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    • gpr109a inhibitor br Possible reasons for the divergent

    2019-06-05


    Possible reasons for the divergent results for the predictive value of PES for cardiac events First, there were methodological differences in the stimulation protocols used for PES, including the number of extrastimuli, the minimum coupling interval used (up to 200ms or refractoriness), the site of stimulation (right ventricular apex [RVA] and/or right ventricular outflow tract [RVOT]), and the amplitude of the electrical impulse during stimulation. In the studies by Brugada et al., stimulation was delivered only from the RVA with up to 3 extrastimuli, with a minimum coupling interval of 200ms [11]. The FINGER study and 2 recent multicenter prospective studies from Japan used a PES protocol for stimulation from the RVA and RVOT with up to 3 extrastimuli. In the FINGER study, a minimal coupling interval was 200ms, whereas the Japanese studies went up to ventricular refractoriness [6,14]. The stimulation protocol markedly influences the extent of inducibility of VF or VT in BS [17]. To solve this methodological issue, both a single center study and a multicenter study were recently performed using a uniform protocol for PES. Makimoto et al. performed PES using a uniform protocol in 108 consecutive patients with type 1 Brugada ECG (26 VF, 40 syncope, 42 asymptomatic) in a single center [18]. A maximum of 3 ventricular extrastimuli were delivered from the RVA and RVOT up to ventricular refractoriness, or until the coupling interval reached 180ms. The basic gpr109a inhibitor length was 500ms. VF or VT were induced in 4 patients by a single extrastimulus, in 41 by double extrastimuli, and in 36 by triple extrastimuli, and were more frequently induced from the RVOT (70%) than from the RVA (30%). During a mean follow-up period of 79 months, the overall inducibility of VF or VT was not associated with an increased risk of VF (P=0.78). However, patients with VF or VT inducible by single or double extrastimuli had a worse prognosis than those in whom VF or VT was inducible by triple extrastimuli; this was significant in all patients (P=0.004) and in patients without documented VF (P=0.001). Positive and negative predictive values of VF or VT inducible with up to 2 extrastimuli (36% and 87%, respectively) were better than those inducible with up to 3 extrastimuli (23% and 81%, respectively). They concluded that single or double extrastimuli at PES were adequate for a prognostic indicator in BS, and that site of stimulation and coupling interval of extrastimuli were not prognostic indicators in BS. Priori et al. reviewed the PRELUDE prospective registry to assess the predictive accuracy of inducibility of VF or VT by PES performed using a uniform protocol in 10 centers [19]. A total of 308 consecutive patients with type 1 Brugada ECG and without history of cardiac arrest were enrolled. The PES protocol consisted of 2 basic drive cycles (600 and 400ms, S1) and up to 3 extrastmuli (S2–S4) delivered from the RVA and RVOT. The minimal coupling interval of extrastimuli was set to 200ms for S2 and S3 and to ventricular refractoriness for S4. They also assessed short-term reproducibility of PES. In 126 of 308 patients (41%), VF or polymorphic VT was induced. Of the 126 inducible patients, 5.5% were induced by single, 44.5% by double, and 50% by triple extrastimuli. The site of inducibility was equally distributed among the RVA (46.0%), the RVOT (46.8%), and both (7.2%). A reproducible outcome of PES was only 34%. During a mean follow-up period of 36 months, the overall inducibility of VF or polymorphic VT was not associated with the occurrence of arrhythmic events (VF or appropriate ICD interventions) (3.9% in inducible individuals vs. 4.9% in noninducible individuals, P=0.67). Although the stimulation protocol used in this study was more aggressive than that in the study of Delise et al., the negative predictive value of PES was lower than that (100%) in Delise\'s study [13]. When restricted to patients inducible with single or double extrastimuli, inducibility of VF or polymorphic VT was not associated with the occurrence of arrhythmic events either (P=0.89). The sensitivity and specificity of VF or polymorphic VT with up to 2 extrastimuli were 25% and 74.2%, respectively, and 35.7% and 58.8%, respectively, with up to 3 extrastimuli. Priori et al. concluded that the inducibility of VF or polymorphic VT had no predictive value for the occurrence of arrhythmic events, even for PES performed with up to 2 extrastimuli. This conclusion agrees with the results of the 2 meta-analyses, the FINGER study and the Japanese multicenter prospective studies, but differs from the results of Makimoto et al. Interestingly, although the inducible rate of VF or VT was identical in the PRELUDE registry and in the study of Brugada et al. [11], the rate of cardiac events during follow-up is much lower in the PRELUDE registry (1.5% per year in the PRELUDE registry vs. 4.1% per year in the study by Brugada et al.) [11]. Despite the similar rate of inducibility with up to 3 extrastimuli, the evaluation of the predictive value of PES was completely different.