New Devices Versus Conventional Balloon Technology in Patients with Coronary Artery Disease

DAVID R. HOLMES, JR., M.D.

From the Mayo Clinic, Rochester, Minnesota

Introduction

Since its introduction in 1977, the use of percu- taneous transluminal coronary angioplasty (PTCA) has grown exponentially so that in 1990 it is estimated that approximately 400,000 proce- dures were performed. The initial indication was the presence of a single discrete noncalcified sub- total stenosis in a proximal nontortuous coronary arterial segment in a patient with stable angina and well preserved left ventricular function. Once the concept of percutaneous nonsurgical coro- nary revascularization was proven, the approach grew rapidly. Technological advances with the in- troduction of new guiding catheters, smaller low profile balloons, over-the-wire systems, and more flexible steerable guidewires were associ- ated with increased success rates. These im- proved success rates and increased operator ex- perience have fostered the changes in selection criteria, which have resulted in the growth of these procedures.

What can be said in 1992 is that PTCA is a strikingly successful procedure. Success rates in recent series are approximately 95% in selected patients. ' The incidence of complications is low; coronary bypass graft surgery required in 1%-2%, myocardial infarction occurs in < 5%, and death in approximately 0.5%-1 .O%. These

Address for reprints: David R. Holrnes, Jr., M.D., Depart- ment of Cardiology, Mayo Clinic, Rochester, MN 55902. Fax:

Submitted for publication September 10, 1991 ; accepted Sep- tember 23, 1991.

(507) 284-5470.

success and complication rates are documented despite the fact that patient and angiographic se- lection criteria have broadened to include pa- tients with less ideal anatomy, multivessel dis- ease, prior coronary bypass graft surgery, acute ischemic syndromes, and depressed left ventricu- lar function. Despite these excellent initial out- come rates, higher risk patient subsets recogniz- able by either angiographic anatomy or clinical factors, can be identified in which expectations are generally lower and risks are higher. Overall, however, in selected patients, dilatation has revo- lutionized the modern day practice of cardiology.

Despite the impressive success rates and low complication patterns of PTCA, the technique has limitations that either limit the applicability of the technique (an example would be the pres- ence of a chronic total occlusion or small dif- fusely diseased calcified vessels) or relate to safety issues (although dilatation could be per- formed, the risk of dissection, abrupt closure, or branch vessel occlusion may make conventional dilatation at higher risk). Finally, other limita- tions relate to the long-term problem of restenosis that has been documented in 35%-50% of pa- tients; a phenomenon that results in the need for repeat procedures and a loss of the initial eco- nomic gain compared to coronary bypass graft surgery as well, which carries with it the potential for increased patient morbidity.

Throughout this last decade of rapid growth of dilatation procedures, there has been the devel- opment of new devices broadly grouped as ather- ectomy, lasers, and stents.*-I0 These new devices have different effects on the coronary arterial

Vol. 5 , No. I , 1992 Journal of lnterventional Cardiology 47

tree; some have been developed as a means to debulk atheromatous plaque compared to the plaque fracturing and stretching of the more nor- mal arterial wall that are the pathophysiological hallmarks of conventional PTCA; others have been developed as mechanical supports for the arterial wall such as stents. The aim of some of these devices is to extend the application of per- cutaneous revascularization strategies while that of others is to make dilatation safer.

It must be kept in mind that these devices are in their early development stage; even though multiple iterations have been tested, rapid tech- nological improvements are still being made in device flexibility, efficacy, size, and ease of use.

The aim of these devices varies; some have been developed to address the aforementioned limitations of PTCA and thus to either extend the application of the strategy to lesions and patients who would not be candidates for conventional dilatation, to make percutaneous revasculariza- tion safer with less risk, or to prevent restenosis. Some of these aims are based upon theoretical advantages, for example, the postulate that ather- oma removal will result in better long-term out- come than plaque fracturing. Other aims are based upon actual performance such as the use of stents to treat dissection and abrupt closure. It is important to keep these distinctions between actual performance and theoretical advantages clear in selecting optimal treatment strategy for a specific patient. It is also important to remember that the riskhenefit ratio of these new devices is often less well understood than that for conven- tional PTCA. In addition, there may be unique risks to the new devices that pose problems not seen with conventional dilatation such as perfora- tion that remains a reportable event with conven- tional PTCA but may occur in 1% to 2% of pa- tients with new devices such as excimer laser an- gioplast y.

Evaluation of the role and impact of new de- vices for the treatment of coronary artery disease should proceed through several stages. After test- ing the design concepts in vitro and then in animal models, these devices have usually been tried in peripheral arterial beds in patients. Provided that performance characteristics are acceptable, human coronary arterial studies are cautiously in- itiated at selected centers. With some devices,

these initial coronary arterial studies have been performed in the operating room. Initial studies often involve treating lesions that would be well suited for conventional PTCA. These initial appli- cations in patients with ideal lesions are required to document safety and efficacy. After this initial experience, the number of investigative centers can be increased and angiographic subsets of pa- tients expanded. This phase is aimed at identify- ing specific subsets with improved short- and long-term outcome compared to what might have been expected with conventional PTCA. Such as- sessments of improved outcome are fraught with hazard because they involve historical controls that may have had different clinical and angio- graphic characteristics; in addition, dilatation technology has also improved substantially." The next phase involves vigorous scientifically controlled randomized studies in comparable pa- tient subsets comparing short- and long-term out- come of specific new devices with conventional PTCA or with other new devices. It is this stage that we are currently at with several new devices, for example, directional atherectomy and intra- coronary stents. Only after this important step can we be certain of the relative merits of the different technology.

What then can be said about the impact of new devices on PTCA? At the present time and for the foreseeable future, conventional PTCA will remain the mainstay of interventional cardiology with its multiple iterations of devices, its long track record, and its documented safety and effi- cacy. Widespread routine use of new devices without specific protocols or as a marketing tool should be discouraged. At the present time, a substantial amount of clinical information is available on several new devices: directional cor- onary atherectomy, which is currently approved; excimer laser angioplasty , which has been ap- proved by the FDA Advisory Panel for selected angiographic subsets; three intracoronary stents (Schatz-Palmaz [Johnson & Johnson Interven- tional Systems Warren, NJ, USA], Gianturco- Roubin [Cook, Bloomington, IN, USA], and Wallstent [Medinvent, Plymouth, MN, USA]); rotational atherectomy; and to a lesser extent, transluminal extraction atherectomy. None of these new devices is a panacea that has solved all of the problems of conventional dilatation; in-

HOLMES

48 Journal of lnterventional Cardiology Vol. 5 , No. 1 , 1992

NEW INTRACORONARY DEVICES VERSUS CONVENTIONAL PTCA

Table 1. Role of New Technology ~~~~~ ~~

Directional coronary atherectomy: discrete eccentric lesions in proximal nontortuous large

0 ostial left anterior descending 0 removal of discrete limited dissection flaps after PTCA

short diffusely diseased lesions with calcification

tubular or long lesions in vein grafts

0 treatment of threatened or abrupt closure due to

possible reduction in restenosis in large vessels with

coronary arteries or vein grafts

Rotablator:

Transluminal extraction:

Stents:

dissection after PTCA

single stents Excimer laser:

0 concentric diffuse lesions in straight coronary arterial

possible treatment of ostial lesions segments

deed, for some of these new devices, the risk/ benefit ratio may not be improved but may just be different than with conventional PTCA.

There is a growing body of data that suggests a potential important role for each of these devices (Table 1) although in many of these angiographic subsets, conventional dilatation could be per- formed if new technology were not available. For some of these new devices, the application will be a limited niche with the device being a “bou- tique” item. With other devices, the application may be broader, for example, bailout stents to treat abrupt closure from dissections.

At the present time new devices should be se- lectively used and intensely studied, ideally within the context of well designed randomized trials. Given that no device will ever be perfect, however, the goal should be to match the specific

device to treat the specific patient and lesion most safely and effectively.

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