Current management of myocardial contusion is based on experience with ischemic heart disease, but the mechanism responsible for cardiac dysfunction may be quite different. The purpose of this study was to characterize the pathophysiology of myocardial contusion in a controlled animal model. Sprague-Dawley rat hearts were prepared on a standard Langendorff apparatus, and myocardial function (DP, + dP/dT, – dP/dT) measured via a left ventricular balloon. Bipolar atrial and ventricular leads were placed to define conduction changes. Coronary sinus effluent was sampled for pO2, pH, creatine phosphokinase (CPK), and lactic dehydrogenase (LDH). The hearts were freeze-clamped to measure phosphocreatine (PC) and adenosine triphosphate (ATP). Myocardial contusion was produced by a single blow with a weighted pendulum. Hearts were divided into control (n = 5), moderate impact—Group I (n = 5), and major impact—Group II (n = 5). Group I sustained a 25% decrease in function after an impact of 78 ± 5 mJoules/gm, and Group II a 50% deficit after 87 ± 7 mJoules/gm. Impact resulted in complete electrical arrest, followed by sequential ventricular, atrial, and AV nodal recovery; recovery time correlated directly with degree of injury. Coronary flow at 2 min postinjury was decreased (p < 0.05) in Group I (12.8 ± 0.8 ml/min) and Group II (11.5 ± 1.3) compared to control (17.2 ± 0.5), and returned to baseline levels at 20 min. LDH and CPK levels were twice as high in Group II as in Group I. The PC/ATP ratio in Group II increased from 1.63 at baseline to 2.54 (p < 0.05) at 25 min, confirming ischemic reperfusion. In this study, myocardial dysfunction was due to: A) transient reduction in coronary blood flow resulting in global ischemia and electrical instability; and b) direct irreversible myocyte damage reflected by cardiac enzyme release.
|Original language||English (US)|
|Number of pages||307|
|Journal||Journal of Trauma - Injury, Infection and Critical Care|
|State||Published - Oct 1988|
ASJC Scopus subject areas
- Critical Care and Intensive Care Medicine