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The influence of infused calcium on the postischemic myocardium
Insights
Calcium infusions in the postischemic myocardium are safe, even at higher concentrations during initial reperfusion. This study found no negative impact on left ventricular contractile function recovery after cardiac surgery.
Area of Science:
- Cardiology
- Cardiovascular Physiology
- Cardiac Surgery
Background:
- Calcium is commonly used post-cardiac surgery despite concerns of myocyte damage.
- The safety and impact of varying calcium concentrations during reperfusion remain incompletely understood.
Purpose of the Study:
- To investigate the effects of incremental ionized calcium doses on postischemic myocardium.
- To correlate reperfusion calcium levels with left ventricular (LV) contractile function recovery.
Main Methods:
- Rabbit hearts (N=38) underwent 40 minutes of global ischemia.
- Hearts were reperfused with variable initial calcium concentrations (0.6-5.0 mM) for 5 minutes, followed by sustained reperfusion.
- Left ventricular developed pressure (DP) +/- dp/dt and end-diastolic pressure (LVEDP) were monitored.
Main Results:
- No significant differences in final DP +/- dp/dt or LVEDP were observed between groups.
- Variable calcium concentrations during early reperfusion did not impair long-term LV function recovery.
Conclusions:
- Physiologic range calcium infusions during early reperfusion are safe for the postischemic myocardium.
- Impaired LV function recovery is likely due to mechanisms independent of reperfusion calcium loading.
- Inotropic calcium administration is a safe therapeutic option in the postischemic heart.
Abstract:
Despite evidence for calcium-induced damage in the postischemic myocardium, calcium remains a frequently used inotropic agent following cardiopulmonary bypass surgery with cardioplegic arrest. The purpose of this study was (1) to challenge the postischemic myocardium with incremental doses of ionized calcium, and (2) to relate postischemic calcium reperfusion concentration to final recovery of left ventricular contractile function. Rabbit hearts (N = 38) were perfused and equipped with a ventricular balloon to monitor developed pressure (DP) +/- dp/dt, and left ventricular end diastolic pressure (LVEDP). Hearts underwent 40 min of global ischemia. Hearts were then assigned to one of four groups to receive a variable calcium concentration (0.6, 1.2, 2.5, 5.0 mM) for the initial 5 min of reperfusion followed by 55 min of reperfusion (Ca+2 = 1.25 mM). No differences were found between groups for final recovery of DP +/- dp/dt, or final LVEDP. It was concluded that: (1) within the physiologic range, variable calcium infusions during the first 5 min of postischemic reperfusion do not impair final recovery of LV contractile function, (2) irreversible partial recovery of left ventricular function appears due to mechanisms other than mitochondrial or myofibrillar calcium loading during reperfusion, and (3) infused calcium is a safe inotropic agent even in the postischemic myocardium.