The authors Nascimento et al., published an important work demonstrating the value of myocardial perfusion scintigraphy (SPECT-Gated) to identify cardiac dyssynchrony (CD) and with posterior implantation of left ventricle (LV) electrode in the area with higher dyssynchrony, with favorable correlation with clinical results and cardiac function. The study rises important issues in the attempt to reduce non-respondent rate (30-40%). These high rates are due to implants in very advanced or irreversible phases of the disease or to positioning of the LV electrode in areas with fibrosis or due to absence of dyssynchrony.

All the current directives take the indication of cardiac resynchronization therapy (CRT) in consideration, based on electrical dyssynchrony criteria, in detriment of mechanical dyssynchrony criteria. The Echo CRT study confirmed the unfavorable results in patients submitted to CRT in absence of CD, minding it may be a deleterious therapy.

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