Younosuke Kitahara

Atrial natriuretic peptide with artificial pacemakers

Abstract Accumulating evidence indicates that atrial natriuretic peptide (ANP) is a circulating hormone in humans. 1–4 Plasma levels of ANP increase in patients with various heart diseases such as paroxysmal atrial arrhythmias 2 and congestive heart failure. 3,4 If atrial stretching due to increased atrial pressure stimulates ANP secretion, 4 plasma ANP levels may be altered in patients with bradyarrhythmias and in those with pacemaker syndrome, a major clinical complication in patients in whom artificial pacemakers are implanted. 5 To clarify the role of ANP in the pathophysiology of these states, we examined plasma ANP levels in patients with bradyarrhythmias and in those treated with pacemakers of various modes.

A new model for infective endocarditis of the mitral valve in rabbits

To produce an experimental model of infective endocarditis without inserting catheters into the heart, we injected a bacterial suspension into rabbits in which mitral complex lesions had been induced by electrical stimulation of the cervical vagus. Typical infective vegetations grew on the surface of the mitral valves 1 week later. The formation of vegetations was related to the timing of the inoculation. Streptococcus viridans injected just after vagal stimulation produced vegetations in 10 of 17 animals (58.8%), but the same bacteria injected 14 days after vagal stimulation did so in only 2 of 11 animals (18.2%). The incidence of infective endocarditis was significantly higher after early inoculation compared with delayed inoculation (p < 0.01). The susceptibility to infection depended on the species of bacteria injected. Both S. viridans and Pseudomonas pseudoalkaligenes injected just after vagal stimulation produced vegetations in 10 of 17 (58.8%) and 6 of 13 (46.2%) animals, respectively, but Staphylococcus epidermidis injected just after vagal stimulation did not produce vegetations in any of the 10 animals. S. viridans injected into nine normal animals never produced vegetations. These findings indicate that infective endocarditis develops after intravenous injection of bacterial suspensions alone in rabbits with mitral complex lesions.