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 3 – Correlation between SD and HBW before cardiac resynchronization therapy (R 2 : 0.78) 300 200 100 100 250 150 50 20 40 60 80 0 0 y = 2.6028x + 4.1788 R 2 = 0.7853 Correlation between SD and HBW Figure 4 – Distribution of the mean pre- and post-cardiac resynchronization therapy left ventricular ejection fraction according to clinical response to implantation. Pre‑CRT LVEF PRE: pre-cardiac resynchronization therapy left ventricular ejection fraction; Post-CRT LVEF: post-cardiac resynchronization therapy left ventricular ejection fraction; RESPOND: responder group; NONRESPOND: non-responder group. (Student t test). 60% 50% 40% 30% 20% 10% Pre-CRT LVEF Post-CRT LVEF RESPOND NONRESPOND On GATED SPECT, SD and HBW could assess mechanical dyssynchrony before CRT. On the assessment 6 months after CRT, those variables showed no significance, probably because not all patients had the LV lead positioned in the maximally delayed segment. On GATED SPECT, the significant cardiac function data were LV ESV and LV mass, probably due to reverse remodeling determined by CRT. In the search for a relationship between responders to CRT and the presence of mechanical dyssynchrony on myocardial perfusion imaging, responders had higher SD and HWB values as compared to non-responders (HBW of 177° vs 76°, and SD of 62° vs 36°, respectively). Such findings are aligned with those reported by Henneman et al., 16 whose study showed significantly higher values of dyssynchrony parameters in responders as compared to non-responders (HBW of 175° vs 117°, and SD of 56° vs 37°, respectively). In addition, responders had longer QRS duration than non-responders, supported by the finding of the direct relationship between them. When assessing the maximal delay site of LV activation, the presence of fibrosis in the site and adjacent to it can be determined, which can influence the response to CRT. Daoulah et al. 17 have shown that the presence of transmural fibrosis in the posterolateral region before CRT is associated with a 75% lower chance of echocardiographic or clinical response to that therapy. In our study, 11.1% of the patients had the lead implanted in the posterolateral region; however, no fibrosis was reported in that region in our sample, and 7 patients had history of previous myocardial infarction. The LV lead implantation in the viable maximal delay site could increase the frequency of reverse remodeling and decrease symptoms. 18,19 611