Alterations in norepinephrine content and beta adrenoceptor regulation in myocardium bordering aneurysm in human heart: their possible role in the genesis of ventricular tachycardia.

Abstract

On the assumption that alterations in the adrenergic system may play a role in generating ventricular tachycardia in patients with myocardial post-infarction apical aneurysm, we evaluated norepinephrine concentration, number and affinity of both beta 1 and beta 2 adrenoceptors in perianeurysmatic tissue in twelve patients operated upon for congestive heart failure and recurrent sustained ventricular tachycardia. Concentration of norepinephrine in perianeurysmatic tissue was 0.1 +/- 0.05 micrograms g-1 tissue (n = 8), this value being much lower than that found in papillary muscle (n = 10) from patients with mitral valve stenosis (0.8 +/- 0.02 micrograms g-1 tissue) (P less than 0.01). The total number of beta adrenoceptors (71.4 +/- 7.8 v. 48.0 +/- 5.1 fmol mg-1 protein; P less than 0.01) and the percentage of beta 1 subtype were found to be higher in perianeurysmatic tissue (approximately 90%) than in papillary muscle (approximately 68%). Out of twelve patients with aneurysm, beta 2 adrenoceptors had considerably decreased in three patients and were absent in the remaining nine. Decrease in the neuronally released norepinephrine associated with contrasting behaviours of beta 1 and beta 2 adrenoceptors suggests the presence of a profound alteration in the sympathetic innervation of the perianeurysmatic myocardial tissue that may contribute to the genesis of sustained ventricular tachycardia in patients with postinfarction apical aneurysm.