Chronic kidney disease ups sudden cardiac death risk.

SAN FRANCISCO -- A declining glomerular filtration rate is a strong and independent predictor of sudden cardiac death in patients with significant coronary artery disease, Dr. Thomas R. Smarz reported at the annual meeting of the American Society of Nephrology.

For every 10-unit decrease in the glomerular filtration rate (GFR), the risk of sudden cardiac death (SCD) increased by 12.5%, according to the results of this single-center, observational cohort study.

"The loss of kidney function creates an insidious environment that increases risk for SCD," said Dr. Smarz of Duke University, Durham, N.C.

The study included all patients in Duke's databank for cardiovascular disease who underwent cardiac catheterization in 1995-2006 and who also had significant coronary artery disease. The investigators excluded patients with repeat catheterizations, those with an implanted cardioverter defibrillator, those undergoing evaluation for transplant, and those with shock, congenital heart disease, severe liver disease, pericardial disease, or hypertrophic obstructive cardiomyopathy. In all, the investigators included 21,845 patients in the study.

Of those patients, 74% had normal or mildly lowered GFR values (greater than 60 mL/min per 1.73 [m.sup.2]) and 26% had stage 3 chronic kidney disease or worse (GFR values less than 59 mL/min per 1.73 [m.sup.2]). Of the total cohort, 2.2% had stage 5 chronic kidney disease, defined by GFR values less than 15 mL/min per 1.73 [m.sup.2].

Compared with patients whose GFR values were greater than 60 mL/min per 1.73 [m.sup.2], those with stage 3 or stage 4 chronic kidney disease had an unadjusted 83% increased risk of SCD. Stage 5 chronic kidney disease was associated with a 4.6-fold increase in the risk of SCD.

In the multivariable model, which was adjusted for cardiac risk factors, chronic kidney disease emerged as a significant, independent predictor of SCD.

Dr. Smarz acknowledged several limitations of the study. For example, the cohort--by design--had significant coronary artery disease. This may limit broader generalization to all chronic kidney disease patients. There also were potential biases toward patients referred to tertiary care and toward those who underwent angiography.

The factors underlying the association between chronic kidney disease and SCD will have to be determined in future studies, Dr. Smarz said. These factors may include cardiac remodeling, myocardial fibrosis, metabolic derangements, or electrophysiologic disturbances that are unique to patients with chronic kidney disease.

BY ROBERT FINN

San Francisco Bureau