Percutaneous Coronary Intervention
Amar Krishnaswamy
Samir R. Kapadia
I. INTRODUCTION
A. Coronary atherosclerosis may result in a flow-limiting stenosis that leads to myocardial ischemia and/or myocardial infarction (MI). Andreas Gruentzig first managed these lesions percutaneously on September 16, 1977, when he advanced a fixedwire, distensible balloon across a stenosis in the mid—left anterior descending (LAD) artery and briefly inflated it to 6 atm (90 psi). This procedure was termed percutaneous transluminal coronary angioplasty (PTCA). With the advent of stents and other therapeutic coronary devices, these procedures are now more broadly termed percutaneous coronary intervention (PCI). It is estimated that more than 1 million PCI procedures are completed in the United States and approximately 2 million worldwide annually.
B. The field of interventional cardiology continues to rapidly evolve, as a result of many important advances in equipment, strategies, and adjunctive medication. These advances have been paralleled by a concomitant improvement in the safety and efficacy profile of PCI. The assimilation of a large body of basic and clinical research encompassing all areas of interventional cardiology continues to redefine the standard of care paradigm.
II. PCI INDICATIONS
A. Central tenet.
Although there is no substitute for sound clinical judgment, PCI is generally reserved for patients in whom there is an objective demonstration of myocardial ischemia or symptoms as well as angiographic demonstration of obstructive coronary disease. PCI may not be indicated for asymptomatic or mildly symptomatic patients who have only a small area of viable or jeopardized myocardium, have no objective evidence of myocardial ischemia, have other life-limiting disease processes, or have lesions that have a low likelihood of success (Tables 65.1 and 65.2).
B. ST-segment elevation myocardial infarction (STEMI). Primary PCI should be the preferred treatment strategy for patients presenting with STEMI to a facility experienced with and capable of performing PCI.
Randomized trials have demonstrated that clinical outcomes are improved when such patients are emergently transferred to centers able to perform primary PCI as opposed to therapy with thrombolytics—despite a significant delay (mean time of 44 minutes) in time to therapy due to transport. This seems especially true of patients presenting 3 to 12 hours after symptom onset, where the superiority of primary PCI becomes clearly evident. In those presenting within 3 hours of symptom onset, mortality data would suggest that either therapy is equally efficacious in appropriate candidates. For a more thorough discussion of the management of STEMI, please refer to Chapter 1.
C. Non—ST-segment elevation acute coronary syndrome (NSTEACS).
Unstable angina and non—ST-segment elevation myocardial infarction (NSTEMI) are considered part of the spectrum of NSTEACS. Given that individual patients presenting
with unstable angina/NSTEMI are at widely varying risk for subsequent morbidity and mortality, early and aggressive risk stratification including cardiac catheterization with subsequent percutaneous or surgical revascularization (rather than noninvasive stress testing) is recommended. This recommendation is supported by a number of clinical trials comparing an early invasive to delayed conservative strategy. For a more thorough discussion of the management of NSTEACS, please refer to Chapter 2.
with unstable angina/NSTEMI are at widely varying risk for subsequent morbidity and mortality, early and aggressive risk stratification including cardiac catheterization with subsequent percutaneous or surgical revascularization (rather than noninvasive stress testing) is recommended. This recommendation is supported by a number of clinical trials comparing an early invasive to delayed conservative strategy. For a more thorough discussion of the management of NSTEACS, please refer to Chapter 2.
TABLE 65.1 Standard Prepercutaneous Coronary Intervention Evaluation | ||||
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TABLE 65.2 Considerations for Every Percutaneous Coronary Intervention | ||||||
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D. Chronic stable angina.
It is estimated that > 85% of all PCI procedures are performed in the elective setting for chronic stable angina. While recent trials have
questioned the mortality benefit of PCI or coronary artery bypass grafting (CABG) over optimal medical therapy in stable coronary artery disease (CAD), revascularization still remains the most rapidly effective treatment strategy for patients with angina. For a more thorough discussion of the management of stable CAD, please refer to Chapter 6.
questioned the mortality benefit of PCI or coronary artery bypass grafting (CABG) over optimal medical therapy in stable coronary artery disease (CAD), revascularization still remains the most rapidly effective treatment strategy for patients with angina. For a more thorough discussion of the management of stable CAD, please refer to Chapter 6.
III. CONTRAINDICATIONS.
The only absolute contraindication to PCI is significant active bleeding, given the absolute need for procedural anticoagulation and continued dual antiplatelet therapy (DAT). Relative contraindications include a bleeding diathesis, unsuitable or high-risk coronary anatomy (e.g., chronic total occlusion in the absence of ischemia or diffuse distal disease), recurrent in-stent restenosis (ISR), and a short life expectancy because of a comorbid condition.
IV. PROGNOSIS.
A patient’s clinical status and coronary angiogram are powerful predictors of outcome. Certain clinical and angiographic variables have repeatedly been associated with adverse events (Table 65.3).
V. ANGIOGRAPHIC/PROCEDURAL/CLINICAL SUCCESS.
Angiographic success is defined as a residual stenosis < 50% with PTCA or < 20% with stenting and is achieved in 96% to 99% of patients. The definition of procedural success is angiographic success without major in-hospital complications (i.e., death, CABG, or MI). Clinical success is defined as procedural success with relief of the symptoms and signs of myocardial ischemia.
VI. COMPLICATIONS
A. The incidence of complications (death 0.5% to 1.4%, periprocedural MI [defined by creatine kinase-myocardial band, CK-MB, elevation more than three times the upper limit of normal] up to 8%, and emergency CABG surgery 0.2% to 0.3%) has consistently decreased over the past 20 years with the advent of stents, new and more effective antiplatelet therapies, improved equipment, and increasing reliance upon evidence-based strategies.
B. Abrupt closure is the most common cause of a major adverse cardiac event (MACE) and typically occurs within 6 hours of intervention. The most common cause of abrupt
closure is suboptimal stent expansion or dissection followed by thrombus, spasm, and side branch occlusion. In the mid-1980s, the risk of abrupt closure approached 5%. The common use of periprocedural glycoprotein (GP) IIb/IIIa and/or direct thrombin-inhibiting anticoagulants and stent deployment has reduced this risk to < 1% in modern practice. Risk factors for abrupt closure include presentation with acute MI, poor coronary flow postintervention (i.e., less than Thrombolysis in Myocardial Ischemia [TIMI] II), complex lesion morphology (i.e., class C lesions), and suboptimal result as judged by angiography or intravascular ultrasound (IVUS) imaging.
closure is suboptimal stent expansion or dissection followed by thrombus, spasm, and side branch occlusion. In the mid-1980s, the risk of abrupt closure approached 5%. The common use of periprocedural glycoprotein (GP) IIb/IIIa and/or direct thrombin-inhibiting anticoagulants and stent deployment has reduced this risk to < 1% in modern practice. Risk factors for abrupt closure include presentation with acute MI, poor coronary flow postintervention (i.e., less than Thrombolysis in Myocardial Ischemia [TIMI] II), complex lesion morphology (i.e., class C lesions), and suboptimal result as judged by angiography or intravascular ultrasound (IVUS) imaging.
TABLE 65.3 Clinical and Angiographic Predictors of Adverse Outcomes | ||||||
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C. Atheroembolism and thromboembolism probably occur to varying degrees in all interventions, but are most frequently encountered in cases involving degenerated vein grafts, in patients presenting with acute coronary syndromes (ACSs), and in cases using directional/rotational atherectomy. Distal embolization can result in “no-reflow” (decreased coronary flow), abrupt closure, and periprocedural MI. Thromboembolism can be minimized by using aspiration catheters (e.g., Pronto, Export, Extract) or rheolytic thrombectomy (Possis AngioJet) to remove thrombus as well as routine anticoagulant and antiplatelet therapy. The prevention of atheroembolus, most often encountered during vein graft intervention, is frequently addressed with the use of a filter device (e.g., FilterWire EZ or PercuSurge GuardWire) or proximal flow occlusion device (e.g., Proxis) to trap and remove the debris before it reaches the distal vascular bed. Intracoronary administration of vasodilators such as adenosine (36 to 72 µg repeatedly), nitroprusside (50 to 200 µg), and verapamil (200 µg) has been shown to prevent and manage no-reflow, but have no effect in preventing CK-MB elevation.
D. Coronary perforation is typically identified using the Ellis classification: Type I: extraluminal crater without extravasation; Type II: pericardial or myocardial blush without contrast jet extravasation; Type III: extravasation through frank (> 1 mm) perforation; Type III cavity spilling: perforation into an anatomic chamber, coronary sinus, etc. Coronary perforation is estimated to occur in 0.1% to 1.14% of routine PCI cases, 0.25% to 0.70% of cases using directional atherectomy, up to 1.3% of cases using rotational atherectomy, 1.3% to 2.1% of cases using extractional atherectomy, and 1.9% to 2.0% following excimer laser angioplasty. Contrast extravasation is typically evident in the majority of cases at the time of PCI; however, up to 20% of cases can present several hours after the procedure and are frequently due to hydrophilic wire perforation of a small vessel. Treatment usually requires prolonged balloon inflation (consider a perfusion balloon) and reversal of anticoagulation. Transthoracic echocardiography should be immediately performed in the setting of clinical instability in order to evaluate for the presence of a pericardial effusion and/or tamponade, in which case urgent pericardiocentesis is required. Covered stents, coils, or surgical repair may be required for definitive management.
E. Vascular access site complications remain the most common complication of PCI and occur in up to 5% of patients. The most common are blood transfusion (3%), arteriovenous fistula (< 2%), pseudoaneurysm (up to 5%), acute arterial occlusion (< 1%), and infections (< 0.1%). Shorter anticoagulation regimens, weight-adjusted heparin, use of bivalirudin, early sheath removal, vigilant monitoring of activated clotting times (ACTs), smaller sheaths, and avoidance of routine venous sheath insertion have all contributed to a reduction in complications. Stopping heparin after PCI and substituting clopidogrel for warfarin has also resulted in a reduction of bleeding and coronary complications.
F. Contrast-induced nephropathy occurs in 3% to 7% of patients, and the risk increases tenfold for patients with serum creatinine > 2.0 mg/dL, especially in the presence of diabetes mellitus. Data regarding methods to prevent renal failure are not definitive, but the most proven benefit is seen with conservative contrast utilization. In addition, use of biplane imaging can significantly reduce the amount of contrast required. Numerous studies have provided mixed results on the benefits of saline infusion before catheterization, administration of N-acetylcysteine (NAC) 600 mg po or IV bid for 1 day before and after the day of catheterization, single bolus dose
NAC prior to contrast load, using nonionic contrast dye, and infusion of a sodium bicarbonate solution.
NAC prior to contrast load, using nonionic contrast dye, and infusion of a sodium bicarbonate solution.
G. Contrast-mediated reactions can be serious. Anaphylactoid reactions occur in 1% to 2% of patients receiving iodinated contrast. These reactions can be severe in 0.10% to 0.23% of patients. The risk of a severe reaction can be effectively decreased by using nonionic contrast, preprocedural corticosteroids (i.e., prednisone 40 to 60 mg) given the evening before and the morning of the procedure, and the use of H1 and H2 blockers. If a patients presents for emergent PCI (i.e., STEMI) without having undergone preprocedural steroid preparation, the emergent administration of hydrocortisone 100 mg IV and diphenhydramine 25 to 50 mg IV is reasonable and is shown to be safe in small series. In patients undergoing an elective procedure, caution is prudent and a full premedication regimen is recommended.
H. Stent thrombosis (ST) is discussed later in Section XI.D.
VII. EXPERIENCED OPERATORS/CENTERS
A. Procedural volume is an important predictor of PCI complications. Elective PCI should be performed in high-volume centers (> 200 interventions per year, with an ideal minimum of > 400 cases per year) by operators with an acceptable annual volume (> 75 cases per year) at institutions with fully equipped interventional laboratories, experienced support staff, and an on-site cardiovascular surgical program. Primary PCI for STEMI should be performed in similarly experienced/skilled centers by operators who perform > 75 elective cases per year and intervene on at least 11 cases of STEMI per year. Elective PCI should not be performed by low-volume operators (< 75 cases per year) in low-volume centers (< 200 cases per year), regardless of the availability of on-site cardiothoracic surgery, because of the increased risk of suboptimal outcomes. Referral to a larger regional center is recommended in this situation.
B. In cases of STEMI, there is an inverse relationship between the number of primary angioplasty procedures performed by an operator and in-hospital mortality. The data suggest that both door-to-balloon time and in-hospital mortality are significantly lower in institutions that perform a minimum of 36 primary angioplasty procedures per year.
VIII. SURGICAL BACKUP.
Emergency surgical intervention is a rare event and is required in 0.3% to 1.0% of cases of PCI, usually because of complications that cannot be addressed percutaneously or to provide urgent hemodynamic support. The most common reasons for emergency CABG surgery are dissection resulting in acute vessel closure, perforation, inability to retrieve a stent or other device, or aortic dissection. Emergency CABG after PCI has a mortality rate of 15% and periprocedural MI rate of 12%. The internal mammary artery may not be harvested, and surgery should not be delayed due to abciximab. Perfusion balloons may temporize a life-threatening perforation or dissection, and an intraaortic balloon pump (IABP) can minimize ischemic injury and stabilize hemodynamics. Data from the Atlantic Cardiovascular Patient Outcomes Research Team (C-PORT) and Primary Angioplasty in Acute Myocardial Infarction with No Surgery On-Site (PAMI-No SOS) trials suggest that primary PCI for STEMI can be safely and effectively performed in centers that do not perform elective PCI and do not have on-site cardiac surgery capabilities if they implement a carefully developed and proven strategy capable of rapid and effective PCI (including an experienced operator with > 75 total PCIs and at least 11 primary PCIs for STEMI per year) with a predetermined transfer plan to a nearby center with on-site surgical backup.
IX. SHEATHS, GUIDES, AND WIRES
A. Typical arterial access involves placing a 6F to 8F short sheath in the common femoral artery using the modified Seldinger technique. Using fluoroscopic guidance when entering the femoral artery above the inferior margin of the femoral head but below the pelvic rim increases the likelihood of entering the common femoral artery
at a compressible site above the common femoral artery bifurcation and below the inferior epigastric artery. The superficial/profunda femoral artery bifurcation is best seen in the ipsilateral 30° to 40° projection. The brachial and radial arteries can accommodate up to 7F and 6F sheaths, respectively. Ulnar artery and digital arch patency should be confirmed via the Allen test in case the radial artery becomes occluded (approximately 5%). Radial access improves hemostasis and earlier ambulation but increases radiation exposure, lengthens the procedure, and limits the choice of coronary equipment (6F compatible).
at a compressible site above the common femoral artery bifurcation and below the inferior epigastric artery. The superficial/profunda femoral artery bifurcation is best seen in the ipsilateral 30° to 40° projection. The brachial and radial arteries can accommodate up to 7F and 6F sheaths, respectively. Ulnar artery and digital arch patency should be confirmed via the Allen test in case the radial artery becomes occluded (approximately 5%). Radial access improves hemostasis and earlier ambulation but increases radiation exposure, lengthens the procedure, and limits the choice of coronary equipment (6F compatible).
B. Larger guide size (7F or 8F) provides extra support and permits the use of larger rotational atherectomy burrs and use of kissing balloons. For straightforward lesions, a 6F system is typically adequate. The XB (extra backup) and Amplatz guiding catheters provide good support; the Amplatz guide is especially effective in cases of an acutely angled left circumflex artery, anomalous left circumflex artery originating from the right sinus, very anteriorly originating right coronary artery, or a tortuous/calcified right coronary artery. The Amplatz guide catheter is also the most likely catheter to traumatize the ostial/proximal coronary artery in inexperienced hands due to its tendency to deeply engage the vessel.
C. The coronary lesion is initially crossed with a 0.014” diameter coronary wire, which serves as a “rail” for devices such as balloons and stents. The choice of a wire depends on the wire tip’s stiffness, lubriciousness, and support characteristics. Stiff tips are helpful to penetrate chronic total occlusions but increase the risk of vessel dissection or perforation. Hydrophilic wires are quite slippery and may be used to cross tortuous high-grade lesions, but can easily cause dissection or end-vessel perforation. Support wires also typically have stiffer tips and are primarily used as a supportive rail to deliver coronary equipment through tortuous vessels. Generally, most operators routinely use a “workhorse” wire (i.e., Prowater or Balance Middle Weight) and have “favorite” stiff (e.g., Miracle Bros series), hydrophilic (e.g., Whisper and Pilot series), and support (e.g., GrandSlam and Balance HeavyWeight) wires for use in appropriate situations. Both short (approximately 180 cm) and long (approximately 300 cm) wires are available. Most operators prefer the routine use of a rapid exchange (Rx) system, which uses a monorail that permits easy exchange over a short wire, although situations that require an over-the-wire system may be better served with the use of a longer wire to avoid dislodging the wire during equipment exchanges.
X. DIAGNOSTIC ADJUNCTS
A. IVUS (anatomic)
1. An IVUS catheter generates a cross-sectional tomographic image of both the lumen and the vessel wall. This complementary imaging modality can be invaluable when repeated angiographic views fail to determine the mechanism and/or significance of a coronary lesion. IVUS has proven helpful in assessing adequacy of coronary stent deployment, mechanism of ISR (neointimal hyperplasia versus inadequate stent expansion), a coronary lesion at a location difficult to image by angiography, a suboptimal angiographic result after PCI, coronary allograft vasculopathy after cardiac transplantation, coronary calcium when considering rotational atherectomy, and plaque location/circuinferential distribution to guide directional coronary atherectomy (DCA). Further, IVUS can be indispensible in assessing the appropriate vessel size, especially during ACS when factors such as thrombus and vasoconstrictive substances can lead to significant stent undersizing.
2. IVUS provides anatomic, not physiologic, information. However, a lumen area < 4.0 mm2 in the proximal LAD, left circumflex, or right coronary artery or < 6.0 to 7.0 mm2 in the left main trunk suggests the presence of a hemodynamically significant lesion.
B. Optical coherence tomography (OCT).
Similar to IVUS, OCT images are obtained by passing the catheter over a guidewire in the coronary artery. The catheter
acquires images during an automated pullback over 5.6 cm and requires the clearance of blood in the vessel, thereby necessitating a 15 to 18 cc contrast injection with each acquisition. In comparison with IVUS, it provides much greater image resolution but a more shallow penetration. Outside of research use, OCT is finding a place in the clinical armamentarium. The superior image quality allows an evaluation of stent apposition, poststent dissection, and analysis of plaque characteristics and plaque rupture. Recently, investigators have used OCT to evaluate endothelial stent coverage, which in the future may allow a further tailoring of antiplatelet therapy at the patient-specific level. Currently, there is a paucity of clinical outcomes data using OCT, but interest in this imaging modality is gaining momentum, with supportive data likely to follow.
acquires images during an automated pullback over 5.6 cm and requires the clearance of blood in the vessel, thereby necessitating a 15 to 18 cc contrast injection with each acquisition. In comparison with IVUS, it provides much greater image resolution but a more shallow penetration. Outside of research use, OCT is finding a place in the clinical armamentarium. The superior image quality allows an evaluation of stent apposition, poststent dissection, and analysis of plaque characteristics and plaque rupture. Recently, investigators have used OCT to evaluate endothelial stent coverage, which in the future may allow a further tailoring of antiplatelet therapy at the patient-specific level. Currently, there is a paucity of clinical outcomes data using OCT, but interest in this imaging modality is gaining momentum, with supportive data likely to follow.
C. Angioscopy (anatomic).
Angioscopy uses a balloon-tipped catheter with a fiber optic viewport at the distal tip that allows direct visualization of the lumen. Angioscopically evident thrombus has been shown to be angiographically silent in up to 50% of patients. This imaging modality is only used for research purposes.
D. Coronary flow reserve (CFR) (physiologic)
1. A 0.014” wire capable of measuring coronary flow velocity permits assessment of epicardial and microvascular resistance. This information is helpful in determining whether a moderate-grade coronary stenosis (i.e., 30% to 70% stenosis) is hemodynamically significant. The ratio of hyperemic to basal flow is known as the CFR and is determined by giving an intracoronary vasodilator such as adenosine (36 to 64 µg). A normal CFR is 3 to 5. A CFR < 2.0 is abnormal and is consistent with a flow-limiting epicardial stenosis or increased microvascular tone.
2. The effect of the microvasculature can be eliminated by measuring the CFR in two vessels: the lesion-containing vessel and a normal-appearing vessel. This allows calculation of the relative coronary flow reserve velocity (rCFR= CFRtarget/CFRreference). A nonhemodynamically significant stenosis has an rCFR value of < 0.8 and is similar in prognostic value to negative stress testing. Unlike fractional flow reserve (FFR), CFR depends on hemodynamic and microcirculatory changes. In general, FFR is the preferred diagnostic modality for assessing the hemodynamic significance of a coronary lesion.
E. FFR (physiologic).
A 0.014” wire with a pressure transducer is placed distal to a coronary stenosis and the translesional gradient measured. This allows calculation of the FFR, which is the ratio of this distal coronary pressure to aortic pressure during maximal hyperemia. A vasodilator such as adenosine (IV infusion 140 µg/kg/min or intracoronary 36 to 64 µg) is used. A coronary artery without flow-limiting coronary obstruction would have an FFR of 1.0. An FFR value of < 0.75 to 0.80 is consistent with a hemodynamically significant obstruction and positively correlates with myocardial ischemia on stress testing. Unlike CFR, the FFR reflects only the epicardial artery lesion. Prospective studies have demonstrated that an FFR-guided strategy to direct PCI of intermediate lesions results in less stents deployed, with a significant decrease in morbidity and mortality compared with an angiography-only strategy (8.4% vs. 23.9%, p = 0.02).
F. Pulmonary artery catheter (physiologic).
A balloon-tipped Swan-Ganz catheter advanced to the pulmonary arteries allows measurement of right and left heart filling pressures as well as the cardiac output. This information can be helpful in patients presenting with cardiogenic shock, during high-risk PCI in the setting of severe left ventricular (LV) dysfunction, when there is a question of pericardial tamponade, or when the cause of hemodynamic deterioration is unclear.
XI. THERAPEUTIC DEVICES
A. Percutaneous transluminal coronary angioplasty.
The coronary balloon remains the backbone of endovascular intervention, although its sole use is in decline. The initial gain in the coronary lumen achieved by balloon inflation results in localized dissection of the intima (and often the media) plus distension of the adventitia. The
dissection is covered by platelet-rich thrombus and later by new intimal layers. As a result of these inevitable dissections, the abrupt closure rate is 4% to 7%, although the use of GP IIb/IIIa inhibitors has reduced this rate. The 6-month angiographic restenosis rate of 30% to 40% is another downside to PTCA. Furthermore, the risk of cardiac morbidity, including anginal symptoms, progressively increases with subsequent episodes of ISR following balloon angioplasty. It is recommended that patients determined to have significant ISR following PTCA should be strongly considered for coronary stent implantation.
dissection is covered by platelet-rich thrombus and later by new intimal layers. As a result of these inevitable dissections, the abrupt closure rate is 4% to 7%, although the use of GP IIb/IIIa inhibitors has reduced this rate. The 6-month angiographic restenosis rate of 30% to 40% is another downside to PTCA. Furthermore, the risk of cardiac morbidity, including anginal symptoms, progressively increases with subsequent episodes of ISR following balloon angioplasty. It is recommended that patients determined to have significant ISR following PTCA should be strongly considered for coronary stent implantation.
PTCA alone may still have utility in patients presenting with ACS found to have multivessel disease suitable for urgent/emergent CABG (e.g., PTCA alone rapidly restores patency to the infarct-related artery but may allow a break in the need for antiplatelet therapy, thereby allowing the patient to proceed to surgery without delay). Even in these situations, however, aspiration thrombectomy alone may be preferred if it provides reasonable flow to the infarct artery in order to avoid the risk of mechanical complications with PTCA, such as dissection or perforation, that would require stent deployment.
B. Bare-metal stents (BMSs)
