Autonomous influence on sinus node and AV node function in the elderly without significant XXXX : assessment with electrophysiological and autonomic tests.

@entity1169 @entity1 @entity3798 @entity10804 @entity1817 @entity3897 @entity299 @entity3044
Eighteen volunteers with a mean age of 63.3 years, who were asymptomatic and without significant @entity299 , were investigated with standard electrophysiological tests, performed before and after inhibition of autonomous neural tone with @entity1169 (0.1 mg . kg-1) and @entity3897 (0.02 mg . kg-1). In addition heart rate responses to maximal exercise, carotid sinus pressure and bolus injection of @entity3044 (0.01 microgram . kg-1) were studied to evaluate the relation between different functional qualities of the cardiac conduction system. Autonomous tone inhibition (ATI) caused significant reductions in the mean PP-interval, sinus code recovery time (SNRT) and corrected sinus node recovery time (CSNRT). Furthermore, the precision of CSNRT determinations increased after ATI. In contrast, the AV-node effective refractory period and conduction time ( @entity3798 ) did not change after ATI. A significant correlation existed between CSNRT and heart rate after ATI, both variables reflecting sinus node @entity10804 , while no covariation was found between CSNRT and the response to @entity3044 stimulation. AV-node refractoriness and conduction time showed covariation after, but not before, autonomous inhibition. As elderly asymptomatic non- @entity1 were examined the use of the presented group characteristics as reference values for diagnostic investigations is suggested. For example pre-drug CSNRT above 545 ms (mean + 2 SD) or above 505 ms after ATI, indicates @entity1817 .
