CRT Improves Left Ventricular Filling Dynamics: Insights From Echocardiographic Particle Imaging Velocimetry
What is the impact of abrupt withdrawal of cardiac resynchronization therapy (CRT) on the timing of left ventricular (LV) diastolic vortex formation and cardiac time intervals?
In 11 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. The TDV was defined as the interval from mitral valve opening to the appearance of the main diastolic vortex formation (determined from the diastolic ascent of the vortex strength curve).
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 prolonged the isovolumic contraction interval, which closely correlated with the changes in the TDV.
The authors concluded that CRT plays an important role in optimization of LV diastolic filling.
The study suggests that CRT acutely affects diastolic filling, and the change can be measured as change in TDV. Furthermore, LV filling is improved immediately after CRT reactivation due to optimum TDV formation with shortening of the isovolumic contraction interval. Thus, echo-particle image velocimetry may be a useful technique for elucidating the acute hemodynamic effects of CRT. Further studies are indicated to assess whether optimization of diastolic filling characteristics via variations in the pacemaker settings or lead positioning may be useful for predicting clinical outcomes after CRT.
Keywords: Heart Diseases, Rheology, Heart Failure, Risk Factors, Pacemaker, Artificial, Diastole, Heart Ventricles, Mitral Valve, Hemodynamics, Cardiac Resynchronization Therapy
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