Effects of low perfusate Ca2+ concentration on newborn myocardial function after ischemia.
A greater dependence on transsarcolemmal Ca2+ flux and immaturity of Ca2+ sequestration capacity may potentiate Ca2(+)-mediated reperfusion injury in the newborn myocardium. The effect of serum ionized Ca2+ concentration on left ventricular systolic and diastolic function after ischemia was studied in 5-7-day-old piglets undergoing a 90-minute period of cold-blood cardioplegic arrest. In the control group, Ca2+ was maintained at 1.2 mM (Group A [n = 6]). The cardioplegic solution and bypass perfusate were modified to achieve a low Ca2+ concentration, 0.25 mM, in Group B (n = 6). Left ventricular pressure-volume loops were acquired by using high-fidelity pressure-sensor-tipped and volume-conductance catheters. Ventricular function was assessed from the slope of end-systolic (Ees) and end-diastolic (k) pressure-volume relations during transient caval occlusion. Both groups showed a significant reduction in Ees after ischemia (p less than 0.05). Intergroup comparison of Ees after ischemia demonstrated a better recovery of the systolic function in the low Ca2+ group, 64 +/- 7% versus 49 +/- 6% in the normal Ca2+ group (p = 0.05). There was a significant increase in chamber stiffness index in group A (k, 0.48 +/- 0.06 to 0.65 +/- 0.05 ml-1, p less than 0.01) versus no significant change in group B. This study shows 1) the feasibility of acquiring continuous pressure-volume data in neonatal hearts by using a conductance catheter system, and 2) better preservation of systolic function and diastolic compliance in normal newborn myocardium by low Ca2+ concentration in the peri-ischemic period.
Caspi
J
J
Division of Cardiovascular Surgery, Hospital for Sick Children, Toronto, Canada.
Herman
S L
SL
Coles
J G
JG
Benson
L N
LN
Radde
I
I
Augustine
J
J
Hamilton
F
F
Castellarin
S
S
Kumar
R
R
Wilson
G J
GJ
D000818:Animals; D000831:Animals, Newborn / Q000502:physiology*; D002118:Calcium / Q000494:pharmacology*; D015220:Calcium Channels / Q000187:drug effects; D002314:Cardioplegic Solutions / Q000494:pharmacology*; D006321:Heart / Q000187:drug effects; D009200:Myocardial Contraction / Q000187:drug effects*; D015428:Myocardial Reperfusion Injury / Q000503:physiopathology / Q000517:prevention & control*; D013552:Swine; D016277:Ventricular Function, Left / Q000187:drug effects*
D015220:Calcium Channels; D002314:Cardioplegic Solutions; D002118:Calcium