Clinical and angiographic outcome following percutaneous coronary intervention

Abstract

This volume contains a series of linking chapters that follow the evolution of percutaneous intervention from conventional balloon angioplasty in the early to mid 1990s to stent implantation which has now become standard practice. It describes contributions to the extension of clinical situations in which percutaneous intervention has been found to be efficacious as well as refinements in practice and technique. I was fortunate to have been a fellow and then staff member of the Cardiology department of the Thoraxcenter, Rotterdam from 1993-1995, which was then, and remains, at the forefront of the development of percutaneous coronary interventional techniques. My continued links with the Thoraxcenter as well as new projects have allowed me to continue my research and complete this thesis. Part 1 contains two chapters on balloon angioplasty which was standard clinical practice for suitable obstructive coronary lesions until the mid 1990s. The first chapter describes an audit of immediate clinical outcome and thus rates of procedure related complications of contemporary practice in a high volume unit following 970 balloon angioplasty procedures over a one-year period. Although the rate of adverse events appeared to remain static when compared to the previous decade, the requirement for emergency bypass surgery appeared to be diminishing and it is suggested that may be due to the increasing availability of stents for "bail-out". The second chapter studies the long-term outcome with respect to major adverse clinical events in 856 consecutive patients treated by balloon angioplasty from 1980-1985. Although the long-term outcome was good and comparable to results of coronary bypass surgery, most patients suffered a further cardiac event during the 10 years following balloon angioplasty, most of which were repeat revascularisation. Part 2 contains four chapters that describe and document contributions to the evolution of percutaneous coronary interventional practice from balloon angioplasty to stent implantation. Chapter 1 is a review of the literature that describes the evolution of stenting from early animal experiments through early human studies to current practice and on to a vision of the future. Chapter 2 describes follow-up of patients enrolled in the Benestent I study, which was pivotal to the introduction of stenting into clinical practice. Patients, in many centres world-wide, were randomised to balloon angioplasty or stent implantation and underwent 6-month clinical and angiographic follow-up. We report the extended one-year clinical outcome. Chapter 3 documents the landmark Benestent II study. This was a randomised comparison of 827 patients in many centres worldwide (including Auckland) who were allocated to balloon angioplasty or a heparin-coated stent plus treatment with the anti-platelet agent ticlopidine. Patients randomised to stent implantation suffered fewer adverse events and less restenosis but this treatment was found to be more costly than balloon angioplasty. Chapter 4 analyses in more detail some data from the Benestent II study. As well as being randomised to balloon angioplasty or stent implantation, patients were also sub-randomised to 6 month clinical only or clinical and angiographic follow-up. We therefore set out to assess whether management and outcome were influenced as a result of a follow-up angiogram. We found that more interventions were undertaken in those who underwent angiography with no adverse effect on outcome. As a result of the above and other studies, stenting has become routine clinical practice with most patients (approximately 90%) undergoing percutaneous coronary intervention receiving a stent. Part 3 describes several studies which have expanded our knowledge of stenting in various clinical situations and conditions, and also incorporates studies that have added refinement to the technique of stenting. Chapter 1 studies the intermediate term clinical outcome of stent implantation in degenerated saphenous vein grafts. Although the immediate outcome is good, with respect to adverse clinical events, the long-term benefit is limited indicating that with the available technology and medication percutaneous treatment of vein graft is a palliative procedure. Chapter 2 describes the results of a prospective multicentre study assessing the outcome of stenting long native coronary artery lesions. The rates of restenosis were acceptable. The study also provides us with an opportunity to analyse, using quantitative coronary angiography, the location of and give insights into, the mechanism of the restenosis process. Chapter 3 studies the outcome of stenting smaller coronary arteries. Its unique design, in that patients were required to have a lesion in a "small" and a "large" vessel, has provided us with the opportunity to compare both the rates and nature of the restenosis process in the same patients. In this way we abolished clinical and procedure related variables that confound the results when using historical comparisons. Chapter 4 describes the introduction of a new stent, the MultiLink stent, into everyday clinical usage. As with all new devices and minor variations of contemporary devices, which slowly undergo small progressive changes, a careful assessment and audit must be undertaken to ensure it has resulted in improvement in, or at least no detriment to patient care. This chapter audits the clinical outcome of a new stent implanted in the first 126 patients in Auckland and Monash Medical Centre, Melbourne. Chapter 5 is a study that tests a refinement in interventional technique. With refinement and miniaturisation of angioplasty equipment including the profile of balloons and stents, the possibly of implanting a stent without predilating the lesions with a balloon was raised. In this study 81 patients with suitable coronary artery lesions were randomised to stenting with and without predilatation. It was found that in selected patients a strategy of direct stenting was feasible, faster and more rapid than stenting after predilatation. Chapter 6 describes a study which analyses data from 10 studies co-ordinated and managed by the Cardialysis core laboratory in Rotterdam The inclusion of risk factors allows the opportunity to perform meta-analyses looking for factors that may influence outcomes. In this case we attempted to identify clinical and angiographic factors that influence asymptomatic restenosis following percutaneous coronary intervention. Chapter 7 gives an overview of angioplasty numbers and practice in New Zealand by summarising data from the National Angioplasty Registry for the years 1995-1998. This period saw a steady growth in patients with coronary artery disease treated by percutaneous intervention and the number of patients who received stents rose from 23% in 1995 to 84% in 1998. This data attests to the data and results of the earlier studies reported in this thesis.