23 Left ventricular dyssynchrony and assessment by echocardiography Flashcards
What are the 3 types of dyssynchrony?
Atrioventricular (AV), interventricular (VV) and intraventricular (LV).
What are the effects of LBBB on the heart?
LBBB delays LV contraction causing dyssynchrony. This increases isovolumic contraction and relaxation times which decreases ejection and filling times relatively, decreasing SV and CO.
LBBB causes interventricular septal dyskinesis (paradoxical septal motion) in which the septal wall contracts before the lateral wall.
LBBB causes decrease in peak LV systolic pressure which impairs MV closure and increases functional MR.
How are the 3 types of dyssynchrony assessed?
AV dyssynchrony is assessed using PWD of the MV inflow. The time between the start of the E wave and the end of the A wave is measured (LV filling time) and a time <40% of the cardiac cycle indicates AV dyssynchrony.
VV dyssynchrony is assessed using PWD of the LVOT or RVOT. The time between the start of the QRS and the start of aortic or pulmonary flow is measured and a time >40ms indicates VV dyssynchrony.
LV dyssynchrony is assessed using PWD of the LVOT. The time between the start of the QRS complex and the start of AV flow is measured (aortic pre-ejection time) and a time >140ms indicates LV dyssynchrony. LV dyssynchrony is also assessed using M-mode in the PLAX view. The time between start of the QRS complex and the peak of LV septal and posterior wall contraction is measured and a time >130ms indicates dyssynchrony.
How is CRT optimised?
The AV and VV delays are adjusted to increase LV filling time, LV ejection (SV) and LVEF and improve functional MR.
Adjust the AVD in increments of 20ms and perform PWD of the MV inflow. The intention is to increase LV filling time and the MV inflow VTI whilst avoiding shortening of the A wave and pre-systolic MR. Increase the AVD and perform CWD of the AV. The intention is to increase AV VTI.
