Dr. Ole A Breithardt
Assessment of left ventricular function for the identification of advanced systolic heart failure and exclusion of severe valvular disease is a prerequisite before implantation of implantable devices for cardiac resynchronisation therapy (CRT) and is usually performed by transthoracic echocardiography (TTE). Beyond this essential information on global function, TTE allows to assess the presence and extent of mechanical dyssynchrony by multiple parameters and techniques. However, in several multicentre controlled trials no single echocardiographic dyssynchrony parameter has yet proven to be superior to the simple measure of QRS duration with respect to patient selection. Despite these discouraging results, there is still a wide belief that a comprehensive assessment of dyssynchrony by multiple conventional echocardiographic parameters and by newer, more robust techniques for quantification of myocardial deformation will help to characterize CRT candidates more precisely and to improve CRT outcome. On this background, the session on “Optimising patient success and outcome” in CRT provided practical information on how to analyse and interpret cardiac dyssynchrony in patients with non-ischemic and ischemic cardiomyopathies.
In the first talk, Dr. Erwan Donal (Rennes, France) focused on the population with a non-ischemic etiology and provided a comprehensive overview on the available set of dyssynchrony parameters. First he reminded the audience of the limited value of the QRS complex as the sole criterion for electrical dyssynchrony: even with a high cut-off value of 163ms the sensitivity of the QRS width to identify a responder is only 57% and the specificity 53% (Delgado-V et al., Circulation 2011) and up to one-third of patients with a QRS>120ms do not show any evidence of mechanical dyssynchrony. He then argued elegantly for a multi-parametric approach to quantify the often complex pathophysiology of dyssynchrony and stressed the importance of the relatively simple and robust conventional Doppler and M-mode parameters. The different levels of dyssynchrony can be easily assessed with a measurement of the pre-ejection time intervals at the pulmonary and aortic valves (interventricular delay representing interventricular dyssynchrony) , the transmitral inflow duration (E- and A-wave duration, atrio-ventricular dyssynchrony) and the identification of septal flash on M-Mode (intra-leftventricular delay). A more precise assessment of intraventricular dyssynchrony can be obtained by 2D strain imaging. Taken together, such a multi-parametric assessment of dyssynchrony has the potential to identify possible CRT responders with an excellent specificity of more than 90% and a positive predictive value above 65% (Lafitte-S et al., Eur Heart J 2009). Beyond the assessment of dyssynchrony, it is also important to assess right ventricular function and - in particular in very advanced dilatation with poor ejection fraction - the presence of contractile reserve, both important predictors for long-term CRT success (Muto-C et al. Heart Rhythm 2010). Finally, he presented the strain delay index (SDI) as a new, promising parameter for identification of dyssynchrony with an excellent positive and negative predictive value above 80% for a SDI >25% (Lim-P et al., Eur J Heart Fail 2011). The second speaker, Prof. Jens-Uwe Voigt (Leuven, Belgium) stressed in in his introduction, that although echocardiographic dyssynchrony assessment is not part of CRT patient selection according to current guidelines, it may nevertheless be of particular importance in borderline patients with a lesser degree of QRS prolongation (<150ms) and with complex comorbidities, such as pulmonary hypertension or in particular in patients with extensive ischemic myocardial disease. Both the location and the extent of myocardial scar after myocardial infarction have a negative influence on CRT outcome and have to be evaluated before CRT implantation. Deformation imaging by echocardiographic 2D speckle tracking technology is in his view the preferred modality for dyssynchrony assessment as it is may differentiate better (although not perfectly) than other techniques between active contraction in viable myocardium and passive motion in scarred segments. The septal flash phenomenon is related to early, presystolic activation of the septum and can also be seen by deformation imaging from the apical views. Early septal contraction and delayed lateral wall activation results in a pathologic motion in the left ventricular apex (apical rocking), which also can be quantified by tissue Doppler and strain imaging. In the final discussion, the panel concluded that echocardiographic dyssynchrony assessment, in particular with the use of strain imaging techniques, continues to play an important role in the pre- and post-implant assessment of CRT patients and that pre-implant assessment of conventional Doppler parameters is particularly useful for post-implant follow-up and verification of the resynchronisation success . However, a comprehensive assessment with the use of multiple parameters will be necessary to characterize the complete extent of the complex patterns of mechanical dyssynchrony.
Cardiac resynchronisation therapy: optimising selection and success
Our mission: To reduce the burden of cardiovascular disease
© 2017 European Society of Cardiology. All rights reserved