Longitudinal evaluation of left ventricular performance in dogs following nonpenetrating cardiac trauma

To investigate the temporal changes of global left ventricular function following nonpenetrating cardiac impact, studies were performed in ten purpose-bred dogs. Under full anesthesia and after hemodynamic and angiographic measurement, a midline thoracotomy was performed and a 12 m/sec blunt impact was delivered to the anterior surface of the heart in eight dogs with an air-pressurized impactor. Two dogs were sham operated and did not undergo trauma. After closing the chest, the hemodynamic measurements were repeated at 3 hours, 3 days, 2 weeks, and 5 weeks after impact. Hemodynamic measurements included left ventricular end-diastolic pressure and peak left ventricular positive and negative rates of change of pressure. Left ventricular ejection fraction was calculated from ventriculograms obtained with the dog positioned on its right side. All indices of left ventricular performance in dogs that underwent trauma were depressed at 3 hours after impact and recovered gradually to near normal levels at 2 to 5 weeks after trauma. Recovery of left ventricular function occurred in spite of residual patchy scarring of the left ventricular myocardium in the region of impact. No variability of left ventricular function indices was observed over the course of the study in the two sham-operated dogs. The results indicate that blunt cardiac impact can cause depression of left ventricular performance in the immediate post-impact period, but near complete recovery of function occurs within 2 to 5 weeks after the injury, in spite of residual scarring.