Table of Contents

Part 1: Webcasts and presentations

Part 2: Teaching course on CRT

Part 3: Clinical Cases

Part 4: References and Library

Part 5: Frequently Asked Questions

Part 6: Pathophysiology of electromechanical dyssynchrony

Part 7: Webinars

 

  • Is echocardiography helpful to indicate CRT?
    • According to current ESC Guidelines, assessment of left ventricle ejection fraction is necessary to indicate CRT. Due to its widespred availability, two-dimensional echocardiography is the most used imaging technique for ejection fraction calculation. Class I indications to CRT do not require any other information coming from cardiac imaging techniques. However, for patients with right bundle branch block and QRS duration >120 ms (class II indication), echocardiography could be used to support indication to CRT showing the presence of significant cardiac dyssynchrony at baseline.
  • Is three-dimensional echocardiography necessary for evaluation of left ventricle ejection fraction?
    • Three-dimensional echocardiography is not necessary for evaluation of left ventricle ejection fraction because this can be calculated using two-dimensional echocardiography (particularly the biplane Simpson’s method) as it was done in most clinical trial on CRT. However, three-dimensional echocardiography allows a more accurate estimation of ejection fraction, which can be advantageous especially for repeated studies during follow-up to reduce the error of the estimation and increase reproducibility.
  • Is echocardiography helpful in patients with narrow QRS?
    • According to current ESC Guidelines, CRT is not indicated in patients with narrow QRS (defined as a QRS duration <120 ms). Therefore, echocardiography should not be used to support the implant of a biventricular pacemaker in patients with heart failure and narrow QRS.
  • Is  echocardiographic dyssynchrony helpful to predict the CRT response?
    • Many studies showed that cardiac mechanical dyssynchrony evaluated by echocardiography can predict response to CRT. In general, the more the mechanical dyssynchrony, the better the CRT response. It should be underlined that predictivity of different dyssynchrony indices may vary, therefore selection of the dyssynchrony index is extremely important.
  • Is stress echocardiography helpful to predict the CRT response?
    • The increase in cardiac function during stress echocardiography has been repeatedly reported to be a predictor of response to CRT. Left ventricular function is generally evaluated as ejection fraction but other parameters have also been used. The most used stressor is dobutamine but exercise has also been utilised.
  • How many types of mechanical dyssynchrony exist?
    • Mechanical dyssynchrony is a complex phenomenon. In general, three types of dyssynchrony are distinguished: atrio-ventricular (AV), interventricular and intraventricular. This latter can occur within the right and the left ventricle, but generally the left intraventricular dyssynchrony is studied, which, in turn, can be distinguished in a number of types: radial, circumferential, longitudinal and torsional. Although all these types of dyssynchrony are evaluated separately, they occur simultaneously during cardiac contraction.
  • Can mechanical dyssynchrony be diastolic or only systolic?
    • Most indices of intraventricular mechanical dyssynchrony are calculated during systole. However, it is also possibile to calculate post-systolic or diastolic indices of dyssynchrony. The clinical meaning and the response predictivity of the diastolic indices of dyssynchrony have been less studied compared to the systolic indices. 
  • Is mechanical dyssynchrony  always the consequence of electrical dyssynchrony?
    • No, mechanical dyssynchrony can also occur in absence of electrical dyssynchrony. For example, in patients with narrow QRS, a significant left intraventricular dyssynchrony can be related to regional differences in myocardial contractility and load.
  • Is mechanical dyssynchrony static or dynamic?
    • Mechanical dyssychrony is a dynamic phenomenon. In fact, it varies during cardiac contraction and with exercise. Stress echocardiography may be helpful to evaluate the dynamic component of cardiac dyssynchrony.
  • Which echocardiographic index can be used for atrio-ventricular dyssynchrony assessment?
    • In general, the AV dyssyncrony is evaluated using the Doppler technique (both pulsed and continuous wave Doppler) at the level of the mitral valve. Presence of pre-systolic (or diastolic) mitral regurgitation on the continuous wave Doppler trace is an index of AV dyssynchrony. Also, the mitral inflow pattern can show partial or complete fusion of the E and A wave because of the “anticipated” atrial systole (corresponding to a long PR interval on the ECG).
  • Which echocardiographic index should be used for interventricular dyssynchrony assessment?
    • In general, the interventricular dyssynchrony (or interventricular contraction delay, IVCD)  is evaluated using the pulsed wave Doppler of the pulmonary and aortic systolic flow and calculating the Qa-Qp index. Qa is the time to onset of the aortic outflow (aortic valve opening) and Qp the time to onset of the pulmonary outflow (pulmonary valve opening). There are other methods to evaluate the interventricular dyssynchrony which are much less used.
  • Which echocardiographic index should be used for intraventricular dyssynchrony assessment?
    • There is a wide number on left ventricluar dyssynchrony indices based on different ultrasound techniques and particularly tissue Doppler imaging,  speckle tracking echocardiography and three-dimensional echocardiography. Because echocardiography is not suggested by current ESC Guidelines to indicate CRT, the use of echocardiographic dyssynchrony indices has reduced in clinical practice. However, some of these indices have shown the capability to predict response to CRT. 
  • Is echocardiography helpful to guide the LV lead implant?
    • Some studies reported that, when the left stimulation is at the site of the segment which has the most delayed contraction, the response to CRT is better. It has also been shown that the response improves when the stimulated myocardial segment is viable. Therefore, echocardiography can guide the implant of the left lead indicating both viability and contraction delay of the left ventricular myocardial segments.
  • Which echocardiographic method can be used to guide the LV lead implant?
    • Myocardial viability has been evaluated using longitudinal, radial and circumferential strain by speckle tracking echocardiography. Contraction delay of the myocardial segments has been evaluated with a number of different methods, mainly based on tissue Doppler imaging, speckle tracking echocardiography and three-dimensional echocardiography.
  • Is echocardiography helpful for optimisation of CRT?
    • Today echocardiographic optimisation of CRT is suggested only for selected patients, precisely those who are probably going to be worse responders (for example, patients with ischemic heart failure and large transmural scar areas) and those who actually did not respond to the CRT.
  • What is the best echocardiographic method to optimise the AV interval?
    • In general, conventional pulsed wave Doppler assessment of the mitral inflow is used to optimise the AV interval. Diffent methods can be used. One which is frequently used is the iterative method, which consists in repeating the assessment of mitral inflow at different AV intervals. The device is optimised when the maximal filling of the left ventricle is obtained mantaining distinguished E and A waves on the mitral inflow Doppler trace.
  • What is the best echocardiographic method to optimise the VV interval?
    • As for the AV interval, the optimisation of the VV interval is generally done using conventional echocardiography. The most used method relies on the pulsed wave Doppler assessment of the aortic outflow at different VV interval. The optimisation is reached at the greatest aortic outflow.
  • What is the best echocardiographic parameter to assess the response to CRT?
    • CRT response can be evaluated by echocardiography using the left ventricle ejection fraction and the end-systolic volume. In general, a variation of end-systolic volume >15% after six months from baseline is considered as a positive response to CRT.