Is Hemodialysis Bad for the Heart?

Frequent Hemodialysis Schedules are Associated with Reduced Levels of Dialysis-Induced Cardiac Injury (Myocardial Stunning). Jefferies HJ, Virk B, Schiller B, Moran J, McIntyre CW. Clin J Am Soc Nephrol 6: 1326–1332, 2011 Cardiovascular disease (CVD) is now well recognized as the leading cause of death among hemodialysis (HD) patients (1), and HD patients are more likely to die of CV events than the general population (2). The excess morbidity andmortality fromCVD inHDpatients have prompted investigators to explore both traditional and nontraditional CVD risk factors among patients with chronic kidney disease (CKD), including those on dialysis. One recently explored line of inquiry has focused on whether the HD treatment itself contributes to some of this excess CVD risk. Recent studies of myocardial stunning during HD suggest that there are opportunities to improve its delivery and reduce adverse cardiac effects induced by these treatments (3). During thrice-weekly HD, some patients experience intradialytic hypotension and resultant transient myocardial hypoperfusion, placing myocardium at risk for ischemia. Experimental studies have previously demonstrated that cardiac ischemia without infarction can lead to progressive segmental cardiac dysfunction (4) and that repetitive ischemia and reperfusion induce reversible fibrotic remodeling and ventricular dysfunction, with increased interstitial myocardial collagen depositionwithin days of the ischemia ⁄ reperfusion injury (5). Studies in HD patients without overt evidence of cardiac dysfunction have shown reversible deterioration of cardiac function measured with use of pulsed tissue Doppler imaging by echocardiography (6) and intradialytic positron emission tomography (PET) scanning (7). In the earlier of these two studies (6), this deterioration was related to the ultrafiltration rate and was considered a reflection of myocardial stunning. In the latter study (7), an acute reduction of intradialytic global myocardial blood flow was seen in four HD patients without hemodynamically significant coronary artery disease; segmental blood flow reductions were associated with reversible regional wall motion abnormalities thought to be a manifestation of myocardial stunning. Others have shown that intradialytic hypotension is associated with increases in cardiac troponin I and T levels (8). Myocardial stunning related to intradialytic hypotension has also been seen in children undergoing HD, suggesting that stunning can occur without underlying CAD and is due to the HD process itself (9). Myocardial stunning is reduced when intradialytic hemodynamics are improved by using biofeedback during HD (10) as well as with cooled dialysate (11). Regional wall motion abnormalities and myocardial ischemia are rare during peritoneal dialysis exchanges (12). What, then, are some of the potential consequences of this repetitive myocardial stunning and should nephrologists be concerned about this? In a study of 30 patients known to have HD-induced myocardial ischemia, areas of regional hypoperfusion withHD at baseline showed a small but consistent decline in systolic function over the ensuing 12 months (13). Furthermore, among 19 patients with fixed segmental systolic reductions of >60%, global cardiac ejection fraction (EF) at rest and during HD declined over 12 months, whereas EF remained unchanged in patients without such fixed defects. Patients with fixed cardiac defects experienced a reduction in systolic BP at rest and during HD over the year of follow-up, whereas there was no change in these parameters in the other patients. In the study that is the subject of this Summary and Comment, effects of different HDmodalities on dialysisinduced myocardial stunning were examined, testing the hypothesis that modifying ultrafiltration volume and rate with more frequent HD sessions would decrease HD-induced myocardial stunning (3). The study was a cross-sectional observational assessment of 46 chronic HD patients treated with conventional thrice-weekly in-center HD (12 patients), short daily in-center HD with HD five or more times a week (12 patients), daily home HD five or more times a week (12 patients), or home nocturnal dialysis five or more times a week (10 patients). Patients werematched for baseline characteristics in terms of age, gender, and diabetes only among the in-center groups; the home HD groups compared with other patients had with a longer HD vintage, a lower prevalence of diabetes, and less use of antihypertensive agents. Resting cardiac EFwas similar among all groups (NYHA IV patients were excluded). The authors report a strong association between the occurrence of myocardial stunning (defined in this study Address correspondence to: Jeffrey S. Berns, Hospital of the University of Pennsylvania, 3400 Spruce Street, Philadelphia, PA 191904, or e-mail: Jeffrey.Berns@uphs.upenn. edu. Seminars in Dialysis—Vol 25, No 1 (January–February) 2012 pp. 86–87 DOI: 10.1111/j.1525-139X.2011. 01043.x a 2012 Wiley Periodicals, Inc.