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 of mechanical dyssynchrony. Thus, it is worth studying the ventricular synchronism before CRT to estimate the patient’s response, because the procedure involves high costs. Phase analysis to assess left ventricular (LV) dyssynchrony has been incorporated into gated myocardial perfusion SPECT (GATED SPECT). 8 In addition to the synchronism parameters and in a highly reproducible way, phase analysis provides the assessment of the last ventricular segment to contract. Patients with LBBB tend to begin LV mechanical contraction earlier in the cardiac cycle in the septal wall, and later in other myocardial regions because of the deceleration of the nervous impulse propagation along the conduction system, causing late activation, the most common last site of contraction being located in the posterolateral wall. 9 The present study aimed at assessing the ability to analyze LV synchronism by use of GATED SPECT to predict the response to CRT and guide LV lead implantation. Methods The present study contains national data that are part of the international multicenter project VISION CRT, which assesses the value of phase analysis by use of GATED SPECT in patients who will be submitted to CRT, coordinated in multiple countries by the International Atomic Energy Agency. It is a non-blind clinical trial that included consecutive patients, who underwent 12-lead electrocardiogram at rest immediately before undergoing GATED SPECT and speckle-tracking echocardiography. In addition, the patients answered the Minnesota Living with Heart Failure Questionnaire (MLHFQ) within 4 weeks before the implantation of the CRT device and 6 ± 1 months after that implantation for comparison. Thus, the scintigraphic parameters of ventricular function [LVEF, end‑diastolic volume (EDV), end-systolic volume (ESV), LVmass] were assessed, as were the parameters to assess dyssynchrony by use of phase analysis. The analysis of GATED SPECT with the software ECT Synctool, version 3.0, used the following parameters for mechanical dyssynchrony: standard deviation (SD) > 43° and histogram bandwidth (HBW) > 135°. The inclusion criteria were as follows: patients stable and older than 18 years, in NYHA FC ≥ II, with LVEF ≤ 35% of ischemic or non-ischemic cause, sinus rhythm, QRS duration ≥ 120 ms, LBBB morphology, being followed up at or referred to two tertiary institutions of the Brazilian Unified Health System. Patients with cardioverter-defibrillator implanted for primary or secondary prevention of sudden cardiac death were included. Patients with any of the following characteristics were excluded: severe disease and life expectancy shorter than 1 year; right bundle-branch block; pregnancy or breastfeeding; acute coronary syndromes; coronary artery bypass grafting or percutaneous coronary intervention within 3 months from study entrance and up to 6 months after CRT. The definition of ‘responder to CRT’ considered the presence of two of the following findings: 1. improvement of at least one NYHA FC; 2. improvement of at least 5 points in the MLHFQ; 3. improvement of LVEF ≥ 5%; 4. reduction in ESV ≥ 15%; 5. reduction in HBW < 51°. The categorical variables were presented in nominal and ordinal forms. The LV pacing lead position was classified as follows: 1. concordant, when positioned in the maximally delayed segment; 2. adjacent, when located in up to one segment away from the maximal delay site; and 3. remote, when located more than one segment away from the maximal delay site. This project was approved by the Ethics Committee in Research of the Antônio Pedro University-affiliated Hospital/ Fluminense Federal University (No 884844). Statistical analysis Statistical analysis was performed with EXCEL (2010, Microsoft Corporation) and SPSS software, version 21.0 (2012, IBMCorporation), and data were shown as means and standard deviations. The categorical variables were compared by use of Fisher exact and chi-square tests, while paired Student t test was used for numerical variables. The Kolmogorov-Smirnov test showed the normal distribution of the continuous variables. Pearson’s linear correlation coefficient was calculated for the continuous variables. The significance level adopted in the statistical analysis was 5%. Results From July 2014 to August 2016, 15 patients were included in the study and 2 patients were lost to follow-up because of death (Table 1). Mean follow-up was 193 ± 16 days. All QRS intervals had a duration longer than 150ms and LBBB morphology. After CRT, a significant reduction was observed in the duration of QRS intervals (212 ms vs 136 ms; p < 0.001) and of PR intervals (179 ms vs 126 ms; p < 0.001). No change was observed in the QT interval after CRT. The impact of CRT on the quality of life was recorded by use of the MLHFQ, with significant response (p=0.0002) when comparing the mean score before and after CRT (Figure 1). Analysis with HBW (Figure 2) showed that the longer the QRS duration, the higher the HBW value, showing that HBW and SD also have a direct relationship, because their linear correlation coefficient is good (Figure 3). The group of patients with a significant improvement in LVEF 6 months after CRT (6 patients) had a lower pre-CRT LVEF than that of non-responders (7 patients) (Figure 4). When assessing the electrocardiographic parameters associated with clinical response to the CRT device, the responder group showed a significant reduction in the PR interval in ms (p < 0.0001), which did not reach significance in the non-responder group (p = 0.09). This is influenced by the need for constant ventricular stimulation in CRT, which normally leads to more reduced PR intervals. When classifying the patients as responders and non‑responders, the SD and HBW values were higher in responders than in non-responders. The HBW difference between the groups showed statistical significance by use of Student t test (Figure 5). During follow-up, 2 patients without mechanical dyssynchrony before the CRT device implantation became non-responders in the reassessment 6 months after CRT. Thus, we deduced that patients with exclusive electrical 608