Optimizing the results of balloon coronary angioplasty of nonideal lesions

Optimizing the Results of Balloon Coronary Angioplasty of Nonideal Lesions

David R. Holmes, Jr, Howard A. Cohen, and Ronald E. Vlietstra

A S ORIGINALLY described, percutaneous transluminal coronary angioplasty (PTCA)

was indicated in patients with “ideal” lesions, namely, those that were proximal, concentric, subtotal, and noncalcified and did not involve major side branches (Fig 1).i9* These initial indications were appropriate given the type of equipment originally available and the lack of experience with the procedure. Since this initial description, however, the clinical as well as the angiographic indications for PTCA have broad- ened considerably. Currently, a minority of patients treated with PTCA have anatomy that would be considered ideal. As the anatomic challenges that are being treated become more complex, it becomes increasingly important to consider more technical options. This goal has been aided by the proliferation of new catheters and guidewire systems.

This article details an approach to common angioplasty questions, problems, and attempted solutions. It does not consider other aspects, such as patient selection or care, because these have been addressed elsewhere.3-6

OPTIMAL DILATION SYSTEM

The optimal dilation system for PTCA de- pends in large measure on the characteristics of the arterial tree and the lesion to be dilated. Every system includes a guiding catheter, guidewire, and a dilation catheter. In addition, optimal dilation requires excellent visualization. High-quality cineangiography and optimal video images are essential to document the extent, severity, and location of coronary arterial disease, particularly when nonideal lesions are to be treated.

Guiding Catheter

Guiding catheters are available in a wide variety of shapes and sizes. The optimal guiding catheter should have a large internal diameter for good visualization with injection over the guidewire and dilation catheter. With the smaller diameter dilation catheters that are currently available, the internal diameter of the guiding catheter may be less critical. It remains an

important feature, however, particularly if multiple guidewires or dilation catheters are to be used through a single guiding catheter.

An atraumatic tip is another important feature, particularly if there is disease in proximity to the tip of the guiding catheter where the coronary artery is to be engaged. Guiding catheters with soft tips have become increasingly popular. The most distal portion of these catheters which engages the coronary ostia is deform- able and less traumatic. An atraumatic tip is especially desirable if the guiding catheter is required for additional backup support to apply longitudinal force to the dilation catheter in an effort to cross a severe lesion. Achieving such backup support may require gently advancing the guiding catheter a short distance into the coronary ostium. This maneuver increases the chance of damage to the native coronary arterial tree and has been postulated to result in new arterial stenoses. This concept of backup pressure was of greater importance with earlier dilation catheters that had comparatively larger profiles. As dilation catheters have achieved progressively lower profiles, this need for backup pressure has become less important. Neverthe- less, even with the lowest possible profile, backup pressure may be important, particularly with technically difficult lesions such as distal severe stenoses, diffuse long stenoses, or excessive tortuosity. When possible, the principle of profile rather than pressure should be used. This principle is particularly important in the right coronary artery, where deep engagement and extensive backup pressure can easily lead to dissection of the artery proximally.

Preformed catheters positioned via the femoral approach are generally sufficient. Occasion- ally, however, standard preformed catheters are inadequate because of poor intubation or angula-

From the Division of Cardiovascular Diseases and Inter- nal Medicine, Mayo Clinic and Mayo Foundation, Roches- ter, MN and St John’s Hospital, Santa Monica, CA.

Address reprint requests to David R. Holmes, Jr, MD, Mayo Clinic, 200 First St SW, Rochester, MN 55905.

8 1989 by W.B. Saunders Company. 0033-0620/89/3202-0002$5.00/0

Progress in Cardiovascuku Diseases, Vol XXXII, No 2 CSeptember/October), 1989: pp 149-l 70 149

HOLMES, COHEN, AND VLIETSTRA

tion at the ostium of the coronary artery. In these circumstances, it is necessary to reshape the guiding catheter with a heat gun and use the stiff end of a 0.063-inch guidewire as a mold bent into the appropriate configuration.

Guidewire

The ideal guidewire should have excellent torqueability, tip flexibility, and enough body or stiffness to allow tracking of the dilation catheter

Fig 1. Proximal, concentric, subtotal, noncalcified lesions (arrow) were originally

described as ideal for PTCA. Patients with thisanatomy form s minority of those currently undergoing dilation. (A) and (6) Right anterior oblique views of

left coronery artery before (A) and after (B) PTCA. (A. re- printed with permission.‘)

through tortuous and diffusely diseased vessels. The distal tip of the guidewire must be densely radiopaque to allow for good visualization of the working end of the wire as it is passed through a lesion and into a distal vessel. The more proximal portion of the guidewire, with the exception of the few centimeters at the tip, may be relatively less radiopaque. Although the wire in general is then more difficult to visualize, only the distal tip actually needs to be seen. This is of particular

OPTIMIZING ANGIOPLASTY OF NONIDEAL LESIONS 151

importance for over-the-wire injections because an invisible wire allows for better visualization of the lesion.

In general, the ideal guidewire should have excellent flexibility at its tip and more body in the proximal portion. The transition from tip to the more proximal portion must be gradual, however, to allow easy passage of the guidewire through tortuous and diffusely diseased vessels. The tip of the guidewire should also be easy for the operator to shape in conformity with the particular anatomy under consideration. In certain circumstances, excellent flexibility may be a disadvantage in diffusely diseased vessels. Al- though increasing the stiffness of a guidewire could increase the potential for arterial injury during passage through the coronary arteries, it may be required to complete a procedure successfully, particularly for chronic coronary occlusions (see below).

Dilation Catheter

Dilation catheters that are currently available are of two basic types: over-the-wire catheters or catheters with a fixed wire at the tip. Ideally, over-the-wire catheters should be trackable and flexible and have as low a profile as possible. They should also be inflatable to high pressure without rupturing. The low profile and flexibility should make up for the ability to push the catheter through a tight stenosis. With a lower profile, trackability, and flexibility, the ability to push through a lesion should not be a necessary feature most of the time. For very severe obstruc- tions, the smallest balloon catheter available should be used initially, and then the balloon Wize can be increased appropriate to the size of the artery;’ this technique should decrease the need for “pushability” in exceedingly tight lesions. Although this requires the use of two dilation catheters, it usually results in an ultimately shorter procedure.

Dilation catheters with a fixed distal wire are available (Advanced Cardiovascular Systems, Temecula, CA). These catheters offer a low profile, flexibility, and steerability. Because it is not an over-the-wire system, the operator must forego the safety feature of using a guidewire across the dilated segment after the dilation catheter has been withdrawn. A variant of this is

a catheter that has a guidewire that can be advanced distally through the distal tip of the balloon but cannot be removed completely from the balloon. These catheters are more steerable than fixed guidewire systems but have the potential disadvantage that exchange wires cannot be used.

More recently, the balloon-on-a-wire catheter has become available, offering the lowest profile. In addition to low profile, this catheter offers the flexibility of a guidewire at its tip but more stiffness proximally. Given the very low profile of these catheters, if a guidewire can be passed across a lesion, it is almost always dilatable.

Balloon material is generally polyethylene or a material derivative, polyethylene terephthalate (PET). The latter allows for a very low profile and high pressure inflation. The compliance of this material is low, and full inflation of the balloon is achieved at relatively low pressure. Furthermore, increased pressure results in little overexpansion of the balloon.

Two important potential problems with this balloon material are worth mentioning. First, because of the thinness of the balloon material, it may become wrapped upon itself and cause problems with inflation and, more importantly, with deflation. This is particularly a problem with the larger balloon-on-a-wire type catheters. Caution must be used, therefore, not to over- torque the catheter, and it should be used very carefully or even avoided in very tortuous or diffusely diseased vessels in which considerable torquing is required to reach or cross a lesion. This problem may be obviated by the use of a long, narrow sheath that is inserted over a guidewire to or through a lesion, which then allows passage of the Probe (USC1 Division, C.R. Bard, Inc, Billerica, MA) without torquing. New generations of these catheters recently have become available (for example, the Ace, Sci- Med Corp, Minneapolis) that are less susceptible to overtorquing.

The second potential problem is pinhole rupture of the balloon at high pressure, which may cause severe dissection of the artery. A pinhole rupture may be caused by injury to the PET balloon as it is passed through a luer lock metal end of the guiding catheter, or it can be caused by spicules of calcium in the dilated segment. This

152 HOLMES, COHEN, AND MIETSTRA

problem can be reduced by inserting the balloon through a protective sleeve when it is advanced into the guiding catheter.

These balloon-on-a-wire systems may be particularly valuable for distal, very severe stenoses. Thomas et ah7 in an initial experience, documented that this type of catheter was effective for dilating 16 (76%) of 21 lesions that could not be crossed and dilated with conventional over- the-wire systems.

Visualization

High-quality cineangiography and video images are essential for optimizing dilation. Video images have assumed greater importance because the results of dilation are monitored before tine development. Digital-based image enhance- ment has been shown to improve image quality and to reduce radiation exposure. Tape recorders with high-quality resolution and the capability to store images of the coronary arteries during dilation are required for optimizing the procedure. Detailed requirements for the procedure room and x-ray imaging equipment have been published elsewhere.*

If fluoroscopy and road-mapping capability are assumed to be excellent, certain principles of optimal visualization are worth mentioning. A guiding catheter with a large internal diameter allows for excellent visualization of the anatomy. Visualization is of utmost importance when the guidewire has passed across the lesion to be dilated and into the distal vessel. The long-wire technique popularized initially in Europe and later in the United States and the Monorail system (Schneider-Shiley, Minneapolis) opti- mized this initial visualization by using a guidewire alone in the guiding catheter as the lesion was crossed. Once the guidewire is passed across the lesion, the dilation catheter can then be passed over the guidewire and across the stenosis. Furthermore, when dilation is com- pleted, the dilation catheter can be completely withdrawn from the guiding catheter; repeat angiography with only the guidewire in place allows optimal visualization of the dilated segment. This technique is particularly valuable when there is a dissection or inadequate dilation requiring recrossing of the stenosis for repeat dilation. Although lesions that have been dilated can be recrossed, it is sometimes safer to assess

the adequacy of dilation with a guidewire maintained across the lesion and with excellent proximal injection unimpeded by a dilation catheter within the guiding catheter.

The outcome of dilation is in large part dependent on the details of the coronary pathology. With ideal lesions, success rates of approximately 95% can be achieved. With less ideal lesions, success and complication rates may be different. With these nonideal lesions, the approach to dilation may need to be modified to optimize the results.

CLINICAL PROBLEMS

Common clinical problems are listed in Table 1. Table 2 lists the frequency of occurrence of these lesions in 709 patients during 1987 at the Mayo Clinic. Twenty-six percent had no adverse factors, 34% had one, 25% had two, and 15% had three or more.

Major Branch Involvement

Small (< 1 mm) side branches usually pose no significant clinical problem even if they occlude during angioplasty. However, angioplasty at the site of a major branch may cause two major problems. First, attempted dilation may jeopardize the branch. Second, dilation of branch lesions may jeopardize the major vessel to be dilated (Fig 2). There are several potential mech- anisms of occlusion, including a shift of the atherosclerotic plaque, coronary dissection, the development and progression of coronary thrombus, and coronary spasm.

The risk of jeopardizing the side branch is dependent on the relationship of the side branch to the stenosis to be dilated and on the presence or absence of an ostial stenosis of the side branch. In a series of patients undergoing dilation, Vetro-

Table 1. Common Arteriographic Challenges

Major branch involvement

Coronary thrombus

Distal severe stenoses

Tandem lesions

Sharply angulated lesions

Excessive tortuosity or shepherd’s crook

Ostial lesions

Circumflex dilation

Diffuse, calcific, severe stenoses

Graft stenczsas

Internal mammary artery stenoaes

Complete occlusion


Table 2. Frequency of Nonideal Lesions in 706 Mayo Clinic

Patients, 1987

LWiOn %ofPatiants

Major branch involvement 10

Coronary thrombus 40

Distal severe stenoses 5

Tandem lesions 2

Sharply angulated lesions 3

Circumflex dilation 26

Calcium in stenosis 11

Graft stenoses 6

Complete occlusion (chronic) 11

vet et al9 reviewed 97 cases of major side branch involvement. An ostial stenosis was found in 52 of these patients, whereas no ostial stenosis was found in 45. If an ostial stenosis was present, there was progression of the stenosis in 27%. Only 4% of the patients without ostial stenosis developed a new ostial lesion. This experience and the outcome are similar to those reported by Meier et al,” who found that 14% of branch vessels with significant ostial involvement occluded during dilation compared with only 1% of branch vessels without ostial involvement.

In the past, bifurcation lesions were difficult. The approach to bifurcation lesions ranged from benign neglect to a protective guidewire technique to the use of a double-balloon technique.““’ This was complicated by the need for long exchange wires or the need to place bilateral femoral arterial sheaths or to combine brachial with femoral access in order to use two guiding catheters. All of this has changed since the introduction of the Probe and other extremely low-profile dilating systems (Fig 3).‘*i6 Because of their low profile, two of these catheters can be inserted through a single guiding catheter. A double Touhy Borst connector facilitates the insertion of each dilation catheter. There is still a port for proximal contrast injection. With the use of these two Probes, a “kissing balloon” technique is accomplished relatively easily in a short time. This has resulted in increased success rates. Alternatively, it is possible to protect a jeopar- dized side branch with a long exchange wire and to pass a Probe through the same guiding catheter to dilate the primary lesion. If the side branch occludes, a low-profile dilation catheter can then be passed over the exchange wire with the Probe either in place or withdrawn. With large internal diameter g-French catheters, other combinations

Fig 2. Cranial left anterior oblique views of left ooro- nary artery. Origin of large first diagonal branch is involved with significant stenosis (A). After PTCA, there is some improvement in the left anterior descending artery but the diagonal branch is occluded (6).

of dilating catheters within the same guide can be used.

It must be remembered that even with two Probe dilating wires, stasis exists within the coronary arteries. Therefore, the procedure must be performed as expeditiously as possible and adequate anticoagulation must be used. We generally use 10,000 to 15,000 units of heparin before the procedure and then begin a constant heparin infusion. In addition, antiplatelet agents


are given before dilation to lessen the risk of acute thrombosis.”

Coronary Thrombus

The earlier use of coronary angiography during acute ischemic syndromes has led to an increased recognition of the role of coronary thrombus (Fig 4). From a dilation standpoint, the problems with coronary thrombus are that it is a marker of lesion instability and the potential for acute occlusion and distal embolization is

Fig 3. Right anterior oblique views of severe circumflex stenosis that involves origin of large obtuse marginal vessel

(A). Two USC1 Probes are inserted through same guiding catheter. After simultaneous inflation (6). improvement is excellent ICI.

increased.‘*-** In a series of patients with preexist- ing intraluminal thrombus, Mabin et al’* reported a 67% incidence of acute occlusion with angioplasty. This report first drew attention to the problem; since then, increasing attention has been paid to it. In a subsequent review of 297 patients undergoing dilation, thrombus was seen before dilation in 34.19 Intensive heparinization and antiplatelet agents were given before dilation. This resulted in a decrease in the incidence of occlusion to 24%. In approximately 50% of


Fig 4. Cranial left anterior oblique views of left coronary

artery. Multiple filling defects on proximal left anterior descending artery are consistent with intrecoronary thrombus

(A). During PTCA, occlusion occurs at site of diletion (B).

these occlusions, the lesion could be recrossed and successfully dilated. Although the frequency is still higher than that for patients who have conventional dilation, this is clearly an improvement. In a series of 140 dilation procedures complicated by acute closure, multivariate analy- sis documented that thrombus present before dilation was associated with an increased incidence of occlusion.20 In the setting of acute infarction, thrombus is equally important; a large thrombus (>5 mm) has been associated with decreased procedural success.23

It has been recognized recently that the heparin needs of patients undergoing PTCA are variable. Even a bolus dose of 10,000 units yielded a subtherapeutic activated clotting time five minutes later in approximately 10% of patients in a study by Ogilby et a1.24 Routine checking of the activated clotting time, a simple laboratory step, may help better regulate the dosage of heparin. During acute interventional procedures such as PTCA during infarction, this assumes even more importance because of the underlying thrombogenic arterial pathology.

In the patient with coronary thrombus, there are several potential approaches. (1) Before dilation, intensive therapy with anticoagulants and antiplatelet agents may help to lyse the thrombus.2s Recently, thrombolytic therapy has been used before dilation. In our experience, this often has resulted in lysis of the thrombus and has facilitated subsequent uneventful dilation. During dilation itself, careful attention must be paid to the use of optimal anticoagulants. (2) An over-the-wire system is used preferentially so

that if occlusion does occur, it can be easily recrossed. (3) If additional thrombus develops during the procedure, the use of slightly larger balloons and longer inflations to optimize resid- ual stenosis may be of benefit. After the last dilation in a vessel with thrombus, we routinely wait ten minutes to be certain the result is stable, also checking that the activated clotting time is therapeutic, Often (in approximately 20% of cases) after ten minutes there is increased stenosis from thrombus, and repeat dilation is then required. After the procedure, heparin adminis- tration is continued for 24 to 48 hours and antiplatelet agents are given.

Weyne et alt2 described two patients in whom intracoronary thrombus was recognized before PTCA. Abrupt reclosure after dilation was treated by successful redilation. However, coronary embolization of thrombus debris occurred downstream in one patient and into an adjacent coronary branch in the second patient. If distal embolization occurs in these circumstances, balloon dispersal of the thrombus or retrieval with an atherectomy catheter may be achievable.

Distal Severe Stenoses

The problems with distal severe stenoses (Fig 5) are related to difficult visualization, inability to reach and cross the lesion, and the subsequent development of occlusion or dissection. For the patient with distal severe stenoses, care must be taken to match the balloon catheter, the guiding catheter, and the guidewire. For the balloon catheter, it is important to use a very low profile. This allows for easier passage through the tight


stenoses. It is also important that the balloon be trackable. We, in general, avoid “Dottering” with repeated longitudinal force on the stenosis because this can result in arterial damage or even occlusion of a severe stenosis. The use of a stiffer catheter that can be pushed through the lesion is another alternative. Perhaps the best alternative is to use the lowest-profile system to pass the stenosis easily (Probe, Mini [Advanced Cardio- vascular Systems, Temecula, California], DGW “Skinny” or “Ace” [Sci-Med Corp, Minneapo- lis]). As documented above, in a series of 21 patients with very severe, often distal, stenoses in whom a conventional balloon system was unsuc- cessful, a very-low-profile balloon-on-a-wire system (Probe; USC1 Division, C.R. Bard, Inc) was successful in 76%’ At times, “sizing up” is of benefit. Use of a small balloon initially allows expeditious crossing and dilation of a severe stenosis. This is followed by dilation with a balloon appropriate for the size of the artery.

A well-chosen guiding catheter is also important. It should provide a stable position but without deep penetration of the coronary artery. This situation may be associated with an in- creesed incidence of trauma to the ostium of the coronary artery (Fig 6) and has been implicated in the development of new stenotic atherosclerotic lesions.26 Large-lumen catheters are also helpful so that adequate injections can be made. If an over-the-guidewire system is selected, the guidewire should be very flexible and steerable to allow easy access down to the distal severe stenosis.

Fig 6. Right anterior oblique views of left coronary ar-

tery. Distal left anterior descending artery is occluded, and distal vessel is poorly visualized (AL After PTCA. flow is excel-

lent (6).

The expected introduction of the Monorail balloon catheter system may allow for distal guidewire placement and more easy passage of balloon catheters of various sizes2’ This system (Schneider-Shiley, Minneapolis) consists of a single-lumen shaft and the distal balloon. There is a short central tube within the distal portion of the balloon. There are openings at the very distal end of the catheter and proximal to the balloon. The guidewire runs through the catheter only in the short distal central tube; for the rest of its

Fig 6. Left anterior oblique view of left coronary artery. Engagement of ostium was difficult with multiple manipula- tions using an Amplatz guiding catheter, which resulted in extensive dissection of left main coronary artery.

OPTIMIZING ANGlOPLASlY OF NONIDEAL LESIONS

length, the guidewire runs parallel but outside the catheter. With this system, the guidewire is positioned across a stenosis, after which the balloon is placed over the guidewire and crosses the lesion to be dilated. Success rates of approximately 95% have been reported.*’ An alternative is placement of a long guidewire initially, which also may be of value to expedite catheter exchanges.*’

In distal severe stenoses, particularly if the segment is diffusely diseased, great care must be taken to avoid oversizing in an effort to decrease the frequency with which dissection occurs.” In a randomized trial of 336 patients,29 169 were randomized to PTCA with a large balloon size and the remainder had dilation with a small balloon. The patients with larger balloon-diameter ratios had an increased incidence of emergency operation and myocardial infarction.

Tandem Lesions

Tandem lesions (Fig 7) are also a problem, presenting the potential for occlusion or overlap- ping dissections. Our approach is to select a catheter system with exchange or extension wire capability. Having passed the wire through the distal lesion, various dilating catheters can be

157

advanced through the tandem sites. The use of low-profile balloons with a relatively stiff shaft is also helpful so that the catheter can be pushed through the lesions if necessary. This feature is particularly important if the distal lesion appears to be difficult to cross. When both lesions are severe, an attempt should be made to dilate the proximal stenosis first to allow easier crossing of the distal lesion. In any case, the operator should move expeditiously to lessen the risk of acute thrombosis. Longer balloons can also be helpful, particularly if the lesions are close together. These can then be used to dilate both lesions simultaneously.

Sharply Angulated Lesions

The problem with sharply angulated lesions is the disparate application of force to the arterial wall, resulting in an increased occurrence of dissection. There are several approaches to sharply angulated lesions. We empirically use low-inflation pressure and gentle inflation in an attempt to decrease the force on the vessel wall. Other options are available. One can use a short balloon to avoid the angulated segment. The introduction of angulated balloons may help in this regard (Fig 8). It is important in this setting

Fig 7. (A) Right anterior oblique view of right coronary artery with tandem lesions. Dilution is performed with over-the-wire system with inflation in proximal stenosis: initial result in proximal stenosis is excellent. (B) Left anterior oblique view.

HOLMES, COHEN, AND WETS

Fig 8. Angulated lesion in middle right coronary artery, right anterior oblique (A), and left anterior oblique (8) views. Angulated balloon is used (CL resulting in excellent improvement in stenoaia (D and E).

OPTIMIZING ANGIOPLASTY OF NONIDEAL LESIONS

to use a movable guidewire system so that if dissection occurs, it can be more easily crossed and redilated. It also allows better visualization during injection of the artery when the balloon catheter is withdrawn.

If dissection occurs, the use of prolonged inflations with low pressures may be helpful for tacking up the intimal flap. This can be successfully done approximately 50% of the time. The development and widespread application of intracoronary stents should help in this regard.30 For example, Sigwart et a13* recently described their initial experience with emergency implantation of stents for acute occlusion complicating coronary balloon angioplasty. They argued that most occlusions in this setting are due to dissection and subintimal hemorrhage. Nine patients received one stent, and two patients received two stents. Implantation was technically successful in all patients; there were no deaths or myocardial infarctions and there was no need for emergency operation.

Of utmost importance is the decision-making process regarding early surgery. If it appears that the lesion cannot be successfully opened and significant ischemia is present, surgery should be undertaken as quickly as possible to prevent or reduce the chance for a perioperative infarction. The use of bailout or perfusion balloon catheters

159

in this circumstance is important (Fig 9).32 If the lesion can be recrossed, some flow can be restored with the use of passive perfusion catheters.

Various bailout reperfusion and perfusion catheters are available.33 Most commonly they have multiple side holes toward the distal portion of the catheter. The side holes are positioned across the occluded segment or dissection. Blood pas- sively enters the catheter lumen from the coronary artery proximal to the occlusion and then leaves the catheter lumen distal to the occlusion because of the large pressure gradient. In a group of 20 patients undergoing emergency surgery after failed angioplasty, a reperfusion catheter could be passed successfully in 18 (90%).32 After insertion, 16 of these 18 patients had good anterograde flow, which was associated with improvement in ischemia. It must be remembered that the patient’s blood pressure must be well maintained to allow and foster such passive reperfusion. In the patient with severe hypoten- sion, a bailout catheter may help by stenting the artery open, but it will not allow substantial flow. Intraaortic balloon pumping may help augment flow. Other options are being developed. Intravas- cular stents may help to restore long-term patency. 3o Alternatively, if surgery is to be performed because patency cannot be maintained,

Fig 9. Left anterior oblique views of right coronary artery. During dilation, proximal right coronary artery occluded. A guidewire was passed (A). Bailout catheter was then inserted, which restored flow to distal artery (B) and allowed atabilixation for surgery.

160 HOLMES, COHEN, AND VLIETSTRA

percutaneous femoral-femoral bypass may stabi- lize the situation.34

The use of a percutaneous or semipercutane- ous approach for cardiopulmonary support is increasing. With this approach, 18- to 20-French cannulas are placed into the arterial and venous circulation via a femoral approach either percuta- neously or with a cutdown. The venous catheter is placed in the right atrium. With available devices, up to 4 to 7 L/min can be achieved independent of cardiac rhythm. These devices reduce central venous and wedge pressure and reduce myocardial oxygen demand. Currently, they are positioned prophylactically in patients at very high risk during dilation-for example, those with only one patent coronary artery supply- ing the entire myocardium or those with very poor left ventricular function and an ejection fraction ~20%. After successful dilation, the devices are removed. Alternatively, if a complication occurs during dilation, they may be placed as a bridge to operation. The optimal role for these devices requires further evaluation.

Excessive Tortuosity or Shepherd’s Crook

The problems with excessive tortuosity include failure to enter the appropriate arterial branch, failure to cross the lesion, and poor visualization of the stenosis. Excessive tortuosity is most commonly a problem with the right coronary artery. With the tortuous shepherd’s crook right coronary artery, there is an additional problem of disengagement of the guiding catheter as the balloon is advanced through the tortuous segment. The approach to these problems includes selection of the optimal guiding catheter and the appropriate dilating system. The optimal guiding catheter should provide a stable position. The use of an Amplatz-type or an Arani catheter is often helpful. Alternatively, a multipurpose catheter used from below via the femoral route or by a brachial approach may be helpful. Given the deep engagement that is often needed, we use a soft-tip guiding catheter whenever possible.

The dilating system in this setting should have three characteristics. First, given the fact that there is limited ability to push through the lesion after it is around several bends, a low-profile catheter should be used. Second, a very flexible, trackable system is important to decrease the amount of resistance to forward movement (Fig

10). Third, an invaluable approach is to position a guidewire and then winch the balloon around (that is, withdraw the guidewire simultaneously as the balloon catheter is advanced) (Fig 11). Withdrawing the guidewire as the balloon is advanced pulls the balloon around the tortuous bends.

Ostial Lesions

Ostial lesions present problems similar to tortuous vessels, including an unstable guiding catheter position, poor test injection capacity, and the potential for dissection (Fig 12). Our approach is to use a soft-tip guiding catheter, often with side holes to try to increase distal perfusion. Flush injections are performed. A generous segment of guidewire is advanced through the stenosis. This provides some anchoring and allows the catheter to be winched across the stenosis. After dilation, it is important to use gentle injections because more forceful injections can result in dissection of the ostial lesion that has just been dilated.

Ostial lesions of the circumflex and left anterior descending arteries pose additional problems. During dilation, the left main coronary artery may be occluded, particularly if it is short. If the ostial plaque involves the left main artery, coronary bypass grafting is preferable. Another problem is that if dissection of the lesion occurs, it may involve the left main artery with attendant severe hemodynamic compromise. Finally, the ostia of the left anterior descending and circumflex arteries (as well as the right coronary artery) may be spongy and may recoil rapidly, yielding unsatisfactory results. If ostial lesions of the circumflex or left anterior descending artery are to be dilated, balloon inflations should be short if dilation results in transient occlusion of the left main artery.

Circumflex Dilation

Success rates for dilations of the circumflex coronary artery have been lower than those for left anterior descending or right coronary artery stenoses. The problems with circumflex dilation center on the angle of takeoff from the left main artery, particularly if the circumflex artery an- gles posteriorly. This angle may prevent entry of the guidewire or balloon catheter into the circumflex artery, or it may limit the steerability of the wire (Fig 13). A unique problem that may occur


Fig 10. Right and left anterior oblique views of very tortuous right coronary artery with distal occlusion before PTCA (A and BI. Dilation was achieved by changing guiding catheter and using a very trackable dilating system IC). Angiographic result was excellent (D).

in this setting is when the guidewire can be placed in the circumflex coronary artery, but each time the balloon is advanced over the guidewire the whole dilating apparatus is pro- lapsed into the left anterior descending artery.

There are several approaches to optimizing dilation in this situation. Very careful attention must be paid to selection of the appropriate guiding catheter. The use of an “upsized” Jud- kins’ catheter, for example, going from a 4- to a 5-French catheter, may help advance the guidewire into the circumflex artery itself. Out- of-plane circumflex guiding catheters are also available that may be of help. Finally, an Am- platz or a multipurpose catheter can be used

selectively to engage the circumflex artery itself. This is possible only if the left main artery is relatively short. It is important to remember that if the circumflex artery is selectively engaged with either of these techniques, flow down the left anterior descending artery often is diminished markedly and there is a potential for significant ischemia during dilation of the entire left system. We would, in general, upsize the Judkins’ catheter initially before trying an Amplatz or a multipurpose catheter for selective intubation. The Amplatz catheter must be used with caution because of the potential for arterial trauma due to the deep intubation (Fig 6).

Attention must also be paid to the guidewire


and balloon catheter itself. Use of a soft, flexible shaft wire that can be advanced easily into the circumflex artery is very helpful (for example, Hi-torque Floppy, Advanced Cardiovascular Sys- tems, Temecula, CA; Hyperflex, USCI, Biller- ica, MA). A balloon catheter system with a movable but not removable core, for example, a

Fig 11. Winching maneuver. Balloon catheter is placed in proximal coronary artery (A). Guidewire is advanced through stenosis (8). Withdrawing

guidewire (1) while simultaneously advancing balloon catheter (1) pulls the balloon into coronary artery around bends to cross the stenosis (C) and facilitate dilation ID).

Hartzler Micro system, may also work well. The guidewire then can be placed distally in the circumflex artery. After distal placement of the guidewire, an easily trackable balloon catheter can be advanced over the guidewire. It is important also to winch the balloon around with selective advancement of the balloon while the

Fig 12. (A) and (B) Successful dilation of ostium of right coronary artery (left anterior oblique views).


Fig 13. Right (A) and left (6) anterior oblique views of left coronary artery. Left main artery was long and angle of takeoff of circumflex artery was sharp, making intubation diicult. After placement of guidewire. balloon catheter was finally positioned in stenosis and dilation was successful (C and D).

guidewire is being withdrawn. This maneuver prevents prolapse of the entire system down the left anterior descending artery. Once the circumflex artery has been entered with the balloon itself, steerability may be a problem. In this setting, decreasing the amount of protruding guidewire can improve steerability. Often, the Probe catheter or other balloon-on-a-wire catheters are not easily manipulated into a circumflex artery. A newly marketed intracoronary guiding catheter (the USC1 Probing catheter) may be

useful in this regard by providing a conduit for the stiffer Probe catheter.

Diffuse, Calcific, Severe Stenoses

The problem with diffuse, calcific, severe stenoses relates to the markedly increased resistance to passage of the balloon through the stenosis as well as to an increased tendency for dissection.35*36 Meier et a13’ looked at the effect of length and eccentricity of the lesion on the outcome of dilation. The incidence of complica-

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tions with long and eccentric lesions was twice that with short and concentric lesions, with a specific increase in the potential for side branch occlusion and a greater risk of dissection. This problem is even worse if the diffuse severe stenoses are calcified (Fig 14). For these cases, it is important at least to consider other options such as surgical therapy while recognizing that the results of surgery may not be ideal either.

If balloon dilation is selected, we generally use a graduated balloon approach, in which we would initially select small balloons for dilation. Following that, if needed, larger balloons can be


used. Inflation in such situations should be low pressure if possible to prevent more arterial damage than needed. Finally, we select a system with exchange wire capabilities. This allows easy access back to the dilated segment if occlusion or a large dissection should occur. It also allows better contrast injection by withdrawing the balloon catheters out of the ostium of the coronary artery back into the guiding catheter or even completely out of it with an extendable wire, yet maintaining the guidewire across the treated site. It is important to remember that in some patients, “perfect is the enemy of good.” The aim

Fig 14. Diffuse. saver8 in middle left anterior dea artery (A). During dilation. tion and then occlusion de (BJ.

disease canding

dissac- lvelopad


of dilation in patients with diffuse severe stenoses is improvement, not necessarily a perfect angiographic image.

Graft Stenoses

The number of patients undergoing dilation after bypass grafting has increased (Fig 15).37-44 This increase has been the result of improved technology that facilitates access to these bypass grafts, realization of the increased risks of second or third operations, the progressive nature of coronary artery disease, and the increasing number of patients who have undergone coronary bypass grafting. Bypass graft stenoses have the advantage that there are no side branches and thus once access is obtained, stenoses usually can be crossed. The problems with bypass graft stenoses, however, are obtaining a stable guiding catheter position, the tortuosity (particularly of internal mammary arteries) being approached, the potential for distal embolization of atherosclerotic graft debris within the grafts, and the increased restenosis rates.37-44 This restenosis rate is dependent on the location of the stenosis within the graft. Stenoses involving the aortic ostium and the body of the graft have restenosis rates of up to 50%; stenoses at the distal anastomosis are not increased above that normally seen. Fortunately, restenosis can usually be treated with repeat dilation. In the future, stents or

165

atherectomy may make this an even more control- lable and more effective approach.

Obtaining a stable guiding catheter position is often a significant problem. If the surgeon has used ring markers to identify the graft, ostial intubation is often considerably easier and quicker (Fig 15). Several guiding catheters are now available that improve intubation of vein bypass grafts. The use of a vein bypass graft catheter, either left or right, is often sufficient. Frequently, the takeoff is angled in a cranial direction and an Amplatz catheter or an Arani catheter can help. The terminal hook shape of an internal mammary artery guiding catheter may even help entry into a severely angulated vein graft origin. Attempts should be made to obtain such a stable guiding position before proceeding with dilation. This is especially important in tortuous grafts so that the stenosis can be crossed easily with the best platform possible.

When a dilating catheter is selected, it is important to use the most trackable system possible and to optimize the size of the balloon, again because of tortuosity within the graft (Fig 15). Because platform support is often poor, it may not be possible to exert sufficient push to cross very tight stenoses with a balloon that is too large. Optimally sizing the balloon can help. If the lesion is still significant after initial inflations with a smaller balloon, then a larger balloon size

Fig 16. Stenosis at snastomosis of saphenous vein bypass graft with first obtuse marginal artery before (A) and after (B) PTCA. Bypass graft is very tortuous. For successful dilation, stable guiding catheter position and very trackable system are required.

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can be selected. It is important to remember that the body of grafts is often very large. One of the potential reasons for restenosis is inadequate initial dilation. Thus, after the initial dilation, we often increase the size to slightly oversize the balloon for the body of the graft.

The guidewire must also be selected with as much care as the guiding catheter. Optimal placement through the lesion with the potential again to winch and track is important.

Because atherosclerotic lesions within the body of grafts may contain a significant amount of loose atheromatous material, the potential for embolization exists.45 In older grafts with bulky lesions, this may militate against the use of dilation. In patients with more discrete lesions, dilation remains very successful. If distal embolization occurs, the atheromatous material can often be dilated and fragmented to a smaller size so that flow is improved.

Internal Mammary Artery Stenoses

Recently, stenosis of internal mammary artery grafts has been a growing indication for angioplasty (Fig 1 6).46-50 This can present unique technical problems. Access can be obtained either through the retrograde femoral approach for either the right or left internal mammary artery or through the brachial approach. If the brachial approach is selected, the ipsilateral brachial artery must be used. For retrograde femoral access, an internal mammary guiding catheter is ideal. Various techniques can be used for intubation of the mammary artery. A long exchange wire can be positioned beyond where the internal mammary artery arises. The catheter can then be placed over it and pulled back selectively to engage the origin. Alternatively, a more torque- able guidewire can be used to obtain access. A movable core wire may help by providing the option of greater tip trackability through the tortuous subclavian artery. Care must be taken

HOLMES, COHEN, AND MIETSTRA

to avoid trauma to the origin of the internal mammary artery itself. ” Localized spasm may occur in this area. Damping also may be a significant problem, particularly if the patient is significantly dependent on the mammary artery.

Because of the marked tortuosity of the internal mammary artery, use of a low-profile and trackable system is very helpful (Fig 16). Such systems can improve the ability to engage and cross the stenoses that are most common at the distal mammary artery-coronary artery anastomosis. Another problem with internal mammary artery dilation includes difficult visualization of the distal stenoses. A left lateral projection is usually excellent for visualization of the graft- to-artery anastomosis. The use of a guiding catheter with a large internal diameter and a low-profile dilating system is helpful.

Shimshak et a15* described 45 patients who underwent balloon angioplasty within an internal mammary graft (21 patients), beyond the distal anastomosis (19 patients), or at both locations (5 patients). In 55 (95%) of 58 lesions, successful opening of the stenosis was achieved. Follow-up, averaging more than 1 year, revealed a good result from this approach, with approximately 90% of patients reporting no or only mild angina pectoris.

Complete Occlusion

Complete occlusions initially were thought to be contraindications for dilation. Several early series and continued experience have changed this opinion.53-55 If the occlusion is t3 months old, success rates approach 70%. Although these rates are significantly less than those for more ideal cases, they are often clinically acceptable. Problems with chronic occlusion include the failure to cross with either the wire or the balloon, the potential for distal embolization, perforation, and guidewire entrapment, and increased restenosis.


A stable guiding catheter position is essential for the considerable amount of manipulation that is often required to cross occlusions. The occlusion should be visualized in the view where the tip or the nipple of the occlusion can be best seen. Probing this outpouching often results in crossing the complete occlusion. It is important that the guidewire not be forced through this area because perforation or significant arterial damage may occur. The type of equipment used does vary. In general, a stiffer wire is required. Proba- bly the best approach is a steerable 0.016-inch wire to pass through the occlusion. Careful manipulation is required. It is important to avoid continued torque on the guidewire while the tip of the guidewire is buried within the occlusion. This can result in incarceration and subsequent unraveling and separation of the guidewire tip.56 In some patients, it is helpful to shorten the length of protruding guidewire. This increases the stiffness of the system and can facilitate crossing of the occlusion.

Rarely, a distal guidewire segment will frac- ture during vigorous attempts to cross a chronic coronary occlusion. In such cases, a well- anchored retained fragment may be benign. By contrast, if the wire fragment protrudes into a patent part of the coronary circulation, it is probably wisest to minimize any thrombotic risk by surgical or transluminal means. In a series reported by Hartzler et a1,57 angioplasty components were retained in 0.2% of cases. Extraction of three intracoronary wire fragments was successfully accomplished by catheter entwining or withdrawal of the inflated balloon catheter.

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When the guidewire is seen to cross the complete occlusion, it often seems to lurch forward. Test injections are helpful to document its intraluminal position. After the guidewire is passed, usually a low-profile catheter is initially winched through the stenosis for initial dilation. Good backup pressure with a stable position of the guiding catheter is essential in this situation. In some patients it is possible to get a guidewire through the chronic occlusion but a balloon catheter will not pass (Fig 17). In these patients, the stiff 0.016-inch guidewire may create a track through the occluded segment. In such circumstances, a Probe or other balloon-on-a-wire catheter with its increased stiffness but very low profile can follow the track made by the stiff guidewire and cross the occlusion. Similarly, the very trackable low-profile Mini may work. In this case, initially the Probe or Mini may work. In this case, initially the Probe or Mini is used to pass through the stenosis for initial dilation. After this, a larger catheter can be used. Given a higher propensity for acute reocclusion in these patients, a ten-minute angiogram is mandatory to look for thrombus accumulation at the PTCA site.

Investigators in Frankfurt have used a new technique for crossing chronically occluded seg- ments in the peripheral arteries.58 This involves low-speed (200 rpm) rotation of a ball-tipped catheter that snakes its way through the occlusion with just slight axial thrust. A modification that allows application in the coronary arteries already has proved successful for chronic occlusions of up to 5 years’ duration.59 Developments

Fig 17. Occluded proximal right coronary artery. A 0.01~inch wire could be passed through occlusion, but a conventional balloon would not cross. Wire was removed, and a Probe was inserted, passing through track of guidewire. Inflation resulted in excellent improvement.

168

with this exciting option are awaited with inter- est.

CONCLUSION

Complex coronary angioplasty may be opti- mized with a thorough understanding of the multiple technical options available to the operator. A thorough understanding of the physical characteristics of any system used, including balloon compliance, flexibility, conformance, trackability, guidewire compatibility, and de- flated and inflated profiles is required. It is important to realize that a full understanding of these physical characteristics comes only with hands-on experience. This experience is of cru- cial importance and forms a basis for comparison of these various characteristics. Systems cannot be compared and decisions about which system might be better in one circumstance v another cannot be made unless there is a reservoir of experience to call on. A manufacturer’s claim is in no way a substitute for hands-on experience.


Optimal angioplasty includes not only an excellent angiographic result but an expeditious procedure that uses minimal contrast and radiation. An optimal angiographic result may be obtained, for example, during a procedure that takes far longer than it should. Complex angioplasty sub- jects both the patient and the operator to increased risks-complications for the patient and increased radiation to the operator. This risk may be reduced and the chance for success increased by planning dilation strategy, consulting with experienced colleagues, and continuing medical education.

Finally, it is likely that other interventional methods, such as atherectomy, laser, and stent placement, will soon be included in the strategy for nonideal lesions. To the extent that they solve some of the already existing problems with balloon angioplasty described in this review, they could become important partners for the balloon method or, indeed, serious competitors.

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Documents

Optimizing the results of balloon coronary angioplasty of nonideal lesions