Changing Paradigms Of Coronary Revascularization

When the era of interventional cardiology began with the pioneering work of Andreas Gruntzig on plain balloon angioplasty, percutaneous coronary intervention (PCI) was a treatment option only for isolated proximal coronary lesions not involving the ostia or the left main stem. In the late 1980s, coronary stents were developed with the goals of reducing the risk of restenosis and achieving a more predictable acute result of angioplasty, thus avoiding the dreaded abrupt closure due to dissection. As shown subsequently, stents were successful in achieving this goal. Nevertheless, they created a new problem: subacute stent thrombosis. After intense research on peri-interventional and postinterven-tional antithrombotic treatment, the concept of dual or triple antiplatelet therapy emerged, which largely resolved the issue of subacute stent thrombosis. The use of coronary stents in conjunction with optimized antithrombotic treatment extended the spectrum of coronary lesions for which PCI was considered a reasonable treatment option and thereby led to a substantial expansion of interventional techniques. With the large number of patients being treated with coronary stents, restenosis due to neointima formation became a serious problem. Although various studies demonstrated that stents reduce the need for reintervention compared with plain balloon angioplasty,1-3 restenosis rates continued to be relevant, ranging from just above 10% in the most simple lesions to more than 50% with diffuse disease in patients with diabetes.

Therefore, it is not surprising that the community of interventional cardiologists celebrated the advent of the new drug-eluting stents as a major breakthrough, given that the initial studies suggested zero restenosis rates. It has become clear that drug-eluting stents reduce the need for target vessel reintervention by about 80% compared with a bare metal stent, thereby largely reducing but not eliminating the problem of restenosis. Subsequently, drug-eluting stents led to another massive expansion of the proportion of patients treated with PCI. With the widespread use of drug-eluting stents for PCI, reports appeared pointing toward a new problem that was not perceived with bare metal stents: late (>30 days to 1 year) and very late (>1 year after stent implantation) stent thrombosis. Thorough reevaluation of the data from randomized trials with uniform application of definitions for definite, probable, and possible stent thrombosis showed no difference in stent thrombosis rates between drug-eluting stents and bare metal stents until 1 year after stent implanta-tion.4-7 However, there was evidence of a slight, 0.1%

to 0.2% per year increase in the risk of very late stent thrombosis associated with drug-eluting stents until 4 years after stent implantation. Although there were no significant differences in the cumulative rates for death or myocardial infarction at 4 years, as compared to bare metal stents, the impact of drug-eluting stents on serious late complications is a major scientific and clinical challenge, due to their overall low incidence and the long follow-up periods needed. A tradeoff between the marked reduction in target vessel revascularization on one hand and death or myocardial infarction (MI) on the other hand would not be acceptable in the presence of alternative treatment options such as bare metal stents or bypass surgery. (A list of trial abbreviations and acronyms is presented in Table 6-1.)

Despite remaining issues to be addressed, the use of PCI has increased exponentially over the past decades. Initially, this increase came at the expense of lone medical therapy. However, with the advent of drug-eluting stents, there has been a shift of patients with multivessel disease and other complex coronary anatomies from CABG to PCI. In many countries, this has led to a decrease in CABG procedures, sometimes by as much as 20% per year, because the demographically driven increase in numbers of patients needing coronary revascularization could not compensate for the shift from surgery to inter-ventional cardiology. This shift from surgery to PCI has been facilitated by both physician and patient preference to take the supposedly easier approach to coronary revascularization, given the conception that the problem of restenosis has been largely solved. However, there is reasonable concern that this has led to overuse of PCI and that in many patients PCI, as the easier approach, may not yield the same outcome as CABG, which for a number of indications is an established treatment option with a well-documented survival benefit compared with medical therapy.

When comparing PCI with lone medical treatment or bypass surgery, it is important to scrutinize the evidence indicating that PCI offers at least equal benefit to CABG on the one hand, or superior benefit to lone medical treatment on the other hand. A number of randomized studies and analyses from large-scale registries have been performed. Despite this large database, currently available evidence is difficult to interpret for two reasons. First, because of rapid technologic and pharmacologic development in both the surgical and the interventional field, the therapeutic approaches often are outdated by the time the results of a study appear. Second, with any of the modern treatments, mortality, the most important benchmark for studies, is so low that huge numbers of patients are needed to assess this end point. Therefore, most studies concentrate either on surrogate end points or composite end points that combine events of diverse clinical importance (e.g.,

Table 6-1.

Trial Abbreviations and Acronyms

ACIP

Asymptomatic Cardiac Ischemia Pilot study

ACME

Angioplasty Compared to Medicine

APPROACH

Alberta Provincial Project for Outcome

Assessment in Coronary Heart Disease

ARTS

Arterial Revascularization Therapies Study

AVERT

Atorvastatin versus Revascularization

Treatments

AWESOME

Angina With Extremely Serious Operative

Mortality Evaluation

BARI

Bypass Angioplasty Revascularization

Investigation

CABRI

Coronary Angioplasty versus Bypass

Revascularization Investigation

CASS

Coronary Artery Surgery Study

COMBAT

Randomized Comparison of Bypass Surgery

versus Angioplasty Using Sirolimus-Eluting

Stent in Patients With Left Main Coronary

Artery Disease

COURAGE

Clinical Outcomes Utilizing Revascularization

and Aggressive Drug Evaluation

EAST

Emory Angioplasty versus Surgery Trial

ECSS

European Coronary Surgery Study

ERACI

Argentine Randomized Trial of Percutaneous

Transluminal Coronary Angioplasty Versus

Coronary Artery Bypass Surgery in

Multivessel Disease

FREEDOM

Future Revascularization Evaluation in Patients

with Diabetes Mellitus: Optimal Management

of Multivessel Disease

FRISC

Fragmin and Revascularization during Instability

in Coronary Artery Disease

GABI

German Angioplasty Bypass Surgery

Investigation

ICTUS

Invasive versus Conservative Treatment in

Unstable Coronary Syndromes

ISAR-SWEET

Intracoronary Stenting and Antithrombotic

Regimen: Is Abciximab a Superior Way to

Eliminate Elevated Thrombotic Risk in

Diabetics?

MASS

Medicine, Angioplasty or Surgery Study

MATE

Medicine versus Angiography in Thrombolytic

Exclusion

RESEARCH

Rapamycin-Eluting Stent Evaluated At

Rotterdam Cardiology Hospital [registry]

RITA

Randomized Intervention Treatment of Angina

SIMA

Stenting versus Internal Mammary Artery

SoS

Stent or Surgery Trial

SYNTAX

Synergy Between PCI with Taxus Drug-Eluting

Stent and Cardiac Surgery

TACTICS

Treat Angina with Aggrastat and Determine

Cost of Therapy with an Invasive or

Conservative Strategy

TIMI

Thrombolysis in Myocardial Infarction

TRUCS

Treatment of Refractory Unstable Angina

without Cardiac Surgery

T-SEARCH

Taxus-Stent Evaluated At Rotterdam Cardiology

Hospital registry

VA-Study

Veterans Administration Cooperative Study

VANQWISH

Veterans Affairs Non-Q-Wave Myocardial

Infarction Strategies In-Hospital

VINO

Value of First Day Angiography/Angioplasty in

Evolving Non-ST Segment Elevation

Myocardial Infarction: An Open Multicenter

Randomized Trial

death and target vessel revascularization). Despite these difficulties, it is important to make therapeutic decisions on the basis of evidence as much as possible. This review summarizes and discusses the evidence that is currently available to present a rationale for clinical decision-making.

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