title: Effects of right atrial and ventricular DDD pacing on cardiac function and ventricular contraction synchrony.
abstract: BACKGROUND
  Right ventricular apical pacing has been reported to reduce cardiac performance. But there are few reports on the effects of dual chamber (DDD) pacing on cardiac function compared to sinus rhythm. In this study, we evaluated the effects of right atrial and ventricular DDD pacing on cardiac function and ventricular contraction synchrony using equilibrium radionuclide angiography.
  
  
  METHODS
  Ten patients implanted with a right atrial and ventricular DDD pacemaker underwent equilibrium radionuclide angiography. The scintigraphic data were obtained during sinus rhythm and pacing rhythm. Cardiac function parameters were obtained semimanually. Phase analysis was used to study the ventricular activation sequence and ventricular synchrony.
  
  
  RESULTS
  The left ventricular 1/3 ejection fraction decreased significantly during pacing compared with that during sinus rhythm [(23.4 +/- 6.1)% vs (27.7 +/- 4.5)%, P = 0.01]. Regional ejection fraction also decreased during pacing, although the difference was not statistically significant. Phase analysis showed that the right ventricle was activated earlier than the left ventricle during pacing, and that the phase shift was significantly greater during pacing than that during sinus rhythm [64.13 degrees +/- 16.80 degrees vs 52.88 degrees +/- 9.26 degrees, P = 0.007]. The activation of both ventricles occurred simultaneously during sinus rhythm, with the activation sequence from proximal septum or base of left ventricle to apex. The earliest activation during pacing occurred at the right ventricular apex, and subsequently spread to the base and left ventricle.
  
  
  CONCLUSIONS
  Right atrial and ventricular DDD pacing impairs left ventricular systolic function and ventricular synchrony.
authors.affiliation: Division of Clinical Electrophysiology, Fuwai Hospital, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing 100037, China.
authors.forename: Li-Da
authors.initials: LD
authors.lastname: Zhi
authors.forename: Wei
authors.initials: W
authors.lastname: Hua
authors.forename: Shu
authors.initials: S
authors.lastname: Zhang
authors.forename: Rong-Fang
authors.initials: RF
authors.lastname: Shi
authors.forename: Fang-Zheng
authors.initials: FZ
authors.lastname: Wang
authors.forename: Xin
authors.initials: X
authors.lastname: Chen
mesh_terms: D002304:Cardiac Pacing, Artificial; D006801:Humans; D009200:Myocardial Contraction; D013599:Systole; D016277:Ventricular Function, Left