Special characteristics of atherosclerosis in chronic renal failure

Cardiovascular complications are a major clinical problem in patients with chronic kidney disease and end stage renal failure. Death from cardiac causes accounts for 40%-50% of all deaths in these patients and is thus up to 20 times more common in uremic patients than in the general population. Cardiovascular pathology in patients with renal failure is complex, but accelerated atherosclerosis has repeatedly been discussed as one major cause. The prevalence of coronary atheroma in uremic patients is approximately 30% by autopsy and coronary angiography studies. Not only is the prevalence of atherosclerotic lesions very high, but also the case fatality rate of myocardial infarction. Recently, excess mortality in uremic patients having had a myocardial infarct was noted; the one year mortality was 55.4% and 62.3% in uremic patients with and without diabetes, respectively, compared to about 10-15% in non-uremic patients. This study goes beyond the well-known notion that urea is associated with more severe atherosclerosis and shows that, in addition, the adaptation to coronary perfusion deficits is inappropriate. Recent clinical and autoptical studies in pre-dialysis and dialysis cohorts have documented increased intima and media thickness which appear early in the course of renal disease; Vascular wall thickening in renal failure seems to be modified at least in part by parathyroidhormone (PTH) and endothelin-1 (ET-1) which are both elevated in patients with renal failure. In experimental renal failure a direct effect of high phosphorus diet in arterial wall thickening was also documented. In addition to thickening of the vascular wall marked structural alterations were noted in renal failure i.e. a decrease in elastic fibre content and an increase in extracellular matrix. Furthermore, increased calcification of coronary atherosclerotic plaques and of the media of the aorta and some peripheral arteries has been documented in patients with renal failure. Factors contributing to this increased calcification process may be deposition of abundant circulating calcium, microinflammation, oxidative stress, de novo expression of bone morphogenous proteins and lack of inhibitors of calcifcation. These changes in vascular wall composition may alter vessel elasticity and thus contribute to impaired vessel function in renal failure. It is obvious from the above mentioned facts that cardiovascular disease in the renal patient is certainly multifaetorial in origin. There are, however, important issues to adress in the future, like (I) the characterization of vascular morphology in the different vascular beds, (II) the pathomechanisms of vascular and plaque calcification as well as the potential beneficial effect of rigorous control of non-classical risk factors (i.e. high P or Ca x P, inflammation, oxidative stress, etc.), (III) an additive or supraadditive effect of various classical and non-classical risk factors and (IV) the role of diabetes mellitus in modifying these vascular alterations.