implantation,”—that is, stent implantation without prior dilatation—has developed into the primary therapeutic procedure at many centers. This approach renders a majority of interventions simpler, faster, and safer. Numerous studies indicate that not only cost but also the rate of restenosis can be reduced.

This approach in principle is not different from balloon angioplasty. However, the following special features should be considered:

Intervention with a 5F guiding catheter is possible for lesions with a “simple” morphology.

The profile is higher compared with a balloon and, therefore, the options are more limited for severe, calcified lesions.

Flexibility is less; therefore there is limited capability to cross highly angulated stenoses.

The rate of acute side branch occlusions is higher.

The exact placement of the stent is often difficult for subtotal stenoses with lack of antegrade contrast media flow.

Special care is needed with severely calcified lesions: If the lesion cannot be dilated even with pressures > 20 bar (2 MPa), an incompletely expanded stent remains in the coronary system.

The crossover rate to predilatation with a balloon is 5 to 10 %.

For the operator, coronary interventions are highly demanding in terms of both skill and patient care. Not only does continuous communication between the operator and the patient reduce the fear of the patient when more severe symptoms occur during the intervention, but also it ultimately facilitates the intervention if the patient is able to cooperate well. Furthermore, accurate descriptions of current symptoms are an important criterion for assessing success.

Documentation of the Intervention

Angiographic documentation. During coronary interventions usually only the affected coronary artery or lesion is imaged in two orthogonal planes. The following ate recorded:

Initial findings

Crucial parts of the examination (correct positioning of the wire, individual balloon inflations)

Complications

Final result (without wire)

Protocol. In the PCI protocol, the following data are documented:

Patient data

Clinical diagnosis: cardiac history in note form, current symptoms (CCS classification of angina), relevant prior interventions, and comorbidities

Angiographic diagnosis and indication: crucial findings of the coronary angiography and stenosis morphology according to AHA/ACC; ischemia and viability as assessed in functional tests

Materials: guiding catheter, balloon catheter, stent, guidewire

Vascular access

Fluoroscopy time, radiation dose

Duration of examination

Amount of contrast medium

Hemodynamics: usually aortic pressure

Course of the examination: detailed description of the angioplasty, including number of dilatations, duration of dilatation, dilatation pressure, equipment used (balloon, stent, protection system, etc.), ischemic reaction (ECG changes, symptoms, and hemodynamics), medication with dosage, lack or occurrence of complications, final result with quantification of the residual stenosis, and description of any dissection

Postprocedural care

Postprocedural Care

The following are appropriate for an uncomplicated course and good primary result:

ECG after completion of the PCI

A brief monitoring phase until the arterial sheath is removed (monitoring unit). Blood coagulation usually normalizes only after 4 to 6 hours (sheath removal if ACT < 150 seconds).

After stent implantation, if not already pretreated with clopidogrel: a loading dose of 600 mg orally

Pressure bandage and bed rest for 12 hours

Alternatively:

– Immediate removal of the sheath and primary vessel occlusion with a vascular occlusion device (e. g., Angio-Seal, Vasoseal, Starclose)

– Immediate removal of the sheath and pressure bandage for radial access

Regular monitoring of the circulation, the puncture site, and the pulse

The following are appropriate for high-risk patients such as those with angiographically visible thrombus, with suboptimal primary result (remaining dissection, residual stenosis > 30 %), or with acute coronary syndrome:

Repeat resting ECG immediately after completion of the PCI

Monitoring for additional 24 hours

Sheath removal after normalization of blood coagulation; pressure bandage and bed rest for up to 24 hours

Continuation of effective anticoagulation, for example, with heparin or low-molecular-weight heparin

If appropriate, a GP IIb/IIIa inhibitor IV for up to 48 hours

Nitroglycerin IV for 24 hours

Measurement of cardiac-specific biomarkers (creatine kinase MB, troponin) after 3 and after 12 to 24 hours

Problems Associated with PCI

Dissections

Dissections of the coronary artery occur in ~20 to 45 % of cases of balloon angioplasty. During PCI, the adventitia and media of the vessel are extended. However, the inelastic segments of the intima and the atherosclerotic plaque tear. With further extension the tear becomes larger both circumferentially as well as longitudinally, so that the plaque is partially lifted from the vessel wall.

Localized dissections with a small intimal tear are usually without sequelae, whereas extended dissections regularly result in abrupt vessel closure.

According to the National Heart, Lung, and Blood Institute (NHLBI) dissections are categorized into the following types:

Type A: minor radiolucencies within the coronary lumen during contrast injection without dye persistence (“haziness”)

Type B: parallel tracks or double lumen during contrast injection

Type C: persistent extraluminal contrast cap (partial detachment of the plaque)

Type D1: spiral filling defect with normal contrast flow (spiral dissection)

Type D2: spiral filling defect with delayed contrast flow