title: Noninvasive assessment of cardiac resynchronization therapy for congestive heart failure using myocardial strain and left ventricular peak power as parameters of myocardial synchrony and function.
abstract: BACKGROUND
  Although invasive studies have shown that cardiac resynchronization therapy by biventricular pacing improves left ventricular (LV) function in selected heart failure patients, it is impractical to apply such techniques in the clinical setting. The aim of this study was to assess the acute effects of cardiac resynchronization therapy by noninvasive techniques.
  
  
  RESULTS
  Twenty-two patients enrolled in the InSync trial (age 64 +/- 9 years, 18 men and 4 women; all with ejection fraction < 35% and QRS > 130 msec) were studied 1 to 12 months after pacemaker implantation during pacing, and while ventricular pacing was inhibited. Regional myocardial strains of the interventricular septum, LV free wall, and right ventricular free wall were derived from color Doppler tissue echocardiography. Peak power index was calculated as a product of simultaneously recorded noninvasive blood pressure and pulse-wave (PW) Doppler velocity of the LV outflow tract. The Z ratio (sum of LV ejection and filling times divided by RR interval) and tei index were calculated from PW Doppler data. During pacing, overall regional strain improved (P = 0.01), while the LV strain coefficient of variation decreased from 2.7 +/- 2.4 to 1.3 +/- 0.7 (P = 0.009). Additionally, peak power index improved from 84 +/- 24 to 94 +/- 27 cm x mmHg/sec (P = 0.004). The Z ratio increased from 0.71 +/- 0.08 to 0.78 +/- 0.07 (P = 0.0005), while the tei index decreased from 0.86 +/- 0.33 to 0.59 +/- 0.16 (P = 0.0002).
  
  
  CONCLUSIONS
  Using novel noninvasive indices, we demonstrated that cardiac resynchronization therapy improves LV performance.
authors.affiliation: Cardiovascular Imaging Center, The Cleveland Clinic Foundation, Cleveland, Ohio 44195, USA.
authors.forename: Zoran B
authors.initials: ZB
authors.lastname: Popović
authors.forename: Richard A
authors.initials: RA
authors.lastname: Grimm
authors.forename: George
authors.initials: G
authors.lastname: Perlic
authors.forename: Edward
authors.initials: E
authors.lastname: Chinchoy
authors.forename: Maria
authors.initials: M
authors.lastname: Geraci
authors.forename: Jing Ping
authors.initials: JP
authors.lastname: Sun
authors.forename: Erwan
authors.initials: E
authors.lastname: Donal
authors.forename: Xiao-Fang
authors.initials: XF
authors.lastname: Xu
authors.forename: Neil L
authors.initials: NL
authors.lastname: Greenberg
authors.forename: Bruce L
authors.initials: BL
authors.lastname: Wilkoff
authors.forename: James D
authors.initials: JD
authors.lastname: Thomas
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D001783:Blood Flow Velocity; D001794:Blood Pressure; D002304:Cardiac Pacing, Artificial / Q000379:methods; D018618:Echocardiography, Doppler, Color; D005260:Female; D006321:Heart / Q000503:physiopathology*; D006333:Heart Failure / Q000000981:diagnostic imaging / Q000503:physiopathology* / Q000628:therapy*; D006346:Heart Septum / Q000503:physiopathology; D006801:Humans; D008297:Male; D008875:Middle Aged; D011674:Pulse; D016896:Treatment Outcome; D018497:Ventricular Dysfunction, Right; D016277:Ventricular Function, Left