Predictors of neurocardiogenic injury after subarachnoid hemorrhage

Background and Purpose - Subarachnoid hemorrhage (SAH) frequently results in myocardial necrosis with release of cardiac enzymes. Historically, this necrosis has been attributed to coronary artery disease, coronary vasospasm, or oxygen supply-demand mismatch. Experimental evidence, however, indicates that excessive release of norepinephrine from the myocardial sympathetic nerves is the most likely cause. We hypothesized that myocardial necrosis after SAH is a neurally mediated process that is dependent on the severity of neurological injury. Methods - Consecutive patients admitted with SAH were enrolled prospectively. Predictor variables reflecting demographic ( age, sex, body surface area), hemodynamic ( heart rate, systolic blood pressure), treatment ( phenylephrine dose), and neurological (Hunt-Hess score) factors were recorded. Serial cardiac troponin I measurements and echocardiography were performed on days 1, 3, and 6 after enrollment. Troponin level was treated as a dichotomous outcome variable. We performed univariate and multivariate analyses on the relationships between the predictor variables and troponin level. Results - The study included 223 patients with an average age of 54 years. Twenty percent of the subjects had troponin I levels > 1.0 mug/L (range, 0.3 to 50 mug/L). By multivariate logistic regression, a Hunt-Hess score > 2, female sex, larger body surface area and left ventricular mass, lower systolic blood pressure, and higher heart rate and phenylephrine dose were independent predictors of troponin elevation. Conclusions - The degree of neurological injury as measured by the Hunt- Hess grade is a strong, independent predictor of myocardial necrosis after SAH. This finding supports the hypothesis that cardiac injury after SAH is a neurally mediated process.