Response to Meta-Analysis of the Effects of Treating Blood Pressure on Cardiovascular Outcomes of Dialysis Patients
Goldsmith and Covic1 rightly conclude that it is premature to attribute cardiovascular benefits of antihypertensive drug use in hemodialysis patients to blood pressure (BP) lowering alone. Our meta-analysis points out the sharp difference between cohort studies and randomized trials; the former show harm with spontaneous fall in BP, whereas the latter show a benefit with antihypertensive drug use.2 Heerspink et al,3 in their meta-analysis concluded, “treatment with agents that lower blood pressure should routinely be considered for individuals undergoing dialysis to reduce the very high cardiovascular morbidity and mortality rate in this population.” However, given the problems with the current randomized trials and the heterogeneity in results, we concluded that, “adequately powered randomized trials are required to confirm these observations, especially among those with hypertension.” Our meta-analysis should not be taken as “proof” that BP should be lowered in hemodialysis patients. Indeed, our conclusions are consistent with the urgent call by Goldsmith and Covic1 for well-designed, randomized trials in this vulnerable population.
We had 3 fewer studies in our meta-analysis compared to the 1 by Heerspink et al.3 Two of the 3 studies in the meta-analysis of Heerspink et al3 were published in abstract form. The third study was done in peritoneal dialysis patients to test the notion of whether angiotensin-converting enzyme inhibitors protect the decline in residual renal function; this study was substantially different from other studies in hemodialysis patients, which were designed to study cardiovascular protection.4 Accordingly, we feel that the results of our meta-analysis accurately reflect the state of the art, at least in hemodialysis patients. We, like Heerspink et al,3 found heterogeneity between studies, but unlike these authors we found that the effect on cardiovascular risk was modified by consideration of hypertension status. Therefore, studying hypertensive patients should have a more urgent priority compared with lowering BP among normotensive patients on hemodialysis. If such a trial is undertaken, we recommend that BP monitoring be performed outside of the dialysis unit rather than simply measuring BPs before and after dialysis.5,6
Goldsmith DJA, Covic AC. Meta-analysis of the effects of treating blood pressure on cardiovascular outcomes of dialysis patients. Hypertension. 2009; 54: e6.
Agarwal R, Sinha AD. Cardiovascular protection with antihypertensive drugs in dialysis patients: systematic review and meta-analysis. Hypertension. 2009; 53: 860–866.
Heerspink HJ, Ninomiya T, Zoungas S, de Zeeuw D, Grobbee DE, Jardine MJ, Gallagher M, Roberts MA, Cass A, Neal B, Perkovic V. Effect of lowering blood pressure on cardiovascular events and mortality in patients on dialysis: a systematic review and meta-analysis of randomised controlled trials. Lancet. 2009; 373: 1009–1015.
Agarwal R, Peixoto AJ, Santos SF, Zoccali C. Pre and post dialysis blood pressures are imprecise estimates of interdialytic ambulatory blood pressure. Clin J Am Soc Nephrol. 2006; 1: 389–398.