title: Improved left ventricular relaxation during short-term right ventricular outflow tract compared to apical pacing.
abstract: OBJECTIVE
  Pacing-induced asynchrony may deteriorate left ventricular function; however, limited data exists in humans. The aim of our study was to compare left ventricular hemodynamics during short-term atrioventricular sequential pacing from the right ventricular apex and from the outflow tract of the right ventricle.
  
  
  METHODS
  Three 5-min pacing intervals were applied in a random order, at a rate of 15 beats/min above the resting sinus rate. Atrioventricular sequential pacing from the two sites was compared with atrial pacing. During each pacing mode, left ventricular pressure was recorded, and cardiac output was calculated using Doppler echocardiography.
  
  
  METHODS
  Cardiac catheterization laboratory.
  
  
  METHODS
  Twenty patients (18 male, mean age 62 +/- 11 years) without structural heart disease were studied.
  
  
  RESULTS
  During atrial pacing, maximum negative first derivative of pressure (dp/dt) was 1,535 +/- 228 mm Hg/s; during pacing from the apex it decreased to 1,221 +/- 294 mm Hg/s (p = 0.0001), but was not significantly different during pacing from the outflow tract (1,431 +/- 435 mm Hg/s, p > 0.05). Isovolumic relaxation time constant (tau) during atrial pacing was 39.7 +/- 11.9 ms; during pacing from the apex, it increased to 47.9 +/- 14.0 (p = 0.001), but was not significantly different during pacing from the outflow tract (42.5 +/- 11.2, p > 0.05). Peak systolic pressure decreased significantly during atrioventricular sequential pacing from either site; however, it did not differ between the two sites. No differences in end-diastolic pressure, maximum positive dp/dt, or cardiac output could be demonstrated.
  
  
  CONCLUSIONS
  In patients with no structural heart disease, short-term right ventricular outflow tract pacing is associated with more favorable diastolic function, compared to right ventricular apical pacing.
authors.affiliation: 2nd Department of Cardiology, Onassis Cardiac Surgery Center, Athens, Greece. elbee@ath.forthnet.gr
authors.forename: T M
authors.initials: TM
authors.lastname: Kolettis
authors.forename: Z S
authors.initials: ZS
authors.lastname: Kyriakides
authors.forename: D
authors.initials: D
authors.lastname: Tsiapras
authors.forename: T
authors.initials: T
authors.lastname: Popov
authors.forename: I A
authors.initials: IA
authors.lastname: Paraskevaides
authors.forename: D T
authors.initials: DT
authors.lastname: Kremastinos
mesh_terms: D002036:Bundle of His / Q000502:physiology; D006328:Cardiac Catheterization; D002302:Cardiac Output; D002304:Cardiac Pacing, Artificial; D015150:Echocardiography, Doppler; D004562:Electrocardiography; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009200:Myocardial Contraction; D011690:Purkinje Fibers / Q000502:physiology; D016683:Supine Position; D016276:Ventricular Function; D016277:Ventricular Function, Left; D017725:Ventricular Pressure