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  • VV optimization From the foregoing discussion it is clear

    2019-06-10

    VV optimization From the foregoing discussion, it is clear that AV delay programming to ensure ventricular preexcitation with optimal LV diastolic filling and systolic function is complex, and the optimal method that translates into improved patient outcomes is uncertain. These issues are even more apparent in studies of VV optimization. The landmark trials of CRT in order Epoxomicin failure all demonstrated a benefit of CRT using simultaneous BiV pacing in conjunction with AV delay optimization [3,5,7,9,10,44]. However, it stands to reason that inter-individual variations in ventricular conduction delay in diseased myocardium should affect the timing of ventricular stimulation that results in optimal resynchronization, and this could be targeted to improve response to CRT. Early hemodynamic data from 39 patients in the PATH-CHF studies demonstrated similar improvements in left ventricular contractile function (dP/dt) with either simultaneous BiV or LV-only pacing [45]. In 41 patients from the same study population, AV optimized simultaneous BiV or LV-only pacing resulted in similar improvements in functional capacity and quality of life that was sustained at 12-month follow-up [46]. This suggests that the critical event in CRT is timing of left ventricular stimulation. Other studies have demonstrated acute hemodynamic improvements in invasively measured LV dP/dt with optimization of the VV interval over nominal simultaneous BiV pacing, with significant variation of this interval between patients [24,47,48]. Several noninvasive approaches to VV optimization have been proposed, each with its own limitations.
    Conclusions CRT non-responder rates have remained relatively stable despite attempts to improve patient selection and programming optimization. Many different methods for AV and VV delay optimization have been developed, and all have demonstrated that optimized delays, regardless of the method, result in acute improvements in LV diastolic and systolic function. These functional improvements have unfortunately not consistently translated into improvements in clinical outcomes or response rates to CRT. As routine AV delay optimization was performed in most trials demonstrating efficacy of CRT, it is a reasonable strategy that does not appear to be harmful. More recent data suggest, however, that an empiric AV delay of 120ms is not inferior to available optimization methods. Moreover, 3 large multicenter trials (FREEDOM, SMART AV, and ADAPTIVE CRT) failed to show superiority of IEGM-based optimization over nominal settings or echo techniques. This has led to the evaluation of other techniques for improving CRT outcome, such as placing LV leads in locations of late mechanical [76] or electrical activation [77]. Current techniques and available data make routine VV optimization impractical and unnecessary in the majority of patients. At the present time, the benefit of routine use of AV and VV interval optimization is unclear and may be most useful in the population of CRT “non-responders,” although the benefit of this strategy also requires further study.
    Conflict of interest
    Introduction The optimal management of perioperative anticoagulation in patients on warfarin therapy undergoing cardiac implantable electronic device (CIED) surgery is not yet established. Neither the recent American Heart Association/American College of Cardiology nor European Society of Cardiology guidelines mentioned device surgery in patients on chronic anticoagulation therapy. The 2008 guidelines from the American College of Chest Physicians (ACCP) have recommended the use of bridging anticoagulation with therapeutic dose of subcutaneous low-molecular-weight heparin (LMWH) or intravenous heparin in patients with mechanical heart valves, atrial fibrillation, or venous thromboembolism who are at moderate or high risk for thromboembolic events [1]. This recommendation, however, was largely based on expert opinion. The new ACCP 2012 guidelines considered CIED surgery to be a procedure associated with an increased bleeding risk during perioperative antithrombotic administration [2]. CIED implantation in which separation of infraclavicular fascial layers and lack of suturing of unopposed tissues within device pocket may predispose to hematoma development. However, the updated guidelines did not provide specific recommendations on the management of this patient population. Recent surveys in Canada and United Kingdom revealed a lack of consensus among the CIED implanting physicians on whether to withhold anticoagulation and whether to use bridging therapy [3,4]. As increasing data are emerging during the last decade, we are here to provide an updated literature review and to offer our suggestions on the practical management of this important clinical issue.