title: Influence of right ventricular pacing site on left ventricular outflow tract obstruction in patients with hypertrophic obstructive cardiomyopathy.
abstract: OBJECTIVE
  This study was designed to show the influence of right ventricular pacing site on left ventricular outflow tract obstruction during pacing treatment of patients with hypertrophic obstructive cardiomyopathy.
  
  
  BACKGROUND
  Atrioventricular synchronous pacing has been reported to reduce left ventricular outflow obstruction and symptoms in patients with hypertrophic obstructive cardiomyopathy. A paradoxic septal movement induced by right ventricular pacing has been implicated as the mechanism behind the reduced left ventricular outflow tract obstruction; however, the importance of pacing site has not been clarified.
  
  
  METHODS
  Cardiac output, measured invasively, and left ventricular outflow tract gradient, estimated by Doppler echocardiography, were studied in 15 patients with hypertrophic obstructive cardiomyopathy. Measurements were made with the right ventricular electrode in the septal and apical positions during temporary pacing and during sinus rhythm.
  
  
  RESULTS
  Right ventricular apical pacing reduced the outflow tract gradient in all 15 patients to a mean +/- SD of 38 +/- 24 mm Hg from 96 +/- 33 mm Hg during sinus rhythm. During high septal pacing the outflow tract gradient was not reduced, remaining at 93 +/- 44 mm Hg. No significant changes in cardiac output were seen when levels during sinus rhythm (6.4 liters/min), apical pacing (6.4 liters/min) and high septal pacing (5.6 liters/min) were compared.
  
  
  CONCLUSIONS
  The right ventricular pacing site is of crucial importance for reducing left ventricular outflow tract obstruction when patients with hypertrophic obstructive cardiomyopathy are treated with pacing. Cardiac output is not reduced by apical pacing.
authors.affiliation: Department of Cardiology, Karolinska Hospital, Stockholm, Sweden.
authors.forename: F
authors.initials: F
authors.lastname: Gadler
authors.forename: C
authors.initials: C
authors.lastname: Linde
authors.forename: A
authors.initials: A
authors.lastname: Juhlin-Dannfeldt
authors.forename: A
authors.initials: A
authors.lastname: Ribeiro
authors.forename: L
authors.initials: L
authors.lastname: Rydén
mesh_terms: D000328:Adult; D000368:Aged; D002304:Cardiac Pacing, Artificial; D002312:Cardiomyopathy, Hypertrophic / Q000473:pathology / Q000503:physiopathology / Q000628:therapy*; D005260:Female; D006352:Heart Ventricles / Q000033:anatomy & histology; D006801:Humans; D008297:Male; D008875:Middle Aged; D014694:Ventricular Outflow Obstruction / Q000503:physiopathology*