Introduction:
Response to cardiac resynchronization therapy (CRT) is often defined as reverse remodeling as a reduction in left ventricular (LV) end systolic volume (ESV). How myocardial mechanics are affected by biventricular pacing is not fully clarified. We tested the hypothesis that longitudinal and circumferential function are affected differently by biventricular pacing.
Methods:
Echocardiography (two dimensional) was performed before and 6 months after CRT implantation in heart failure patients with LV ejection fraction (EF) ≤ 35% and QRS ≥ 120 ms. LV function was assessed by EF and by global longitudinal (GLS) and global circumferential (GCS) strain from 16 LV segments by speckle tracking technique. CRT responders were defined as patients with reverse remodeling with a reduction in ESV ≥ 15% at 6 months.
Results:
We included 138 heart failure patients (65±10 years, 22% women, NYHA functional class 2.8±0.4, 48% ischemic cardiomyopathy). In the total population, GLS did not change (-8.5±3.9% to -8.9±4.7%, p=0.31) after 6 months with biventricular pacing, while GCS (-11.3±3.3% to -14.2±4.5%, p<0.001) and EF (27±9% to 36±12%, p<0.001) improved. Analyzing CRT responders (62%) and non-responders separately, GLS improved in responders (-8.4±3.8% to -9.5±3.8%, p=0.02) but not in non-responders (-8.7±4.1% to -7.9±4.5%, p=0.30) (Figure). GCS improved in both groups (-11.3±3.0% to -15.0±4.3%, p<0.001 and -11.4±3.8% to 13.0±4.7%, p=0.01). ΔGLS was a predictor of CRT response (OR 0.84 (0.75-0.95), p=0.009) and of ΔESV (1.62 (0.45-2.79), p=0.007) independently of ΔGCS.
Conclusions:
Biventricular pacing by CRT generally induced less changes in GLS than in GCS and EF. Importantly, GLS improved only in CRT responders with reverse remodeling. We suggest that reverse remodeling is more dependent on improved longitudinal function than circumferential function.
Cardiac index in atrio- and interventricular delay optimized cardiac resynchronization therapy and cardiac contractility modulation
