Effects of beta-adrenergic stimulation on atrial latency and atrial vulnerability in patients with paroxysmal supraventricular tachycardia.
To assess the effects of beta-adrenergic stimulation on atrial latency and atrial vulnerability, the electrophysiologic properties of the atrium were studied before and during intravenous infusion of isoproterenol at 2 to 5 micrograms/min in 11 patients with paroxysmal supraventricular tachycardia exhibiting atrial latency during programmed atrial extrastimulation. In all patients, the isoproterenol infusion reduced the extent of maximum atrial latency (from 86 +/- 19 to 62 +/- 16 ms, p less than 0.001). This was accompanied by a significant shortening of both effective and functional refractory periods of the atrium (from 213 +/- 31 to 174 +/- 40 ms, p less than 0.005 and from 259 +/- 31 to 215 +/- 29 ms, p less than 0.001, respectively). The intra-atrial and interatrial conduction times were also significantly reduced (from 24 +/- 15 and 63 +/- 17 to 15 +/- 10 and 48 +/- 15 ms, p less than 0.005, respectively). In 3 patients with demonstrable atrial vulnerability, the isoproterenol infusion abolished the inducibility of repetitive atrial responses or atrial flutter, or both. Although the clinical significance of the suppressive action of beta-adrenergic stimulation on atrial vulnerability remains to be determined, the present study has demonstrated that beta-adrenergic stimulation significantly reduces atrial latency.
Nguyen
N X
NX
Division of Cardiology, San Francisco General Hospital, California 94110.
Yang
P T
PT
Huycke
E C
EC
Keung
E C
EC
Deedwania
P
P
Sung
R J
RJ
D000328:Adult; D000368:Aged; D002304:Cardiac Pacing, Artificial; D004341:Drug Evaluation; D005260:Female; D006325:Heart Atria / Q000187:drug effects / Q000503:physiopathology*; D006329:Heart Conduction System / Q000187:drug effects*; D006801:Humans; D007262:Infusions, Intravenous; D007545:Isoproterenol / Q000008:administration & dosage / Q000494:pharmacology*; D008297:Male; D008875:Middle Aged; D011433:Propranolol / Q000008:administration & dosage / Q000494:pharmacology; D011930:Reaction Time / Q000187:drug effects*; D012008:Recurrence; D013614:Tachycardia, Paroxysmal / Q000503:physiopathology*; D013617:Tachycardia, Supraventricular / Q000503:physiopathology*
D011433:Propranolol; D007545:Isoproterenol