Progressive myocardial dysfunction after cardiac resuscitation.

Abstract

To investigate left ventricular function by the Langendorff method after successful cardiac resuscitation in rats. Prospective, randomized, controlled animal study. University research laboratory. Adult, male Sprague-Dawley rats. Myocardial function was investigated in three subsets of isolated, perfused rat hearts that were harvested either before inducing ventricular fibrillation (controls) or at defined intervals after successful resuscitation from ventricular fibrillation. Ventricular fibrillation was induced with an electrode catheter advanced into the right ventricle of 15 mature, mechanically ventilated Sprague-Dawley rats. After an interval of 4 mins of untreated ventricular fibrillation and an additional 5 mins of precordial compression, spontaneous circulation was restored by a direct current, transthoracic countershock. The heart of each animal was then harvested at either 2 or 20 mins after successful cardiac resuscitation. The same model was utilized for harvesting the controls. Animals were randomized to each of the three subsets immediately before induction of cardiac arrest. There was a progressive decrease in myocardial contractility of the isolated, perfused hearts. Mean left ventricular systolic pressure was 128 +/- 8 mm Hg in control animals. In hearts harvested at 2 mins after successful resuscitation, the maximal generated pressure was reduced to 106 +/- 9 mm Hg. When harvested at 20 mins after successful resuscitation, it was reduced to 81 +/- 11 mm Hg. There were corresponding decreases in the mean maximal rate of left ventricular pressure increase (dP/dtmax) from 2880 +/- 110 to 2470 +/- 120 mm Hg/sec at 2 mins and to 1810 +/- 135 mm Hg/sec at 20 mins. These decreases in contractility were associated with striking decreases in myocardial relaxation and compliance. These studies, therefore, document progressive systolic and diastolic myocardial dysfunction immediately after successful cardiac resuscitation with restoration of spontaneous circulation.