Assessment of Systolic Dyssynchrony for Cardiac Resynchronization Therapy Is Clinically Useful

Abstract

T he beneficial effects of cardiac resynchronization therapy (CRT) on morbidity and mortality of heart failure patients with wide QRS complex have been demonstrated extensively. Various single-center and multicenter randomized, clinical trials have shown that CRT improves heart failure symptoms and left ventricular (LV) function and induces a significant reduction in LV volumes and mitral regurgitation. [1][2][3][4] In addition, CRT reduces the number of heart failure hospitalizations and improves long-term survival. [5][6][7][8] More important, unlike other heart failure medical therapies that may lose their effects over time, CRT is a long-term effective therapy. 9 Accordingly, current American Heart Association/American College of Cardiology/Heart and Rhythm Society guidelines consider CRT a class I indication for patients with drug-refractory heart failure symptoms, LV ejection fraction Ͻ35%, and wide QRS complex (Ͼ120 ms). 10 Response by Sung and Foster on p 655Despite these encouraging results, cumulative evidence shows that only 60% to 80% of patients exhibit a favorable clinical or echocardiographic response to CRT. 1 For example, in the MIRACLE (Multicenter InSync Randomized Clinical Evaluation) and the MIRACLE-ICD (Multicenter InSync Implantable Cardioverter Defibrillator) trials, more than 30% of the patients fulfilling the aforementioned inclusion criteria did not show a favorable clinical response to CRT. 5,8 Several single-center studies have reported similar nonresponse rates and have questioned the accuracy of these inclusion criteria to identify patients who will respond to CRT, which has encouraged the research of novel indices and strategies that can reliably predict response to CRT.One of these indices is LV mechanical dyssynchrony. In the last decade, multiple single-center trials and the Cardiac Resynchronization in Heart Failure (CARE-HF) trial have demonstrated that LV mechanical dyssynchrony indices (most of which are based on echocardiographic measures) have superior accuracy compared with LV electric dyssynchrony (based on QRS duration) to predict response to CRT and long-term outcome. 7,11-13 However, those results were challenged recently by the multicenter PROSPECT (Predictors of Response to CRT) trial, in which no single LV mechanical dyssynchrony parameter could accurately predict response to CRT. 14 In this controversy, we advocate the use of LV mechanical dyssynchrony as an additional selection criterion for CRT and address the strengths of current imaging modalities to evaluate LV mechanical dyssynchrony. In addition, the different pathophysiological factors that may determine CRT response will be discussed. Finally, the use of an integrated approach, including LV mechanical dyssynchrony, LV lead position, and extent of myocardial scar, will be proposed as a potential optimal strategy to evaluate candidates for CRT.

Temporal diffeomorphic free-form deformation: Application to motion and strain estimation from 3D echocardiography

“…This is a pre-print version The final version can be downloaded from http://www.sciencedirect.com/ between mechanical dyssynchrony and response to CRT is still a controversial issue (Delgado and Bax (2011);Sung and Foster (2011)), particularly limited if a single parameter (measured strain) is considered in the analysis. Comparing the measured strain to the deformation patterns of specific mechanisms involved in CRT response may be a more relevant strategy (Parsai et al (2009)) and this could be achieved with the use of 3D strain analysis by using such a tool as the one we present.…”

Robust and automatic diagnosis of the intraventricular mechanical dyssynchrony for the left ventricle in cardiac magnetic resonance images

“…In recent years, a lot of efforts had been put in the auto-diagnosis of cardiac mechanical dyssynchrony [1][2][3][4][5][6][7][8][9][10][11][12][13][14]. However, existing methods lack robustness and no existing LV mechanical dyssynchrony measurement methods could predict the response to CRT robustly [15,16]. In this paper, an data-driven approach is proposed to measure the mechanical dyssynchrony of the left ventricle automatically by utilizing effective image and signal processing methods.…”

“…Past trials demonstrate that LV mechanical dyssynchrony has superior accuracy compared with LV electric dyssynchrony to predict response to CRT [13,14]. However, a recent trial showed that no single LV mechanical dyssynchrony parameter could predict the response to CRT robustly [15,16]. In [17], the authors pointed out that "although sophisticated cardiac imaging modalities have been intensively utilized for improving patient outcome, it seems that many mechanical dyssynchrony measures suffer from technical limitations and from difficult interpretation of the complex signals, which lack reproducibility outside highly specialized laboratories."…”

Cellular and Molecular Aspects of Dyssynchrony and Resynchronization

“…However, of the patients who receive CRT, approximately one-third show no clinical or morphometric response to the therapy [22,23]. This "non-responder" rate has plagued the field, and despite significant efforts, has remained steady.…”