Prevention of Cardiovascular Complications in Dialysis Patients

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Abstract

Introduction
Despite many technical advances in the field of dialysis, patients undergoing chronic renal replacement treatment (RRT) display a significantly lower life expectancy compared with their counterparts in the general population. Most of this excess mortality is due to cardiovascular disease. Indeed, half of the deaths in dialysis patients and about one-third of hospitalisations are of cardiovascular origin 1 and the incidence of cardiovascular deaths occurring among dialysis patients is approximately 20 times higher than that in the general population. 2 In this context, the understanding and proper management of the determinants of cardiovascular disease in the dialysis population become a challenge of major importance for the nephrologists in the current management of dialysis patients.
The high prevalence of cardiovascular disease, either clinically or simply echocardiographically detected, among dialysis patients at the beginning of RRT 3,4 suggests that the pathogenetic mechanisms leading to the development of cardiovascular complications begin to operate very early in the progression of chronic kidney disease (CKD), far before patients reach the need for dialysis. This underlines that the prevention of cardiovascular disease in these patients should begin as early as possible during the course of their disease, taking care of the cardiovascular risk factors optimally.

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Cardiovascular Risk Factors in Dialysis Patients
The pathogenesis of cardiovascular damage in dialysis patients is far more complex than in the general population, as they are exposed to a number of cardiovascular risk factors. They not only include those identified in the general population, whose prevalence is far higher among dialysis patients (they are often elderly and/or affected by diabetes or secondary hypertension), but also additional risk factors specific to CKD, eventually exacerbating after the start of dialysis due to the decline in the residual renal function, and to the dialytic treatment itself.

CKD-related cardiovascular risk factors include haemodynamic overload due to plasma volume expansion and arterio-venous fistula, anaemia, disorders of calcium-phosphate metabolism, electrolyte imbalances, chronic inflammation, increased oxidant stress, 6 hypercatabolism and even uraemia, per se. Haemodynamic stress due to intraand interdialytic changes in cardiac filling and fluctuations of blood pressure, rapid changes in serum electrolyte levels, bioincompatibility of dialytic membranes and dialysate impurity further contribute to the excess cardiovascular risk of these patients because of the dialytic procedure.

Hypertension
Hypertension is very common among CKD patients and its prevalence increases nearly linearly with the decline in renal function, so that the vast majority of patients with significant renal failure display high blood pressure values. 7 It has been suggested that hypertension plays a major role in determining cardiac damage in dialysis patients, as well as in the general population, mainly because it significantly contributes to the development of left ventricular hypertrophy (LVH). It has been observed that blood pressure control in hypertensive dialysis patients leads to a substantial regression of LVH.

Considering the detrimental consequences of LVH on patient morbidity and mortality, adequate blood pressure control must therefore be a major objective in the management of these patients. Considering that hypertension in dialysis patients is essentially due to volume retention, the cornerstone of this strategy should be keeping patients as close as possible to their dry weight, but this objective is not always achievable.

When antihypertensive drugs are needed, it should be remembered that, currently, there is no proof that any class of antihypertensives is superior to another in preventing cardiovascular disease in dialysis patients when blood pressure is adequately controlled. However, the observation that inhibitors of the renin-angiotensin system have beneficial effects on the haemodynamic profile and on left ventricular geometry, together with the results of the Heart Outcomes Prevention Evaluation (HOPE) study showing that angiotensin-converting enzyme inhibitors lead to a better prognosis in patients at high cardiovascular risk than other anti-hypertensive drugs, suggest that these drugs should probably be the first choice in dialysis patients. In this population these agents need to be managed carefully, given the risk of hyperkalaemia. />/>/>/>/>/>/>/>/>/>

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References

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