title: Intramural dyssynchrony and response to cardiac resynchronization therapy in patients with and without previous right ventricular pacing.
abstract: OBJECTIVE
  Right ventricular (RV) pacing is an iatrogenic cause of heart failure (HF) that has not been well studied. We assessed whether HF patients paced from the right ventricle (RVp) adversely remodel and respond to cardiac resynchronization therapy (CRT) in a similar way to HF patients without right ventricular pacing (nRVp).
  
  
  RESULTS
  Echocardiograms were performed before and ∼5 months after CRT in 31 RVp and 49 nRVp HF patients. Longitudinal intraventricular dyssynchrony using tissue Doppler imaging (TDI) was calculated as the standard deviation of time to peak systolic displacement by tissue tracking (SD-TT) of 12 segments. Longitudinal dyssynchrony within a wall (intramural dyssynchrony) was assessed by two methods: quantifying the number of segments with initial abnormal apical displacement (IMD score) and using a cross-correlation synchrony index (CCSI). Despite similar ejection fractions (EFs) of 28% prior to CRT, left ventricular end-diastolic volume was significantly smaller (143±54 vs. 183±62, P=0.004) in RVp. The standard deviation of time to peak systolic displacement by tissue tracking (83.4±34.9 vs. 67.9±26.6, P=0.03) and IMD score (3.1±1.8 vs. 1.3±1.7, P<0.001) were greater in RVp. Cardiac resynchronization therapy significantly improved EF and volumes in both groups. Ejection fraction increased more in RVp (12.8±9.2% vs. 7.4±7.6%, P=0.007). Intraventricular dyssynchrony and both measures of intramural septal dyssynchrony improved to a greater extent post-CRT in RVp.
  
  
  CONCLUSIONS
  Right ventricular pacing patients differ from nRVp HF patients in that they have smaller ventricles and greater intraventricular and intramural septal dyssynchrony. Right ventricular pacing HF patients respond better to CRT with greater improvements in EF, and intraventricular and intramural septal dyssynchrony.
authors.affiliation: St Paul Heart Clinic, 225 N. Smith Ave. #400, St Paul, MN 55102, USA. abank@stphc.com
authors.forename: Alan J
authors.initials: AJ
authors.lastname: Bank
authors.forename: Christopher L
authors.initials: CL
authors.lastname: Kaufman
authors.forename: Kevin V
authors.initials: KV
authors.lastname: Burns
authors.forename: Joshua S
authors.initials: JS
authors.lastname: Parah
authors.forename: Lauren
authors.initials: L
authors.lastname: Johnson
authors.forename: Aaron S
authors.initials: AS
authors.lastname: Kelly
authors.forename: Sanjeev G
authors.initials: SG
authors.lastname: Shroff
authors.forename: Daniel R
authors.initials: DR
authors.lastname: Kaiser
mesh_terms: D000368:Aged; D000465:Algorithms; D000704:Analysis of Variance; D001281:Atrial Fibrillation / Q000628:therapy*; D058406:Cardiac Resynchronization Therapy / Q000379:methods*; D002908:Chronic Disease; D005260:Female; D006305:Health Status Indicators; D006333:Heart Failure / Q000000981:diagnostic imaging / Q000628:therapy*; D006801:Humans; D016014:Linear Models; D008297:Male; D012189:Retrospective Studies; D013223:Statistics as Topic; D018709:Statistics, Nonparametric; D013318:Stroke Volume; D013997:Time Factors; D018608:Ultrasonography, Doppler; D018497:Ventricular Dysfunction, Right / Q000000981:diagnostic imaging* / Q000473:pathology; D016278:Ventricular Function, Right