CRT improves LV filling dynamics: insights from echocardiographic particle imaging velocimetry.

Echocardiographic particle imaging velocimetry allows blood flow visualization and characterization of diastolic vortex formation that may play a key role in filling efficiency. We hypothesized that abrupt withdrawal of cardiac resynchronization therapy (CRT) would alter the timing of left ventricular diastolic vortex formation and modify cardiac time intervals. In patients with heart failure (HF) who had chronically implanted CRT devices, the timing of the onset of the diastolic vortex (TDV) from mitral valve opening, transmitral flow, and cardiac time intervals was measured at baseline and after deactivation and reactivation of CRT. Compared with control patients with cardiovascular risk factors but structurally normal hearts, TDV was significantly delayed in patients with HF. Deactivation of CRT resulted in striking delay in TDV due to disorganized flow and reduced flow acceleration, and reactivation reversed these characteristics instantly. In addition, CRT deactivation also prolonged the isovolumic contraction interval, which closely correlated with the changes in the TDV. These data suggest that CRT plays an important role in optimization of left ventricular diastolic filling.