Purpose: To investigate the connection between sympathetic function and neurogenic cardiomyopathy (NC), and to determine whether NC is mediated primarily by circulating adrenal epinephrine (EPI) or neuronally transmitted norepinephrine (NE), following subarachnoid hemorrhage (SAH).
Methods: This is a prospective observational investigation of consecutive severe-grade SAH patients. All participants had transthoracic echocardiography and serological assays for catecholamine levels - dopamine (DA), NE and EPI - within 48 h of hemorrhage onset. Clinical and serological independent predictors of NC were determined using multivariate logistic regression analyses, and the accuracy of predictors was assessed by receiver operating characteristic (ROC) curves. Multivariate linear regression analyses were used to evaluate correlations among the catecholamines.
Results: The investigation included a total of 94 subjects: the mean age was 55 years, 81% were female and 57% were Caucasian. NC was identified in approximately 10% (9/94) of cases. Univariate analyses revealed associations between NC and worse clinical severity (p = 0.019), plasma DA (p = 0.018) and NE levels (p = 0.024). Plasma NE correlated with DA levels (ρ = 0.206, p = 0.046) and EPI levels (ρ = 0.392, p < 0.001), but was predicted only by plasma EPI in bivariate [parameter estimate (PE) = 1.95, p < 0.001] and multivariate (PE = 1.89, p < 0.001) linear regression models. Multivariate logistic regression analyses consistently demonstrated the predictive value of clinical grade for NC (p < 0.05 for all analyses) except in models incorporating plasma NE, where NC was independently predicted by NE level (OR 1.25, 95% CI 1.01-1.55) over clinical grade (OR 4.19, 95% CI 0.874-20.1). ROC curves similarly revealed the greater accuracy of plasma NE [area under the curve (AUC) 0.727, 95% CI 0.56-0.90, p = 0.02] over clinical grade (AUC 0.704, 95% CI 0.55-0.86, p = 0.05) for identifying the presence or absence of NC.
Conclusions: Following SAH, the development of NC is primarily related to elevated plasma NE levels. Findings implicate a predominantly neurogenic process mediated by neuronal NE (and not adrenal EPI), but cannot exclude synergy between the catecholamines.
Keywords: Catecholamines; Neurogenic cardiomyopathy; Norepinephrine; Subarachnoid hemorrhage; Sympathetic function; Stress cardiomyopathy; Takotsubo.