Nephronline - Management and Guidance - nearly there with renal NSF document

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Cardiovascular disease in end-stage renal failure (cont.)

General management

Before deciding on the management of a patient, a full assessment should be carried out (Table 3). The diagnostic pathway is dictated by the clinical setting, modulated by the assessment of transplant suitability.

Table 3: Assessment of cardiovascular status

		History
		Examination
		Full blood count
		Biochemistry
		Dialysis adequacy: eg, Kt/V
		Lipid profile
		PTH and calcium phosphate
		Resting ECG
		Exercise ECG
		Dipyridamole exercise thallium imaging
		Echocardiography
		Coronary angiographybnormalities in lipid profile

One area of difficulty remains the diagnosis of myocardial infarction (MI). This is usually made on the basis of a history of pain, ECG changes and changes in cardiac enzymes. However, pain is not a universal feature, ECG changes may be difficult to interpret, and the common serological markers in use within the UK -- creatinine kinase (CK) and troponin (T) -- are difficult to evaluate in patients on dialysis because they often give false positive elevations. Such elevations may also be seen within CKMB, though to a lesser degree. Troponin I is not currently believed to give false positive results in uraemia, so may be the definitive serological marker in the diagnosis of MI in end-stage renal failure.

Non-invasive interventions
All patients should be advised to stop smoking. Adequate dialysis and adequate nutrition should also be achieved. Medical management includes treating underlying diseases.

Hypertension
Hypertension should be managed by fluid removal and the addition of medication where appropriate.

Within the haemodialysis population it is currently unclear at what level and at what time blood pressure should be assessed. Conventional management relies on pre-dialysis blood pressure aiming for levels less than 140/90mmHg for patients under the age of 65 and under 160/90mmHg if the patient is over 65 (Renal Association Guidelines. Second edition). However, pre-dialysis blood pressure is subject to wild fluctuations related to fluid status and, more importantly, the way in which it is measured pre-dialysis.

There is some evidence that blood pressure measured post dialysis is a more accurate reflection of 24 hour blood pressure load and it may be that this is a more robust point for assessment.

The current level of blood pressure to achieve is currently under review by the Renal Association Standards Committee, which is suggesting a level of 130/80mmHg.

ACE inhibitors probably remain the best choice antihypertensive in this population, with their additional benefits on cardiac hypertrophy and heart failure.

Lipids
There is a substantial body of work suggesting that cholesterol lowering -- particularly with the use of HMG CoA reductase inhibitors -- has a beneficial action on outcome in coronary artery disease.

However, by their natures, patients with significant renal disease have been excluded from these studies and there are no prospective randomised studies of outcome using these agents. Moreover, there are concerns about the safety of such agents in patients on dialysis.

Recently, however, a randomised placebo-controlled study of atorvastatin in patients on continuous ambulatory peritoneal dialysis has been published in abstract form (Renal Association Nottingham, April 2001) suggesting that these agents are safe and effective in the short term in lowering serum-cholesterol levels.

Current practice, therefore, is in evolution and needs more data to assess the use of statins within such a patient population. Current anecdotal practice would support the use of statins as secondary prevention in patients with proven ischaemic events, but the question of primary prevention and the use of statins remain unresolved

Anaemia
Attempts should be made to correct anaemia, aiming for haemoglobin levels of greater than 10, and probably between 11 and 12.5, in patients with symptomatic disease.

Control of hyperparathyroidism and calcium and phosphate metabolism
Data would suggest that there are high rates of calcification of both coronary vessels and the myocardium, including the valves, among dialysis patients. The role of intervention in controlling calcium intake and phosphate levels has not been studied. However, Block et al. (Am J Kidney Dis, 2000) demonstrated an increase in mortality with phosphate levels above 6.5 mg/dL. .

In addition, hyperparathyroidism has been implicated in myocardial fibrosis and in abnormalities of intra-cellular calcium handling.

Therefore, no recommendations for calcium and phosphate levels can be given on current evidence other than that attainment of the Renal Association standards may have a beneficial effect on cardiovascular outcome.

Valvular disease
Currently standard indications apply to the replacement of valves and the treatment of endocarditis.

Anecdotally, valve replacement should avoid using tissue grafts, owing to the risk of recurrent calcification, a problem that can arise within one year of replacement (unpublished personal observation). Attainment of good fluid control may reverse, or slow, valve incompetence.

Invasive management
Dialysis patients can be treated by percutaneous transluminar angioplasty (PTCA), with or without stenting, or by coronary-artery bypass grafting. Currently, indications for these are similar to those of subjects with normal renal function.

A number of studies have indicated that the outcome after PTCA is poor compared with non-uraemic patients, suggesting that re-stenosis rates are higher within this group.

This data, however, pre-dates the widespread use of endovascular stenting and the relative contributions of PTCA-with-stent versus coronary-artery bypass grafting have not been assessed.

Currently, interventional therapy is suggested for patients with significant left main coronary artery disease, three-vessel disease and unstable angina, or in those with reduced left ventricular function.

Cardiovascular disease represents a major challenge in patients with end-stage renal failure. There is an increased prevalence of conventional risk factors within the dialysis stock, which is magnified in its severity by factors unique to the uraemic milieu. Mortality has not changed in two decades of therapy, but it is only in the past decade that the additional factors of better control of calcium phosphate, effective therapy for hypercholesterolaemia and the partial correction of the anaemia of chronic renal failure have been addressed. Moreover, the genesis of many of these abnormalities within the end-stage population lies in the years and decades predating their arrival on dialysis. The correction of these factors before patients come on to a dialysis programme may improve the outcome.