Interventional Cardiology Techniques: Percutaneous Coronary Intervention



Interventional Cardiology Techniques: Percutaneous Coronary Intervention


Michaelene Hargrove Deelstra



More than 30 years has passed since the introduction of coronary angioplasty by Andreas Gruentzig in 1977.1 Interventional cardiology has continued to evolve and improve techniques and procedures for percutaneous treatment of coronary heart disease (CHD). Interventional coronary devices used to restore or enhance myocardial blood flow include angioplasty balloons, atherectomy devices, and intracoronary stents. Pharmacological therapies have been an important partner in the development of device technology. This interventional cardiology chapter provides a review and understanding of the evolution of device technology, patient management, the current trends and devices used in the catheterization laboratory today to treat CHD, and a look at percutaneous devices used for the treatment of cardiac structural abnormalities.

The term percutaneous coronary intervention (PCI) refers to the collective group of interventional procedures performed through a percutaneous approach in the coronary arteries. PCI was initially limited to balloon angioplasty but now encompasses other procedures using atherectomy devices, thrombectomy devices, and bare metal and drug-eluting stents (DES). Factors that have improved the overall success and complication rates include operator experience, modifications in procedural instruments, newer interventional devices, and advances in adjunctive pharmacologic therapy. These improvements have led to the expansion of interventional cardiology treatment to higher risk patients with more complex coronary lesions and comorbidities. These improvements have influenced the short- and long-term success of PCI.2


PATIENT SELECTION FOR PCI

The American College of Cardiology/American Heart Association/Society for Cardiovascular Angiography and Interventions (ACC/AHA/SCAI) task force provides broad guidelines and recommendations for appropriate application of PCI technology based on scientific evidence for revascularization. Recommendations for revascularization with PCI include patients presenting with significant ischemia on noninvasive testing, unstable angina, and acute coronary syndrome (ACS). When the patient is considered for revascularization with PCI, the potential risks and benefits should be discussed in detail with the patient and family and be weighed against alternative therapies such as medical therapy or coronary artery bypass graft (CABG) surgery. Patients should understand the possible complications associated with the procedure, the possibility of restenosis, stent thrombosis (see complications) postprocedure, and the potential for incomplete revascularization in patients with diffuse coronary artery disease (CAD). The clinical and angiographic variables associated with increased mortality include advanced age, female sex, diabetes mellitus, prior myocardial infarction (MI), multivessel disease, left main disease or equivalent (severe stenosis of the left anterior descending artery and circumflex arteries proximal to any major branch), a large area of myocardium at risk, pre-existing impairment of left ventricular (LV) function or renal function, and collateral vessels supplying significant areas of myocardium that originate distal to the segment to be treated.3

ACC/AHA/SCAI4 recommends an early invasive strategy with PCI in patients with unstable angina/non-ST-elevation MI (NSTEMI) who exhibit the following:



  • Recurrent angina, ischemia at rest or with low-level activities despite intensive medical therapy


  • Elevated cardiac biomarkers, new or presumed new ST-segment depression


  • Signs or symptoms of heart failure or new worsening mitral regurgitation


  • High-risk findings on noninvasive testing or hemodynamic instability


  • Sustained ventricular tachycardia and prior CABG or reduced LV ejection fraction <.40.


  • PCI is not indicated for a persistently occluded infarct-related artery after NSTEMI or ST-elevation MI (STEMI) older than 24 hours in a stable, asymptomatic patient.

In patients with stable CAD optimal medical therapy alone can be considered versus PCI with optimal medical therapy. PCI when added to optimal medical therapy in stable angina has been shown to reduce the prevalence of angina symptoms but not to reduce long-term rates of death, MI, or hospitalization for ACS.5


Special Subgroups of Patients Receiving PCI


Patients Receiving Fibrinolytic Therapy

Facilitated PCI refers to a strategy of planned immediate PCI after the administration of an initial pharmacological regimen intended to improve coronary patency before the procedure. Clinical trials of facilitated PCI have not demonstrated benefit in reducing infarct size or improving outcomes. In patients with STEMI, a planned reperfusion strategy using full-dose fibrinolytic therapy (Chapter 22) followed by immediate PCI may be harmful and is not advocated.

Coronary angiography and intent to perform revascularization are recommended for patients who have received fibrinolytic therapy, are in cardiogenic shock, are candidates for PCI, and have severe heart failure or pulmonary edema or hemodynamically significant ventricular arrhythmias. Rescue PCI should be considered in patients with STEMI who have received fibrinolytic agents and have evidence of failed reperfusion (ST-segment resolution <50%) 90 minutes after initiation of fibrinolytic therapy, and have a moderate-to-large area of myocardium at risk.4



Women

Women presenting with CHD frequently have increased severity of disease at time of presentation. Women are generally older when they present with their first coronary event, and often have have diffuse atherosclerotic disease and a higher incidence of comorbidities, including hypertension, diabetes mellitus, hypercholesterolemia, peripheral vascular disease, and unstable angina. Women have an excellent long-term prognosis after a successful procedure even though coronary vessel lumen may be smaller. Although newer revascularization procedures with stents and concomitant use of glycoprotein (GP) IIb/IIIa receptor inhibitors have shown similar benefit in women as men, these interventions have not eliminated the gender difference in mortality that has persistently shown higher rates with device treatment in the setting of ACS and elective procedures in women.3,6


Patients With Diabetes Mellitus

Patients with diabetes mellitus account for about 20% of revascularization procedures. PCI in patients with diabetes is associated with less favorable long-term outcomes, need for repeat intervention because of restenosis, multivessel disease, and possible progression of underlying disease. Current guidelines have favored CABG surgery for patients with diabetes who have two-or-three vessel disease because of more complete revascularization and decreased need for repeat intervention.7, 8, 9 Use of DES has improved the long-term outcomes in patients with diabetes who have single-vessel disease.10 An intravenous GP IIb/IIIa receptor inhibitor should be administered for diabetic patients with unstable angina or NSTEMI; GP IIb/IIIa receptor inhibitors appear to improve the outcome of PCI with reduced death, MI and repeat revascularization.11


Patients With Multivessel CAD

The two primary interventions for multivessel CAD are PCI and CABG. Several randomized and observation studies have compared the long-term outcomes of these two interventions before the introduction of DES. These trials demonstrated that in appropriately selected patients with multivessel coronary disease, an initial strategy of standard PCI with bare metal stent (BMS) yields similar overall outcomes to initial revascularization with CABG. An important exception is in the subgroup of patients with diabetes mellitus who had reduced cardiac mortality with CABG compared to PCI. Patient preference, patient compliance with dual antiplatelet therapy, surgical risk, angiographic characteristics, LV function, and co-morbid issues need to be considered before a treatment strategy is selected.12

An observational study from the New York State Registry identified patients with multivessel disease who received DES or underwent CABG. Conclusions from the registry indicated lower mortality rates and repeat revascularization with CABG compared to DES.13 Currently, ongoing multicenter, randomized, controlled trials such as SYNTAX (Synergy between PCI with Taxus and Cardiac Surgery) and FREEDOM (Future Revascularization Evaluation in Patients With Diabetes Mellitus—Optimal Management of Multivessel Disease), are evaluating multivessel DES versus bypass surgery in different subsets of patients and will provide guidance for selection of treatment that will benefit specific groups of patients.12


Older Adults

Patients aged 75 years and older should be considered for PCI in a similar manner as younger patients. Decisions should not be based solely on chronologic age but should be patient centered with consideration of the patient’s general health, functional and cognitive status, comorbidities, life expectancy, and preference and goals. Clinical trials have shown benefits from early invasive procedures with similar success rates as younger patients but with higher risks of bleeding and vascular complications. Older adults often have altered pharmacokinetics, risk of drug interactions, and polypharmacy contributing to complications.14 Increased risk of neurological events secondary to diffuse atherosclerotic disease has also been seen in older adults.


PERCUTANEOUS TRANSLUMINAL CORONARY ANGIOPLASTY

Dotter and Judkins first proposed the concept of transluminal angioplasty in 1964.15 Gruentzig initially applied the technique of percutaneous transluminal coronary angioplasty (PTCA) to human coronary arteries in 1977.1 Since the first PTCA, advances in catheter and balloon techniques have improved immediate and long-term success. Although conventional balloon angioplasty is a core procedure in the catheterization laboratory, it is usually not a stand-alone procedure but is now augmented by adjunctive stenting, which greatly improves procedural success and reduces complication rates.

The desired therapeutic effect of balloon angioplasty is the enlargement of the internal luminal diameter of the diseased artery. Application of balloon pressure to an atherosclerotic lesion results in plaque rupture, disruption of the endothelium, and stretching of the vessel segment, which enlarges the vessel lumen size (Fig. 23-1).

Guiding catheters are used to cannulate the coronary artery and to provide support for delivery of guidewires and interventional devices. In the catheterization laboratory, after the guide catheter is placed and the wire crosses the lesion, a balloon catheter is selected that most closely approximates the diameter of the nondiseased reference segment adjacent to the site to be treated. The prepared and flushed balloon is loaded onto the free end of the guidewire. The balloon is passed into the guide catheter, down the proximal vessel, and across the lesion. Once the balloon catheter is positioned across the lesion, the balloon is inflated using a handheld inflation device equipped with a pressure dial. Multiple balloon inflations of variable pressure and duration are used depending on the type of lesion and the physician preference. The response of the lesion to dilatation is assessed by contrast injection and repeat angiography through the guiding catheter with the guidewire in place. When the lesion in successfully dilated, the balloon apparatus is removed and multiple angiographic projections are reviewed. The guidewire and guiding catheter are removed after an adequate result is obtained.


Cutting Balloon Angioplasty

Cutting balloon angioplasty uses a balloon designed with three-to-four microscopic blades or atherotomes mounted on the balloon surface that protrude slightly above the balloon surface when inflated (Fig. 23-2). The mechanism of action referred to as atherotomy utilizes the balloon device to make three-to-four controlled incisions that score the plaque in an atherosclerotic coronary artery. The noncompliant balloon then dilates the incised areas resulting
in plague compression and less vessel wall expansion. This type of dilatation may reduce the force needed to dilate an obstructed lesion. The cutting balloon has specific, limited indications: lesions that are resistant to dilatation by traditional angioplasty balloons, such as calcific, elastic, and fibrotic lesions; and in-stent restenosis (ISR) to avoid slipping-induced vessel trauma during PCI.16,17 The cutting balloon may be used alone or in combination with stents.






Figure 23-1 Mechanism of intracoronary balloon angioplasty. (A) A balloon catheter is introduced into the coronary artery through a guide catheter in the aorta. (B) A guidewire is advanced across the area of narrowing. (C) The balloon catheter is advanced over the wire across the lesion. (D) The balloon is inflated. (E) Coronary artery after PTCA. (Courtesy of Boston Scientific Corporation, Maple Grove, MN.)


CORONARY ATHERECTOMY, ATHEROABLATIVE, AND THROMBECTOMY DEVICES

Coronary atherectomy (directional and rotational) and excimer laser coronary angioplasty (ELCA) were developed and approved by the FDA for coronary artery use in the late 1980 to 1990s, with hopes of resolving the limitations of PTCA. Atherectomy device technique involves reduction of the severity of coronary blockage by removal of atheromatous plaque rather than compressing and/or fracturing the plaque, or stretching the arterial wall. In theory, this approach was developed to permit a more controlled vascular injury, minimize the degree of arterial mural stretch, create a smoother surface by debulking the vessel, and removal of atherosclerotic plaque that is frequently resistant to balloon dilatation.

Atherectomy devices have been used successfully to remove atherosclerotic plaque but were associated with increased complication rates and restenosis rates similar to PTCA from neointimal hyperplasia. Atherectomy devices now account for less than 3% of current PCI and are being used in very specific subsets of patients. Clinical trials have shown no improvement in long-term results with these devices; many atherectomy devices no longer are used.18,19


Atherectomy


Directional Coronary Atherectomy

The directional coronary atherectomy (DCA) catheter (Guidant Corporation, Santa Clara, CA) consists of a catheter-mounted, cylindrical metallic housing unit (collection chamber, window, and cup-shaped cutter) and a small balloon attached to the housing. When the catheter is placed at the lesion, a balloon is inflated
at low pressure against one wall of the vessel to stabilize the housing chamber and the window against the opposite vessel wall of plaque. Plaque that protrudes into the housing unit through the window is excised with the rotating cutter, which is advanced manually. The device is then rotated and plaque is excised from around the lumen. Combination aggressive plaque debulking with DCA and stenting did not improve short- or long-term clinical outcomes over stenting alone; there is no well-established evidence for efficacy of DCA use in coronary arteries.3,19,20 A modified device is currently used in peripheral vascular interventions.






Figure 23-2 The cutting balloon. (Courtesy of Boston Scientific Corporation, Maple Grove, MN.)






Figure 23-3 Rotational atherectomy catheters in different sizes. (Courtesy of Boston Scientific Corporation, Maple Grove, MN.)


Rotational Atherectomy

The rotational atherectomy device (Rotablator/Boston Scientific, Maple Grove, MN) uses a high-speed, rotating, elliptical burr coated with diamond chips 20 to 30 microns in diameter that form an abrasive surface (Fig. 23-3). When the burr is spun at a high speed (140,000 to 180,000 rpm, depending on burr size), it preferentially removes atheroma because of its selective differential cutting of inelastic plaque rather than elastic normal tissue. The process involves a stepwise incremental increase in burr size to provide a “sanding effect.” Gradual advancement and withdrawal of the burr in 2- to 5-second intervals for up to 20 to 30 seconds in the lesion allows for heat dissipation, improved distal perfusion, and washout of particulate debris. The postablation vessel diameter is equal to the largest burr size used. Adjunctive PTCA and stenting is used to maximize final coronary artery luminal diameter. The debris emitted from the Rotablator ablation process is released into the coronary bloodstream as pulverized microparticles, which can result in “slow flow” and distal microembolization. Rotational atherectomy has been shown to be effective in the treatment of fibrotic and calcified coronary lesions that cannot be crossed by a balloon or adequately dilated before planned stent placement. The use of rotational atherectomy is used very selectively as an adjunct to stenting and was not supported in clinical trials for ISR.17,21


Atheroablative: Excimer Laser Coronary Angioplasty (ELCA)

The concept of applying laser energy to remove, in a percutaneous manner, atherosclerotic coronary obstructions first emerged in the late 1980s. The ELCA produces monochromatic light energy to cause ablation of plaque via the generation of heat and shock waves and plaque disruption. A decline in laser angioplasty occurred because of significant coronary dissections and perforations with early techniques. Laser angioplasty has been used for treatment of ISR with good procedural success but disappointing long-term results. Current guidelines conclude that there is no evidence that ELCA improves long-term outcomes in coronary lesions that can be treated safely with stenting or PTCA alone.3,22


Thrombectomy Devices

The presence of intracoronary thrombus with plaque rupture and ACS or thrombotic material from degenerative saphenous vein grafts may lead to distal embolization and a “no reflow” phenomenon during PCI. Dislodgement of thrombotic material distally can occur with device deployment and contribute to increased MI size. Devices to reduce thrombotic material have produced inconsistent benefits in patients with ACS. However, balloon occlusion devices and aspiration systems during stenting of saphenous vein grafts have shown reduction in major adverse events with conventional PCI.23, 24, 25


Angiojet

The angiojet is a rheolytic thrombectomy catheter (Possis Medical Inc., Minneapolis, MN) designed for the percutaneous disruption and removal of thrombus from native coronary arteries and bypass grafts using high-velocity saline. It consists of a double lumen catheter. The smaller lumen of the catheter is used to supply the catheter tip with saline jets that are generated by an external drive unit. These jets aid in the formation of a recirculation pattern that fragments the thrombotic material and creates a “Venturi effect” that aids in evacuation of the macerated thrombotic material.23,26


Aspiration Thrombectomy

Aspiration thrombectomy catheters are used to manually extract thrombus. These catheters are advanced into the coronary artery and, while suction is applied, pulled back through the thrombus. After aspiration of the thrombus material, PCI with PTCA or stent is performed.


Distal Protection Devices

These devices are designed to provide protection of the distal microcirculation during PCI. One device type is a balloon occlusive system that temporarily occludes the distal vessel during the intervention followed by the aspiration of liberated atheromatous and thrombotic material before it reaches that arteriolar and capillary bed. The other device type is a nonocclusive, filter-based system that preserves coronary blood flow through tiny pores, as low as 100 microns. Atheromatous and thrombotic material is trapped in the filter-based systems and then removed with the retrieval of the device through a retrieval catheter. These techniques can reduce the incidence of cardiac enzyme elevation post-PCI.


CORONARY STENTS

The majority of current PCI involve coronary stenting as a primary procedure or as an adjunct to balloon angioplasty. When PTCA was first introduced, it was plagued by two major limitations: acute or subacute closure, and restenosis. Subsequently, improved intracoronary stent design, techniques, and pharmacological management have contributed to the success of catheter-based revascularization with stents, reducing the incidence of these two major complications
of PCI. The optimal stent should be easily and safely deliverable to various locations in coronary arteries and have the following properties: are flexible, low profile, radiopaque, smooth contour, sufficient radial strength, and tissue and blood compatible.27






Figure 23-4 Stent deployment. (A) Stent in the closed position across lesion on the balloon delivery system. (B) Stent in open position in coronary artery after balloon inflation. (Courtesy of Cordis, A Johnson & Johnson Company, Miami Lakes, FL.)

Dotter first demonstrated the concept of stenting an injured vessel in 1960s. In 1986, Sigwart et al.28 reported use of a percutaneous, self-expanding metallic stent in coronary vessels in humans. The development of intracoronary stents was initiated to provide structural support to an artery opposing elastic recoil preventing vasoconstriction, and preventing or treating dissections of the arterial wall seen with other coronary devices. The stent procedure is similar in preparation to PTCA with a guide catheter in the ostium of the coronary artery and a guidewire passed across the lesion. The lesion can be predilated with an angioplasty balloon or the stent placed without predilatation (primary stenting).

There are a variety of different types of intracoronary stents, categorized by mechanism of deployment, structure, metals, sizes, and stent coating (including bare-metal, drug-eluting, and covered). Stents are deployed using balloon-expandable or self-expandable mechanisms. The most commonly used stents are balloon-expandable and delivered over a guidewire into the coronary artery in a collapsed state and mounted on a balloon delivery system. Self-mounted stents are available in Europe. Once the balloon is positioned correctly across the lesion, the balloon is inflated, expanding the stent. The balloon delivery system is removed and a high-pressure balloon is frequently used to postdilate the stent to assure its full expansion (Fig. 23-4). Adequate apposition of the stent to the arterial wall has been found to be very important for long-term success and reduction of major cardiac events secondary to thrombotic complications. The self-expanding stents are used less frequently in the coronary arteries and more frequently in the peripheral vasculature. They are placed on the delivery system in a collapsed state with a retaining outer membrane. Retraction of the membrane after the delivery system is across the lesion allows the stent to expand. A high-pressure balloon can be used after deployment to completely expand the stent.


Bare Metal Stent (BMS)

Two of the first FDA-approved stents were the Gianturco-Roubin Flex-Stent (Fig. 23-5), which reduced the incidence of emergency CABG surgery associated with PTCA,29 and the Palmaz-Schatz coronary stent. Two landmark clinical stent trials that empowered the stent revolution were randomized trials comparing the Palmaz-Schatz Stent with PTCA. The Stent Restenosis Trial (STRESS) and the Belgium Netherlands Stent Trial (Benestent) found that patients with an intracoronary stent in a de novo lesion had a higher procedural success rate and a less frequent need for revascularization than patients with balloon angioplasty.30,31 However, this benefit was achieved at the cost of a significantly higher risk of vascular bleeding complications and a longer hospital stay. An aggressive regimen of adjunctive pharmacologic agents was used during these trials and during the initial experience of stenting, including ASA (acetylsalicylic acid or aspirin), dipyridamole, warfarin, heparin, and dextran. The initial stent trials were hindered by a high rate of subacute stent thrombosis, embolization of stents, difficulty in stent placement, and groin complications. Improvement in stent deployment techniques, operator experience, elimination of aggressive anticoagulation regimens, and the introduction of antiplatelet therapy facilitated wide spread acceptance of coronary stenting with less complications.






Figure 23-5 The Gianturco-Roubin Flex-Stent. (Courtesy of Cook, Inc., Bloomington, IN.)

These first-generation BMS designs have provided the initial stent model but have been replaced by newer designs with better flexibility, and a wide variety of sizes and lengths. BMSs currently have an excellent procedure success rate of 20% but restenosis rates of approximately 25%.32,33


Drug-Eluting Stent (DES)

Bare metal stents dramatically decreased acute and threatened closure with PTCA but did not eliminate the significant problem of restenosis. The development of the next generation of stents with drug-eluting properties provides successful treatment of coronary lesions with low complications rates and mechanisms to limit the development of neointimal hyperplasia, leading to restenosis seen with PTCA, atherectomy devices, and BMS. Since 2002, randomized trials have shown that DESs, as compared to BMSs, reduce the need for subsequent revascularization procedures and as a result, the use of DES has increased rapidly with current rates in excess of 80% of all stenting procedures.

The concept behind DES is to prevent neointimal hyperplasia and allow normal development of endothelial lining on the stent struts. Endothelialization is important for preventing direct contact between bare metal and circulating blood, a circumstance that can lead to clot formation and stent thrombosis. The stent platform is coated with a polymer that allows the intended antiproliferative drug to adhere to the stent struts and allow local delivery. The stent design, balloon delivery system, drug mechanisms, type of polymer, and release pattern of the drug all are important for effective dilatation and compression of the coronary plaque, ability to safely dispense the drug, and prevention of cell death and necrosis of the
coronary vessel leading to vascular complications. The clinical success of this technology depends on the complex interaction between the stent, coating matrix, drug, and vessel wall.34






Figure 23-6 The BX Velocity Coronary Stent used for delivery of Sirolimus: The CYPHERTM Sirolimus-Eluding Stent. (Courtesy of Cordis, A Johnson & Johnson Company, Miami Lakes, FL.)


Sirolimus-Eluting Stent (SES)

The first DES approved for use in PCI by the FDA in 2003 was the CYPHERTM sirolimus-eluting stent (Fig. 23-6). The CYPHER stent has a stainless steel stent platform, the BX Velocity, covered with a thin polymer coating containing the drug sirolimus. The slow-release formulation inhibits cell proliferation by targeting smooth muscle cells, while simultaneously reducing inflammatory cytokine production and resultant vessel wall inflammation.35


Paclitaxel-Eluting Stent (PES)

The second DES approved by the FDA in 2004 was the TAXUSTM paclitaxel-eluting stent (Fig. 23-7). The Express-2 stent is used as the stent platform and the drug paclitaxel is placed on the stent with a copolymer coating. Paclitaxel is a potent antiproliferative agent released in a biphasic manner, with an initial burst in the first 2 days, followed by lower-level sustained release for 10 days (Fig. 23-8).36 Safety and efficacy have been shown with repeat intervention rates at 30 months to be approximately 10% for SES and 13% for PES.37






Figure 23-7 The TAXUSTM Stent on the Balloon Delivery System. (Courtesy of Boston Scientific Corporation, Maple Grove, MN.)






Figure 23-8 The TAXUSTM Stent. The Express 2 Stent is used as the platform for the Paclitaxel-Eluting Stent. A dime is placed next to the device to represent size. (Courtesy of Boston Scientific Corporation, Maple Grove, MN.)


MANAGEMENT OF THE PATIENT DURING PCI


Preprocedure Management

Preparation for elective or acute PCI requires informed consent after physician discussion of risks and benefits, provisional consent for emergency CABG surgery, and patient education. Patient education includes expectations during the procedure and postprocedural care using visual, written, and verbal information. The nursing history (including all current medications and herbal supplements) and physical examination are documented, with abnormalities reported to the physician and catheterization laboratory staff prior to the PCI.


Patients with Diabetes Mellitus

Oral hypoglycemic agents are usually held prior to the PCI. The combination of contrast medium and metformin should be completely avoided in patients with renal dysfunction, hepatic dysfunction, alcohol abuse, or severe congestive heart failure because all these conditions limit metformin excretion and can increase lactate production, possibly leading to fatal lactic acidosis.38 Insulin dosage adjustments are ordered by the physician. In general,
one-half the usual dose of insulin is given with continued surveillance of blood glucose before and after the procedure. Insulin drips are used for patients with Type I diabetes mellitus, difficult glycemic control, ACS, or who are otherwise unstable.


Patients With Renal Insufficiency

Patients with pre-existing renal insufficiency and/or diabetes mellitus have an increased risk of contrast-induced nephropathy with contrast medium used during PCI. Renal dysfunction is present when creatinine clearance is less than 60 mL/min or serum creatinine is >1.5 mg/dL. Creatinine clearance should be estimated and medication dosage adjusted in patients with altered renal function. Isosmolar contrast agents should be used during PCI. The major preventive strategy includes adequate hydration before and after the procedure. The combination of N-acetylcysteine and sodium bicarbonate infusion before and after contrast administration has been reported to reduce the risk of contrast-induced nephropathy in patients with renal insufficiency.39


Intraprocedure Management

Patient preparation is similar to the patient having a diagnostic cardiac catheterization (Chapter 20). Conscious sedation is given at the discretion of the cardiologist and the patient monitored by the catheterization laboratory staff as per protocol. A sheath is placed in the femoral artery, which is the most common arterial access site. Alternatively, the brachial or radial artery can be used for arterial access.

A bolus of heparin is given to maintain an activated clotting time (ACT) of 250 to 300 seconds. ACT below 250 seconds has been associated with thrombotic complications during PCI with multiple catheters, wires, or devices being placed in the aorta and coronary arteries. Use of low-molecular-weight heparin (LMWH) or direct thrombin inhibitors can be used as an alternative to heparin (see anticoagulation options for PCI).40,41 For patients who undergo PCI with LMWH, specific dosage regimens are available. When fondaparinux (an LMWH) is used prior to intervention, additional intravenous treatment with an anticoagulant possessing anti-IIa activity (such as unfractionated heparin, or UFH) should be used because of the risk of catheter thrombosis.4 Baseline angiographic views are obtained of the coronary artery to be treated using the standard diagnostic catheter or the guiding catheter. Coronary injections may be repeated after administration of intracoronary nitroglycerin to exclude spasm as a significant component of the target stenosis and to minimize the occurrence of coronary spasm during the PCI. The appropriate guiding catheter is positioned in the coronary ostium and a guidewire is directed across the stenotic lesion. After the wire tip is confirmed to be in the distal portion of the coronary artery to be treated, the angioplasty balloon or other device is selected. The patient is monitored for hemodynamic stability and electrocardiographic changes during the procedure.

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Jan 10, 2021 | Posted by in NURSING | Comments Off on Interventional Cardiology Techniques: Percutaneous Coronary Intervention
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