Left Ventricular Size does not Modify the Effect of QRS Duration in Predicting Response to Cardiac Resynchronization Therapy.
BACKGROUND
QRS duration (QRSd) may be impacted by both left ventricular (LV) dilatation and conduction delay. It is possible therefore that the same QRSd may portend significantly different amounts of LV activation delay in patients with small versus large left ventricles. We hypothesized that LV size modifies the effect of QRSd on predicting outcomes in patients undergoing CRT implant.


METHODS
We extracted data on consecutive patients presenting for initial CRT implant. In patients with a follow-up echocardiogram, response was defined as an absolute improvement in LV ejection fraction ≥5%. Multivariate models were created to determine if left ventricular end-diastolic diameter (LVEDD) modified the effect of QRSd on its association with both long-term survival free of left ventricular assist device (LVAD) and heart transplant and echocardiographic response.


RESULTS
464 patients met inclusion criteria. At a mean follow-up of 4.9 ± 2.6 years, there were 210 deaths, 13 heart transplants, and 12 LVAD placements. There was a weak but significant correlation between baseline QRSd and LVEDD (Spearman's Rho 0.106, P < 0.001). In a multivariate analysis, there was no evidence of effect modification of LVEDD on QRSd (LVEDDi*QRS interaction term HR 1.0 [0.995-1.006], P = 0.94). Note that 305 patients had a follow-up echocardiogram, of whom 193 met the criteria for response. In a multivariate analysis, there was no evidence of effect modification of LVEDD on QRSd (LVEDDi*QRS interaction term odds ratio 0.998 (0.988-1.008), P = 0.65).


CONCLUSIONS
LV size does not modify the effect of QRSd and its association with outcomes following CRT. The correlation between LV size and QRSd in patients with a QRSd ≥ 120 ms is weak.
Heart and Vascular Institute Cleveland Clinic, Cleveland, Ohio.
John
J
Rickard
Heart and Vascular Institute Cleveland Clinic, Cleveland, Ohio.
Bryan
B
Baranowski
Heart and Vascular Institute Cleveland Clinic, Cleveland, Ohio.
Richard A
RA
Grimm
Heart and Vascular Institute Cleveland Clinic, Cleveland, Ohio.
Mark
M
Niebauer
Heart and Vascular Institute Cleveland Clinic, Cleveland, Ohio.
Niraj
N
Varma
Heart and Vascular Institute Cleveland Clinic, Cleveland, Ohio.
W H Wilson
WHW
Tang
Heart and Vascular Institute Cleveland Clinic, Cleveland, Ohio.
Bruce L
BL
Wilkoff
D000368:Aged; D058406:Cardiac Resynchronization Therapy / Q000401:mortality* / Q000706:statistics & numerical data; D003936:Diagnosis, Computer-Assisted; D004562:Electrocardiography / Q000379:methods*; D005260:Female; D006333:Heart Failure / Q000175:diagnosis / Q000401:mortality* / Q000517:prevention & control*; D006801:Humans; D017379:Hypertrophy, Left Ventricular / Q000000981:diagnostic imaging / Q000401:mortality* / Q000517:prevention & control; D015994:Incidence; D008297:Male; D009820:Ohio / Q000453:epidemiology; D009929:Organ Size; D017063:Outcome Assessment, Health Care / Q000379:methods* / Q000706:statistics & numerical data; D011379:Prognosis; D015203:Reproducibility of Results; D012189:Retrospective Studies; D012307:Risk Factors; D012680:Sensitivity and Specificity; D015996:Survival Rate; D016896:Treatment Outcome
cardiac resynchronization therapy; left ventricular size; reverse ventricular remodeling; survival