ABC | Volume 111, Nº4, Octuber 2018

Original Article Nascimento et al Electromechanical dyssynchrony and GATED SPECT in CRT Arq Bras Cardiol. 2018; 111(4):607-615 Figure 7 – Fluoroscopy during implantation of the cardiac resynchronization device with left ventricular lead implanted in the maximal delay site determined on GATED SPECT. Considering the present study’s findings, it seems that the use of electrocardiography in isolation, based on QRS duration and its morphology to select patients for CRT, is not a good isolated preditor; however, the association of the duration and morphology criteria with the imaging criteria of mechanical dyssynchrony can provide a better response to CRT. The benefit of using imaging techniques, especially GATED SPECT with phase analysis, to detect mechanical dyssynchrony and to guide lead positioning in the site of maximal conduction delay should increase the number of responders, but larger studies with LV lead positioning guided by imaging techniques are required to draw definite conclusions. Conclusion 1) Patients submitted to CRT have a good clinical response, with a reduction in electrical dyssynchrony assessed on electrocardiography and a reduction in mechanical dyssynchrony assessed on GATED SPECT. 2) Responders to CRT have longer QRS duration before the implantation of the CRT device as compared to non‑responders. In addition, responders had a significant reduction in the PR interval duration as compared to non-responders. 3) Electrical dyssynchrony is not necessarily associated with mechanical dyssynchrony, as shown on GATED SPECT. 4) The phase analysis of GATED SPECT showed that the parameters SD and HBW are associated with higher likelihood of responding to CRT. 5) Although GATED SPECT indicates the last myocardial segment to contract for the LV lead positioning in this site, that is not always possible because of anatomical variability (tributaries) and caliber of the coronary sinus. Author contributions Conception and design of the research and Statistical analysis: Nascimento EA, Reis CCW, Mesquita CT; Acquisition of data and Critical revision of the manuscript for intellectual content: Nascimento EA, Reis CCW, Ribeiro FB, Alves CR, Silva EN, Ribeiro ML, Mesquita CT; Analysis and interpretation of the data and Writing of the manuscript: Nascimento EA, Reis CCW, Silva EN, Mesquita CT; Obtaining financing: Mesquita CT. Potential Conflict of Interest No potential conflict of interest relevant to this article was reported. Sources of Funding This study was funded by Agência Internacional de Energia Atômica. Study Association This article is part of the thesis of master submitted by Erivelton Alessandro do Nascimento, from Universidade Federal Fluminense. Ethics approval and consent to participate This study was approved by the Ethics Committee of the Hospital Universitário Antônio Pedro under the protocol number 884.844. All the procedures in this study were in accordance with the 1975 Helsinki Declaration, updated in 2013. Informed consent was obtained from all participants included in the study. 613