Continuous intravenous phenylephrine infusion significantly increased the shortest atrial pacing cycle length yielding 1:1 AV nodal conduction from 412 to 575 msec (p<0.01).
Does constant intravenous infusion of phenylephrine alter atrioventricular nodal and sinoatrial nodal function in patients?
Continuous enhanced vagal tone via phenylephrine infusion significantly prolongs sinus cycle length and impairs AV nodal conduction during atrial pacing.
Absolute Event Rate: 575% vs 412%
p-value: p=<0.01
A constant intravenous infusion of phenylephrine (0.74 +/- 0.41 micrograms/kg/min) was given to 10 patients to cause a continuous augmentation in reflex vagal tone. After the infusion, the diastolic blood pressure increased from 76 +/- 7 to 89 +/- 11 mm Hg (p less than 0.01). The sinus cycle length and atrial-His (AH) interval were measured, and incremental atrial pacing was performed before and during phenylephrine infusion until atrioventricular (AV) nodal block was achieved. For each patient, the AV nodal function curve (i.e., the AH interval plotted as a function of the atrial pacing cycle length) was compared during both the control state and phenylephrine infusion; the AH intervals during each condition at chosen short (AHS) and long (AHL) cycle lengths were compared. The sinus cycle length increased during phenylephrine infusion from 941 +/- 294 to 1,115 +/- 347 msec (p = 0.013). The AH interval during sinus rhythm was not significantly prolonged (77 versus 82 msec, p = NS). The shortest atrial pacing cycle length yielding 1:1 AV nodal conduction increased during phenylephrine infusion from 412 +/- 120 to 575 +/- 211 msec (p less than 0.01). Of note, the degree of sinus cycle length prolongation did not correlate with the degree of prolongation in the shortest atrial pacing cycle length yielding 1:1 AV nodal conduction. The AV nodal function curve was shifted markedly to the right and only slightly upward.(ABSTRACT TRUNCATED AT 250 WORDS)
Page et al. (Sat,) reported a other. Continuous intravenous infusion of phenylephrine vs. Control state (before infusion) was evaluated on Shortest atrial pacing cycle length yielding 1:1 AV nodal conduction (p=<0.01). Continuous intravenous phenylephrine infusion significantly increased the shortest atrial pacing cycle length yielding 1:1 AV nodal conduction from 412 to 575 msec (p<0.01).