Post-CRT Imaging Based Optimization

The utility of CRT optimization remains to be confi ned to patients whose response to the treatment is either suboptimal or negligible. There are several techniques, mostly echocardiographic, to optimize device settings but none has been universally accepted as gold standard. Methods differ in recording techniques and may therefore vary signifi cantly in performance. Several studies have employed various techniques in interrogating AV interval with or without concomitant V-V interval optimization. Optimization was performed at varying time points. Even the defi nition for favorable response to CRT varied. Optimization of AV and V-V intervals is patient-specifi c and optimal values change over time. This may relate to time-related LV reverse remodeling or to progression of disease. The effects of inter-atrial conduction defect, right atrial pacing, and exercise on AV delay add complexities to performance of AV delay optimization. At the very least, it has to be ensured that the programmed AV delay should neither produce fusion of mitral E and A waves nor truncation of the latter. Despite evidences of hemodynamic benefi ts, the utility of V-V interval optimization remains controversial. Evidence for the incremental long-term benefi ts on mortality and morbidity is still lacking. Three large clinical trials reported confl icting results in terms of clinical and echocardiographic improvement. Differences in the study designs could have contributed to the confl icting results. It is important to remember, however, that simultaneous biventricular pacing is not always synonymous with suboptimal V-V interval, nor should sequential pacing be routinely regarded as ideal.