title: Effects of resynchronization therapy on cardiac function in pacemaker patients "upgraded" to biventricular devices.
abstract: BACKGROUND
  Cardiac resynchronization therapy (CRT) improves echocardiographic measures of cardiac function and has a variable effect on QRS duration in patients with left bundle branch block (LBBB). How CRT affects these indices in patients with right ventricular (RV) pacing-induced LBBB who are "upgraded" with left ventricular (LV) leads for CRT is unknown. We studied the echocardiographic effects of RV pacing and CRT in patients with prior continuous RV pacing after LV lead placement.
  
  
  RESULTS
  Fifteen consecutive patients (age 73 +/- 11 years, LV ejection fraction 24 +/- 6%, QRS duration 190 +/- 27 msec) with New York Heart Association class IIIB-IV symptoms and continuous RV pacing underwent LV lead placement for CRT. Echocardiography and ECG were performed sequentially during RV pacing and CRT. CRT was associated with significantly reduced QRS duration (190 +/- 27 msec vs 165 +/- 18 msec, P = 0.005) and reduced LV electromechanical delay (180 +/- 33 msec vs 161+/- 43 msec). Baseline QRS duration correlated with CRT response. After CRT, patients had significant improvements in indices of systolic function, including LV ejection fraction, myocardial performance index (MPI), and LV ejection time. Abnormal baseline MPI was associated with greater improvement after CRT. LV end-diastolic and systolic volumes were similarly decreased with CRT. Mitral valve deceleration time, an index of diastolic function, was not affected by CRT.
  
  
  CONCLUSIONS
  "Upgrading" RV paced patients with advanced heart failure to CRT improves measures of electrical and LV mechanical synchrony and improves systolic function.
authors.affiliation: Division of Cardiology, UCLA School of Medicine, Los Angeles, California, USA.
authors.forename: Tamara
authors.initials: T
authors.lastname: Horwich
authors.forename: Elyse
authors.initials: E
authors.lastname: Foster
authors.forename: Teresa
authors.initials: T
authors.lastname: De Marco
authors.forename: Zian
authors.initials: Z
authors.lastname: Tseng
authors.forename: Leslie
authors.initials: L
authors.lastname: Saxon
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D002304:Cardiac Pacing, Artificial; D009202:Cardiomyopathies / Q000175:diagnosis / Q000000981:diagnostic imaging / Q000628:therapy*; D002908:Chronic Disease; D004562:Electrocardiography; D005260:Female; D006333:Heart Failure / Q000175:diagnosis / Q000000981:diagnostic imaging / Q000628:therapy*; D006352:Heart Ventricles; D006801:Humans; D008297:Male; D008875:Middle Aged; D010138:Pacemaker, Artificial; D011446:Prospective Studies; D016896:Treatment Outcome; D014463:Ultrasonography