Assessment of cardiac asynchrony by radionuclide phase analysis: Correlation with ventricular function in patients with narrow or prolonged QRS interval

Background: Conflicting data exist on the relation between the synchronism of cardiac contraction and ventricular function. Aim and methods: A resting radionuclide ventriculography (RNV) was performed in 380 consecutive patients to evaluate the relationship between the synchronism of cardiac contraction and ventricular function. Results: A significant, non-linear, relation was found between LVEF and intra-ventricular asynchrony or QRS, but not between inter-ventricular asynchrony and LVEF. A linear correlation was observed between QRS and intra-ventricular or inter-ventricular asynchrony. Intra-ventricular asynchrony was identified as the major, independent, determinant of LV function. With the increase in QRS duration, a decrease in LVEF (p <0.001), and a worsening of either intra-ventricular (p <0.001) or inter-ventricular synchronism (p <0.05), was documented. However, 48% of patients with QRS 120-150 ms had abnormal inter-ventricular and 42% abnormal intra-ventricular synchronism, while 27% of patients with QRS > 150 ms had normal inter-ventricular and 25% normal intra-ventricular synchronism. Conclusions: Intra-ventricular asynchrony was identified as the major determinant of ventricular dysfunction. A consistent proportion of patients had asynchrony despite preserved QRS duration or normal synchronism with a QRS > 150 ms. Fourier phase analysis of RNV may detect asynchrony better than QRS. The role of RNV for detection of individual patients who may most benefit from resynchronization therapy requires additional investigations.