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`Page 1
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`

`

`An Affiliate of Elsevier
`
`The Curtis Center
`Independence Square West
`Philadelphia, Pennsylvania 19106
`
`THE INTERVENTIONAL CARDIAC CATHETERIZATION
`HANDBOOK,
`Second Edition
`Copyright © 2004, 1996, Elsevier Inc. All rights reserved.
`
`ISBN 0-323-02238-3
`
`No part of this publication may be reproduced or transmitted in any form or by any
`means, electronic or mechanical, including photocopying, recording, or any information
`storage and retrieval system, without permission in writing from the publisher.
`Permissions may be sought directly from Elsevier Inc. Rights Department in
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`Support” and then “Obtaining Permissions.”
`
`NOTICE
`Cardiology is an ever-changing field. Standard safety precautions must be followed,
`but as new research and clinical experience broaden our knowledge, changes in treat-
`ment and drug therapy may become necessary or appropriate. Readers are advised to
`check the most current product information provided by the manufacturer of each
`drug to be administered to verify the recommended dose, the method and duration
`of administration, and contraindications. It is the responsibility of the treating physi-
`cian, relying on experience and knowledge of the patient, to determine dosages and
`the best treatment for each individual patient. Neither the Publisher nor the editor
`assume any liability for any injury and/or damage to persons or property arising from
`this publication.
`
`The Publisher
`
`Library of Congress Cataloging-in-Publication Data
`
`Interventional cardiac catheterization handbook / edited by Morton J. Kern – 2nd ed.
`p. ; cm.
`Companion v. to: The cardiac catherization handbook / edited by Morton J. Kern. 4th
`ed. c2003.
`Includes bibliographical references and index.
`ISBN 0-323-02238-3
`1. Cardiac catheterization—Handbooks, manuals, etc. I. Kern, Morton J. II. Cardiac
`catheterization handbook.
`[DNLM: 1. Heart Catheterization—methods—Handbooks. WG 39 I61 2004]
`RC683.5.C25I587 2004
`616.1’20754—dc22
`
`2003066633
`
`Acquisition Editor: Anne Lenehan
`Developmental Editor: Sarah Cameron
`
`Printed in United States of America
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`Last digit is the print number: 9 8 7 6 5 4 3 2 1
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`1
`
`BASIC CORONARY BALLOON
`ANGIOPLASTY AND STENTING
`
`Morton J. Kern
`
`INTRODUCTION
`On September 16, 1977, Andreas Grüentzig performed the first
`human percutaneous transluminal coronary angioplasty
`(PTCA) in Zurich, Switzerland. Until then, coronary artery
`bypass surgery was the only alternative to medicine for the
`treatment of coronary artery disease. Over the last 26 years,
`new developments have resulted in a dramatic growth of
`percutaneous coronary intervention (PCI) as one of the most
`successful methods of coronary revascularization. In 2002
`approximately 750,000 patients underwent PCI in the USA
`alone. PCI is the treatment of choice for discrete single- and
`double-vessel coronary lesions in patients with good left
`ventricular function and plays an important role in complex
`revascularization in patients with multivessel coronary artery
`disease and depressed left ventricular function. Today there are
`many techniques to open a narrowed artery, not only of the
`coronary arteries but also of the peripheral and great arteries of
`the body. The use of various techniques, which include
`balloons, stents, cutters, lasers, grinders, suckers, filters and
`other tools, are collectively called PCI. Percutaneous trans-
`luminal coronary angioplasty (PTCA) will be used to describe
`information and techniques related to use of the balloon infla-
`tion technique alone that was first employed by Grüentzig.
`This chapter will present the basic method and mechanisms
`of balloon angioplasty and stenting as an introduction to the
`practice of interventional cardiology. The various techniques of
`
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`12
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`Interventional Cardiac Catheterization Handbook
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`percutaneous coronary revascularization can be placed into
`niche applications for specific devices (Table 1-1).
`OVERVIEW OF THE BASIC PCI METHODS
`Percutaneous coronary intervention was derived from the basic
`procedures used for diagnostic cardiac coronary angiography.
`PCI begins with vascular access and uses the same techniques
`for the insertion of an arterial sheath through the arm (radial
`artery) or leg as Seldinger’s method (needle and guidewire).
`Specialized larger-lumen “guiding” catheters engage the
`coronary artery in the same manner as those used for diagnostic
`coronary angiography with relatively minor differences.
`Figure 1-1 shows how to perform PCI. A guiding catheter is
`first seated in the coronary ostium. A thin, steerable guidewire
`is introduced into the coronary artery and positioned across
`the stenosis into the distal aspect of the artery. An angioplasty
`catheter, which is considerably smaller than the guiding
`
`Table 1-1
`Niche Applications of PCI Devices
`Balloon/
`Stent
`
`Lesion Type
`
`Rotoblator DCA
`
`Type A
`Complex
`Ostial
`Diffuse
`Total occlusion
`Calcified bifurcation
`SVG Focal
`SVG Diffuse
`SVG Thrombotic
`Complication
`dissection
`Acute Occlusion
`Thrombosis
`Perforation
`
`+++
`++
`++
`+
`++
`±
`+++
`+
`±
`+++
`
`++
`+
`±
`
`++
`++
`++
`+++
`+
`++
`±
`±
`–
`–
`
`–
`–
`–
`
`–
`+
`–
`–
`–
`+
`+
`–
`–
`±
`
`–
`–
`–
`
`Special
`TEC Device
`
`–
`–
`–
`–
`–
`–
`±
`++
`++
`–
`
`–
`+
`–
`
`–
`–
`–
`–
`–
`–
`–
`–
`Angio Jet
`–
`
`–
`Angio Jet
`Covered
`stent,
`perfusion
`balloon
`
`+++ highly applicable; ++ somewhat helpful; + applicable; ± marginal; – not applicable.
`DCA, directional coronary atherectomy; TEC, transluminal extraction catheter.
`
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`13
`
`How angioplasty and stenting works. A, The artery is filled with
`Fig. 1-1
`atherosclerotic material, compromising the lumen. A cross-section of the artery
`is shown on the right side. B, A guidewire is positioned past the stenoses
`through the lumen. C, A balloon catheter is advanced over the guidewire. D, The
`balloon is inflated. E, The balloon is deflated and withdrawn. F, The balloon
`catheter is exchanged for a stent (on a balloon). G, The stent is expanded.
`H, The expanded stent remains in place after the deflated balloon is withdrawn.
`(Reproduced with permission from ‘Your PTCA, our Guide to Percutaneous
`Transluminal Coronary Angioplasty’, American Heart Association, 2001.)
`
`catheter, is inserted through the guiding catheter and is
`positioned (in the artery) across the stenotic area by tracking it
`over the guidewire. Once correctly placed within the area to be
`treated, the balloon on the PCI catheter is inflated several times
`for periods ranging from 10 seconds to several minutes. The
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`inflation and deflation of the balloon in the blocked artery
`restores blood flow to an area of the heart previously deprived
`by the stenosed artery. The stent on a balloon catheter is also
`deployed in the same manner. The definitions of a successful
`PCI procedure are summarized in Box 1-1.
`Figure 1-2 shows the components of the PCI system. There
`are three major difficulties with PCI: (1) stable guide catheter
`positioning; (2) negotiating tortuous vessel segments with the
`guidewire; (3) delivering the stent through tortuous segments.
`To complete the PCI, the operator must control the three
`principal movable components (guide catheter, balloon
`catheter, and guidewire).
`After the balloon catheter is positioned, and compresses the
`stenotic material, a stent will then be delivered. After the PTCA,
`the balloon is exchanged for a catheter carrying a stent. The
`stent is a metal scaffold, compressed on another balloon
`catheter and delivered exactly as the first balloon catheter was
`delivered. The stent should be precisely positioned and is
`inflated with the same pressure gauge syringe (to high
`pressure) for 10–20 seconds. A full opening of the stent is
`important to a good result. After the stent is expanded into the
`artery wall, the balloon is deflated and the delivery catheter and
`guidewire are removed. After final angiography is performed,
`the guide catheter is removed. The arterial sheath is secured, to
`be removed later, or removed and the puncture site sealed in
`the laboratory. The patient is then transferred to his room. If
`no complications occur, the patient is discharged the next
`morning. The patient commonly returns to work shortly
`(<3 days) thereafter.
`
`MECHANISMS OF ANGIOPLASTY
`Several mechanisms of angioplasty have been proposed.
`● Disruption of plaque and the arterial wall. The inflated
`balloon exerts pressure against the plaque and the arterial
`wall, causing fracturing and splitting. Concentric (round or
`circumferential) lesions fracture and split at the thinnest and
`weakest points. Eccentric lesions split at the junction of the
`plaque and the normal arterial wall. Dissection or separation
`of the plaque from the vessel wall releases the restraining
`effect caused by the lesion and results in a larger lumen. This
`is the major mechanism of balloon angioplasty.
`● Loss of elastic recoil. Balloon dilatation causes stretching
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`15
`
`Box 1-1
`Definitions of PCI Success
`PCI success may be defined by angiographic, procedural, and clinical criteria.
`
`Angiographic Success
`A successful PCI substantially enlarges the vessel lumen at the target site. Prior
`to stents, success was the achievement of a minimum stenosis diameter
`reduction to <50% with grade 3 TIMI flow (assessed by angiography). With
`coronary stents, success is a minimum stenosis diameter reduction to <20%.
`
`Procedural Success
`A successful PCI should achieve angiographic success without in-hospital major
`clinical complications (e.g., death, myocardial infarction [MI], emergency
`coronary artery bypass surgery) during hospitalization. MI is often defined as the
`development of Q-waves in addition to a threshold value of creatine kinase (CK)
`elevation has been commonly used. The significance of enzyme elevations in the
`absence of Q waves is controversial. Several reports have identified non-Q-wave
`MIs with CK-MB without Q-waves as an associated complication of PCI.
`If serial determinations are performed, an abnormally high value (CK-MB >1
`times normal) can be expected in 10–15% of PTCA procedures, 15–20% of stent
`procedures, 25–35% of atherectomy procedures, and more than 25% for any
`device used in saphenous vein grafts or long lesions with a high atherosclerotic
`burden, even in the absence of other signs and symptoms of MI. There is no
`accepted consensus on what level of CK-MB index (with or without clinical or
`ECG findings) is indicative of a clinically important MI following the
`interventional procedure.
`Cardiac troponin T and I as measurements of myocardial necrosis are more
`sensitive and specific than CK-MB. However, prognostic criteria based on
`troponin T and I have not yet been developed. In patients in whom a clinically
`driven CK-MB determination is made, a CK-MB of more than three times the
`upper limit of normal constitutes a clinically significant MI.
`
`Clinical Success
`A clinically successful PCI is anatomic and procedural success with relief of signs
`and/or symptoms of myocardial ischemia after recovery from the procedure. The
`long-term clinical success requires that the patient has persistent relief of signs
`and symptoms of myocardial ischemia for more than 6 months. Re-stenosis is the
`principal cause of lack of long-term clinical success when short-term clinical
`success has been achieved.
`
`Modified from Smith SC Jr, Dove JT, Jacobs AK, et al. ACC/AHA guidelines for percutaneous
`coronary intervention (revision of the 1993 PTCA guidelines)—executive summary: a report
`of the American College of Cardiology/American Heart Association task force on practice
`guidelines (Committee to revise the 1993 guidelines for percutaneous transluminal coronary
`angioplasty) endorsed by the Society for Cardiac Angiography and Interventions. Circulation
`2001;103:3019–3041.
`
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`Fig. 1-2
`Diagram of components of percutaneous coronary intervention
`equipment. (From Safian R, Freed M, eds. The Manual of Interventional
`Cardiology, 3rd edition. Birmingham, Michigan: Physicians’ Press, 2001.)
`
`and thinning of the medial wall. Stretching causes the vessel
`wall to lose its elastic (recoil) properties. The degree of elastic
`recoil is affected by the balloon/artery size ratio. Almost all
`vessels that have undergone PTCA have some elastic recoil.
`The major mechanism of stenting is elimination of elastic
`recoil, maintaining a large lumen over time.
`● Redistribution and compression of plaque components.
`During angioplasty, balloon pressure causes denudation or
`stripping of the vessel wall lining (endothelial) cells and the
`extrusion or pushing out of plaque components. There may be
`some molding of the softer lipid material but this effect
`accounts for a very small part of the overall effect of angioplasty.
`INDICATIONS FOR PCI*
`Specific anatomical and clinical features for each patient
`should be considered for the likelihood of success, failure and
`risk of complications with vessel closure, vascular morbidity,
`mortality, and restenosis. Restenosis and incomplete revascu-
`larization must also be weighed against the outcome
`anticipated for CABG. The complete recommendations from
`the AHA/ACC/SCAI PCI guidelines are provided in Appendix I.
`
`*See Guidelines AHA/ACC Task Force Report, Circulation (2000).
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`Basic Coronary Balloon Angioplasty and Stenting
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`17
`
`In General, PCI
`● Angina pectoris unrelieved by optimal medical therapy
`● Mild angina pectoris with objective evidence of ischemia
`(abnormal stress test or abnormal stress thallium) and a
`coronary lesion in a vessel supplying a large area of
`myocardium
`● Unstable angina
`● Acute myocardial infarction in patients as a primary
`approach or who have contraindications to thrombolytic
`therapy or who have evidence of persistent or recurrent
`ischemia despite thrombolytic therapy; direct PTCA without
`thrombolytic therapy is commonly used as the primary
`therapy in many circumstances
`● Angina pectoris after coronary artery bypass graft surgery
`● Symptomatic restenosis after prior PCI
`Relative Contraindications to PCI
`● Unsuitable coronary anatomy (e.g., left main, severe diffuse
`distal disease)
`● High-risk coronary anatomy in which closure of vessel would
`result in death
`● Contraindications to coronary bypass graft surgery (however,
`some patients will have PCI as their only alternative for
`revascularization)
`● Bleeding diathesis (low platelet count, peptic ulcer disease,
`coagulopathy, and so on)
`● Patient noncompliance with procedure and post-PCI
`instructions
`● Multiple PCI restenoses
`Complications of PCI (see also Chapter 4)
`For most elective procedures:
`● Death (0.1%)
`● Myocardial infarction (1–3%)
`● Emergency coronary artery bypass grafting (0.5–2%)
`● All complications that can occur during diagnostic cardiac
`catheterizations can also occur during PCI:
`—Access-site bleeding, especially with larger sheaths and
`prolonged anticoagulation (1:250 patients)
`—Contrast-medium reactions
`—Cerebral vascular accident, myocardial infarction, and so on
`
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`Interventional Cardiac Catheterization Handbook
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`● Vascular injury (e.g., pseudoaneurysm of femoral artery)
`● Restenosis (see Chapter 7).
`Note: Restenosis at the site of PCI occurs in approximately
`10–30% of patients and may lead to recurrence of anginal
`symptoms. Typically, restenosis occurs most frequently within the
`initial 6 months after PCI. This biologic effect is not considered a
`complication but rather a clinical part of angioplasty.
`PCI EQUIPMENT
`The most commonly used PCI equipment consists of four
`basic elements: a guiding catheter, a coronary guidewire, a
`balloon catheter, and a stent (Fig. 1-2, Table 1-2).
`The Guiding Catheter
`A special large lumen catheter is used to guide the coronary
`balloon catheter and other interventional devices to the vessel
`with the lesion to be dilated.
`Functions of the Guiding Catheter
`A guiding catheter serves three major functions during angio-
`plasty: (1) balloon catheter delivery and guidance; (2) backup
`
`Table 1-2
`Approximate Costs of Coronary Angioplasty Equipment
`Equipment
`Cost ($)
`
`Balloon dilatation catheter
`Guiding catheter
`Guidewire
`Exchange guidewire (300 cm)
`Indeflator
`Y connector
`Sheath introducer
`Torque tool
`
`Nonballoon devices
`Stent (noncoated)
`Stent (drug-eluting)
`Directional atherectomy catheter
`Rotoblator
`
`500
`100
`100
`100
`50
`15
`10
`10
`
`1200
`2800
`1200
`1200
`
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`Basic Coronary Balloon Angioplasty and Stenting
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`19
`
`support for balloon advancement; and (3) pressure monitor-
`ing. Construction of a guiding catheter is shown in Figure 1-3.
`Balloon Catheter Delivery and Guidance. To deliver the
`balloon catheter to the coronary ostium, the guiding catheter
`should be seated with the tip parallel to the artery (coaxial).
`Coaxial alignment permits safer transmission of force needed
`to advance the balloon across a stenosis. This act may require
`guide catheter repositioning or deep seating into the artery.
`Adequate contrast injection through the guide catheter is
`critical to position the balloon and depends on the size of the
`guide catheter lumen with the angioplasty device in place.
`A guiding catheter must be large enough to permit adequate
`contrast administration with the PCI catheter in place to
`opacify the target vessel and visualize the lesion. Large,
`nonballoon PCI devices (rotoblator, directional coronary
`atherectomy, Angio-Jet Aspiration catheter, or some stents) in
`small guide catheters may not allow adequate vessel visualiza-
`tion during angiography. This problem has been overcome
`with larger lumen, small guide catheters, and power injectors
`in some labs.
`
`Fig. 1-3
`Construction of a guiding catheter. The features noted differentiate
`it from diagnostic catheters. (From Avedissian MG, et al. Percutaneous
`transluminal coronary angioplasty: a review of current balloon dilation
`systems. Cathet Cardiovasc Diagn 1989;18:263.)
`
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`Operators should select a guide catheter with a lumen
`diameter large enough to allow adequate contrast flow around
`the PCI device to obtain a clear angiographic image of the
`lesion. As balloon and PCI catheters have become smaller, the
`size of internal diameter of the guiding catheter has become
`less important for achieving adequate visualization. A large
`guide catheter lumen, however, is critical to facilitate easy
`passage of atherectomy devices, and double balloon/stent
`systems for complex or bifurcation lesions.
`
`Backup Support for Balloon Catheter and Stent
`Advancement. Support or “backup” for stent advancement is
`achieved after seating (cannulation) the guide catheter in the
`coronary ostium. The guiding catheter provides a platform
`from which one can push the stent over the guidewire through
`the artery and across the stenosis.
`Inadequate backup support will result in failure to cross a
`lesion and an unsuccessful procedure. Backup support requires
`a combination of correct coaxial (in-line with the artery
`ostium) alignment, as well as the ability to provide carefully
`controlled advancement (deep seating) of the guiding catheter
`into the coronary ostium.
`The improved quality and size of currently used stents have
`reduced the need for robust backup support in most situations.
`For more complex and technically difficult lesions, the choice
`of an appropriate guiding catheter for adequate support and
`lesion visualization remains essential (see Chapter 3).
`Although commercially formed catheters are generally
`adequate, a guiding catheter will rarely need to be reshaped in
`the catheterization laboratory using a heat gun for successful
`coronary cannulation and backup support.
`When there is insufficient backup in crossing a very tight
`stenosis, the guiding catheter may be disengaged from the
`coronary ostium and backed out into the aortic root. When
`pressure is applied to the stent catheter during attempt to cross
`the lesion, repositioning the guide catheter in a stepwise
`fashion as the stent is advanced may overcome this loss of
`support. However, aggressive intubation of the coronary
`ostium may damage the vessel, stopping the procedure
`prematurely, and may require additional stenting for an ostial
`dissection.
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`21
`
`Deep seating of the guide catheter is achieved by manipu-
`lating the guide catheter over the balloon catheter shaft, past
`the aortocoronary ostium and farther into the vessel, to obtain
`increased backup support for crossing difficult lesions. This
`maneuver typically is used as a last resort because of the
`increased chance of guide catheter-induced dissection of the
`left main or proximal vessel.
`
`Pressure Monitoring. The guiding catheter measures aortic
`pressure during the case. Pressure wave damping may occur
`during coronary artery engagement if there is plaque in the
`coronary ostium. In addition, pressure measured proximal to
`the stenotic area can be compared to distal transstenotic
`pressure measured with a pressure sensor guidewire for
`assessment of lesion severity before and after PCI. Some
`catheters have side holes near the tip to permit perfusion into the
`artery when the catheter is deeply seated and obstructing flow.
`
`Guide Catheter Construction
`Catheter Characteristics. Compared to the diagnostic
`catheters, the guiding catheters have thinner walls, larger
`lumens, and stiffer shafts. A large catheter lumen is achieved at
`the expense of catheter wall thickness and thus may result in
`decreased catheter wall strength, less torque control, or
`catheter kinking. The guiding catheters are generally stiffer to
`provide backup support during the PCI catheter advancement
`into the coronary artery and, therefore, respond differently to
`manipulation than diagnostic catheters. The guiding catheter
`tip is not tapered. Pressure-wave damping upon engaging the
`coronary ostium is seen more often than with similar-size
`diagnostic angiographic catheters. Some guide catheters have
`relatively shorter and more flexible tips to decrease catheter-
`induced trauma.
`
`Side Holes. Guiding catheters with small side holes permit
`blood to enter the coronary artery when the ostium is blocked
`by the guide catheter. Side holes are used when the guide
`catheter either partially or totally occludes blood flow into the
`coronary artery. The guide catheter coronary occlusion is noted
`by the change in the arterial pressure waveform to one of
`“damping.” Catheter side holes eliminate or reduce ischemia
`
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`22
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`Interventional Cardiac Catheterization Handbook
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`when the guiding catheter is seated in a small artery. However,
`side holes may lead to inadequate artery visualization from
`loss of contrast media exiting the catheter before entering
`the artery. Although side holes may provide reliable aortic
`pressure, coronary flow can still be compromised during the
`angioplasty procedure. The guide catheter and side holes act as
`a “second stenosis” at the coronary ostium.
`
`Small-Shaft-Diameter Catheters. The most frequently used
`size of guiding catheter is currently 6 French. The use of
`smaller-diameter guide catheters, conceptually, will result in
`fewer vascular complications and allow earlier ambulation of
`patients. However, this advantage is offset by the compromised
`quality of coronary angiograms with smaller catheter lumen
`sizes. Small-size (≤5F) guide catheters do not allow for the use
`of some stents. 7 or 8F guide catheters are used for complex
`procedures involving larger PCI devices or bifurcation lesions.
`Balloon Dilatation Catheter Systems
`Types of Balloon Catheter. There are three types of PCI balloon
`catheter (Fig. 1-4): over-the-wire, monorail, and fixed-wire
`balloon catheters. The over-the-wire and monorail balloons,
`but not fixed-wire balloons, are also used to deliver stents that
`are mounted by the manufacturer on a specific balloon. The
`advantages and limitations are summarized in Table 1-3.
`
`Over-the-Wire Angioplasty Balloon Catheters. A standard
`over-the-wire angioplasty balloon catheter has a central lumen
`throughout the length of the catheter for the guidewire and
`another separate lumen for balloon inflation. These balloons
`are approximately 145–155 cm long and may be designed
`to be used with guidewires of various dimensions
`(1.010–0.018 inches). In these systems, the guidewire and the
`balloon catheter move independently. The major advantage is
`the ability to maintain distal artery access with the guidewire
`beyond the lesion while exchanging one over-the-wire balloon
`catheter for another. To exchange balloons, the balloon is
`tracked over the wire to a distal position. The wire may then be
`removed from the balloon. The wire may then be reshaped and
`reintroduced through the central lumen or exchanged for a
`longer guidewire (300 cm) to maintain distal position while
`
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`23
`
`Fig. 1-4
`Three common types of coronary balloon angioplasty catheter
`design. (Modified from Freed M, Grines C, eds. Manual of interventional
`cardiology. Birmingham, MI: Physicians’ Press, 1992: 29.)
`
`the balloon catheter is completely withdrawn over the
`guidewire and another balloon catheter is introduced over the
`same long guidewire for additional dilatations. An alternative
`method of balloon catheter exchange is to “trap” or secure a
`regular guidewire (145 cm) in the guide while the balloon
`catheter is exchanged (see exchange methods later). Over-the-
`wire catheters can accept multiple guidewires, which allows for
`exchanging additional devices that may require stronger, stiffer
`guidewires.
`Over-the-wire angioplasty balloon catheters have several
`limitations. These catheters are, in general, slightly larger than
`
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`24
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`Interventional Cardiac Catheterization Handbook
`
`Table 1-3
`Advantages and Limitations of Angioplasty Balloon Types
`Advantages
`Limitations
`
`Over the wire
`Distal wire position
`Distal port available for pressure
`measurement or contrast media
`injection
`Accepts multiple guidewires
`
`Rapid exchange
`Distal wire position
`Enhanced visualization
`Low-profile balloons
`Single-operator system
`
`Fixed wire
`Enhanced visualization
`Single-operator system
`Use with small guiding catheters
`Low-profile balloons
`
`Two experienced personnel required
`± Larger profile
`
`Exchanging balloons at hemostatic
`valve may be technically demanding
`
`Lack of through lumen
`Inability to recross lesion without removing
`system
`
`Modified from Kern MJ, ed. The cardiac catheterization handbook, 2nd ed. St Louis, MO:
`Mosby, 1995.
`
`the rapid-exchange (monorail) and fixed-wire catheters.
`Additional personnel may be required to help with long
`guidewire exchanges.
`
`Rapid-Exchange (Monorail) PCI Balloon Catheters.
`“Rapid-exchange” monorail catheters were developed to
`improve the exchanging of angioplasty balloon catheters by
`single operators. Rapid-exchange catheters have only a short
`(∼30–40 cm) length of the catheter shaft containing two
`lumens. One lumen runs the entire length of the catheter and
`is used for balloon inflation. The other lumen, which extends
`through only a portion of the catheter shaft, houses the
`guidewire. Because only a limited portion of the balloon
`requires dual lumens, rapid-exchange catheters are smaller in
`diameter than over-the-wire balloon catheters. Figure 1-5
`
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`Basic Coronary Balloon Angioplasty and Stenting
`
`25
`
`IN BODY
`
`EXTERNAL
`
`Over-the-wire
`
`Rapid exchange
`
`Zipper MX catheter
`
`Zipper guideway
`
`Proximal
`shaft
`
`Inflation lumen
`
`The Z component
`facilitates loading and
`unloading of guide wire
`
`The keel
`temporarily separates
`the shaft feeding the guide
`wire into the lumen
`
`The keel
`
`Fig. 1-5
`Zipper balloon (Medtronic, Minneapolis, MN) allows variable
`length monorail to be converted to over-the-wire method at any time.
`
`shows a novel type of “convertible” monorail using a zipper-type
`technique. Figures 1-6 and 1-7 show OTW and monorail
`balloon catheters.
`Rapid-exchange balloon catheters address certain inherent
`limitations of over-the-wire catheters. First, over-the-wire
`balloon exchanges require a long (or extension) guidewire, an
`unnecessary maneuver for the rapid-exchange type. Second, a
`single operator can use rapid-exchange balloon catheters
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`Fig. 1-6
`Quantum Maverick OTW. Over-the-wire “Quantum” Maverick
`Balloon. (Courtesy of SciMed-Boston Scientific, Boston, MA.)
`
`without the aid of other assistants to maintain distal guidewire
`position.
`Limitations of monorail catheters include the need for more
`expertise in manipulation of the guidewire, balloon catheter,
`and guiding catheter. Excessive blood loss at the rotating
`hemostatic valve during removal of the balloon catheter (back-
`out) maneuver may occur but valved “Y” connectors have
`reduced this problem. More caution when moving the balloon
`is needed. If the monorail balloon is advanced beyond the
`wire, the wire may come out of its short lumen, necessitating
`reassembly of the balloon and guidewire, especially when
`monorail catheters with relatively short “rails” are used.
`If the balloon catheter requires force to advance beyond a
`lesion, a loop of guidewire may sometimes form outside the
`guide catheter in the aorta. This loop is nearly invisible but
`should be considered if the operator advances the catheter
`without seeing motion at the balloon tip.
`
`Fixed-Wire Angioplasty Balloon Catheters. The fixed-wire
`catheter has the balloon mounted on a central hollow wire
`with a distal flexible steering tip. The proximal end of the
`catheter consists of a single port connected to a thin metal tube
`(hypotube). A core wire extends from the hypotube to the end
`of the distal steerable tip. This assembly is coated with a thin
`plastic shaft that enhances flexibility. Fixed-wire balloons have
`only one enclosed lumen for balloon inflation.
`The on-the-wire balloon catheter is a fixed wire system,
`where the guidewire cannot be advanced independently of the
`balloon and the balloon cannot be exchanged without
`
`Fig. 1-7 Maverick 2 Monorail. Monorail balloon catheter. (Courtesy of
`SciMed-Boston Scientific, Boston, MA.)
`
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`Basic Coronary Balloon Angioplasty and Stenting
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`27
`
`removing the entire system. Since the wire is attached to the
`distal end of the balloon, there is no central balloon lumen,
`resulting in a lower total profile than an over-the-wire or
`monorail system. Its principal advantages relate to its low
`profile, enabling passage through very tight stenoses, and good
`contrast visualization of the lesion being dilated around the
`balloon catheter.
`The small shaft size provides excellent coronary visualiza-
`tion. Because the balloon is mounted on the distal guidewire,
`the device was designed to be used by a single operator. Fixed-
`wire balloon catheters are particularly useful for distal lesions,
`subtotal stenoses, and lesions located in tortuous vasculature.
`The limitations of fixed-wire catheters include lack of the
`inherent safety advantage of over-the-wire and rapid-exchange
`systems because there is no movable wire available to exchange
`for a stent if a dissection occurs. To exchange this catheter the
`catheter must be removed completely. The lesion is then
`recrossed with a new guidewire and balloon catheter.
`A dissected lesion may not permit recrossing with a guidewire
`or advancement of another balloon catheter. Further attempts
`at recrossing may even close the vessel. In such cases, an
`angioplasty guidewire can be introduced alongside the fixed-
`wire balloon catheter before removing the catheter to assist in
`placing another balloon.
`
`Characteristics of Balloon Catheters. The plastic material of the
`balloon determines its compliance and tensile strength. The
`main differentiation among balloons is related to compliant or
`noncompliant mate