Left ventricular contractility varies directly with blood ionized calcium.
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.
Lang
R M
RM
Department of Medicine, University of Chicago Medical Center, Illinois.
Fellner
S K
SK
Neumann
A
A
Bushinsky
D A
DA
Borow
K M
KM
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
D002413:Cations, Divalent; D002118:Calcium