Abstract:
This Chapter provides an overview of diagnostic and interventional procedures performed in the cardiac catheterization laboratory. It provides a step-by-step description of percutaneous coronary intervention procedures, hemodynamic assessment of stenosis severity and advanced coronary imaging. Commonly used coronary equipment and pharmacology are also discussed.
An introduction to interventional techniques used to diagnose and treat peripheral arterial, valvular and other structural heart diseases is also presented.
Keywords:
angioplasty, stent, valvuloplasty, closure, complication
Percutaneous coronary and structural heart disease interventional techniques are commonly performed after diagnostic angiography for patients with ischemic and structural (e.g., valvular or atrial septal defects [ASDs]) heart disease. The Interventional Cardiac Catheterization Handbook, a companion book to this volume, expands on the concepts presented in this chapter and provides a more detailed foundation for indications, contraindications, and complications of interventional cardiology techniques. Tables 6.1 and 6.2 list diagnostic and therapeutic interventional procedures performed in the catheterization laboratory.
| Diagnostic Procedures | Therapeutic Procedures |
|---|---|
| Coronary angiography | PCIs (balloon, stents, rotablator, cutting balloon, and so on) |
| Ventriculography | Valvuloplasty, TAVR, mitral clip |
| Hemodynamics | ASD, PFO, PDA, VSD shunt closure |
| Shunt detection | Thrombolysis, thromboaspiration |
| Aortic and peripheral angiography | Coil embolization |
| Pulmonary angiography | Pericardiocentesis, window |
| Coronary hemodynamics | |
| Endomyocardial biopsy |
| Special Lesion Type | Stent | Cutting Balloon | Rotablator | Thrombus Aspiration |
|---|---|---|---|---|
| Type A | +++ | + | ± | – |
| Complex | ++ | ++ | + | – |
| Ostial | ++ | ++ | + | – |
| Diffuse | + | + | ++ | – |
| Total occlusion | ++ | + | – | – |
| Calcified bifurcation | ± | ++ | +++ | – |
| SVG focal | +++ | ± | ± | – |
| SVG diffuse | + | ± | – | – |
| SVG thrombotic | ± | – | – | ++ |
| Complication | +++ | – | ± | ± |
| Acute occlusion | ++ | – | – | ± |
| Thrombosis | + | – | – | +++ |
| Perforation | @ | – | – | – |
Percutaneous coronary interventions
Coronary balloon angioplasty was first performed in 1977. Up to that time, coronary artery bypass graft (CABG) surgery was the only alternative to medical treatment of coronary artery disease. During CABG, a segment of leg vein, arm artery, and/or chest wall artery is attached to the heart to detour blood around the narrowed portion (i.e., stenosis) of a coronary artery. Percutaneous transluminal coronary angioplasty (PTCA) (with the introduction of stents, PTCA is now called percutaneous coronary intervention [PCI]) provided an alternative to CABG. Without surgery, PCI selectively enlarges the narrowed portion of the artery by the insertion of a long thin balloon to open the blocked artery. Rarely used by themselves today, coronary balloons are now used to predilate the lesion and facilitate the delivery of coronary stents (metal mesh-like stainless steel or metal alloy implants) and with other devices (such as, cutters, grinders, lasers, and aspiration catheters) to treat a wide variety of artery problems. These methods are collectively referred to as PCI. The nomenclature is informative:
- •
Percutaneous refers to the nonsurgical insertion of a catheter into the body through a small puncture site in the skin, usually into an artery.
- •
Coronary identifies the specific artery to be dilated.
- •
Intervention denotes the technique for remodeling a blood vessel through the introduction of an expandable stent, balloon catheter, or other specialized tools for treating a diseased artery.
Figure 6.1 shows the process of performing PCI. A guiding catheter is seated in the coronary ostium. A thin, steerable guidewire is introduced into the coronary artery to traverse the stenosis into the distal aspect of the artery. A balloon angioplasty catheter, which is considerably smaller than the guiding catheter, is inserted through the guiding catheter and positioned (in the artery) across the stenotic area by tracking it over the guidewire. The balloon or stent is on the PCI catheter. After correct positioning within the area to be treated, the balloon on the PCI catheter is inflated at 10 to 16 atmospheres (atm) for periods ranging from 10 to 30 seconds. The inflation and deflation of the balloon stent in the blocked artery restores blood flow to an area of the heart previously deprived by the stenosed artery. After successful stent implantation, patients usually stay overnight in the hospital and are discharged the following morning. Same-day discharge has emerged as an alternative option for low-risk patients. This strategy was associated with lower costs and was preferred by patients. Patients can usually resume their normal routine within several days.
How do balloon angioplasty and stents work?
Several theories regarding the mechanisms of angioplasty have been proposed.
Disruption of plaque and arterial wall
The major effective mechanism of balloon angioplasty involves a balloon that inflates and exerts pressure against the plaque and arterial wall, fracturing and splitting the plaque. The concentric lesion fractures and splits at its thinnest and weakest point, whereas an eccentric lesion splits at the junction of the plaque and the arterial wall. Dissection, or separation of the plaque from the medial wall, releases the splinting effect that is caused by the lesion and results in a larger lumen. This is the major effective mechanism of balloon angioplasty.
Loss of elastic recoil
Balloon dilation thins and stretches the medial wall, causing the medial wall to lose its elastic properties. The degree of elastic recoil loss is affected by the balloon-to-artery size ratio. Over time (1 to 6 weeks), the artery may re-narrow as a result of elastic recoil, which is prevented by placement of a stent in the artery.
Redistribution and compression of plaque components
Shear pressures cause denudation or stripping of endothelial cells and the extrusion or pushing out of plaque components. Molding of the softer lipid material may occur, but this effect accounts for a small part of the overall effect of angioplasty.
Mechanism of stents
Stents scaffold the lumen and plaque open, holding back dissection flaps, stopping vessel recoil, and re-narrowing the lumen.
Restenosis is the re-narrowing of the vessel after treatment by balloon and stent, leading to recurrence of myocardial ischemia and potentially a return of anginal symptoms. Significant restenosis is not considered a true complication, but it is an event that may require retreatment with PCI or CABG surgery. Restenosis is caused mostly by intimal hyperplasia and rarely by vessel recoil after stenting. Typically, restenosis occurs during the initial 6 months after PCI. The in-stent restenosis rate is <10% with drug-eluting stents.
Stent thrombosis is the abrupt formation of a blood clot inside the stent, which is potentially catastrophic and can lead to myocardial infarction (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 P2Y 12 platelet inhibitors) is prematurely discontinued or the stent is suboptimally expanded.
The indications, contraindications, and complications of PCI are listed in Box 6.1 .
Indications for percutaneous coronary intervention
Angina pectoris causing sufficient symptoms despite optimal medical therapy
Mild angina pectoris with objective evidence of ischemia (by abnormal stress testing or physiology) and high-grade lesion (>70% diameter narrowing) of a vessel supplying a large area of myocardium
Unstable angina or NSTEMI
STEMI as primary therapy or in patients who have persistent or recurrent ischemia after failed thrombolytic therapy
Angina pectoris after CABG
Restenosis after successful PCI
LV dysfunction with objective evidence of viability of a vessel supplying the myocardium
Arrhythmia secondary to ischemia
Contraindications for percutaneous coronary intervention a
Unsuitable coronary anatomy
Extremely high-risk coronary anatomy in which closure of vessel would result in patient death
Bleeding diathesis
Patient noncompliance with dual antiplatelet therapy and unwillingness to follow post-PCI instructions
Multiple in-stent restenosis
Patients who cannot give informed consent
Complications associated with percutaneous coronary intervention
Death (<1%)
MI (<3% to 5%)
Stent thrombosis (∼1%)
Emergency CABG (<1%)
Abrupt vessel closure (0.8%)
Coronary artery perforation (<1%)
All complications that can occur during cardiac catheterization, including access site bleeding, pseudoaneurysm, AV fistula, ischemic vascular complications, stroke, allergic reaction to contrast media, and renal failure.
AV, Atrioventricular; CABG, coronary artery bypass graft; LV, left ventricular; MI, myocardial infarction; NSTEMI, non-ST segment elevation myocardial infarction; PCI, percutaneous coronary intervention; STEMI, ST-segment elevation myocardial infarction.
a If PCI is the only life saving procedure, risk versus benefit is weighed and the contraindication become
Equipment
PCI equipment consists of three basic elements: guiding catheter, balloon-stent catheter, and coronary guidewire ( Fig. 6.2 ).
Guiding catheter
A special large-lumen catheter is used to guide the coronary balloon catheter to the vessel that has the lesion to be dilated ( Fig. 6.3 ). Compared with a diagnostic catheter, a guiding catheter has a thinner wall and larger lumen, which allows contrast injections and accommodates interventional equipment. 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. The guiding catheter tip is not tapered, occasionally blocking the ostium and causing pressure dampening while engaging the coronary ostium. A 6-F guiding catheter is generally used. Some catheters have relatively shorter and more flexible tips than others, theoretically to decrease catheter-induced trauma. Others may have side holes to help maintain blood flow during PCI. Larger guiding catheters (7 F or 8 F) may be necessary for kissing balloons/stents, rotablator burrs >2 mm, and some cutting balloons. The guiding catheter comes in many different shapes for femoral and radial approaches. Guide catheters are shaped for specific anatomic variations.
Functions of the guiding catheter
The three major functions of a guiding catheter during PCI include:
- 1.
Balloon-stent catheter delivery: The guiding catheter is the delivery device of the balloon catheter to 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 is seated in the coronary artery (cannulation) and provides the necessary backup support or platform to push the balloon/stent catheter across the stenosis.
Several terms that are commonly used when referring to guiding catheters are important:
- •
Backing out: The guiding catheter is ejected from the coronary ostium into the aortic root when pressure is applied to the balloon in an attempt to cross the lesion. This is caused by an insufficient support position or a tight stenosis.
- •
Strong backup: A stable support position of the guiding catheter at the orifice of the coronary ostium provides the necessary platform to advance the balloon across the lesion.
- •
Deep seating: The guiding catheter is manipulated over the balloon catheter shaft past the ostium and further into the vessel to increase backup support for crossing difficult lesions. This maneuver is typically used as a last resort because of the increased risk of guiding catheter–induced dissection of the proximal vessel.
- 2.
Contrast injection: The guiding catheter permits visualization of the target by contrast administration with or without the balloon catheter in place. Some large PCI devices may block adequate contrast injection, which makes the procedure more difficult.
- 3.
Pressure monitoring: The guiding catheter lumen measures aortic pressure for determination of the transstenotic pressure gradient for physiologic lesion assessment, ostial lesions (pressure wave damping), and hypotension during prolonged ischemia.
Balloon angioplasty and stent delivery catheters
Technologic refinements of balloon catheters have dramatically improved the success rate of PCI. There are two principal types of balloon-stent catheters: (1) over the wire (OTW) angioplasty PCI systems and (2) rapid-exchange (RX; monorail) PCI catheters.
Over the wire angioplasty percutaneous coronary intervention systems
An OTW angioplasty PCI catheter ( Fig. 6.4 ) has a central lumen throughout the length of the catheter for the guidewire and a separate lumen for balloon inflation. This catheter is approximately 145 to 155 cm long and can be used with a long or short guidewire, usually 0.014 inch.
This catheter can accept multiple guidewires, which allows for exchanging of additional devices that may require stronger, stiffer guidewires. Maintenance of distal wire position beyond the target stenosis is paramount in coronary angioplasty. For an OTW balloon catheter, the guidewire can be extended to help maintain distal position while the balloon catheter is withdrawn completely over the guidewire to permit another balloon catheter to be exchanged and introduced over the same guidewire for additional dilations. A 300-cm exchange wire is commonly used.
One disadvantage of an OTW angioplasty balloon catheter is that a primary operator and an experienced assistant are required to perform catheter exchanges. A technique to make balloon catheter exchanges easier involves a balloon inside the guide catheter inflated to fix a 155-cm guidewire in place, which permits OTW catheters to be exchanged without using a 300-cm guidewire. Dedicated trapping balloons have been introduced to facilitate balloon catheter exchanges.
Rapid-exchange (monorail) percutaneous coronary intervention catheter
An RX balloon catheter is the most popular catheter used today and allows a single operator to exchange PCI catheters unassisted. It differs from OTW PCI catheters in that only a variable length of the shaft has two lumens ( Fig. 6.5 ). One lumen is for balloon inflation and the other, which extends through only a portion of the catheter shaft, houses the guidewire. Because only a limited portion of the balloon requires dual lumens, the catheter shafts can be made smaller than OTW systems.
An RX balloon catheter eliminates the need for a long exchange guidewire and permits an operator to maintain distal guidewire position without the aid of an assistant.
Limitations of a monorail catheter include the need for excellent guiding catheter support and more operator skill for the complexity in manipulating the guidewire, balloon catheter, and guiding catheter. Blood loss during removal of the monorail balloon catheter at the rotating hemostatic valve can be a problem but can be reduced with better technique and attention to the Y connectors.
The advantages and limitations of OTW and RX balloon catheters are listed in Table 6.3 .
| Type | Advantages | Limitations |
| Over the wire (OTW) |
|
|
| Rapid exchange (RX; monorail) |
|
|
Procedural details for percutaneous coronary intervention
After crossing the lesion with the balloon catheter, the balloon is inflated and deflated using a hand-held syringe device with a pressure gauge. Balloon catheter sizes range from 1.5 to 5 mm in diameter (size of the inflated balloon) for coronary arteries and are larger for peripheral arteries. Balloon diameter is selected according to the angiographic size of the vessel to be dilated. The plastic materials of balloon catheter construction determine the flexibility of the catheter shaft and balloon characteristics (e.g., burst pressure and actual diameter under different pressure levels). Special-purpose coronary balloon catheters are available for specific types of lesions. A noncompliant high-pressure balloon is commonly used to optimize stent implantation results to achieve full stent expansion and strut apposition. Balloon lengths vary from 10 to 38 mm in length. A cutting balloon is a special balloon catheter with three to four atherotomes (or blades) that run longitudinally on the balloon to score the lesion in a more controlled fashion.
Angioplasty guidewires
Coronary angioplasty guidewires are small-caliber (0.010-inch to 0.014-inch diameters) steerable wires that are typically 170 to 190 cm long. They are advanced into the coronary artery or branches beyond the lesion to be dilated. The flexible tip may be shaped by the operator to negotiate side branches and tortuous artery curves. The balloon-stent catheter is advanced over the wire and, after artery dilation, removed from the artery with the wire remaining in place beyond the dilated lesion. Extra-long guidewires (300 cm) are used to exchange OTW balloon catheters. Tip flexibility and torque control characteristics of these coronary guidewires vary. Generally, the softer wires are safer and easier to advance into tortuous branches, whereas the stiffer wires give better torque control and may be useful for crossing difficult or total occlusions. Hydrophilic wires, which have special coatings to cross subtotally or totally occluded stenoses better, generally carry a higher risk of perforation if the tip position is not kept in the major vessel lumen and dissection if the guidewire is advanced under an intimal flap.
Exchange and extension guidewires
An exchange guidewire is similar to the standard 180 cm guidewire mentioned previously except that its length is 280 to 300 cm. This long wire replaces the initial wire when the exchange of an OTW balloon catheter is necessary. Alternatively a 120- to 145-cm extension wire can be connected to the end of the initial guidewire to allow balloon catheter exchanges.
Other equipment
Y connector (adjustable hemostasis device)
The Y connector, which comes with a rotating or spring-controlled valve, is an accessory device that minimizes back-bleeding while the balloon/stent catheter is inserted into and removed from the guiding catheter. This device allows the injection of contrast media and pressure monitoring through the guiding catheter, regardless of balloon catheter position.
Inflation device
A disposable syringe device is used to inflate the balloon on the balloon catheter with precise measurement of the inflation pressure in atmospheres, generally ranging from 4 to 20 atm. Although stents may be inflated at 10 to 18 atm, the balloon is typically inflated with sufficient pressure to compress the plaque caused by stenosis and fully expand the dumbbell, or indentation, at the waist of the partially inflated balloon. Occasionally, hard, resistant stenoses (calcium or fibrosis) may require high pressures (>14 atm) to expand the dumbbell indentation. Needless balloon overinflation increases the risk of coronary dissection and perforation.
Torque (tool) device
A small cylindrical pin vise clamp slides over the proximal end of the angioplasty guidewire, permitting the operator to perform fine manipulations of the guidewire by turning the torque tool in a clockwise or counterclockwise direction. Figure 6.6 shows examples of the inflation device, Y connectors, guidewire introducers, and torque tool.
Clinical procedure
The clinical procedure for PCI is:
- I.
Clinical and angiographic indications for proceeding with PCI should be confirmed. Noninvasive testing for ischemia is recommended in patients with atypical anginal symptoms or chest pain syndrome without evidence of clinical ischemia. Before PCI, the following procedures can be performed to obtain objective evidence of ischemia: electrocardiogram (ECG) (for evidence of resting ischemia or recent infarction); stress perfusion imaging or stress echocardiography (either exercise or pharmacologic); or for lesions of uncertain significance, in-laboratory translesional physiology assessment (with the use of fractional flow reserve [FFR] or instantaneous wave-free ratio [iFR]).
- II.
Pre-PCI preparation
- 1.
Patient preparation should include placement of ECG electrodes, pacer/defibrillator pads, and intravenous (IV) line. Make sure you have a list of the patient’s current medications and a signed informed consent form.
- 2.
Perform patient and family teaching, including explaining the procedure, anticipated results, and potential for complications.
- 3.
Give cardiothoracic surgery consultation for high-risk patients and those with multivessel disease (especially patients with diabetes), left main disease, or left ventricular (LV) dysfunction.
- 4.
Do a laboratory blood work check, including complete blood cell and platelet counts and measurements of international normalized ratio (INR), partial thromboplastin time (PTT), electrolytes, blood urea nitrogen, and creatinine.
- 1.
- III.
Patient preparation in catheterization suite
- 1.
ECG (inferior and anterior wall leads): Use ECG with 12 leads (radiolucent).
- 2.
Skin preparation: Prepare inguinal area for femoral artery or wrist for radial artery.
- 3.
Consider femoral venous access for high-risk patients or those with acute MI, rotablator, or thrombus aspiration device. Most PCI procedures can also be performed from the radial approach, with lower bleeding risk obviating the need for a vascular closure device (VCD). Venous access for temporary pacing is no longer routine.
- 4.
Antiplatelet therapy: Aspirin (325 mg orally). Failure to administer aspirin before PCI is associated with a two to three times higher acute complication rate, including acute MI and stent thrombosis. Clopidogrel (600 mg orally) or other P2Y 12 platelet inhibitors, such as prasugrel or ticagrelor, if patient presents with acute coronary syndrome (ACS), should be routinely given before or immediately after PCI.
- 5.
Anticoagulation: Heparin (70- to 100-mcg/kg bolus or lower if glycoprotein [GP] IIb/IIIa blocker is used) with a target activated clotting time (ACT) >250 seconds. Bivalirudin is an alternative to heparin, with reports of lower bleeding risk in some patients.
- 6.
Consider GP IIb/IIIa blockers in patients with complicated procedures associated with thrombus or MI with large thrombotic burden.
- 7.
Give Versed (1 mg IV) and Fentanyl (25 to 100 mcg IV) for sedation.
- 8.
For patients allergic to contrast media, give prednisone (60 mg, 13 hours, 7 hours, and 1 hour before cardiac catheterization). Diphenhydramine (25 to 50 mg IV or orally) and H 2 blockers are used in some centers.
- 1.
- IV.
Guiding coronary angiograms (after 100 to 200 mcg of nitroglycerin IC)
- 1.
Define coronary anatomy and collateral supply (if any).
- 2.
Store guiding shots to use as reference roadmap for balloon-stent positioning.
- 3.
Select device size as judged from known guide catheter diameter to select the balloon-stent diameter.
Note: 8 F = 2.87 mm, 6 F = 2 mm (size of PCI device based on distal artery normal reference segment; balloon/artery ratio <1:1.2)
- 1.
- V.
PCI procedure
- 1.
Select guiding catheter for angle of vessel takeoff and optimal backup support.
- 2.
Ensure the guiding catheter is seated; coaxial alignment is best.
- 3.
Advance guidewire beyond target stenosis to distal position in the vessel.
- 4.
Insert balloon catheter through hemostasis Y valve on guiding catheter and advance into the stenosis, centering the balloon using radiopaque markers on balloon catheter.
- 5.
Inflate balloon to expand fully and remove dumbbell indentation of lesion on underinflated balloon. Balloons and stents may be inflated for 10 to 30 seconds or longer, as tolerated. Then, deflate the balloon.
- 6.
Exchange the balloon catheter for the stent catheter and repeat the process. Using a balloon first opens the vessel, providing pressure and flow to the distal vessel segment. This often enlarges the size of the vessel, possibly changing initial thinking regarding the best stent size.
- 7.
Determine final result after intravascular ultrasound (IVUS) and optical coherence tomography (OCT) with or without high-pressure noncompliant balloon for optimal stent implantation.
- 1.
- VI.
Assessment of PCI result
- 1.
Check for enlarged artery lumen (<10% residual lesion) and good angiographic flow (thrombolysis in MI [TIMI] grade 3).
- 2.
Full stent apposition is based on angiogram and/or IVUS.
- 3.
Check for absence of adverse angiographic complications (e.g., thrombus, dissection, or perforation).
- 4.
Make sure there is no residual ischemia (ECG changes with or without chest pain).
- 1.
- VII.
Considerations for additional stenting
- 1.
New lesion proximal or distal to stent (i.e., edge dissection) may require additional stenting.
- 2.
Large dissection extending in either direction may require additional stenting.
- 3.
Slow flow may require FFR or IVUS to establish cause (i.e., occult dissection).
- 1.
- VIII.
Postprocedure angiograms and access site hemostasis
- 1.
Remove guidewire for final images after administering additional intracoronary (IC) nitroglycerin. Leaving the guidewire in during final angiography may hold a dissection flap in place, which would be missed if the guidewire had not been removed.
- 2.
For the femoral approach, perform femoral angiography before VCD selection (>30 degrees right anterior oblique [RAO] for right femoral artery or left anterior oblique [LAO] for left femoral artery). Avoid VCD in patients with scarring from previous procedures.
- 3.
Alternatively, if no closure device is used, secure sheaths in place for later removal (2 hours) or when ACT is <160 seconds for manual hemostasis for arterial sheaths. Do not use prolonged (>6 hours) heparin infusions unless thrombus or other complications are present. Increased bleeding risk is associated with postprocedure heparin infusions.
- 4.
For radial procedures, apply radial artery compression band with enough pressure to achieve patent hemostasis, maintaining good flow to hand. Remove band in 2 hours. Reapply if hemostasis is not achieved.
- 1.
- IX.
Postprocedure outside laboratory
- 1.
Teach about hospital course and bleeding problems, late complications, and restenosis.
- 2.
Notify referring physician and care team in recovery area or critical care unit (CCU).
- 3.
Use ECG and laboratory and telemetry monitoring of vital signs.
- 1.
- X.
Post-PCI medications
- 1.
The patient should take aspirin (325 mg orally daily for 1 month, then 81 mg/day indefinitely).
- 2.
Prescribe clopidogrel (600-mg loading dose and 75 mg/day orally) for at least 4 weeks after stenting with a bare metal stent and 12 months with a drug-eluting stent. For patients with ACS, prescribe prasugrel (60-mg loading dose and 10 mg/day orally) or ticagrelor (180-mg loading dose and 90 mg/twice daily orally). Second-generation P2Y 12 receptor antiplatelet agents, such as ticagrelor or prasugrel, are commonly used as alternatives to clopidogrel.
- 3.
Initiate statin drugs if not already prescribed.
- 4.
Restart antihypertensive or antianginal medications depending on patient’s clinical needs.
- 1.
- XI.
Follow-up schedule
- 1.
Check access site on first office visit.
- 2.
Do not perform stress testing early after PCI or annually unless symptoms or other clinical indications appear.
- 3.
Repeat coronary angiography if symptoms or signs of ischemia are present early after PCI.
- 4.
Instruct patient to return gradually to activities of daily living.
- 1.
Percutaneous coronary intervention pharmacology
See Chapter 1 for more information about commonly used drugs in the catheterization laboratory.
Oral antiplatelet agents
All patients who undergo PCI receive aspirin (81mg to 325 mg/day), which should be administered >2 hours prior to the procedure with a loading dose of 162 or 325 mg. Current PCI guidelines recommend a loading dose of P2Y 12 inhibitor at the time of PCI. Options include clopidogrel 600 mg, prasugrel 60 mg, or ticagrelor 180 mg. The duration of dual antiplatelet therapy (DAPT) after stent implantation is usually 12 months. Shorter and longer DAPT durations have been proposed for patients with increased bleeding or thrombotic risks, respectively.
Some patients do not respond to clopidogrel because of a genetic predisposition. Clopidogrel is a prodrug and needs to be catalyzed to its active metabolite by the cytochrome P450 2C19 (CYP2C19) enzyme. Some patients are CYP2C19-poor metabolizers, leading to lower levels of the active metabolite of clopidogrel, less platelet inhibition, and increased risk of adverse cardiovascular events, including stent thrombosis, MI, and death.
As an alternate for patients with ACS, prasugrel (60-mg loading dose with 10 mg/day maintenance), a P2Y 12 receptor inhibitor, reduced the combined rate of death from cardiovascular causes, nonfatal MI, or nonfatal stroke but was associated with increased risk of bleeding complications. Contraindications include a history of stroke or transient ischemic attack, age ≥75 years, and weight <60 kg because of an increased risk of bleeding.
ACS patients after PCI who were treated with another antiplatelet agent, ticagrelor, showed improved clinical outcomes compared with clopidogrel. In addition to reduction in the combined endpoints of death from vascular causes, MI, or stroke, ticagrelor was associated with a reduction in mortality compared with clopidogrel. Rates of fatal or life-threatening bleeding were similar with clopidogrel. The loading dose is 180 mg (two 90-mg tablets) and 60 mg and then 90 mg every 12 hours.
Antithrombotic agents
Heparin is a commonly used antithrombotic agent for PCI but is associated with a variety of limitations including variable anticoagulation responses, heparin resistance, need to monitor degree of anticoagulation, risk of heparin-induced thrombocytopenia, and activation of platelets.
Bivalirudin is a direct thrombin inhibitor and, when compared with heparin plus GP IIb/IIIa inhibitor, is associated with fewer bleeding complications across the full spectrum of patients with coronary artery disease who undergo PCI. The HORIZONS-AMI trial reported a reduction in 30-day mortality in ST-segment elevation myocardial infarction (STEMI) patients who underwent primary PCI with bivalirudin compared with heparin plus GP IIb/IIIa inhibitors. However, planned GP IIb/IIIa inhibition is not routinely used in elective PCI, and the use of this agent might explain the increased bleeding found in the heparin groups studied. The MATRIX study compared bivalirudin with heparin, without routine GP IIb/IIIa inhibitors, and found similar rates of ischemic and bleeding events.
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