Refractoriness as a determinant of XXXX inducibility in the right ventricle.

@entity1 @entity340 @entity296 @entity1165 @entity591 @entity299 @entity731 @entity1167
The use of more than one right ventricular site for programmed electrical stimulation has been reported to increase the number of @entity1 in whom @entity1165 can be provoked. To determine a possible reason for these observations, programmed @entity1165 studies were evaluated in 316 @entity1 (185 @entity1 and 131 @entity1 ) with a mean age of 63 +/- 7 years who presented with @entity1165 or @entity1167 . The underlying @entity299 was @entity731 (81%), @entity296 (15%), @entity340 (3%), and miscellaneous conditions (1%). Programmed electrical stimulation studies employed a six-beat pacing train, at a cycle length of 500 msec with the introduction of one to three premature stimuli at twice diastolic threshold at the right ventricular apex. If @entity1165 at the right ventricular apex could not be provoked in a @entity1 , the study was repeated at the right ventricular outflow tract. A total of 36 @entity1 were studied at the right ventricular outflow tract. Eleven (31%) were provoked into @entity1165 , while 25 (69%) were not. No difference existed between the QRS, QT, and QTc intervals between those having @entity1165 provoked at the outflow tract compared to those without inducible @entity591 at the right ventricular outflow tract. The effective refractory period was 280 +/- 5 msec at the right ventricular outflow tract in those @entity1 not inducible, and 226 +/- 4 msec in those inducible (p less than 0.05). We defined the change in ventricular refractory period as the difference in the effective refractory period at the right ventricular outflow tract minus the effective refractory period at the right ventricular apex.(ABSTRACT TRUNCATED AT 250 WORDS)
