title: Association of cystatin C with poor exercise capacity and heart rate recovery: data from the heart and soul study.
abstract: BACKGROUND
  Cystatin C, an alternative serum measure of kidney function, is a stronger predictor of cardiovascular events than creatinine or estimated glomerular filtration rate (eGFR). We hypothesized that serum cystatin C concentration would have a stronger more linear association with cardiovascular functional status than creatinine-based measures in outpatients with established coronary heart disease (CHD).
  
  
  METHODS
  We measured serum cystatin C, serum creatinine, and eGFR in 906 outpatients with established CHD. We examined the association of these 3 measures of kidney function with treadmill exercise capacity (metabolic equivalent tasks achieved) and heart rate recovery (HRR) between peak and 1 minute after exercise by using linear and logistic regression.
  
  
  RESULTS
  Higher cystatin C concentrations were associated linearly with worse treadmill exercise capacity and HRR. The proportion of participants with poor exercise capacity (metabolic equivalent tasks achieved < 5) was 45% (99 of 222 participants) among those with cystatin C levels in the highest quartile (>1.30 mg/L) compared with 12% (29 of 241 participants) among those with cystatin C levels in the lowest quartile (<0.92 mg/L; adjusted odds ratio, 3.2; 95% confidence interval, 1.6 to 6.5; P = 0.001). The proportion of participants with poor HRR (<16 beats/min) was 42% (92 of 214 participants) among those with cystatin C levels in the highest quartile compared with 16% (37 of 238 participants) among those with cystatin C levels in the lowest quartile (adjusted odds ratio, 2.2; 95% confidence interval, 1.2 to 4.0; P = 0.01). The lowest quartile of eGFR (<61.8 mL/min [<1.03 mL/s]) was associated with decreased exercise capacity and prolonged HRR, but no difference was observed across the upper 3 quartiles of eGFR.
  
  
  CONCLUSIONS
  In patients with established CHD, cystatin C concentrations are associated linearly with worse exercise capacity and HRR. Cystatin C detects an association of impaired kidney function with decreased HRR and exercise capacity that is not fully captured using creatinine-based measurements.
authors.affiliation: Cardiology Division, University of Massachusetts, Worcester, MA, USA. mcmanus.dave@gmail.com
authors.forename: David
authors.initials: D
authors.lastname: McManus
authors.forename: Michael
authors.initials: M
authors.lastname: Shlipak
authors.forename: Joachim H
authors.initials: JH
authors.lastname: Ix
authors.forename: Sadia
authors.initials: S
authors.lastname: Ali
authors.forename: Mary A
authors.initials: MA
authors.lastname: Whooley
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D002908:Chronic Disease; D015331:Cohort Studies; D003327:Coronary Disease / Q000097:blood* / Q000503:physiopathology*; D003404:Creatinine / Q000097:blood; D055316:Cystatin C; D015891:Cystatins / Q000097:blood*; D005260:Female; D005919:Glomerular Filtration Rate; D006339:Heart Rate / Q000502:physiology*; D006801:Humans; D007674:Kidney Diseases / Q000097:blood / Q000503:physiopathology; D016015:Logistic Models; D008297:Male; D008875:Middle Aged; D010807:Physical Endurance / Q000502:physiology*; D011237:Predictive Value of Tests; D011446:Prospective Studies
chemical_list: C525030:CST3 protein, human; D055316:Cystatin C; D015891:Cystatins; D003404:Creatinine