Experimental evaluation of magnesium cardioplegia

The effectiveness of magnesium solution in protecting ischemic myocardium was evaluated in a blood-perfused, isolated rabbit papillary muscle preparation. Anoxic cardioplegia was induced by either a control solution containing no magnesium or a test solution containing a magnesium concentration of 160 mEq/L. The magnesium solution induced a very rapid cardiac arrest, less than 1 minute, in contrast to more than 10 minutes with the control solution. Restarting time was not affected by magnesium cardioplegia. Following 30 minutes of anoxic cardioplegia, the magnesium group showed significantly (p less than 0.01) better recovery of myocardial contractility, 91.3% +/- 8.3% (n = 6), than the control group, 77.7% +/- 4.1% (n = 6). These protective effects of magnesium were lost when the ischemic time was longer than 45 minutes.