Left ventricular pacing threshold and outcome in MADIT-CRT.
BACKGROUND
High left ventricular (LV) pacing threshold (PT) may in some cases indicate the presence of scarred myocardium, a predictor of poor outcome in cardiac resynchronization therapy (CRT) treated patients. We hypothesized that intraoperative LVPT can be used to determine echocardiographic and clinical responses to CRT.


RESULTS
The study comprised 975 patients enrolled in the CRT-D arm of the Multicenter Automatic Defibrillator Implantation Trial with Cardiac Resynchronization Therapy (MADIT-CRT). Multivariate regression analysis was performed to evaluate the relationship between LVPT and percent reduction in LV end-systolic volume (ESV) and left atrial volume (LAV) 1 year after CRT. Cox proportional hazards analysis was used to evaluate the relationship between LVPT and heart failure (HF) events or death (primary endpoint) and all-cause death (secondary endpoint). An increasing LVPT was inversely related to percent reduction in both LVESV (P = 0.02) and LAV (P<0.01). Patients with LVPT in the highest quartile (>1.8 V) were less likely to achieve reverse LV remodeling (≥15% LVESV reduction from baseline) than those with LVPT in the lower quartiles (hazard ratios [HR] OR 0.56, P = 0.02). Mean percent reduction in LAV and LVESV was also significantly greater among those with lowest quartile LVPT. Multivariate analysis showed borderline significant 13% (P = 0.06) and significant 22% (P = 0.03) increase in the risk of HF/death and death alone, respectively, per 1 volt increase in LVPT.


CONCLUSIONS
High intraoperative LVPT is associated with significantly lower echocardiographic and clinical response to CRT-D.
the Heart Rhythm Center and Cardiovascular Medicine, St. John Hospital and Medical Center, Detroit, Michigan, USA.
Luis A
LA
Pires
the Heart Research Follow-up Program University of Rochester Medical Center, Rochester, New York, USA.
Scott
S
McNitt
Brigham and Women's Hospital, Boston, Massachusetts, USA.
Scott
S
Solomon
the Heart Research Follow-up Program University of Rochester Medical Center, Rochester, New York, USA.
Ilan
I
Goldenberg
the Heart Research Follow-up Program University of Rochester Medical Center, Rochester, New York, USA.
Wojciech
W
Zareba
the Heart Research Follow-up Program University of Rochester Medical Center, Rochester, New York, USA.
Arthur J
AJ
Moss
D000368:Aged; D058406:Cardiac Resynchronization Therapy; D005260:Female; D006333:Heart Failure / Q000000981:diagnostic imaging / Q000628:therapy*; D006352:Heart Ventricles; D006801:Humans; D008297:Male; D008875:Middle Aged; D016896:Treatment Outcome; D014463:Ultrasonography
cardiac resynchronization therapy; echocardiography; heart failure; implantable cardioverter defibrillator; left ventricle pacing; remodeling