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    • br Benefits and tips for antitachycardia

    2019-05-13


    Benefits and tips for antitachycardia pacing To reduce ICD shocks, antitachycardia pacing (ATP) for terminating lethal ventricular tachyarrhythmias must be programmed. There are 2 main types of ATP: burst (scan) pacing and autodecremental overdrive pacing (ramp pacing). Programming ATP is common for ventricular tachycardia (VT) but there are a few data regarding detailed settings. With regard to the different types of pacing (burst pacing or ramp pacing), there were no significant differences in terminating VT episodes with Tenovin-6 cost length (CL) more than 320ms between burst pacing and ramp pacing [16,17]; however, in the case of fast VT episodes with CL between 240 and 320ms, burst pacing was more effective for terminating VT episodes compared with ramp pacing [18]. Many episodes labeled by ICD as ventricular fibrillation (VF) are sometimes rapid monomorphic VT, particularly when the CL of VT was between 240 and 320ms. Wathen et al. reported that an ATP setting with an 8-pulse burst with pacing train at 88% of VTCL was successful in terminating rapid VT with CL less than or equal to 320ms in 72% of study subjects [19]. Interestingly, the success rate of burst pacing against rapid VT was higher with 2 sequences compared with only one sequence [20]. The second sequence terminated 35% of rapid VT. Moreover, we cannot conclude that ATP was not effective after failing to terminate rapid VT because one failure of an ATP sequence did not predict subsequent failure; thus ATP should be set for rapid VT at all times. According to the number of stimuli and coupling intervals, Peinado et al., compared 4 settings, including burst CL at 91% or 81% of VTCL with 7 or 15 stimuli, and reported that 15 stimuli with a burst CL at 91% of VTCL was the most effective in terminating VT [21]. However, a recent report of the ADVANCED-D trial suggested no significant differences between groups with 8 stimuli and 15 stimuli, with regard to terminating VT with a CL between 240 to 320ms by burst pacing [22]. In cardiac resynchronization therapy devices with defibrillators (CRT-Ds), we can select the pacing mode BiV (right ventricular [RV] pacing with simultaneous LV pacing) or RV only pacing, as ATP in some devices. Gasparini et al. reported that the efficacy of the first ATP in terminating any VT was similar in both groups of BiV ATP and RV only ATP [23]. However, sub-analysis revealed that BiV ATP was more effective for fast VT with CL between 240 and 320ms in patients with ischemic heart disease compared with RV only ATP. Based on these data, we should select BiV ATP, particularly in patients with ischemic heart disease.
    Detection intervals and rates Non-sustained VTs are often detected by ICD devices, which do not require ICD therapy, particularly ICD shock. Thus, it is very important to set a detection interval to recognize whether the arrhythmias have continued or stopped. Although there is a recent trend to use a longer detection interval, we should consider that it is somewhat arbitrary, depending on the patient\'s situation and clinical background, such as ICD indication, baseline LV function, drug use, etc., because longer detection intervals may cause arrhythmic syncope or delay therapy. In the PainFree II study, the detection intervals were set to 18/24 intervals and 34% of fast VTs were self-terminating in the fast VT zone between 240ms and 320ms [19]. Whereas only 1% of ventricular arrhythmias in the VF zone spontaneously terminated using detection criteria of 12/16 intervals in PainFree I [24]. The PainFree II study suggests that a longer delay will reduce unnecessary device detection and therapy. It is, however, likely that a longer duration of tachycardia detection might increase cases of syncope, resulting from delays in therapy. However, longer detection intervals in the PainFree II study (18/24 intervals) proved safe because arrhythmic syncope did not increase compared with PainFREE I. Taking into account recent evidence from the PREPARE [25] and RELEVANT studies [26], we should adopt a longer duration to avoid ICD shocks in primary prevention patients with ICD or CRT-D. The PREPARE study patients were less likely to receive a shock in the first year compared with control patients (9% vs. 17%, P=0.01). The incidence of untreated VT and arrhythmic syncope was similar between the PREPARE study patients and the control cohort. Likewise, in the RELEVANT study of CRT-D patients with non-ischemic heart disease and primary prevention, whose detection interval was much longer in the protect arm (30/40) compared with the control group (12/16), the total number of delivered shocks was significantly lower in the protect group compared with the control group (P<0.0001). Moreover, freedom from the first hospitalization for HF was significantly better in the protect group than in the control group (P=0.038).