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 2 – Gated myocardial perfusion SPECT with analysis of ventricular synchronism in a patient with dilated cardiomyopathy and left bundle-branch block, showing marked dyssynchrony with HBW of 245° and SD of 97°. The population of the present study reflects the profile of patients normally treaded at high-complexity hospitals, and most of them had coronary artery disease. As shown in previous studies, most of our patients had NYHA FC III or IV at the time of CRT. 10 The clinical-functional assessments of the present study, NYHA FC and MLHFQ, confirmed the benefit of CRT reported previously. 10-13 In this study, 77.8% of the patients had a reduction of at least one NYHA FC and a significant improvement in their quality of life, as shown on the MLHFQ after CRT. Although the MLHFQ assesses subjective data, it refers to the patients’ perception of their symptoms, which is aligned with the results of a previous study. 4 In most patients, CRT is associated with clinical benefits. Some electrocardiographic parameters are considered predictors of a higher chance of response to treatment, such as the longer QRS duration, and the benefit increases even more when QRS duration is > 150 ms, as reported by Poole et al. 14 In our study, all patients had QRS duration > 150 ms (mean QRS duration, 212 ms), which increased the likelihood of response. Supporting such data, the COMPANION study has shown no benefit of CRT for patients with QRS duration < 147 ms 12 when assessing the primary outcome of death or hospitalization due to any cause. However, the RAFT study, 13 assessing the primary outcome of death or hospitalization due to HF, has found a higher benefit of CRT in individuals with QRS duration > 150 ms. Our sample did not include patients with non-LBBB morphology, nonspecific intraventricular conduction disorders and/or right bundle-branch block, which might have led to the clinical benefit observed. Those findings have also been reported in several recent studies, 7,15 which have shown a reduction or even absence of CRT benefit in that group of patients. It is worth noting that our study, even recruiting all patients with LVEF < 35%, QRS duration > 150 ms and LBBB morphology, identified 27% of them as non-responders (clinical criteria/death). Those figures are aligned with those reported in the literature. 6,15 We could not demonstrate that patients with higher PR interval had higher benefit, which might be due to the small size of our sample. However, the responder group showed a significant reduction in the PR interval (from 178 ms before CRT to 125 ms 6 months after). 610