Effects of Pravastatin Treatment on Blood Pressure Regulation after Renal Transplantation

HMG CoA reductase inhibitors (statins) for kidney transplant recipients

BACKGROUND

People with chronic kidney disease (CKD) have higher risks of cardiovascular disease compared to the general population. Specifically, cardiovascular deaths account most deaths in kidney transplant recipients. Statins are a potentially beneficial intervention for kidney transplant patients given their established benefits in patients at risk of cardiovascular disease in the general population. This is an update of a review first published in 2009.

OBJECTIVES

We aimed to evaluate the benefits (reductions in all-cause and cardiovascular mortality, major cardiovascular events, myocardial infarction and stroke, and progression of CKD to requiring dialysis) and harms (muscle or liver dysfunction, withdrawal, cancer) of statins compared to placebo, no treatment, standard care, or another statin in adults with CKD who have a functioning kidney transplant.

SEARCH METHODS

We searched the Cochrane Renal Group's Specialised Register to 29 February 2012 through contact with the Trials Search Co-ordinator using search terms relevant to this review.

SELECTION CRITERIA

We included randomised controlled trials (RCTs) and quasi-RCTs that compared the effects of statins with placebo, no treatment, standard care, or statins on mortality, cardiovascular events, kidney function and toxicity in kidney transplant recipients.

DATA COLLECTION AND ANALYSIS

Two authors independently extracted data and assessed risk of bias. Treatment effects were expressed as mean difference (MD) for continuous outcomes (lipids, glomerular filtration rate (GFR), proteinuria) and relative risk (RR) for dichotomous outcomes (major cardiovascular events, mortality, fatal or non-fatal myocardial infarction, fatal or non-fatal stroke, elevated muscle or liver enzymes, withdrawal due to adverse events, cancer, end-stage kidney disease (ESKD), acute allograft rejection) together with 95% confidence intervals (CI).

MAIN RESULTS

We identified 22 studies (3465 participants); 17 studies (3282 participants) compared statin with placebo or no treatment, and five studies (183 participants) compared two different statin regimens.From data generally derived from a single high-quality study, it was found that statins may reduce major cardiovascular events (1 study, 2102 participants: RR 0.84, CI 0.66 to 1.06), cardiovascular mortality (4 studies, 2322 participants: RR 0.68, CI 0.45 to 1.01), and fatal or non-fatal myocardial infarction (1 study, 2102 participants: RR 0.70, CI 0.48 to 1.01); although effect estimates lack precision and include the possibility of no effect.Statins had uncertain effects on all-cause mortality (6 studies, 2760 participants: RR 1.08, CI 0.63 to 1.83); fatal or non-fatal stroke (1 study, 2102 participants: RR 1.18, CI 0.85 to 1.63); creatine kinase elevation (3 studies, 2233 participants: RR 0.86, CI 0.39 to 1.89); liver enzyme elevation (4 studies, 608 participants: RR 0.62, CI 0.33 to 1.19); withdrawal due to adverse events (9 studies, 2810 participants: RR 0.89, CI 0.74 to 1.06); and cancer (1 study, 2094 participants: RR 0.94, CI 0.82 to 1.07).Statins significantly reduced serum total cholesterol (12 studies, 3070 participants: MD -42.43 mg/dL, CI -51.22 to -33.65); low-density lipoprotein cholesterol (11 studies, 3004 participants: MD -43.19 mg/dL, CI -52.59 to -33.78); serum triglycerides (11 studies, 3012 participants: MD -27.28 mg/dL, CI -34.29 to -20.27); and lowered high-density lipoprotein cholesterol (11 studies, 3005 participants: MD -5.69 mg/dL, CI -10.35 to -1.03).Statins had uncertain effects on kidney function: ESKD (6 studies, 2740 participants: RR 1.14, CI 0.94 to 1.37); proteinuria (2 studies, 136 participants: MD -0.04 g/24 h, CI -0.17 to 0.25); acute allograft rejection (4 studies, 582 participants: RR 0.88, CI 0.61 to 1.28); and GFR (1 study, 62 participants: MD -1.00 mL/min, CI -9.96 to 7.96).Due to heterogeneity in comparisons, data directly comparing differing statin regimens could not be meta-analysed. Evidence for statins in people who have had a kidney transplant were sparse and lower quality due to imprecise effect estimates and provided limited systematic evaluation of treatment harm.

AUTHORS' CONCLUSIONS

Statins may reduce cardiovascular events in kidney transplant recipients, although treatment effects are imprecise. Statin treatment has uncertain effects on overall mortality, stroke, kidney function, and toxicity outcomes in kidney transplant recipients. Additional studies would improve our confidence in the treatment benefits and harms of statins on cardiovascular events in this clinical setting.

Blood pressure-lowering effect of simvastatin: a placebo-controlled randomized clinical trial with 24-h ambulatory blood pressure monitoring

Part of the efficacy of statins in the prevention of cardiovascular events can be attributed to their blood pressure-lowering effect, but clinical trials primarily designed to investigate this effect are scarce. In a double-blind parallel placebo-controlled clinical trial with ambulatory blood pressure (ABP) monitoring, 79 hypertensive patients were randomly assigned to 40 mg of simvastatin (n=40) or placebo (n=39) taken in the morning for 2 months. Between-group deltas of ABP change, adjusted for the corresponding baseline BP, were 2.8 mm Hg (95% CI: 0.4-5.1; P=0.02) for 24-h diastolic blood pressure (DBP), 4.2 mm Hg (95% CI: 0.1-8.4; P=0.04) for daytime systolic BP and 3.1 mm Hg (95% CI: 0.4-5.9; P=0.02) for daytime DBP. There was no effect on nighttime BP. There was an interaction between baseline cholesterol levels and treatment effect, which was restricted to patients with cholesterol above the median of the whole sample. There was no significant change in office BP. In conclusion, simvastatin lowers ABP in patients with hypertension, particularly in the presence of higher levels of cholesterol. This effect may contribute to the beneficial effects of statins in the prevention of cardiovascular disease.

Does the blood pressure-lowering effect of statins contribute to their beneficial cardiovascular effects?

Not all cardiovascular protection provided by statins is explained by their beneficial effects on lipoproteins. Old (e.g., clofibrate) and new (e.g., torcetrapib and ezetimibe) agents, with similar or more intense beneficial effect over lipoproteins, do not reproduce the beneficial effects of statins. Besides their anti-inflammatory and other pleiotropic effects, a blood pressure-lowering effect could be an additional mechanism of cardiovascular protection of statins. Large trials of statins in the primary and secondary prevention of cardiovascular disease did not report an effect on blood pressure, but the use of blood pressure-lowering agents was left to the discretion of physicians during the trial. Post hoc analyses of small trials and a meta-analysis of some of them have suggested that statins could lower systolic blood pressure by approximately 4 mmHg, particularly in patients with high blood pressure. Most studies, however, had small samples and were not blinded. Others had a cross-over or observational design. The overall view of these studies rules out a substantial blood pressure-lowering effect of statins. An effect restricted to subjects with high blood pressure could ultimately derive from the anti-inflammatory effect of statins, since higher levels of C-reactive protein are associated with higher blood pressure. An unequivocal demonstration of an antihypertensive effect of statins, however, is still lacking, and a randomized trial with enough power to evaluate blood pressure variation in a large range of blood pressure values is required to demonstrate whether statins definitely have an antihypertensive effect.