title: Left ventricular contractility varies directly with blood ionized calcium.
abstract: OBJECTIVE
  To determine the effect of variations in blood ionized calcium (Ca2+) on myocardial contractility independent of changes in loading conditions and other biochemical variables.
  
  
  METHODS
  Hemodialysis done in a randomized, double-blind manner with dialysates differing in calcium concentration only. Left ventricular contractility was assessed using the load- and heart rate-independent relationship between end-systolic wall stress (sigma es) and rate-corrected velocity of fiber shortening (Vcfc).
  
  
  METHODS
  In-hospital dialysis unit and echocardiography laboratory of a university medical center.
  
  
  METHODS
  Seven patients with stable, chronic renal failure maintained on regular hemodialysis.
  
  
  METHODS
  Each patient was hemodialyzed three times within 1 week with dialysates differing in calcium concentration only. Ultrafiltration was adjusted to achieve the same postdialysis weight. Immediately after dialysis, two-dimensionally targeted M-mode echocardiographic and calibrated carotid pulse tracings were recorded over a wide range of left ventricular end-systolic wall stress values (a measure of left ventricular afterload) generated by either methoxamine or nitroprusside.
  
  
  RESULTS
  After dialysis, three statistically distinct levels of Ca2+ were achieved. When Ca2+ was 1.34 +/- 0.03 mmol/L, Vcfc, calculated at a common level of afterload (sigma es = 50 g/cm2), was 1.01 +/- 0.05 cir/sec; at low Ca2+ (1.02 +/- 0.02 mmol/L), Vcfc fell to 0.89 +/- 0.04 cir/sec (P less than 0.001 compared with medium); at high Ca2+ (1.68 +/- 0.07 mmol/L) Vcfc rose to 1.10 +/- 0.03 circ/sec (P less than 0.001 compared with medium and low).
  
  
  CONCLUSIONS
  Variations in Ca2+ are directly correlated with clinically significant changes in myocardial contractility.
authors.affiliation: Department of Medicine, University of Chicago Medical Center, Illinois.
authors.forename: R M
authors.initials: RM
authors.lastname: Lang
authors.forename: S K
authors.initials: SK
authors.lastname: Fellner
authors.forename: A
authors.initials: A
authors.lastname: Neumann
authors.forename: D A
authors.initials: DA
authors.lastname: Bushinsky
authors.forename: K M
authors.initials: KM
authors.lastname: Borow
mesh_terms: D000328:Adult; D000368:Aged; D002118:Calcium / Q000097:blood*; D002413:Cations, Divalent / Q000097:blood; D004452:Echocardiography; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009200:Myocardial Contraction; D006435:Renal Dialysis; D013599:Systole; D016276:Ventricular Function
chemical_list: D002413:Cations, Divalent; D002118:Calcium