THE CLINICAL EPIDEMIOLOGY OF CARDIOVASCULAR DISEASES IN CHRONIC KIDNEY DISEASE: Introduction

During the past decade there have been major advances in the epidemiology of cardiovascular disease (CVD) in chronic kidney disease (CKD), and it appears that more randomized clinical trials in this area will be undertaken in the next decade. This volume attempts to summarize these recent advances. It is now apparent that the adverse consequences of cardiac disease—death, heart failure, myocardial infarction, angina, arrhythmias, dialysis hypotension, etc.—are most frequently the result of either cardiomyopathy or ischemic heart disease (IHD), and that vascular disease, whether arteriosclerotic or atherosclerotic, predisposes to cardiac disease. Heart failure, the clinical consequence of left ventricular (LV) pump failure, may result from either systolic or diastolic dysfunction. Although LV pump failure is usually the result of cardiomyopathy caused by LV pressure and/ or volume overload, IHD may also be a predisposing factor. Myocardial infarction/angina, the clinical consequences of IHD, usually result from critical atheromatous coronary artery disease. However, a substantial minority of CKD patients with IHD may have nonatheromatous disease, resulting from small vessel disease and cardiomyopathy. Volume overload also predisposes to arteriosclerosis, which itself may predispose to left ventricular hypertrophy (LVH) and to diminished coronary perfusion. In his contribution, Dr. Gerard London from Paris examines the pathophysiology of these conditions, thus setting the stage for detailed examination of the clinical epidemiology of LVH, heart failure, IHD, and their associated risk factors in the various stages of CKD. Whether renal insufficiency per se is an independent cardiac risk factor is a controversial issue, which is discussed by Dr. Bruce Culleton from Calgary. Clearly the presence of CKD is a marker for more severe cardiac disease, and in cohorts with high degrees of comorbidity, CKD predicts more adverse outcomes. However, there are few longitudinal studies in cohorts with low degrees of comorbidity studying the risk of atherogenic and cardiomyopathic clinical outcomes. At present it appears that CKD is a cardiomyopathic state, as a result of hemodynamic overload, characteristic of chronic uremia. Whether CKD is a state of accelerated atherosclerosis independent of the high prevalence of coronary risk factors is less evident. Dr. Adeera Levin from Vancouver examines the clinical epidemiology of CVD in predialysis CKD, the phase of disease best open to cardiac prevention strategies. This group of patients has not yet been well studied, and is likely to be the group most suited to the identification of novel uremia-related CVD risk factors. Renal transplant recipients are a model of CKD (despite the ubiquitous immunosuppression) and are an attractive group for study because of the ‘‘captive’’ nature of their care. Dr. Claudio Rigatto from Winnipeg reports on the various longitudinal studies exploring cardiac risk factors in this group. Dialysis patients have an extremely high CVD event rate, partly because they usually have been exposed to a long period of cardiomyopathic and vascular risk predialysis, partly because of the high prevalence of traditional cardiac risk factors, and partly because of the hemodynamic and metabolic perturbations characteristic of chronic uremia which predispose to LVH and vascular disease. Dr. Robert Foley from Minneapolis summarizes recent advances in this group of patients. Cardiac risk factors in CKD may be classified as traditional or uremia related. The latter may be hemodynamic—volume overload, fistula, anemia, arteriosclerosis, valve stenosis—or metabolic in nature. Metabolic, uremia-related risk factors may be specific to the uremic state—dyslipidemia, divalent in abnormalities, oxidative stress—or of greater magnitude than in the general population—inflammation, hyperhomocysteinemia, prothrombotic factors, Lp(a) lipoprotein. Adequately designed longitudinal studies of cardiac risk in CKD are few. Such studies require 1) incident patients in the same disease phase, 2) separation of the period of risk from outcomes, 3) measurements of incident cardiac events in addition to death, 4) multivariate modeling of all the potential risk factors, 5) big sample sizes with appropriate description of the risk factors and outcomes, etc. Table 1 summarizes the current evidence concerning cardiac risk Address correspondence to: Patrick S. Parfrey, MD, Department of Medicine, Division of Nephrology, Health Sciences Center, Memorial University, St. John’s, NF, Canada A1B 3V6, or e-mail: p.parfrey@mun.ca. Seminars in Dialysis—Vol 16, No 2 (March–April) 2003 pp. 83–84