Nocturnal Dialysis Improves Heart Disease In Patients With End-stage Kidney Failure

This study specifically examined endothelial progenitor cells (EPCs)which reside in the bone marrow and contribute to the regeneration andrepair of blood vessel walls, and may well play a significant role ingenerating new blood vessels at the site of an injury. Studies haveshown that an infusion of EPCs into the heart after a heart attack orinto limbs that have constricted blood flow do improve blood flow andaid in healing injured tissue.

"Endothelial progenitor cells are like 'handymen' entering thebloodstream to get into areas of blood vessel injury to help repair thedamage which occurs on a daily basis," Chan explained, adding thatdepletion or reduced function of these cells likely contributes toblood vessel disease. "If we can manipulate EPCs to directly targetvascular and cardiac injury, we may unlock an important mechanism bywhich we can address the high cardiovascular morbidity and mortality ofthis patient population," Chan said.

The study found that there was a five-fold decrease in EPCs inpatients on conventional dialysis compared to the healthy participantsand the patients on night hemodialysis. Moreover, patients onconventional hemodialysis also had higher blood pressure than patientson night-time dialysis (mean of 143 vs.128) and significantly higherleft ventricular mass index (LVMI) scores, indicating abnormal leftventricular heart mass.

Chan and Verma studied and compared three groups of patientscross-matched for age, gender and reasons for dialysis: 12 conventionaldialysis patients, 10 nocturnal hemodialysis patients and 10 healthypatients who do not need dialysis.

The four key outcome measures included: Numbers of EPCs circulating inthe blood stream; migration function of these cells, measuring whetherthe cells were able to migrate into the blood stream to get to aninjury site; LVMI, which measures the weight of the heart (a thickenedheart cannot pump blood efficiently and results in eventual heartfailure); and blood pressure.

Results on all measures showed a significant difference between thepatients on conventional hemodialysis and the two other groups: thosepatients receiving night hemodialysis and the healthy control group.Compared with the healthy participants and the ones on nighthemodialysis, EPC number and migration function were markedly impairedin conventional dialysis patients, along with a poorer LVMI and higherblood pressure. In contrast, EPC number and migration function werenormal in night-time dialysis patients.

"These results show that with night-time dialysis, the numbers andfunction of these specific cells are similar to our healthy studyparticipants," said Chan, "and given the critical importance of thesecells in vascular repair and regeneration, this study adds support tothe growing evidence of cardiovascular benefits of night-timehemodialysis."

Verman note that "In the Sept. 8, 2005 issue of the The New EnglandJournal of Medicine, we learned that the number of circulatingendothelial progenitor cells predicts the occurrence of cardiovascularevents and death from cardiovascular causes, further reinforcing theimportance of the current findings."

Cardiovascular disease is the principal cause of death in end-stagerenal (kidney) disease patients, with many patients also having highblood pressure and diabetes. However, these additional illnesses onlypartially explain the high cardiovascular risk associated withend-stage renal failure. In particular, conventional dialysis does notsubstantially decrease this risk. Of the 15 - 20% annual mortality rateof conventional dialysis patients, about 50% is due to cardiovasculardiseases.

Chan noted that nocturnal hemodialysis is the more optimal therapy forpatients with end-stage renal disease since it more closely mimics whatour own kidneys do in our bodies.

The increased frequency and duration of night hemodialysis(about six sessions per week, approximately 8 hours per session) haspreviously shown to improve blood pressure, lower use ofanti-hypertensive medications and improve cardiovascular measurescompared to patients on conventional dialysis. Additionally, patientson the thrice-weekly conventional dialysis (about four hours persession) have complications such as abnormal thickness of the heart,low energy and retention of fluids in the body, necessitating a strictdiet and liquid-intake regimen.

TGH currently has 67 patients on nightly home hemodialysis, making itone of the largest programs in the world. Patient training for nightlyhome hemodialysis takes from six to eight weeks, and includes hands-onlearning about the dialysis machine, medications, problem-solving inthe event of a machine malfunction, IV medications and blood work.

Source and funding

"Nocturnal hemodialysis is associated with restoration of impairedendothelial progenitor cell biology in end-stage renal disease" appearsin the October issue of the American Journal of Physiology-RenalPhysiology, published by the American Physiological Society. Researchwas by Christopher T. Chan, Shu Hong Li and Subodh Verma. Chan is atthe Division of Nephrology, Department of Medicine, and Shu Hong Li isat the Division of Cardiac Surgery, Dept. of Surgery, both at TorontoGeneral Hospital. Verma is at the Division of Cardiac Surgery, St.Michael's Hospital, Toronto, Ontario, Canada.

The Heart and Stroke Foundation of Ontario provided funding for this study.