CHARACTERIZATION OF THE CARDIAC EFFECTS OF ACUTE SUBARACHNOID HEMORRHAGE IN DOGS

Background and Purpose We know that significant cardiac involvement ca n occur in patients with acute intracranial hemorrhage, particularly i n those with subarachnoid hemorrhage. These patients may present with electrocardiographic abnormalities that were previously thought to be benign. However, many die of cardiovascular sequelae, which suggests m ore serious cardiac problems. To characterize the cardiac, rhythmic, a nd myocardial disturbances that occur 2 to 4 hours after subarachnoid hemorrhage, we conducted an experimental study using autologous blood (7.9+/-0.3 mL) injected into the right frontal lobe and subarachnoid s pace in canines. Methods Nine adult mongrel dogs were anesthetized wit h isoflurane and their rectal temperatures maintained at 37 degrees C. Electrocardiogram, heart rate, mean arterial pressure, mean pulmonary artery pressure, and intracranial pressure were continuously measured . Transesophageal echocardiography was performed to assess myocardial wall motion changes and aortic and pulmonary flow velocities before, i mmediately after, and 2 and 4 hours after intracranial hemorrhage. Blo od samples were collected and analyzed for catecholamines and cardiac enzymes, and cardiac output was measured. Animals were killed at 2 to 4 hours after subarachnoid hemorrhage, and a piece of the myocardium w as freeze-clamped for analysis of tissue catecholamines. Light and ele ctron microscopy were used for histopathologic assessment. Results Sub arachnoid hemorrhage produced significant increases in intracranial pr essure, cardiac output, and aortic and pulmonary flow velocities. Also , significant changes in creatine kinase and catecholamines were obser ved. Electrocardiographic recordings showed changes of tachycardia, ST -segment depression, inverted T wave, and premature ventricular contra ctions in four animals at 1 to 5 minutes after injection, and echocard iographic changes were evident in all animals at 20 to 240 minutes. Mi croscopic examination of the heart showed evidence of myocardial chang es in one animal with the use of light microscopy and in nine with the use of electron microscopy. Conclusions This study demonstrates the h igh incidence of cardiac involvement, specifically wall motion abnorma lities, that occur after subarachnoid hemorrhage and suggests the impo rtance of continuous cardiac monitoring, particularly echocardiographi c measurements, in those patients.