Intravenous digoxin blunts the rise of inotropy induced by isometric exercise: a noninvasive study in healthy volunteers.
Nine healthy volunteers were studied with echocardiography and systolic time intervals at rest and after 3 minutes' isometric exercise by hand grip. The recordings were repeated after intravenous administration of 1 mg digoxin before and after autonomic blockade induced with atropine and propranolol. During hand grip the heart rate rose from 61 +/- 3 (mean +/- SEM) to 73 +/- 5 bpm (p less than 0.05). Afterload, i.e. left ventricular systolic wall stress, increased by 21% from 260 +/- 19 x 10(3) dyn/cm2 (p less than 0.05). Preload, i.e. left ventricular end-diastolic diameter (LVEDD), fractional shortening and the ratio of the pre-ejection period to the left ventricular ejection time (PEP/LVET) did not change, indicating increased contractility. After digoxin heart rate rose during handgrip from 50 +/- 2 to 65 +/- 5 bpm, and wall stress increased by 19% from 274 +/- 21 x 10(3) dyn/cm2 (p less than 0.01 for both). Even though LVEDD rose from 44.8 +/- 1.4 to 46.6 +/- 1.3 mm (p less than 0.05), fractional shortening decreased from 33 +/- 2 to 30 +/- 2% (p less than 0.05) and PEP/LVET increased from 0.292 +/- 0.014 to 0.327 +/- 0.014 (p less than 0.01). This suggests that autonomic reflexes due to digoxin obscured the increase in inotropy during static exercise. Autonomic blockade raised heart rate under digoxin from 50 +/- 2 to 90 +/- 4 bpm and mean blood pressure from 87 +/- 2 to 99 +/- 3 mmHg (p less than 0.001 for both) without changes in loading conditions.(ABSTRACT TRUNCATED AT 250 WORDS)
Partanen
J
J
First Department of Medicine, University Central Hospital, Helsinki, Finland.
Pellinen
T
T
Nieminen
M S
MS
D000328:Adult; D001285:Atropine / Q000494:pharmacology*; D001340:Autonomic Nerve Block; D004077:Digoxin / Q000008:administration & dosage* / Q000097:blood; D004452:Echocardiography; D005260:Female; D006339:Heart Rate / Q000187:drug effects*; D006439:Hemodynamics / Q000187:drug effects; D006801:Humans; D007275:Injections, Intravenous; D007537:Isometric Contraction; D008297:Male; D009119:Muscle Contraction; D011433:Propranolol / Q000494:pharmacology*
D004077:Digoxin; D001285:Atropine; D011433:Propranolol